|Last year I swiped an idea from Firewire surfboards and installed a springer into the neutral axis of the board. Well, what I thought was the neutral axis. In the last year there have been some changes and it seems the neutral axis on a surfboard has either changed, or been abandoned in favor of recessed on the deck side. |
My build thread from last year is here
The changes in Firewire's tech is here
If you notice the propaganda from the Firewire site, they are describing layers, like the leaf spring of a car, which is the graphic also. Last year I just used a thick Balsa board, which was ok, but there really isn't much flex return as the minimal amount of flex we get with our boards didn't engage the balsa board. I needed to tighten up the response.
If you "glue" three things together, no matter what the material - say playing cards they become incredibly stiff resisting any forces that try and deflect it. Carbon has great flex return and retains that characteristic when included in an epoxy matrix.
So my springer for this build is 3 layers of 6 oz CF sandwiching 2 layers of 1/16" Balsa.
I'll be incorporating the sandwich springer into a composite sandwich board.
CF/Balsa/CF/Balsa/CF laminate stack:
|The general location of Firewire's springer circa LAST year. |
|i wish you would use CF tape|
|I am too CHEAP! I am using up old scraps of B and CF. |
|and dont forget the vent|
|LOL yes mom! Reminds me of last night. Judy "gently" reminds me not to bring epoxy and EPS into the house. So I typically try and clean up before going inside. Last night I must have wiped my hands on my shirt and not realized it. I'm heading to bed and go to take my T-shirt of and I've laminated it to my stomach!!!! I effectively gave myself a stomach waxing instead, using epoxy You know...that hurts!!!!!|
| oops , i think it was the lighting that does it ( lack of ) , so now what is your status|
|That's a funny story. When I went to pull the T-shirt off, I truly waxed lyrical (pun sooooo intended ). Poopy! (or word(s) to that effect) I exclaimed. Judy, ever attentive to my exclaiming Poopy! (or word(s) to that effect) asked: What's wrong? |
I explained the small matter of being one with my T-shirt and the epoxy. Upon hearing this, she went into some type of convulsion that included writhing on the floor and hysterical laughter. Poor thing.
I removed the slack in my T-shirt and on the count of three, pulled with all my might in a swift upward motion. THAT caused, once again, a waxing lyrical: Poopy! (or word(s) to that effect). And was also effective in separating the T-shirt and a certain amount of stomach hair, from my person.
So, for the time being, I am smooooooth as a baby's butt, slightly red and irritated in an isolated spot, but sans T-shirt.
Thanks, ever so much, for your inquiry, which allowed me to relive that glorious moment, once again.
|This build will be a composite sandwich, utilizing corecell rails and divinycell skins. |
I'm not a big fan of divinycell (cl pvc) in the 3mm thickness for the skins, preferring corcell (san). The more brittle cross-linked PVC foams crumble and shear under severe impact, and are better used in low-impact areas. Brittleness also lowers the resistance to crack propagation. Once there is a crack, such as the 45° crack
occurring under impact, it can easily propagate as the sandwich panel continues to flex.
This first picture is of some H-80 D-cell you can see the jagged edge - it tears like construction paper.
The next picture is A550 Corcell, 3mm and it's virtually impossible to tear.
|Divinycell has a number of features, it's readily available, about 50% cheaper than the stronger Corecell and in comparable densities is "floppier" than Corecell - bending around tight corners is pretty easy with D-cell - a tight radius tends to just snap the Corecell. |
|I'm using H45 D-cell, it's a 3'ish pound foam. Anything less than 5 pound density isn't structural, so my H45 will basically crush unless I stiffen it up. Further, this low density d-cell offgasses like your grandfather after a mexican meal It will need to be sealed to reduce that OG and to increase the resin at the surface, which will help stiff the skin. |
It's hard to see in this picture but the D-cell's porosity is so extreme that there are holes thru the 3mm cross-section.
|The board in the background is this same basic construction, with the exception of the rails, which in this case were H45, also. |
|The skin will be sandwiched between two different fabric, the underlayment will be 4oz Zylon as on the exterior of the board above - Zylon in a epoxy matrix exceeds all technicals of aerospace grade CF and it comes in a 4 oz weight. |
On the exterior, I am going to use a carbon and kevlar hybrid. It offers the stiffness of CF and the impact resistance of Kevlar. I'm sure it will be a mess as the Kevlar won't sand, but I like the look of it.
|It seems that mills are routinely dying the Kevlar different colors - strictly cosmetic, but I like the look. |
|[insert after crack propagation p ] |
Klegecell, Divinycell, Herex are cross-linked PVC foams, they're actually blends of PVC and di-isocyanates, a very brittle urethane foam component. In fact, the PVC / di-isocyanate blend is a good compromise. It makes it easier to foam the PVC, and to produced different densities of that foam. The di-isocyanate gives the PVC two properties it lacks; good mechanical strength and better heat distortion. However, it imparts its brittleness in the process. Elongation in cl PVC foam is only about 10% vs SAN Corecell at 60% which is why I was able to tear the D-cell.
|aha, and have you seen holographic CF? Board from it must be eyecatching |
|I've seen that stuff! So many interesting fabrics.|
|Examples of the holographic CF that Petr refers to. The website where I swiped the pictures indicates that it's hard to capture the reflective quality of the fabric in the picture. |
|looks like snake skin|
|just holgraphic |
|holgraphic, that's funny. It does that that irridescent snake skin look. |
So I've been working with texturing the epoxy, on the deck so that I can reduce traction/wax, at least outside the area where the EVA traction will go and on the bottom to aid release.
The excellent idea about sand, I've used before and didn't care for the results, but I may go back to that. Instead I used a metal wet out roller after the epoxy started to gel just a bit. It left bumps, that are similar to sand, without any real sharp edges...I think that may work.
This is a close up after the texture coat and I shot some primer today.
|Towards the end of last year, I built this board: |
I shot the paint with three layers - black, white and red. So the red was proud from the rest of the paint. It didn't seem to slow the board any, but if it can go 14 and get there quickly, that's enough. What it DID do was release really well. The water didn't seem to stick to it at all. So I wanted to add a texture to the bottom of a board that didn't require so much paint build up.
|Epoxy is miserable stuff to work with, it fish eyes and seperates and seems to be impossible to gloss...so I thought, how can I use that to my advantage here (and be lazy). I laid down a solid hoatcoat to ensure the fabric was sealed, then I got my hands dirty and oily using a tiny bit of baby oil and I rubbed and scratched my dog Woofie for about 10 minutes. After doing that I touched the hotcoat - just doing EVERYTHING wrong for a good gloss. Then I squeeged on a very thin gloss coat of epoxy so that there wasn't enough to self level and viola - a textured bottom. Oh! and a happy dog. |
|I hope to paint it so that the depressions are one color and the peaks another...my plan is to shoot the whole thing black, then go back and lay on a really thick wet coat of red, following quickly with a squeegee to strip the red from the peaks and if I'm lucky it will be a sort of mottled look, with the texture still in place...we'll see. |
|There is a similar concept in the kneeboard and surfing shapes - they are called jet bottoms, but they are actually shaped and glassed into the bottom of the board. A few simple pictures, there are some incredibly intricate shapes in the genre. |
I can't even imagine shaping something like that, let alone glassing 'em.
|I swiped two quotes from sway's about the theory of Jet Bottoms: |
There's conflicting views out there but if you read carefully, it seems that the closer studies have found that micro-turbulence prevents macro wake turbulence behind curves by keeping the boundary layer energetic. This became a diminishing return when ridges or whatever extended beyond the boundary layer.
While not absolute proof, it gives credence to the claim that by deliberately inducing turbulence, you can break up the adhesion layer of water which sticks to your board, thereby slowing it down. Breaking up this surface tension may result in a faster, looser, more responsive board, which is what riders of these bottoms claimed.
In my experience, there wasn't any speed increase or degredation for that matter. So, speed didn't seem affected by the a roughened surface - whether I had just scratched the bottom with 60 grit, of the traverse ridges from the paint. However, I have consistently found the boards released better, so there was less adhesion of the wtare to the board.
|look at shark skin - there answer - it is milion years of development |
The structure of shark skin has another function besides protection. The streamlined shape of
the scales decreases the friction of the water flowing along the shark's body by channeling it
through grooves.The grooves are so closely spaced, they prevent eddies from coming into
contact with the surface of the shark's moving body. This reduces the amount of "drag" as the
shark swims, enabling the creature to glide farther on a given amount of energy.
Scientists have found that the ridges created by shark scales can reduce drag in the water by
as much as 8 percent. Golf balls and many military aircraft and vessels employ similar
I think its kinda nanotechnology (geckos already use it)
Also new fabric of Speedo wetsuit for British Olympionics was banned because of speeding effect. Call Speedo, buy some and glue it on bottom
|Or you could go Shark Fishing!!!!|
|LOL! Shark fishing! I can't even catch a bluegill! |
I have read "some" of that literature Petr, but around the 6th paragraph my eyes glaze over From what I have been able to glean is that the sharks skin is a ORGANIZED channeling of water - so something TOTALLY unlike my desk. Whereas the jet bottom and my separation bottom are chaotic, JUST like my desk. The organized channeling tends to speed things up, while the chaotic channeling, I think, really only loosens things up...but there are those that same the chaotic does both.
|Sorry Jeff even I dont have time and energy to read it all but its very interesting so I posted all I found. |
Shark skin is compound of hard ribleted sheets inserted in soft underlay. But I dont know real size of this texturing which is crucial for proper function. If tis in mm, microns etc.?
These hi-tec swimsuits provide also some floatation becase small air bubles catch in riblets.
look at this drag reduction product KISS-COTE
they talk about 1-2% or 4% reduction
drag science - very interesting and short text
Its all about directed turbulence
(Message edited by hawaj on September 29, 2009)
|Here we go - that film is made by 3M and each V-shaped groove measures 150 micrometers across -- approximately twice the width of a human hair. So we can imprint this pattern from some film to gloss coat. I think that maybe some PE or PVC thin plastik sheets are made with this texture. |
|Its all about directed turbulence |
they talk about 1-2% or 4% reduction
I don't doubt that for a minute. I think that in Olympic level swim events that can be decided by 1/1000 of a second any advantage is helpful. I'm not so sure that has any practical application behind the boat.
In the picture below - I'm in the realm of 16 mph, but I'm pumping like mad and have to be careful not to engage the rocker on the face of the wake. That REALLY is the fastest that board would go with me riding it. The increase in speed with the organized flow is possibly TO 16.16 mph up to a maximum of 16.64 mph. I'm not sure that's even a perceptable difference, let alone usable difference.
To me, acceleration or squirt are more important once you have a board that can operate in a speed range above your wake speed. Theoretically, our boats are running around 11 mph. If your board can operate at 12mph easily - at trim, then that's probably enough, but you'd want to get from 11mph to 12mph instantaneously...you attempt a 3 and you're fading out the back, lean forward and you automatically are going faster than the boat - THAT's usable squirt or acceleration.
As for the difference between organized and chaotic flow. Personally and this is just my opinion, organized flow, while quantifiable, isn't practical in this application. If chaotic flow doesn't degrade speed by more than that .16 to .64 mph and DOES have some impact on the release of the board, THAT is a more useful application of the texturing.
OR not. So much of this is subjective and may even be unrelated to the texture itself. Although I do enjoy the discussion of theory. Thank you for your input Petr! I wish that I had a better grasp of it all.
|ooops - picture below |
|yep increase is not so big its good to know something more |
I like to think about all posibilities and unconventional things around that other peoples are scary off
(Message edited by hawaj on September 29, 2009)
|yes - you've always been way ahead of the curve! |
I was just organizing some of my notes and remembered finding some info on Tom Morey's Air Lubricated boards. In one of the articles Tom is quoted: "Once I knew for a fact that a wide board given freedom from drag would really fly, I was mentally free to think in terms of wide flat stone-skipping proportions, which in a way led to the development of the first boogie boards, which, in fact, given decent size waves, really scream along."
I was thinking about Shred Stixx and Inland Surfer - both Jerry Price and Jeff Page are exceptionally innovative and will forget more than I'll ever learn. They both seemed to grasp on to that wide board with no drag pretty early on. I think both of their companies are constrained by perceptions - you can't sell something that is TOO advanced otherwise it scares people - like you mentioned Petr.
Anyway back to the Air Lubricated boards of Morey. He put steps in the boards, these pictures illustrate:
I wonder if surfcraft being partially submerged and partially airborne have a greater reliance on that boundary of water and air. Shark's are fully submerged and so there really isn't the introduction of air into the boundary layer as would be possible with surfcraft. It seems to me, and I'm probably all wet here (I loved that pun ), that there is a potential for reducing drag and thereby increasing speed and acceleration, by trapping or creating air bubbles in the hundreds of recesses.
I tried something over the weekend. I have a tsunami pump with cheap clear tubing. You can see the water flowing through the tube, but mostly because of the occassional piece of gunk that zips by. I pinched the tube, just a bit, enough that it created a convex shape in the path of the water. On the trailing edge of the convex there was a turbulent distruption and the formation of bubbles - lots of air. It was funny, because there didn't seem to be any air in the flow before the convex...my guess is that it's there and not magically created, but probably along the surface of the tubing and the restriction mixes it into the flow of water. If that's the case, I'm hoping the same thing can happen with the "dimples" and the result will be a more slippery board.
|I think that NAVY after riblets developed some system which distribute air thru small holes under body of ship to decrease drag of water. |
Read this article:
... very interesting
|That is interesting, I just scaned the first little bit, I'll read it in a bit - thanks for the link Petr. |
NOT the dramatic effect I was hoping for, but fun nonetheless.
|From that article: The optimal arrangement, Koeltzsch said, is when the distance between the peaks of the riblets is half the diameter of the vortices. In this case, the fluid caught by the vortices only contacts the peaks of the riblets and not the walls of the pipe, so friction is reduced and the fluid moves faster. |
How does one determine the diameter of the vortices?
|he he you must simply measure it lets say from photography |
Call some hydro lab where they have hydro tunnel put board there and lets water flow and take picture. Maybe colored streams will help.
Or wakesurf in very clear water and put camera under board.
I think that maybe some students at university can by interested in this and you can make some colaboration project. You get accest to hi-tec lab and some answers and they will get interesting theme
|fin tip vortexs |
|low speed hydrodynamic tunnel |
|beware Jeff - surboard science!! |
I dont read it! Just posting
(Message edited by hawaj on September 30, 2009)
|I love the intro to your last post beware Jeff! |
In looking at one of those articles, I read this:
Even the slightest roughness such as scabs of wax on the bottom of the board can make the difference in avoiding a wipe out. These small imperfections cause enough friction with the water that a turbulent flow results, decreasing speed.
I guess my position is I don't believe that, or perhaps my position is best stated as; Yes that's true, but the degradation in speed is so minute as to be imperceptible. However, the increase in release or looseness is significant and easily felt, if not easily quantifiable.
I need to find a fluid dynamics class interested in surfboard design.
In looking at the vortices in the one picture, I would think that only the first one is significant, because that's where you want to place the second row of tips - or actually at the mid point. It seems, though, that there is a leading ramp, which has to be based upon speed - slower the speed the less that lead in and possibly the larger the diameter of the vortex. I wonder if there isn't some formula to predict the diameter of the vortex given the height of the tip, density of the fluid and speed of the tip through the fluid...sheesh then there would also have to be some angle of attack. OK OK OK, I give up!
|By Petr (hawaj) on Wednesday, September 30, 2009 - 10:02 am:
|Interesting Jeff, I must read it all after my work is done ... |
And please dont forget that we are at field of water mixed with air bubles (plus foam at sea) and not only in pure water, so it can make difference than pure fluid dynamics.
What I like from that first article is that sharks which move quicker have different skin than others and that scientist started to study pinguins and seal fur - ie how fibers can decrease drag
|By Petr (hawaj) on Wednesday, September 30, 2009 - 10:07 am:
|Wonder how looks speed fishes skin like swordfish etc. Do they have that fish skin slime like other ones? So what about to put some slime or vaseline on board? Only measuring and testing can show the difference|
|By Petr (hawaj) on Wednesday, September 30, 2009 - 10:12 am:
|and if you can find it ... |
Hendricks, Terry. Surfboard Hydrodynamics, Part 1: Drag. Surfer Magazine January 1969.
ok here it is
(Message edited by hawaj on September 30, 2009)
|By Petr (hawaj) on Wednesday, September 30, 2009 - 10:32 am:
|Another concept from Bourton - cathedral hull |
|By Petr (hawaj) on Wednesday, September 30, 2009 - 10:37 am:
|and Jeff do you know this Findesigner software |
they promised some add modules but it was long long time ago
- Comparative flow analysis and pressure distributions add-on modules
- Comparative drag and lift analysis add-on modules
|All done, we'll see if the bottom texture theory is 'all wet' |
|I ordered a few sections of nomex, I think it will give a uniformly "dimpled" surface rather than the random surface pattern with the separated epoxy. I'm also interested in how the honeycomb will work as a skin. |
|How are you going to use Honeycomb as a skin. Are you going to have at least one layer of fiberglass over the honeycomb? My friend used honeycomb as a core for some speaker enclosures he built, with a couple layers of fiberglass. He used a vacuum bag technique, and he was left with little dimples in his end product. This could be a good idea! Can't wait to see the end result. Jon T|
|In both the d-cell and hc skins I'll have fabric over and under the skin core. My general approach is to shape the 1# EPS core and then bag the bottom skin to that shaped EPS. I intend to use 4 oz zylon as the sandwich layer in both of the builds. I'll do a few test panels to make sure it's all working, but I think I can achieve the results I want with 10" of vaccuum. |
This picture is a from a few years ago where I was discussing that it wasn't necessary to bag to a tool of any kind, just lower the vacuum and leave the EPS core unshaped on the top, so that it's thick and will resist bending, and the 3mm skin will conform to the shape.
I'll then go back and laminate the exterior, most likely again with the bag.
|Ok, so time to get down to business. These boards will be a composite sandwich - a low density core 'sandwiched' between high density skins. The skins get the tension and compression forces and the core some compression and sheer. MOSTLY the core just keeps the skins separated and prevents them from bending. |
This illustration shows the various forces on the components of the sandwich.
|I use 1 pound EPS for the core. It's low density gives it great sheer properties and lowers the weight close to 40% when it's complete. |
There is a fairly new "flavor" of EPS referred to as EDRO that makes EPS virtually impervious to water. EPS is a closed cell foam, but in this low density it's most air and pentane, the blowing agent inside the pellets. The gaps between the pellets can fill with water in the case of a puncture.
For my purposes I use the cheaper non molded EPS. I get the EPS in billets that are 4'x8' and I typically have it cut 4" thick.
|I use a simple circular saw to hack the 4'x8' into 3 pieces, 2 - 2'x5' and the residual 3'x4'. Depending upon the rocker I can net 3 to 6 cores from that, which is about $4 to $8 each. The 1# foam is super cheap. |
|I hotwire the bottom rocker and leave the deck unshaped at this point. I have a set of rocker templates made from masonite. That material allows the hotwire to slide along the cirve of the rocker smoothly and melt the EPS as it goes. |
I put alignment marks on each side so that the hotwire templates match and I'll create a flat rocker. I attach the templates to the foam using simple wood screws.
|I have a 28" Tekoa hotwire bow and transformer - they call it a thermal generator |
The 1# pound foam melts like butter under a hot knife. After making sure that the rocker is square, I remove the rocker templates and hang them up.
|So, the textured bottom doesn't seem to have impacted the speed either positive or negative. My guess is that it does add drag, but it's so negligible as to not be perceptible, but it does have a definitive sense of release. The board isn't loose, due to the fins, but it's not stuck to the surface. I'd like to try it with a less chaotic texture. |
|Jeff, the with you on the board it still looks stuck to the water.|
|LOL! I represented that it released really well, NOT that it was magic. The magic board is slated for construction in January. |
|After hotwiring the core I shape the core to accept high density rails. I like to glue them up with a single layer of 6 oz Carbon Fiber that acts somewhat like perimeter stringers. |
I take an existing shape and lay it on the core so that I get a rough idea where the final outline will be. In this build I'm using 1/2" A550 Corecell for the rails. I want to leave just a hair of the rail material beyond the final outline so that I have some excess to play with when I go to shape the rails. Once I have the general outline drawn on, I lay an outline template on the centerline and mark my cut line.
|I use a jig saw to cut along the outside of the cutline and a sanding block to square the cut up, as well as, bring it down to the inside of the cut line. In this situation my foam is a tad thicker than the depth of my jiggy blade so I use a hand saw to finish that part up. Lather, rinse and repeat on the opposite side. |
|I forgot to mention, that I don't trim the tail back where the tail block will go. The HD rails are bent into the curve of the tail, and I don't have the ability to size those accurately during the prefab, so I cut the core and rails after glueup so that I get a straight cut for the tail block. |
The rail material, as I mentioned is corecell. It's very stiff and has great shear resistance, but when stressed too much it tends to snap. Attempting to bend the rail material both INWARD to follow the outline of the board AND UPWARD to follow the rocker tends to put too much stress on the 1/2 thick material. So, I cut the rocker into the rail material and then only need to worry about the bend in towards the outline.
I use a simple single edge razor to cut the corecell, using the hotwire template as a guide. The rocker will be slight different when it is finally shaped, but it's pretty close at this stage.
|I was going to glue up the rails, but I seemed to have stocked out of bag! Anyway...while ordering the bag, I thought about peel ply to give the bottom surface some texture. Peel ply is non porous and leaves a slight texture to allow secondary bonding, I'm hopeful that will give me the release in a more uniform/less chaotic fashion. |
My intention will be to lay it over a wet gloss coat and leave it to cure.
|While I'm waiting for my nomex, bagging film and peel ply, I got my rails ready for glue up. In the above photo you can see the rails are @ 2" wide. Up at the nose, that will exceed the thickness of the EPS core. When the bag starts to consolidate the rail material, the area that is proud of the core will tend to bow inward and force the bottom away from the core. It's a little hard to see, but I've trimmed that area even with the deck of the core. |
I've also trimmed the two pieces where they'll meet at the nose to about 45 degrees. Also, it doesn't show, but I've kerfed the last 4 inches of the rail material where it bends the tightest.
I have also cut two strips of 6 oz CF that I will sandwich between the rail material and the core.
I'm ready to glue as soon as the bag arrives.
|I didn't get pictures of the assembly, but a quick overview is: I mix up about 3 oz of epoxy, paint a very thin layer on all of the foam that comprises the rails. I use the residual epoxy to wet out the CF strips. With the resin spread, I smooth the CF on the EPS core, align the Corecell and tape it in place. With boths sides glued up and taped up, I place it on the rocker bed and tape the "blank" to the bed so that I can slide the whole shee-bang into the bag. |
The blank, in the bag, as the vacuum is being pulled.
|The blank with about 1/2 an atmosphere being pulled. It's enough to hold the rail material to the EPS without deforming/crushing the EPS. Probably the most troublesome area is up at the nose. The curve of the nose rocker tends to fight the curve of the rail inward towards the point of the nose. As the vacuum is being pulled, I work the rail material in and down against the rocker bed. If it's fighting me, I can stop the vacuum just long enough to work the foam into place and then start it back up again. |
In place and I'll leave it like that overnight.
|Surfboards or surf style wakesurfs have long had perimeter weighting and stiffening. The process of lapping the rails (where the fiberglass from the deck is "lapped" over the rails to the bottom and the reverse with the bottom to the deck) puts extra glass and resin on the rail and, as such, the perimeter of the board. The perimeter weighting helps sink teh rail in the wake and reduces rail twist-off some. |
The high density foam rail material will aid this perimieter weighting AND help protect the board as rail dings are one of the most prevelant types of "injury" to a wakesurf.
|The rocker bed I use is oversize from the shape I normally make. It allows me about 4 inches of apex adjustment and @ 1 inch of nose rocker and 1/4 inch of tail rocker adjustment. I can make changes to the rocker by adding shims under the nose or tail, as needed, as I am bagging the deck skin. In this build, I am moving the apex forward a few inches, by sliding the board backwards on the rocker bed.|
|The "blank" out of the bag this morning and ready for shaping. I'll shape the deck last, as the extra thickness helps when trying to mow the 1 pound EPS - it's floppy. |
I'll attach the tail block next and then shape the bottom 'cave.
|Jeff, Can you explain the tail block and what its purpose is?? Thanks Jon T!|
|You bet Jon and thanks for following along. I think most typically you'll see nose and tail blocks with HWS construction. These blocks make it easier to align veneer's or more appropriately elimiate the need Also, they help protect the nose and tail from damage by inserting more robust material. Lastly, as you can see in the images - they can add aesthetics. |
Some examples of nose and tail blocks - the nose block is from a Paul Jensen HWS.
|In my build, I will be embedding the springer into the deck of the board before laminating the deck skin down. I want something in the tail to help keep the springer "located" so that it can be loaded up and "hopefully" will unload with some extra pop. One of the advantages of the sandwich build is that the board can be broken down into constituent components and different materials used. So for my build the rail material is different than the core and skins, I could have used different rail material for the left and right sides of the board. |
I don't know that such flexibility is useful, but it's possible
|Tail block attached! I use 5 min epoxy and slather it everywhere. |
|I shaped a single 'cave in the bottom. |
|I'm going to skin this board with Divinycell H45, it's a 3 pound foam. I buy it in 1/4 sheets from Aircraft Spruce, so I have to cut the outline diagonally. The shear of d-cell is poor, so it cuts with a pair of scissors easily. Just be careful at tight corners as it will rip. |
|D-cell has a very porous surface. It's a closed cell foam, but the surface is basically tons of tiny crevices. If the surface is left unprepared, the epoxy will pool in some depressions more than others and create an unbalanced and possibly poorly glued skin. I also want to trap as much of the resin at the surface as possible. I seal both the the d-cell and EPS core with spackle. |
|Tomorrow, I'll bag the bottom skin using a 2 oz Kevlar sandwich layer.|
|Thanks for showing the Tail block, I might have to try that on one of my boards. I defiantly like the wood look, that is sweet! To bad I probably won't get to ride them till next year! Dang! |
Also, wouldn't you get a better bond if the surface is rough and porous? I thought this would give you more surface area to bond to? If you bond to the spackle, will you still have a good bond between the spackle and the foam? I can see where it would give you a better resin distribution though! Do you think some of the resin will still seep through the spackle, giving you a good bond to the foam?
Also, Thanks for sharing the board builds. A person can learn so much from these, I have!!
|some of the resin will still seep through the spackle |
Exactly! You're brillant! Under the pressure from the vacuum, the spackle will act as a wicking agent. There is still a considerable amount of foam that will be "accessible" to the resin, but there is no longer any trapped air that would impede the resin's contact with the structural components of the foam, plus the resin will now penetrate to a uniform depth in all of the pockets.
The problem with the rough surface is that the epoxy will flow into those depressions and pool there, potentially starving the surrounding area of resin. In effect that area will have very poor adhesion, and there won't be a uniform distribution of the resin across the board...potentially creating a weak spot just waiting to snap! Also, I'm onloy going to be using about 2 oz of cloth and 2 oz of resin, so I need 100% contact (or as close as possible) to the bonding surface as my matrix is pretty minimal - no extra resin to add weight or fill pockets.
Thanks for following along Jon, I'm glad you are enjoying it and I hope to see your inspired creations/builds this winter!
|I like pictures! I so need a new box of crayola's though. |
This might give a better idea of how the resin will flow or be absorbed into the foam.
The air that gets trapped in the pockets will rise and allow the resin to sink, creating a weak area, whereas the spackle will displace the air and cause a uniform distribution of the resin and keep it closer towards the surface.
Is this great art or what?!
|Well I don't know about brilliant, but I did get a degree in this stuff, so it helps a little! Thanks for the visuals, it always helps me out! If wakesurf boards don't end up being your thing, I am pretty sure Art might be your path less traveled |
|That's funny! Reminds me of Robert Frost's poem the Road Not Taken. The last line of the first stanza: "To where it bent in the undergrowth;" I can remember a discussion in some class about that representing the unknown either the future or a calling unstudied, etc. I think I remember responding - couldn't he just have lost the map? I think I failed that class. BTW, where is that art map, anyway. |
|Thumbs up on spackle , Ialso will keep fisheyes under control when you go to hotcoat.|
|I've found that I had a bunch of 2oz Kevlar left over so I decided to use that as a sandwih layer. It's not stiff like CF, but it's equal to about twice the weight in e-glass. Kevlar is miserable stuff to work with, it doesn't sand, it fuzzes and it degrades in UV so needs to be hidden or used with a good UV inhibiting epoxy. |
My Kevlar was on a 50" wide roll, so I can get a top and bottom from the one length cut.
|Another of the characteristics of Kevlar is that it doesn't cut. You need special shears or these electric cutters. |
I trim the Kevlar so that it is inside the rails, because you can't sand it. I mark the fabric with a pen and then cut on the line to fit.
|Supplies needed for the rest - gloves, mixing bucket, stir stick, squeege and a ratty paint brush. |
Because the sandwich layer fabric doesn't extend out to the edge of the rails, I paint on a 1 inch band of epoxy all around the edge of the dcell skin to insure a good bond at the rail.
|The residual epoxy from the painting, I use to wet out the Kevlar. Kevlar is pretty stiff in it's natural state and is easy to saturate and apply to the board. I lay it down on the core, making sure that it doesn't extend past the rails. |
|I lay the dcell skin on top of the core and wet out Kevlar and then attach some tape to keep the dcell in place while I work it into the bag. |
|I want the skin to adhere to the 'cave shaped earlier and here is my trick for doing that on the rocker bed. The board/skin combo is in the bag, but the rocker bed isn't. The bag will pull tight up into the 'cave and I'll lay the board down on the rocker bed to insure the rocker remains. |
|This gives a better shot of how the skin is forming top the 'cave under vaccuum. |
|The skin being attached, the whole mess sitting atop the rocker bed. |
|Out of the bag ready for trimming the bottom skin and then shaping the deck. |
|dont see a shoe in the last pic.|
|I wanted to go back over some of the design elements when considering sandwich layer fabrics. The deck of the board receives compression forces and the bottom tension. Fiberglass isn't great at anything, but it also doesn't have any glaring shortcomings - like Kevlar that can't be cut, sanded or exposed to UV. In general FG is about twice as strong in tension as it is in compression - it's one of the reasons that a typical shortboard will have double the amount of FG on the deck as on the bottom - it creates a balance. |
On the sandwich layers, both the deck and the bottom, are receiving some compressive and tension forces. The skin is acting like a very thin, small board so the deck sandwich layer has compressive, but because it's also under the deck skin there is a measurable tension force being applied.
It's possible to use straight 4 oz on all layers internal and external, or like me the Kevlar internally and something else externally.
The sandwich construction offers a unique opportunity, and challenge, to incorporate various design elements into the construction because the board is broken down into components.
|@ jimbeam. LOLOLOL I forgot it! That was great fun. |
|arrgh those shoes really distracted me so I forgot to watch boards |
(Message edited by hawaj on October 09, 2009)
|lolol - the only thing you guys can see is the SHOEEEESSSSSS! |
I try and take as much of the EPS off with a hotwire, the rest I just mow with a plane.
I will be adding 1/8" with the deck skin, so I shape the foil down to that much less. The only area that is tricky is the nose, the thickness is just over 1/4" with skins, so the core is very thin. I just go slow and set the plane depth at it's lowest setting.
|One of the problems with shaping the blank with HD rails and a LD core is that the core knocks down much quicker than the rails...so I do the rails first, get them to spec and then bring the core down so it's flat and level. |
|This board looks like a squash tail I round the corners to make it a semi-roundtail. I also add the material to make the wings. |
|Tomorrow I'll do the rail bands, inset the springer and seal all the foam. Maybe, I'll get the top skin into the bag. |
Currently the blanks weighs about 1.25+ pounds.
|looks great , are you using a tucked under edge on the bottom|
|Thanks! Yes, I will, although I haven't shaped that in yet. The H45 shapes really easily and a Fred tool will tend to tear chunks out if I use too much pressure. What I'll do is, hit the bottom of the rail really lightly with the Fred and then finish up with 40/60/100 sanding blocks/paper.|
|It was a little early in the morning to run any of the power tools, so I cut the deck skin and sealed it. |
|I shaped a domed deck, I wanted to be sure to leave a flat'ish area down the middle to accomodate the springer. Then planed the deck and rails down. |
Then I use a surform and sanding block to finish rounding the rails.
|Now comes the fun part! I want to inset the spring so that it's flush with the top of the core at the deck. I align it down the center and mark the outline that I'll route out. Then set the depth of my router so that it is a tiny bit shallow. |
|I route around the outline, leaving the center in place as this will aid removing it later. After the outline is gone, I route side to side rather than lengthwise as the center section provides a bit of support as I remove it. |
And test fit the springer into the recess.
|I want the springer to be free-floating, I'm not sure how well I'm going to achieve that, but I'll give it a try. |
I'm going to leave the recess unsealed and then I waxed the springer with mold release, I'm hoping that will be enough to allow the springer to move separately from the core and skin of the board.
|I sealed the eps, save the recess and also fixed up two gouges. At the nose, I cut off a chuck of the corecell and something similar at the tail. A mixture of 'balloons and epoxy does the trick. |
|I like to put a deck patch under the feet. I used to make it shaped like the outline, but concluded that an hour glass shape did the same thing with less weight and waste. I save the offcut between the top and bottom cuts and use that as my foot patch. |
Kevlar cut to size.
|The assembly process - springer in, wetted kevlar down, then the skin and into the bag. |
The springer seemed to form to the rocker without issue and it doesn't appear visible from the deck.
|In looking at the rocker, it just seemed to be begging for a tad more nose flip, so I am adding about 1/2 in the last 3 inches or so. Fancy rocker tables that are adjustable don't need the wooden shims |
|how about wrap spinger in wax paper|
|That's a great idea brewkettle. I was looking for some PE and couldn't find any. I'll try that if I do another springer build. |
Out of the bag and ready to finish shape.
|I use a single edge razor to trim the excess skin, it saves a ton of sanding. |
|All shaped and ready to be laminated - it's about 2.25 pounds, the springer added about 6 oz net. |
|And NOW you know why no one makes these for retail. What is that, like 12 hours just to get to a shaped blank that using traditional close tolerance blank might take an hour? |
Standard vac bag lamination, perforated peel ply, but I ran out of breather. You can find that at most fabric stores called batting and it's much cheaper than the breather. I use papertowels, about 1/3 of a roll does the same thing and is cheaper still.
|I wrap the whole thing in a mattress topper foam. In molding with a film, they call such "stuff" intensifiers - it helps push laminations into deep corners where the bag might bridge the gap. My foam also allows the air to be drawn out and apply an even pressure across the entire lamination. |
|I forgot the most important shaping photo! |
|Deck lamination out of the bag, I probably won't get to the bottom until Monday evening, then all that's left is boxes and my superlative artwork! |
|I was able to get the bottom in the bag. The temp's are dropping, so I draped an electric blanket over it just to be safe. |
|I had some trouble resizing this picture, but the board is fully laminated! |
|I'm trying something with the hotcoat on the bottom. I want to apply a texture, but in a less random fashion that the "failed" gloss coat test. I applied a layer of peel/release ply on the wet epoxy hotcoat. This peel has an extra coating of release agent, but it's still a PITA to remove. |
In vacuum composite construction a peel ply is used to impart a texture so that a second layer of resin and/or resin fabric matrix has something to adhere to.
I've left a bunch extra so that I have some leverage to get the release started. Once it's going, it's just elbow grease to yank it apart.
|whoa free moving springer!|
|Is there any concern of the free moving springer adding concentrated stress points in the board? Maybe the top sheet, or the foam? Could it move enough to where it might move even more than you expected over time?|
|Umm, no. |
|I was just giving you a hard time Jon! Good questions and again, thanks for following along. |
I'm using 1 pound EPS as the core and it is something like 92% air and pentane (the blowing agent trapped in the eps beads). It's pretty interesting stuff, you can walk on it and the foam will compress, but it regains it's shape in a few minutes. Unless you rip the beads apart, after a day you can't tell you walked on it.
The flex that we are talking about here, is also incredibly minute. Maybe, 1/4" max deflection upon landing or loading up in an aerial. That load is distributed pretty well along the length of the springer. The deck side is a double 2 oz of kevlar and so has great impact resistance (bullet proof! ) The core side of the springer is in tension and so isn't really exerting much in the way of force on the underlying eps, with the exception of landing from aerials. My "hunch" is that will be like walking on the EPS and won't permanently deform the EPS, to the point of disabling the springer's effectiveness - ASSUMING it's effective to start with.
Great question, I appreciate your thinking the structural elements through.
If the springer is effective, I'd like to develop a tray like device that would allow interchanging different springers. Possibly stiffer for bigger wakes with a great lip (or mybe it's softer) and then softer for something else. We've been to numerous contests where the wake is significant different between practice and the contest, perhaps being able to tailor the "pop" of the board could overcome a soft wake on contest day.
|Hahah point taken!! Thanks for the explanation, and the tray idea sounds cool/complicated. |
Also, My buddy has a new AR-15. If you want to send us the board after you are done with it, I am sure we could test that bullet proof theory for you!!:-)!
|LOL - gives me a great theme for a graphic! I think that Kevlar vests have a minimum of 8 layers up to 25. I'm doubtful my 5 layers would stop a .223. I'd bet a .22 short wouldn't exit, though. That's funny...test the boards for exit wounds. |
|Fin boxes curing. All that's left is to hotcoat the deck, then paint! |
|The secret to productivity: hotcoat at 4:30 am. |
|Looks like its snowing|
|It's 80! Definately not snow. |
This board was exceptionally drivey. The springer aided pumping - it would squirt forward powerfully. I was able to fiddle around at the back of the pocket, basically one leg in the curl/wash and it would pump forward. There isn't any useful body of knowledge as to what works or doesn't when incorporating a springer into the onstruction...I don't think I want to be the CREATOR of that info!
|I have a few additional CRAPPY PICTURES! They do give a rough idea. We used these cool camera mounts for an HD video camera. Dennis also had a remote so that he could turn the cam's on and off. The mounts are interesting because they have a suction cup base and you can place them anywhere on the boat with a relatively flat surface. |
The two cam angles and Dennis with the remote.
|The cam's save the video in an .MOV format and my FREE MS Moviemaker application doesn't recognize that so I had to convert from MOV to WMV and the image quality went to crap. Also the one angle we used, probably wasn't a good choice as mostly we got the image of the back of a hairy beast! |
Anyway - just for fun, some additional images
|So did you like the board? I read this whole thread to not even get much of a review. |
The springer adds drive when pumping, you can feel there is some sort of pop or snap at the end of a bottom turn or when James was popping off the lip. It wasn't worth the extra hassle of building, but what I don't know is if it can be improved by changing the construction of the springer or by relocating the springer closer to the neutral axis (or for that matter where the neutral axis actually IS in the board. )
I liked how snappy it was, how much squirt the springer added. It was a HUGE PITA to build and I don't know if this is the best that could be achieved, or if there are improvements that can make the responsiveness better...and I don't think I want to build a bunch to check.
|Much better |