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Old    surfdad            10-20-2007, 4:00 PM Reply   
Compsand for short. :-)

Matt E, Matt S, Petr and I have been chatting about this for a bit and I am going to give it a shot.

A composite is simple any constructed item composed of two or more different materials. For purposes of my board the different materials will be PVC foam in the form of D-cell, EPS foam and fiberglass.

The sandwich construction is what it sounds like, layers of material, typically skins and a core.

My design is taken directly from Bert Burgers tutorial on Swaylocks, with a few changes to tailor the board for wakesurfing.

The concept of the composite sandwich is to provide a lighter and stronger board that offers flex where it's needed and stiffnesses where THAT attribute is needed. By using different materials (different glass weight, different density foam) flex, strength, stiffness can be engineered into the design.

The board will have the following layers, from the top down

4 oz e glass
1/8 H-80 dcell skin
1.4 oz e glass
1# EPS core
1.4 oz e glass
1/8 H-80 dcell skin
2 oz e glass

The rails will be made of 1/2 h-80 dcell.

The shape will be similar to an F-18, roundtail with a slight concave.

The first step is to trace the outline on the 1# EPS foam. I just don't have the skills to manage wings, so this board will not have that.

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Old    surfdad            10-20-2007, 4:04 PM Reply   
In the picture above you'll see two outlines from the nose almost to the tail. As I mentioned above, the board will have dcell rails. The widest outline is the actual outline of the board I want when finalized. The inside outline is what I need to cut the core too, to allow attachment of the 1/2 inche dcell rails.

The outline cut and the rail lines cleaned up.

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Old    surfdad            10-20-2007, 4:08 PM Reply   
D-cell is a PVC foam, as oppossed to the EPS foam that the core is made of. Also, the rails will be made of H-80 grade which is a 5# density foam, the core is 1# density foam.

Dcell typically comes in a sheet 48" x 96"

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Old    surfdad            10-20-2007, 4:13 PM Reply   
Now in the BB tutorial, the core is cut with a rocker, my is a straight slab that will be formed to the rocker table. Accordingly, my dcell rails aren't cut with the rocker outline, and are just straight cuts off the end.

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Old     (bigshow)      Join Date: Feb 2005       10-20-2007, 6:02 PM Reply   
Dang jeff, how many boards do you make in a year?
Old     (smedman)      Join Date: Feb 2006       10-20-2007, 6:16 PM Reply   
Jeff -- looking cool. Interested to see how the PVC composite comes out? What is the density / weight of the PVC stringer and rails as opposed to a 2# EPS stringerless blank by itself? Just wondering if the PVC addition to the 1# EPS will bring the "dry weight" (before glassing) up to what a plain #2 would be. Probably not, but had to ask. :-)
Old     (poser007)      Join Date: Nov 2004       10-20-2007, 6:57 PM Reply   
Impressive
Old    surfdad            10-20-2007, 6:59 PM Reply   
Ed,

I don't do any (ac)counting at home :-) More than 1 I can verify that. :-)

Matt, a man after my own heart :-) it's pretty interesting. The 2 pound stringerless I hotwired from the 6" slab:

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Old    surfdad            10-20-2007, 7:11 PM Reply   
The 1 pound core when whittled down to the final shape will be 3 oz, it's currently 12 oz in the photo above. The two dcell rails are 3.7 oz in total. I haven't cut the dcell skins, but I'm guessing that they will come in at 8 to 10 oz in total. I'm guessing that the combined dry weight will be in the 13-14 oz range.

I have an American Blanks blank that is cut to the outline, but not shaped that is 65.3 oz.

My 1.7 oz stringerless without the fin boxes or glassing, but fully shaped was just about 21 oz. I have one layer of 4 oz glass on the bottom and it's about 25 oz. It feels "floppy" so I think it's going to need 2 layers of 4 oz on the top.

The 2# stringerless pictured above is 18.2 oz. It has a little bit of spackling that needs to come off, but I'll need to seal it. so I'm guessing that blank ready for boxes will be right around 20 oz.

So what is the score?

Just using the shape I'm contemplating:

Composite sandwich, I believe will be in the 13-14 oz range.

A standard polyu blank shaped would be in the 38-40 oz range.

A stringerless 1.7# blank came in at 21 oz.

I believe that the 2 pound blank that I am shaping will be right at 20 oz.

I know that we are only talking 6 oz, which is so minimal it's hard to consider it meaningful. In terms of %'s. The composite is almost 33 1/3 % lighter than a 2 pound stringerless blank and 66% lighter than a shaped polyu blank.

If, I can TRULY engineer the ride, by placing stiffer laminates where I need and heavier materials, then it becomes: lighter, stronger and a better engineered board than an equivalent PolyU AND a straight 2 pound EPS.
Old     (smedman)      Join Date: Feb 2006       10-20-2007, 8:45 PM Reply   
Wow, that is a nice weight reduction!
Old     (goatroper222000)      Join Date: Dec 2006       10-21-2007, 6:04 AM Reply   
Awesome. you guys never cease to amaze me.

By the way, considering all these new boards you are makeing, you can send that useless WP in the background of the second pic my way whenever you are ready :-)
Old    surfdad            10-21-2007, 6:46 AM Reply   
Josh you goof! :-) That's my pattern and mold and third hand when I need something held down and just about anything else I need in a pinch. :-)

Yeah Matt, %-wise it's a substantial reduction. I think more importantly - well to me at least, the construction isolates the various components:

Deck
Hull
Rails - theoretically - darkside and right rail too.

Plus different materials connecting it all. Stiffer epoxy on the deck lamination sandwich layer, different weight fiberglass - or maybe carbon in between the layers.

I would think that for a performance board, we'd want a stronger, stiffer rail for better rail set and less flex. Doubling the density of the foam at the perimeter seems like a logical concept to achieve that. Maybe we want the darkside rail (or vice versa) to be less stiff/lighter. To me, it's exceptionally interesting (and challenging) to think about all the various combinations of the compentry.

I think that the independent manufacturers understand this stuff and to some degree are implementing it in a production environment - Jeff P at Inland Surfer with the woodloc, Mike A at Calibrated with the ABS rails, Jerry P of Shred Stixx on the Chase Hazen pro model with the suspension system and I think that is Carbon Tape connecting the rails and boxes.

I wish I had the decades long experience of those folks I mentioned and the likes of Cabazes bro's, Alan B, etc...

I'm not sure that this building methodology makes sense in a production environment, maybe as I get better at it...or IF I get better at it is a more appropriate statement. :-)
Old     (mhetheridge)      Join Date: Aug 2006       10-21-2007, 7:50 AM Reply   
This will be interesting and exciting to follow. How thick does the dcell stuff come? My wife was just telling me "wouldn't it just be cheaper to buy a new board every year"?
Old     (bigshow)      Join Date: Feb 2005       10-21-2007, 7:51 AM Reply   
Substantial reduction, ha. I reduced weight from my first board to my second by a whole order of magnitude!
Old    surfdad            10-21-2007, 8:11 AM Reply   
Ed, that so doesn't count! Any weight reduction off of a 25 pound board is NOT a success! :-) I would guess that a pressure dent on the first effort would result in a weight savings. :-)

Hey Matt,

Diab Group is the manufacturer. www.diabgroup.com. There are 4 "grades" of the stuff - from the H grade which I used, up to some aerospace grade. Then in densities from 3 pounds up to almost 16 pounds. I have seen dcell in thicknesses up to 1 1/4 inch thick. The issue I have is locating what I want. I tried to find h45 or h60 for the rails, but all I wanted was a single sheet. You can get a carton full, but that was like $1,500. Sheesh, even I am not THAT obsessed. :-)

You have gotta love your wife's perspective. It's certainly not about saving money. :-) It's interesting to be delving into a technology that isn't available at retail - IF it can be made to out perform what is available at retail. I guess that is the big question mark. It certainly has the potential.
Old    surfdad            10-21-2007, 8:12 AM Reply   
Oops. I meant to list my source for the dcell:

http://www.fiberglasssupply.com/Product_Catalog/Core_Materials/core_materials.html
Old     (hawaj)      Join Date: Aug 2005       10-21-2007, 5:02 PM Reply   
Wow Jeff you are jumping from one project to another with a speed of lightning.
And I really like it this way it so inspiring.
Old    surfdad            10-22-2007, 8:54 AM Reply   
I'm multi-tasking Petr :-) which reminds me of the saying: "wealth is created through multiple streams of income."

Anyway, back to the composite sandwich. I'm making some notes and sharing that with the group :-)

A typical surfboard is a composite sandwich...fiberglass/polyu core/fiberglass. I would guess that it's possible to build a surfboard of nothing but fiberglass, no core material, but you can see how 2 inches of fiberglass would be exceptionally heavier than the fiberglass/polyu core/fiberglass.

There is a formula that can be simplified to mathematically represent the flexural rigidity of a sandwich, and Ed S, feel free to expound or correct me. This formula is actually gigantic, but given a number of circumstances (low density core in relation to the skin density, etc) it can adequately represent the stiffness of the surfboard structure at least for comparisons in changing dimensions, etc.

The formula is represented as:

Flexural rigidity (stiffness) =

Elastic modulus of the facings (the amount of deflection of the skins under a load) times

width of the board times

thickness of the facings (skins) times

distance between the facings squared

all divided by 2.

All of the components of the equation are linear EXCEPT for the distance between the skins.

To give some contest to this, let's just substitute some numbers into the formula. Let's assume a perfectly flat cross section of the board...say under the feet of the surfer is 1 7/8 inches, 1.875 in decimal notation. 1.875 squared is 3.515625. So the numeric representation of the stiffness of a board could be:

1 x 24 x .125 x 3.515625 / 2 = 5.273

Now, I'm just making up numbers to test the difference in stiffness of the board by changing the distance between the skins. Let's leave everything the same, except let's change the distance between the skins from 1.875 to 2 inches (2 squared is 4) and see what it does to our stiffness representation:

1 x 24 x .125 x 4 / 2 = 12.

So, in summary, the increase in the distance between the skins of 1/8 inch or approximately 6% increased the stiffness representation by approximately 127%.

I've had discussions with folks about the thickness of a surfboard, especially when compared to a skimboard. It's not uncommon to find a skimboard with a uniform thickness of 5/8 to 1 inch. The thickness of the board, in terms of bouyancy doesn't seem to have a huge impact, but the thickness does have a direct impact on the rigidity of the board. So...while a surfboard can be made of 2 pound density foam 2 inches thick, a thinner profile board (all other dimensions being equal) would need to have a higher density foam, heavier glass/laminate schedule or something to increase the elastic modulus. It's not uncommon to see skim style boards made of 5 pound density dcell.

The above discusion is a drastic over-simplification, but in our design, changing the thickness of the core in strategic locations can yield dramatic increases in stiffness to the board. Also, the converse is true.
Old     (masonwakerider)      Join Date: May 2003       10-22-2007, 12:49 PM Reply   
jeff your formula for the 2" board comes out 6 not 12. 14% increase
Old    surfdad            10-22-2007, 2:27 PM Reply   
You're right - forgot the division by 2 :-) So a 6% increase in the distance results in a 14% increase in stiffness - makes more sense. Thanks WA.
Old    surfdad            10-23-2007, 6:37 PM Reply   
I'm using a dcell skin. Other options are balsa wood, corecell, etc. I have enough foam to try a few woodies, so those will be in the future. For now, 100% foam construction. :-)

I bought two sheets of h80 in 1/8" for the skins. The sheets come in a 48" x 86.5" in rectangle, so some fancy arrangements are necessary to get 3 skins out of each sheet.

They way it arrived :-)

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Old    surfdad            10-23-2007, 6:38 PM Reply   
and laying out the cuts

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Old    surfdad            10-23-2007, 6:48 PM Reply   
Now comes some decision making. The boards that we build will hopefully have a "usable" amount of flex. Too much flex and the board surfs like a wet noodle, not enough or no flex and it isn't alive. Finding the balance will be the challenge.

Water is pretty mushy, especially at 10-12 mph, so my "guess is that we'll need to make an effort to actually develop any flex at all. There is a decision to be made with the skins. We want effort or force applied on the deck (top) of the board to translate into motion, so the top deck will be attached to the core and the rails. The deck is said to be in compression, that is the force on this surface is compressing the skin and the top of the EPS core.

What happens on the deck is opposite what is happening with the hull or bottom of the board. So while there is compression on the deck, there is tension (stretching if you will) on the bottom.

You'll remember above that we cut separate rails and we've said that we want to attach the deck to the rails to transfer the force to the rails. We have a decision to make with the hull. We can butt the skin up to the rail, but not overlap or attach it. This will allow the board to flex more. The bottom will be connected via 'glass along the rails, but not directly to the rails. It will also be glassed to the core.

Once I make a determination as to what I want to do with the bottom skin on this first board, we can begin the bagging process.

Flip a coin? Heads attach, tails free? :-)
Old    surfdad            10-24-2007, 9:01 AM Reply   
Morphing bottoms. :-) I love saying that. There are a bunch of different bottom contours, typically we use some form of single concave. One of the issues with the single concave, however, is that it requires a continuous rocker in order to break free of the water - it's sticky.

Many boards that have a flat bottom are very fast, but rail to rail responsiveness sufferes. The single concave, with less volume in the rails, "typically" is more responsive rail-to-rail.

A board with a limited amount of flex can actually produce both bottom contours, although the morphing bottom is created by the deck shape.

Typical surfboard decks are domed or flat, but if you place a concave in the deck, along with some flex, the bottom of the board will change. Interestingly enough, pressing down on a concave deck, cause an increase in rocker and simultaneously an increase in concave by pushing down on the rails.

To get a visual, take a piece of binder paper and turn it width-wise and form a concave so that the outward edges of the paper are above your hands. Each hand should be holding the lowest portion of a U. Then very gently and slightly push your hands together. hat you should see, is tha bottom of the paper forming greater rocker, but interestingly enough the two edges that would represent the rails are moving down towards your hands.

If we convert that to the board, the deck concave running lengthwise on the board...pushing down on the deck with both feet, should provide greater rocker (short quick turns) and simultaneoulsy create a concave for more speed. That's in theory, at least. :-) If THAT can be made to happen and controlled, the ability to change a board from a flat planing bottom, to a deeper rocker and concave on demand, could proof very useful.

So anyway, I'm going to connect the bottom to the rails, with the idea that the downward movement of the rails will help shape the concave. I could be wrong on that - it could be that NOT connecting the bottom to the rails will allow greater movement - if so, then...board number 2 has a design change. :-)

For tonight, I need to fashion high density foam for the fin boxes. The 1# eps is a bit floppy to keep the boxes in place, so I will make an insert and place those into the foam before attaching the bottom skin.

This picture gives a visual reference:

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Old    surfdad            10-24-2007, 7:56 PM Reply   
Fin box inserts. As mentioned above I need some higher density foam for the fin boxes. I had some left over strip from the rail bands, and I used a section of that for this purpose.

This board will have a 1/8" skin of 5# density foam, and so I needed 5/8" more of high desnity foam. The rail bands are only 1/2, so I just said - close enough on the depth...about 1/8 of the box will extend into the EPS.

The first thing I did was cut the two pieces of left over rail band to size and rounded the corners. The only reason I did this was so that I didn't have to mess with the hole I route.

Then I measured out the location for the fin boxes and made sure that my inserts were centered over this. My inserts are bigger than the box, so I have a little leeway if I miss calculate.

Picture of the insert and location for the routing:

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Old    surfdad            10-24-2007, 7:58 PM Reply   
Break out the big gun for this :-) The 1# eps is easy to cut but this router has 1/1000 increment adjustment on a dial, so it easy to get the right depth. Right tool for the job. :-)

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Old    surfdad            10-24-2007, 8:01 PM Reply   
Insert recesses cut and now it's just a matter of mixing up some epoxy and stik the inserts in. These will be covered with the skin, so my superb routing job will be hidden. :-)

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The next step is to bag the lower skin and glass to the core.
Old    surfdad            10-25-2007, 7:58 PM Reply   
Attaching the bottom skin this evening - thankfully my 'bro Dennis stopped by - I need the extra hands! :-)

I had squeezed 3 skins out of the d-cell and as such, I had weird shapes - I won't do that in the future. What we did was cut the 'glass to fit the shape and so after I wetted the glass it was almost impossible to get it laid out on the d-cell lining up the strange shape. Next time I'll just waste the extra glass and d-cell and use a rectangle.

I couldn't have done it without you Dennis! Thanks!

The rocker bed, and dry skin layers.

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Old    surfdad            10-25-2007, 8:00 PM Reply   
How the blank will line up. There are several marks that I use to line the blank up on the rocker bed.

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Old    surfdad            10-25-2007, 8:02 PM Reply   
This is AFTER the wetted 'glass was laid out on the d-cell. It was ugly. :-) Now we have the blank lined up and ready to be taped in place, then the whole mess is slid into the bag.

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Old    surfdad            10-25-2007, 8:06 PM Reply   
And once everthing was in the bag, I pulled the vacuum. Hopefully in the morning, we have a good cement. :-)

The inside 'glass weighs, in total, 1.2 oz and that is the same amout of epoxy we used. Just to give you an idea it is about 2.5 teaspoons of epoxy. It was NOT easy wetting the glass out. :-)

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Old     (mhetheridge)      Join Date: Aug 2006       10-26-2007, 6:55 AM Reply   
Jeff, once you slide that into the bag and initiate the vacuum, will the board "compress" any?
Old    surfdad            10-26-2007, 7:26 AM Reply   
Hey Matt,

I adjusted the vacuum down to 10" of mercury. At 4-8" of mercury it will suck the core down to the rocker bed. At 20" it starts to deform the EPS, at this lower setting, I get a little rounding of the edges on the top, but the thickness of the board is within 1/16 of an inch of the non-vac'ed thickness.

I was talking to Dennis about using the vacuum as a shaping tool, increase the vac setting and crush the lower rail edges onto some type of mold - viola, no shaping! :-)
Old    surfdad            10-26-2007, 8:16 PM Reply   
The next composite sandwich will have balsa rails and bala skins, ala Ed S. :-) This will be the bottom skin. When the bag is empty, I'll wet out some glass and place this on the fabric, then into the bag.

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Old    surfdad            10-27-2007, 5:53 AM Reply   
Out of the bag and ready for trimming. Rocker set, bottom skin and inside laminate cured. At this point the board weighs 16.6 oz, has 1 layer of glass, and 1 layer of 5# density foam.

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Old     (smedman)      Join Date: Feb 2006       10-27-2007, 8:09 AM Reply   
Looking great Jeff - I'm really excited to see how the balsa will turn out.
Old    surfdad            10-27-2007, 9:22 AM Reply   
Thanks Matt. Yeah, the balsa will be sick. The test panels just look gorgeous. I think the first one I do will just be straight lengthwise, then I'd like to get fancy and do some diagonal pieces...not only for the apperance, but the diagonal pieces will offer greater stiffness vs. lengthwise orientation, in those sections.

Back to the work at hand. Bagging the perimeter/parabolic stringers/rails.

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Old     (bigshow)      Join Date: Feb 2005       10-27-2007, 10:18 AM Reply   
I'm not sure I understood the difficulty with the glass. Looks like you left it lay flat and vacuumed the EPS on top of it. Were you trying to leave it lay flat or did you intend to lap it over top?

Then you put outer d cell stringers rails on and vacuum bagged again. But the outline of the glass is a little greater than the outline of the core and the d cell stringer. When you’re done vacuum bagging I suppose you'll trim the glass back?

It's tough to beat the inherent beauty of wood. Are you going to stain the wood? Mine looked better stained. Be sure to sand away the glue at the seam first.

I just love seeing all the step by step progress.
Old     (fuller313)      Join Date: Oct 2006       10-27-2007, 4:44 PM Reply   
Keep it up Jeff. Looking Awesome!!
Old     (goatroper222000)      Join Date: Dec 2006       10-27-2007, 5:16 PM Reply   
Mr. Jeff,

Are you saying a proffesional shaper, like yourself, doesnt have all the shapes and specs he wants in his boards memorized???!!!
Old     (hawaj)      Join Date: Aug 2005       10-27-2007, 6:31 PM Reply   
Oh my gosh Jeff I am speechless!
I think that you need your own web blog or disscusion forum.

Yep hi density foam for fin inserts are on my mind for long time, balsa skin too

(Message edited by hawaj on October 27, 2007)
Old    surfdad            10-27-2007, 8:26 PM Reply   
Hey Petr,

Thanks. The folks over at wakeoutlaws.com have given me a blog space, I hope to get more of the build details on this series of boards over there.

Jeff - sick name. :-) Thanks.

Josh, I'm lucky if I can remember what day of the week it is! :-)

Ed, it would probably help to give you some perspective. I'm not a great laminator, but I'm not the worst either. About the best I can do with a hand layup is around 3 or 4 : 1 resin to glass by weight. One of the issues with this ratio is that the resin/glass matrix takes on MORE of the characteristics of the resin. As I'm sure you know, in aerospace vacuum bagging and vacuum infusion it's common to get the resin/glass ratio down below 1:1. This is my goal for each layer of glass, to have a 1:1 ratio of glass to epoxy.

Now, the first layer of glass weighed only 1.2 oz, which was the amount of epoxy that I used. It translates to something like 2.5 teaspoons. Once you start laminating you'll see how hard it is to spread that minimal amount of epoxy across a 4'5" piece of fiberglass. :-)

So a quick trick, but don't tell anyone. :-) I took the glass and folded it up into a small square and put it into the bucket with the epoxy. I allowed the epoxy to soak into the glass and then picked it up to drape over the d-cell skin.

I could have done the resin work on the d-cell, but it would have taken probably 4 times as much epoxy and would also impart more of the characteristics of the epoxy than the glass...which is "brittle".

I changed my mind about attaching the bottom skin to the rails. Instead, the bottom skin isn't overlapping the rails. One of the GREAT advantages of this method of construction is seperating each "element" and then building specifically for that element. So what I did after yanking the blank from the bag, was to use a jig saw to take the overhang off, then I sanded it down to the underlying core. If I had decided to connect the rail and bottom skim, I would have epoxied the rails to the glass and skin, as well as the core.

I think that I am going to leave the balsa untreated. When I laminate it with the glass top and bottom it gets a rich golden tone. I more than likely won't glue up any of the skin. Keep an eye on this thread as I move on to the next compsand! :-)
Old    surfdad            10-27-2007, 8:31 PM Reply   
Initial shaping. Just planer, sandpaper and surfoam. Weight is now 18.2 oz.

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Old     (hawaj)      Join Date: Aug 2005       10-27-2007, 10:30 PM Reply   
Sweet
Old     (mhetheridge)      Join Date: Aug 2006       10-28-2007, 7:30 AM Reply   
Nice looking board. I bet that balsa will really pop once you laminate it. You're going to need to rent a warehouse pretty soon. Maybe make a factory and then begin employing people to make these boards..... Nice though. I've kind of been put on restriction for the time being. I've got 7 boards right now. Mostly surfboards though. I am heading to the east coast in the next few weeks and I think 2 ten foot blanks and 4 shorter blanks may end up in my vehicle on the return trip.
Old    surfdad            10-28-2007, 8:12 AM Reply   
Thanks Matt. Stealing a joke from my 'bro Dennis: I know how to make a small fortune in wakesurf construction - start with a LARGE fortune. :-)

7 boards is not nearly enough Matt, I think that a count in the triple digits is pushing it, so...999 is probably too many. :-) I hope Judy doesn't read this right away.

Where do you get your building materials at?
Old    surfdad            10-28-2007, 1:47 PM Reply   
Deck skin is in the bag as I type this. I have been using 10 inches of mercury for all of this bagging.

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Old    surfdad            10-28-2007, 1:51 PM Reply   
I have been using medium period system three epoxy in all of this construction. The ambient temperature has been in the high 70's, low 80's during the day. This epoxy is design for a temperature of 77 degrees, but will cure down as low as 55. The other evening it came close to dropping below this, so I use a remote temperature sensor to keep track of the air temp around the bag.

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Old    surfdad            10-28-2007, 1:57 PM Reply   
Tail block glued up and the deck concave shaped - I'll try and remember to chat about how this technology is "supposed" to work.

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Old    surfdad            10-28-2007, 1:58 PM Reply   
I cut the deck skin to the shape of the outline using a pair of scissors.

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Old    surfdad            10-28-2007, 2:02 PM Reply   
I want the deck to be a bit stiffer than the bottom, so I have laid up two layers of glass. The first covers the entire inside surface of the deck, the second in the high traffic areas. :-)

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Old    surfdad            10-28-2007, 2:06 PM Reply   
As mention earlier, I wanted this skin to be stiffer, so I am going to do my resin work directly on the and with 1.5 times the total weight of glass. I measured out the epoxy and then drizzled it all over the glass covering the dcell on my "wetout table". Which is also my rocker table when not covered with polyethelyne. :-)

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Old    surfdad            10-28-2007, 2:10 PM Reply   
After the dcell and glass is wetted out, I picked the whole thing up and placed it on the shaped blank. A few strips of masking tape to prevent the skin from moving while I slid it into the bag.

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Old    surfdad            10-28-2007, 2:12 PM Reply   
In the bag and sealed, read to pull a vacuum.

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Old     (bigshow)      Join Date: Feb 2005       10-28-2007, 2:12 PM Reply   
Jeff, When you lay up multiple layers of glass do shapers always put both sheets down at the same time or do they glass one and let it cure before doing the second?
Old    surfdad            10-28-2007, 2:14 PM Reply   
and finally...the vacuum pulled

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Old    surfdad            10-28-2007, 2:41 PM Reply   
Referring back to our flexural rigidity formula the distance between the centeroids of the composite saw an exponential increase in stiffness. If you think about the deck of a board, it is typically 2 layers of glass...maybe a few mm's thick, no distance between them. This deck will have 4 layers of glass, plus 1/8 of 5# density foam. It is very robust and weighs no more than a stadard glass job. Also, the 5# density foam is very stiff. I was unable to put my thumb into the deck...as BB suggests.

The composite structure as suggested by Burger and Nev offer up higher strength and impact resistance and a lower overall weight.
Old    surfdad            10-28-2007, 8:35 PM Reply   
Out of the bag, needs final trimming and then the the exterior glass. Weight is at 30 oz. I believe that this board will come in around 3 pounds.

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Old    surfdad            10-28-2007, 8:36 PM Reply   
Can anyone think of a name for this board? :-)

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Old     (dennish)      Join Date: May 2005       10-29-2007, 6:44 AM Reply   
"half a bubble out of level" or "The Mantis" duh
Old     (mhetheridge)      Join Date: Aug 2006       10-29-2007, 7:25 AM Reply   
I get my supplies from surfsource.net. You convinced me that I need to get more boards in my garage. Thanks. What's worse is that my buddy who would see a board in a shop and go "whoa, I've got to have that board" would just buy it without any thought. Now, we've reversed roles. He's the thinker. I'm buying boards. I think I'm going to start a thread "Let's see your quiver".
Old    surfdad            10-29-2007, 8:00 PM Reply   
You're welcome Matt - everyone needs to have more boards. :-)

Last bit of shaping on the board. I bagged the deck skin yesterday, so today I trimmed and blended the deck skin into the rails. I used a razor blade in a box cutter to rough the edges off. The 1/8" d-cell is very easy to whittle. :-) Then I took a power sander to get the edges close to the final shape and then finally a sanding block to feather the edges into the rail.

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Old    surfdad            10-29-2007, 8:03 PM Reply   
Hey Dennis I didn't mean to ignore you, even though I often try. :-) Too funny the out-of-plum reference.

Next on the agenda is the installation of the fin boxes. I double checksed the measurements and marked out the location for the cut.

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Old    surfdad            10-29-2007, 8:08 PM Reply   
I use the futures installation kit, which includes the centering template, router collar and outline plate, as in the above picture.

You may remember that I installed reinforcing plugs for the fin boxes, BUT that my d-cell stiffener was only 1/2 thick. The fin box depth is 3/4, so I was expecting the last little bit the cut to hit EPS.

I inspected the cut to see if it came out like I was expecting - note the depth of the d-cell and out cut is totally in the insert. So we are golden!

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Old    surfdad            10-29-2007, 8:11 PM Reply   
Now is the time to correct any mistakes, since I tripled checked my measurements, we didn't have anything to correct, so I made the flange cut and then repeated these steps on the other box.

A quick test fit of the box, just to be sure the depth is good.

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Old    surfdad            10-29-2007, 8:17 PM Reply   
The final step before epoxy'ing the boxs in (and I just use 5 minute epoxy from ace hardware for these minimal glue-ups) is to tape off the fin slot and the set screw hole threads. The box will be UNDER the external glass and we don't want the epoxy to get into the hole or fin slot. Once the final lamination is done, I'll grind off the epoxy and glass to expose the screw hole and fin slot.

I like to gently rough up the flange on the fin box to make the external glass "grip" more.

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Old    surfdad            10-29-2007, 8:27 PM Reply   
The board now weighs 30.4 oz. It has three layers of glass and the fin boxes are installed. When it's done it will have 5 full layers of glass. Compare this with James TWP Bullet that has only 3 layers of glass. Further, the entire "epidermis" of the board is 5# density foam, as opposed to the 2.3# of a polyU or the usual 2# density foam in stringered EPS blanks.

I didn't take advantage of it in this construction, but it would be possible to use different epoxy's in the different segments. So for example, I could have used a flexible epoxy on the bottom skin and a stiffer epoxy on the rails and deck skin...or whatever made sense.

Further, with the interior glass I could have laid the bias on a diagnonal, 90 degrees or lengthwise.

It would seem that this method of constrution would allow significatly tailoring the feel of the board SHOULD you know what you want in terms of stiffness and/or flex and where you want those attributes.
Old    surfdad            10-29-2007, 8:28 PM Reply   
Next? :-)

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Old     (bigshow)      Join Date: Feb 2005       10-29-2007, 8:31 PM Reply   
Looking very good Jeff! I love all the detail. I knew you were going to make d cell outer stringers but didn't get the top and bottom part of the sandwich construction until you posted the outer d cell layer steps.
Old     (ecuadorianwakesurfer)      Join Date: Oct 2007       10-29-2007, 9:20 PM Reply   
jeff,

where do you get the foam from??

i would like to try and build a wake surf by my self, maybe you could help me with the foam info and where can I buy it...

thanks,

Rob
Old    surfdad            10-30-2007, 5:05 AM Reply   
Hey Ed,

I must not have been clear...this construction methodology is pretty similar to surftech you might remember that 5'8" Barney we bought not to long ago - same sort of construction. Also Flexlite - I do believe that Josh Sleigh's Placebo is built in a similar fashion. Although both of those methods are extremelt stiff. Glad you liked the steps - anything that I missed or that is unclear for someone wanting to try it on their own?

Hey Rob, I'd be happy to help you. I have to be honest, this construction methodology is not a good first choice for building. In order to get the skins attached you have to use a vacuum so that you get even pressure and that by itself is an undertaking.

I got the foam from several sources. The EPS core is from INSULFOAM, they have several processing plants here in the states. The D-cell is manufactured by Diab Group and their web site lists regional distrubutors, I just sent an email to the northwestern US distributor and he connected me with local retailers.

For you, though, I'd recommend you start out like Ed is, with a Pre shaped blank. Personally, I think that Polyester is easier to work with, than epoxy so I'd reommend that you look at a Polyurethane blank. There must me foam blanks available in your country?
Old    surfdad            10-30-2007, 5:28 AM Reply   
Hey Ed, sorry I missed your glassing question.
When you are doing a layup you want the best bond as possible between the layers of glass, so doing them both in the same resin matrix is "theoretically" a stronger bond.

It's so easy to do two layers of glass at a time that I have always seen it done this way. The dry spots show up as "white" patches, so you can pull your resin onto that area, or if you've reserved some in your bucket, just pour a bit over that area and work it in.

As I mentioned in a preceeding section, I folded the textile into a small square and stuffed it into the bucket with the epoxy. Nothing was dry after that. :-)

Working with epoxy is a bit different than polyester. With PloyE you are drawing the resin thin and spreading it all over. If you do this with epoxy it foams. :-) (however, that is an interesting concept should I ever get on board with resin infusion, as Inland Surfer is doing - intentionally introducing air bubbles into the epoxy - possibly with a fish tank air pump) So with epoxy you let it soak into the textile and move it around...this is why the textile in the bucket works so well...it's like the epoxy wicked into all of the weaves. The speed with which polyester gels would preclude this.
Old    surfdad            10-30-2007, 5:30 AM Reply   
One last note...I mentioned resin infusion in a comment...I didn't use any consumables in this build, no breather, no peel ply and I believe that I will get 6 vac's out of the bag film. Careful measuing of the epoxy and the dry outside skins allowed me to skip the use of the consumables.
Old     (smedman)      Join Date: Feb 2006       10-30-2007, 7:49 AM Reply   
Jeff - That D-cell looks super smooth!

Did you lay the two layers of glass pictured above between the EPS and D-cell? You said 5 layers of glass, but didn't quite follow.
Old    surfdad            10-30-2007, 10:25 AM Reply   
Hey Matt,

The D-cell is rather pitted on the surface, I'll have to get an upclose photo for you. I liked the contrasting rails against the EPS foam...that was cool. I had originally planned to use h-60 for the rails, which is a dull green, and that would have been a good look contrasting the grey skins.

You are absolutely correct, Matt. There is a layer of glass (two on the deck) between the EPS core and the skin. Then I will laminate the exterior as normal. So the board as you see it already has 3 layers of glass on it and I will then lam' the exterior with 1 layer top and bottom for a total of 5 layers of glass.

What I find interesting is that I believe I can get this board finished with 5 layers of glass and a hot coat and still have it weigh under 3 pounds with fin boxes installed.

It currently weighs roughly 30 oz. I intend to laminate the bottom with 2 oz glass and the deck with 4 oz glass. I "believe" I can do both of those at about 7 oz +/-. So, my hope is that after the exterior glass, but before the hotcoat, the board will weigh 38 oz. I then think a hotcoat at 4 oz total is doable, so my goal is a total weight of 42 oz, or 2 and 5/8's pound. This is with 5 layers of glass and a 5 pound density epidermus.
Old    surfdad            10-30-2007, 8:15 PM Reply   
Ok, so this evening I laid up the deck textile. I am going to do the deck and bottom without laping the rails and then do a tape to cover the rails. I want the top and bottom to move indepedently and so lapping the rails where the textile was connected directly to the deck and/or bottom would hinder that (in theory :-) )

This will be the first use of some consumables, in particular perforated peel ply and breather. I cut all of the materials to shape.

If you look carefully at the picture, you can see the 'glass, the perforated peel ply and the breather. The little dots on the peel ply are holes that allow the excess resin to pass thru into the breather material, also the peel ply is coated with a release agent so it doesn't stick (hopefully!) to the textile. You can use paper towels for breather, but how cool is the little cotton blanket? :-)

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Old    surfdad            10-30-2007, 8:17 PM Reply   
I won't be using the rocker table at this point, the rocker is set in the board and so I won't need it here.

It's best to have everything laid out and connected to the bag, so that when the board is ready to slip into the bag, you're organized.

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Old    surfdad            10-30-2007, 8:22 PM Reply   
The on/off switch :-) This simply pinches off the hose to the bag. As you are pulling the vacuum on the textile, you might get a wrinkle or don't like one of your pleats, by pinching off the hose you stop the vacuum and can pull wrinkles out of the bag. Also remember, disconnecting the hose stops the whole process so that you can start over - one of the HUGE benefits of epoxy as compared to polyester is that epoxy just gels slowly and you have a ton of working time. One of the BAD things about vacuum bagging compared to resin infusion is that your on the clock in this method, the textile is wet and cooking. With resin infusion you pull the vacuum on all dry materials. If it's not set up, the clock isn't running...just stop and rearrange then start over - everything is still dry.

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Old    surfdad            10-30-2007, 8:25 PM Reply   
Bagged and blotchy :-) The breather is doing it's job and is soaking up the excess resin that is being squished through the perf. peel ply. Nice and tight and hopefully in the morning it's GOREGEOUS. :-) The perf. peel ply, typically leaves a fairly nice finish except for the bumps, a light sand will take that out and I might be able to get away with a sanded finish.

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Old    surfdad            10-30-2007, 8:28 PM Reply   
My autoclave :-)

I don't have heat where I'm building, so I toss an electric blanket over the bag and then cover all of that with 4 mil plastic. I use the remote temperature sensor to let me know that the temp under the blanket is above 55 degrees. Right now it's 65.2, but it will bring it to a steady temperature of 71.2 throughout the night.

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