Composite sandwich perimeter stringer build

I have projects

It's building season again. I won't go into significant detail on the sandwich process as there is a ton in the archived section.

This build will refine a concept that I had some success with last year. It will have a 5# corecell skin, 1# EPS core and basswood perimeter stringers.

The 1# EPS is floppy, but light. The corecell is relatively stiff and has some recoil, it also doesn't compress like 2# EPS, so it transfers energy better. This is very similar to the construction that Eric Roush used on the board he built for us.

I started by connecting my rocker templates to the EPS billet for hotwiring. The second picture is the rocker 'wired into the billet.

I have another template that I use for hotwiring cores for for attaching the perimeter stringers. Those blanks are not shaped as they are run through a CNC. This project I'll be doing by hand, so I wired the rocker and now will cut the outline by hand.

The outline is such that the fin boxes will interest the stringers. As we've talked about before, the 1# foam is flimsy, the stringers will keep the fin boxes from moving during pumps/turns when the fins are under a load.

I am saving the offcuts for this project, as I'll wrap the foam with the cirecell. In the picture at the start of the thread, I am using higher density foam for the rail material.

That's all for this evening. The next step will be gluing up the stringers to the core.

The bottom rocker is the most important area on the stringers. You can't quite use the rocker template as a guide, because as the stringer bends in, it also warps up. I wrap the stringer around the inside core, then mark it with a pencil to get an exact match. I'm using really thing 1/16" Basswood for these stringers, those can be cut with a razor blade.

Gorilla glue is the best stuff ever for gluing up stringers!

I slather the stringer with glue and wet the foam. Let it sit per the instructions and then assemble it.

I use the vacuum for clamping pressure, but pipe clamps could also be used.

Looking like its progressing pretty fast! I can't wait to see how it is when its finished. You make this stuff look way too easy Jeff. Seeing all these different build threads that are on here has me wanting to check it out.

And is that a GTX in the background that I see??

What a great eye you have TXSurf. That's actually a '69 Roadrunner. It's a project that James and I have been working on for a number of years. I bought it when he was...oh shoot, maybe 10? Sort of a father/son project. Now, it's all James' other than when he can't quite figure out wiring things or needs money. He's taking auto shop in high school and while the other kids are working on their Chevy Aveo's he's working on a 750 CFM Holley on a 451.

It originally had a 383 and automatic trans, it's got a built 400 (it's a 451 - 440 crank in the 400 block) and manual tranny.

I do love to generate interest by folks, it's great fun to build your own board.

Thats awesome Jeff! I was up in the air between the roadrunner and the gtx. I thought I saw a few subtle differences, but the hood threw me. Thats awesome he's getting to do that in his auto shop class. That will definitely be THE CAR at his school. My dad got me into cars before I could walk, between him and my uncle, they turned me into a car addict. I just actually left a job building high performance street and drag cars to move to the service advising and management side of the biz. Thats got to be neat to see him building up that car.

As for the board building, I've been contemplating it, but I guess I've just been putting it off. I'm sure I could find some local sources for the supplies around here

(Message edited by bac on August 29, 2008)

I also glued stringer with PU based glue which create foam which go deep thru the cells of EPS

I love the foaming PU glues. James and I stopped by Nick Palandroni's shop in Santa Cruz and he was building these wild stringers with inlays of various woods and then using the foaming PU glue to build the blanks.

On a different topic, and it relates to composites and glassing. This board is rather unique.

The appearance is that it's Carbon, which is accurate, but misleading. Bayer Materials and Entropy Research Labs built that board back in '06 using nanotech. The epoxy is impregnated with carbon nanotubes, so there is no fabric it's just the blank painted with the epoxy.

The process eliminates all of that time consuming layup of fabric, plus it seems to reduce the weight considerably. Just think - no rail laps! Rather than messing with Tex or Carbon textiles, the core carries all the flexural properties. I think the perimeter stringers with HD rail materials and the Nano-impreg. epoxy will deliver a sweet ride, and a ton less labor intensive. I hope to have be able to crank one out this winter.

Hey TxSurf, the hood is the road runner with some crazy aftermarket 'glass scoop. That was all the rage back in the early 70's.

You'd have loved our 451 build! Great fun. We'll have to talk cars sometime.

My first car was a Black 73 Road Runner. Only had a 318 so it was pretty tame. Now I have a bad ass black boat.

There is a 70'ish RR at a used car lot on the way to the lake. It's been tubbed, has something crazy like 24 inch wide cheater slicks and I think it's got an old 426 wedge motor. I don't think you can event but parts for that, but it's a great relic!

Back to the build. I rough cut the outline, getting within 1/4 inch or so and then use a surfoam to bring it to tolerance. Then 60# sandpaper to square it up.

I use an electric planer to bring the deck down to get close to the thickness I want. I'll use block plane on the stringers and surfoam and sandpaper to shape it up.

The next step is to shape the rails, in anticipation of attaching the deck skin. I have thinned the board to 1/8" less than I want the final thickness, to accomodate the addition of the Corecell deck skin, which is 1/8" thick.

The rails need to be shaped prior to skinning the deck, as that skin will overlap the rails somewhat.

The next step will be to cut the Corecell skin to fit the deck.

Corecell is a very stiff foam. D-cell H-80 is the same 5# density, but easily bends and will cold mold around a very small diameter. I chose the corecell because of this stiffness, I am hoping it will prove to be more lively than a d-cell equivalent.

The first step is to trace the outline of the board onto the corecell, then cut that shape with a razor. After I 'bag that skin to the core using a 2 oz eglass and epoxy layer, I'll feather the edge smooth with the rail.

I've wetted out 2 oz glass and laid that between the corecell and EPS. The vacuum bag will keep the corecell tight to the EPS until the epoxy has cured. I am not bagging to a rocker bed as I have started some preliminary bottom shaping. The rocker is already carved into the EPS, so it won't deform during this skin attachment phase.

I wanted to show this board built by Eric Rousch, and it caught my eye that he placed a Surftech sticker on the board. I read somewhere that Surftech cranks out 160,000 boards a year. I had to do the math, assuming an average $800 retail price that's 128,000,000 in retail sales. I then converted that back to boat sales, assuming 80,000 per boat, I think that's 1,600 boats per year. That would be HUGE!

The board above also has a corecell deck and some sort of XPS core. You'll notice all the rail artwork, that's how Eric is hiding what he's doing with the rails, but also, where the Corecell feathers into the rails.

This is NOT a good picture, but I have feathered the corecell into the rail. It's smooth and lays flat, but it looks ragged. In a production environment, you'd almost have to be sure the rails were painted to make it saleable.

The deck is done, so I am working on the bottom contours. I intend to shape a single concave throughout the length and then four channels out the tail. The channels will be INSIDE a single concave, rather than a single into the channels. You can see in the pictures, the marks for the four channels.

The two inside channels are cut at an angle and they meet in the middle with a V. The V aids, a bit, in rail-to-rail responsiveness and releases quite well.

The channels, by themselves, add a bit of drive and also aid in landings from aerials.

just small color correction for more details

Thanks Petr! I didn't notice that you had cleaned that photo up and kept thinking, I could have sworn I posted some steps after that picture AND it doesn't look as bad as I remembered it!

Channels and fin box holes cut.

I hear that laminating grooves is challenging.

Yeah - the reason you don't see more of them in boards, I firmly believe, is that every glasser that attempts them, commits suicide an hour later

Wow Jeff!!! That thing is coming out looking absolutely awesome!!! Ever since I saw those pics of Eric's boards from the pics you shared, I've been very interested to see how that shape would ride behind the boat. I'll definitely be attemping my first build soon, its look fun, stressful fun at times I'm sure, but fun none the less.

Off the topic, I would love to talk cars sometime! I used to work for Hennessey Performance Engineering until about a year ago. I enjoy ungodly fast cars I like the new fast stuff, but I'm a diehard old school muscle fan, nothing touches it!

Also Jeff, do you have any more links to read up on that carbon nanotube board? I've heard alot about carbon nanotubes and read a little, but never heard of them being used in a surfing application

TxSurf, did you turn wrenches at Hennessey? I'd love to hear about those builds!

The Nanotube stuff is crazy expensive. It's not easy to find and when you do it's research grade LNC for something like $100 an oz. Sounds like street drugs.

Some non-techy articles below, let me know if you want more hardcore reading - great for when you can't sleep, it cures that

A narrative of the board pictured above

The same principal using nano 24897,20122672-16681,00.html,titanium

I'm having trouble imbedding that link on the nano titanium surfboard, so here it is longhand

http://www.australianit.news.com.au/story/0,24897,20122672-16681,00.html

This article talks about large sheets of nano carbon

There is some current development where the blank is shaped and then "dipped" in a combination of epoxy, liquid nano carbon and liquid nano kevlar. No separate fabric beyond the nano carbon and nano kevlar. The construction above, uses nano that is mixed with the epoxy, but doesn't eliminate the fabric.

(Message edited by surfdad on September 02, 2008)

I've sealed the black with fast 'n final spackle and the fin boxes are epoxied in place. I'm waiting for some C-5 boxes to be delivered and then I can 'glass it.

Jeff, that board is looking sweeet!!! Ever since I saw those pics of the Roush board, I've been interested in how that would ride behind the boat.

Thanks for the links too on the nanotubes and carbon. Some interesting stuff for sure. And at those prices that would be one expensive board.

Ya, when I was at Hennessey I turned wrenches and was working alongside the special vehicles ops manager. I've seen and been in some crazy vehicles. Not to go off topic, but this was one of the sadder sights I saw, transport driver's son decided to try and take it for a spin around the block before a delivery, here's what it looked like after he put it into a pole - only 700 miles or so on the car - totalled by insurance - $245k car with the mods

Ouch! Ok, that is begging the question. What sort of mod's does someone make to a 600 hp V-10? I need just a tad more power, can you add another 600 horses?

What is the base price of that car 90K? So 155K in modifications? I have to hear about that.

That particular car had just about every option that Hennessey offered. 1200 hp, 1150 or so ft/lb of tq, twin turbos, 522 stroker, all balanced and blueprinted, all custom hand welded headers and intake and custom exhaust, all internal parts are forged, head porting and polishing, new rear diff thats custom spec, complete racing suspension, brake system upgrade, aero body kit, if I remember correctly, this particular one also had an automatic transmission installed, interior is totally custom with aftermarket stereo, 3 piece racing wheels etc... thats most of it, but not everything. I could write a whole page just on the engine work done to these things. And that 1200 hp is at low boost, around 10 lbs or so. But as most of these are actually street driven, he keeps its low on purpose.

Minus the automatic and few other subtle changes, this is the same setup on the viper that outran the Bugatti Veyron.

As for pricing, you're about dead on, base viper anywhere from $85k - $90k and then $150k or so for everything. However, he will not perform certain mods, like stroking one, unless other mods are done as well. The vipers were fun, but the trucks with this setup were insane!

That's some serious change$!

Back to it after the WWSC. All of the bottom contours and fin boxes installed.

'Glass cut and trimmed. You'll note that I am not lapping the tail into the channels with this first piece of glass.

Wetted out and curing.

That looks nice Jeff!!! What is the true function of the step down in the center of the tail? You just keep pushing me closer to the edge of making my own board

You need to TXSurf! It's great fun. The step in the rail does a few things. Principally it's narrowing the tail down. It allows me to keep the waist/hip part of the outline at a wider dimension and then bring the tail down narrower quickly, without an extended taper. It also gives a point to turn off of. We had some luck with the double wing, allowing James to turn off two differnet parts of the tail. It's pretty subtle, but it seemed to work for James.

Makes sense. I like the sounds of that shape, and I think it looks good too

How difficult are the grab rails to cut out? Do you just use a router?

LOL no, that's too difficult. Don't forget I'm lazy. I use a 1.5" piece of 1/2" plastic tubing and then I taped a 1 inch piece of sandpaper to it. Then sort of "scootch" it to make the indentation.

That board does look awesome! I can't wait to see it after it's glassed.

D

That actually sounds like a nice way to do it. I can see where a router could easily make a mess of things and in a hurry. I just may have to learn to scootch on some practice foam first.


I like that word, scootch

Thanks Derek, I'm hoping to get a layer on the bottom tomorrow, the final layer on the top will have to wait until Sunday or Monday.

"Scootch" is seriously cool word! It's shaperspeak for push forward and downward simultaneously, while making slight horizontal sawing motions - scootch.

Glass for the bottom cut, it lays pretty well in the channels.

Wetted out and curing.

I found the key to getting the channels to wet out, was to work from the center outward, leaving the rail "side" of the fabric dry until I had worked the corners and then move outward towards the rails. Once that was completed wetted, I worked the excess resin out lengthwise. Any rail to rail "scrapping" would pull the fabric from the opposite side corner, requiring that I press that back down.

Thats a sick looking board!

Thanks 'bro.

Jeff, you glassed the deck first, why?

Hey Show,

On this one, the corecell wraps the rails, but not all the way. I wanted that sealed and laminated so that I didn't risk sliding the spreader between the EPS and Corecell. I lapped the bottom and covered that gap, without that risk of stuffing the spreader into the gap. It's only because of the corecell skin that I swapped the lamination processing, if you will.

There's always a reason

that things sick

Thanks Johnny. I got a sneak peek at the new Shred Stixx web site - Jerry's really stepping up!

I'm basically finished with this prototype. I'm not going to add any artwork or polish it, in case it turns out to be crap.

In case it DOES work I am contemplating doing a fully skinned composite sandwich. I have a full sheet of 1/8" H80 new formula dcell. The new formula will cold mold a 1/4" radius. I may have to fill in any cracks with bondo, but I think that I can get the channels to mold with the dcell.

This board was incredibly fast. In this first picture we are going 13 and in order to catch back up with the boat I just leaned forward. Any pumping and the board was on the swim deck in an instant.

It seemed to be loose enough. I'm running the 4.51 Scimitar's on this and the channels aided drive without overly locking the tail down. Yet it seemed to carve very well, too.

The release wasn't up to the rest of the performance. It's going to need some additional work on that. The release was there, but is probably best described as marginal.

The next iteration. The board above had a pretty significant concave - the concave effectively removes the rocker from the board which aides speed. The offset, is the release suffers. I thought I had left enough tail rocker in, but such wasn't the case.

There is another interesting phenomenon in tail shape. A slight cup or pocket towards the tip seems to create turbulance and that can aid in release. Imagine the concave side of a spoon, turned upside down.

5# rails, 2# core, channels just through fins and the pocket described above, although it doesn't show well in the picture.

This is a visual representation of the term obsessed:

Foreground laminated board curing, midground poured PolyU foam in the mold, background new latex glove mold in production.

yo jeff, what kinda chopper was that you had in your garage burried in all that stuff?

Hey Johhny,

The engine in that is an old ricer - I think it's an '83 CB 650 CV carbs and some light work on the cam and induction. The cases and barrels were powder coated red before assembly. The frame is one off and I believe that I used a 90's GSX'er swingarm - all polsihed up nicely. Triple clamps are cnc'ed from aluminum billet and the rest of the goodies are off-the-shelf stuff meant for an HD Sporty.

I'll have to post a few pictures of it - it's great fun.

haha yea sounds rad. i want to build a little chopper. something really cool yet simple.

Board looks awesome Jeff! Thanks again for sharing the build pics.

I'm really interested in seeing how this second one turns out

Thanks TXSurf, the second one is ready for traction!

Not great pictures Johnny, this was a simple build, other than the frame. Mostly it's scavanged and polished parts from various other bikes. I remember the front brake reservoir is from a yammie, I think it's an old XS 650. The clutch cover was chromed, little stuff like that.

that is the sickest thing i have ever seen. if you ever decide to get rid of it, make sure to tell me fist.

this is the only bike i have. its not a chopper but i still have fun!

Thanks Johnny, I'll put you at the top of the list, should I sell it. RM250? Very nice. I still have an old KX250, but - sheesh I got tired of fouling plugs. James and I have a pair of XR 400 thumpers. Heavy as all get out, but great fun for trails and GREEN STICKER!

haha yea no green sticker for me. i have to run from the cops! this bike has been good to me. i havent fould a plug yet. i want to get a new rmz 450. they are sooooo fast and sooooo fun.

sorry every one else! haha were gettin side tracked.