C-Forum

That subject heading should make Mike W. and PAC drool if nothing else:)

The Maven is getting closer, and I'm contemplating layups now...my intent is to make the inital boat with a gel-coat (best for initial release (after curing mold releases) from what I've heard, mostly glass (keep the cost down in case something goes wrong).

BUT, if that goes OK, I'd like to build ME one...I'm thinking Carbon Kevlar, of course . In terms of working with the materials, I'll have professionals assisting / laughing at me, so I'm not worried about air bubbles and the like. What I AM worried about is how many layers? I see PS Composites has a 4/5 layup, and Angst seems to go with a 6/8 (mostly glass for angst it seems). Any thoughts? Also...how many layers on the seams? I had always assumed one outside, two inside, but it appears that Angst uses 3 and 4?

Any words of wisdom from those of you who have been there are greatly appreciated! I'm used to some of the ins and outs of seam tape vs. just cutting cloth on the bias, etc...., but any other hints are also welcome (and yes, I do have Walbridge's manual...I'll be re-reading parts of it, and although I feel it is a GREAT text I also believe a lot has happened in the composit world since it was written.)

For those of you who have not been following my "little" project the "Maven" is a C1 squirt boat of rather low volume...think of it as a boat with the volume of an Oxygen (and with a turret), but <hopefully> with the stability / speed of an Acrobat.

Yup, you've got me drooling So, you're boat is not going to be s-glass, alpha-jewel, carbon? That would be so awesome. Alpha-jewel, red would be hot too

I like the IDEA of my proposed layup, but my "this would be cool" layup may not be practical...and that's what I'd like to find out....

For those that are wondering I'm thinking a 4/5 or 5/6 layup (first number is deck, second is hull), SCKS/SCKCS (S being S glass, C being carbon, K being Kevlar...). S glass on the outside primarily for repairability and durability. Alpha jewel (sparkles that Mike W is SO fond of) between outside S glass and first Carbon layer. No gel coat, of course (adds weight!).

Hi Adam,
Just my opinion, but carbon has no place in a whitewater boat. It's unbelievably stiff which is great, until you hit a rock.
Buy some bias Kevlar (Twaron) seam tape from JR and do 2 layers inside and 2 out. Seams are the most important part of the boat.
JKaz

Hey Adam,

First off, I have never built a boat myself, so I am no expert in the field whatsoever , but from an engineering point of view the strongest layers should be the outer layers where when hitting rocks and such the highest stresses will ocurr, while the center layers are much less stressed, so from this point of view the carbon and kevlar should be on the outside and the glass in the center of the layup.

As far as carbon in a boat is concerned, both Martin Du Toit as well as Gwyn Ashcroft's Shaggy Sith have (as well as mine) a layer of carbon layer as outermost deck layer (which looks really cool ), and both their boats are at least 3-4 years old and they have not had any problems with them. Martin took his down the Blackwater this spring, and his boat was, aside from some abrasion on a seam, fine with no damage to hull or deck of the boat.
Just my 2cents on my own observation .

martin

In actual practice it makes more sense to keep all glass fabrics on the outside and aramids on the inside. Do not sandwich a piece of glass between 2 layers of Kevlar, and vice versa. It creates lots of stress. I'm sure John Sweet could answer your laminate schedule questions.
JK

Adam
You are correct I am very interested. Keep us posted.
Question for you - do you think this will be the "on spec" boat or will some tweaking still take place?
I'm not a master (or novice) boat builder what I do remember when helping out is the first out of the model was the demo / disposable to tweak out the finished product.
That version always always very lightly laid up (race minus) and usually had a shorter river life (unless in the hands of a skilled paddler - not me). But they were the learning tool to determine final lay up and outfitting tweaks.
Just a thought that although it might be more expensive in the short run it may pay off in the long run. But then you might have the plug dialed in! Which I'm hoping you do!
Have you asked the composite Yak builders for their input (As Kaz stated Mr. Sweet would have great insight too!)?
My $.01! Paul C1

Listen to Kaz and JRS. They are the voice of experience!

Congrats on finishing the mold! Did you polish it out with 1200 grit wet paper? Are you following JRS's advice about sealing/buffing etc.?

If so, no need to worry about sticking the first boat. Gel coats are not needed, or even a good idea, IMHO. Use layup resin for a glass and nylon boat to check the design and to get good at hand layup/seaming/cockpit rims/endpours, etc. Pay particular attention to the resin content of each layer. You will have to educate your eye to what is the correct amount to leave in/extract from the cloth.

You want about 30 oz of cloth in the deck, and about 40 oz in the hull. "Number of layers" is misleading because some cloths are 5 oz per sq yd and others are 10 oz. Pay attention to the total ounces in the deck and hull, not the number of layers.

While the Walbridge book is dated, it is still excellent advice for the home builder. Stick to the tried and true methods for economical results.

The first two boats will be less than what you wanted. The third has a good chance of being a winner, so wait until then to use the expensive cloths. By the fifth boat, you will be getting good.

Good luck!

Thank you for all the suggestions! I'll keep the 30 oz / 40 oz in mind. I have a few folks helping me at this point who are "experts" and build 200+ ultra-light canoes (flatwater) a year (all hand laid, of course).

The deck mold is complete, the hull mold is still in progress (when I posted I thought they were spraying the gelcoat on the hull and we'd be laying up after that...BUT old gel-coat that they didn't trust was all they found they had, so new materials were ordered:).

I'm trying to take it slow and be as patient as I can....

Adam,
When designing your laminate, you want to keep in mind that Kevlar is really strong in tension, but very poor in compression, therefore it is best suited to the inside layers. Kevlar will add stiffness.

E-Glass and S-Glass are good in compression, but poor in tension, so they are best used on the outside layers. Wallbridge's book has some good illustrations of this.

Carbon will provide the best stiffening capability, but is brittle. It also tends to have a fairly broad weave which can make filling all of the gaps difficult - it is also 2x more expensive than Kevlar and 3 - 4 x the cost of Glass. I prefer to use it inside of a layer of glass.

Back when I was building a lot of boats, a typical race layup was 3/4 (SKK/SKKK or SKK/SSKK) with an extra layer in the cockpit and ends, 2/3 Seams (2 G outside, 1 G, 2 Poly or Kevlar inside)

A Play layup was typically 4/5 (SSKK/SSKKK or SKKK/SKKKK) again with an extra layer in the cockpit and ends , 2/3 Seams (2 G outside, 3 Kevlar inside)

You can easily replace the S-glass with carbon or co-fab (hybrid Kevlar/Carbon) - at least 1 layer. It also has a cool look.

For first time molds, I usually put a few extra coats of wax, and
usually 2 coats of PVA. I have always tried to avoid Gelcoats - they add weight, tend to flake off, and is a pain to aply.