balsa core, endgrain or not?

[sigurd]

You are probably right about "severe"! Sometimes there is ice though.

Putting glass outside the wood, sure, it would protect the wood, until it is breached, then the veneer will get waterlogged, heavy and rotten. The glass is only 50gsm so it won't stand the abuse that the veneer can, I think. Besides, if the veneer is breached, no harm done as long as the glass is still there - plenty of time to glue a piece of veneer there, without getting waterlogged in the meantime. Guess I'll try to glue a sample piece and see if I change my mind about it.

Kevlar is too expensive - more than 40 dollar per meter. Would be nice to try it though.

Beeswax is a solid (I think), unlike tar and oils, so it stays within the leather without getting washed out as fast. Having tried both tar-based, silicon based and many other shoe waxes, I have come to the conclusion that snoseal, which is beeswax, is the best for shoes. Therefore I think it is probably also best for boats? With heat, it would probably saturate the veneer. Noone uses it for wood finishing?

Originally Posted by sigurd

Beeswax is a solid (I think), unlike tar and oils, so it stays within the leather without getting washed out as fast. Having tried both tar-based, silicon based and many other shoe waxes, I have come to the conclusion that snoseal, which is beeswax, is the best for shoes. Therefore I think it is probably also best for boats? With heat, it would probably saturate the veneer. Noone uses it for wood finishing?

Use some common sense ! Does your wax harden your shoes ? Does it keep ALL moisture out ?
You ask high tech questions and after receiving some high knowledge advice you go back to linseed and wax ???
Regards
Richard
BTW: I would buil it in a simple, classical, cheap and strong strip planked Epoxy glassed way.

[robherc]

Originally Posted by sigurd

Kevlar is too expensive - more than 40 dollar per meter. Would be nice to try it though.

How about $13.57/yd @ 38" width (0.91m X 0.96m width), Would that make the Kevlar seem like a better idea to you?
That price list is from: www.fiberglasssupply.com
Also, for your canoe, you could probably get away with 12" (0.3m) tape, or cut the standard width kevlar fabric in thirds lengthwise. If you used 3 layers that way, it'd be almost bulletproof (or at least HIGHLY rock & ice resistant)!

[sigurd]

"Does your wax harden your shoes ? "

no

" Does it keep ALL moisture out ? "

yes

"You ask high tech questions and after receiving some high knowledge advice you go back to linseed and wax ??? "

don't be mad. I thought I had made an argument for why. I didn't mention the UV problem with epoxy, ofcourse not applicable under water.

"BTW: I would buil it in a simple, classical, cheap and strong strip planked Epoxy glassed way."

So, how much glass would you use, inside and outside, for a 3mm spruce core?

[sigurd]

robherc, 13.57 is for 150yd, but the prices are still good! thanks!

[robherc]

I build multi-hulls...they use a LOT more fabric for abrasion-resistance...go figure.

[sigurd]

Well, mine is much like a multihull too, except it has only one hull...

[eponodyne]

And here's another though: Instead of balsa, which has all the rot resistance of bumwad (Dunnyfodder), has anyone considered the use of cork as a core material? Sheets made from granulated cork, with a polyurethane binder (thus necessitating a PU resin for layup, I'd guess?) are readily available at about $4US/sq. ft ($40/SqM) in thicknesses of 1/2" (13mm) at a density of about 16 lb/cu.ft (~250 kg/SqM). Cork is quite rot-resistant, I know, but I also have no idea how it would hold up in shear strength.

Just a thought.

[sigurd]

All I know is it's comfortable and funny! It would add great impact resistance as a deck surface at least... Is it really that rot resistant?

What is better, makore or sapele veneer? Somebody commented on the great rot resistance of sapele.

[robherc]

Cork has nearly 0 shear strength, has little compressive strength, and is not at all stiff. At best, the cork would act as a sponge, and absorb 10x its weight in resin. Then the resin would act as a core material and give a very stiff, strong, and HEAVY laminate (kinda like using 1/2" of cast fiberglass/resin, but cheaper).
Good idea on the rot resistance side, completely unusable for anything but flotation material in the end, though.

sigurd-
Yes, so you only have to protect the bottom of one hull, in a cat I'll be using twice as much Kevlar (2 hulls), and with a trimaran, depending on the sizes of each hull, maybe up to 3 times as much... at which point I might as well buy the roll & save the leftovers for the next boat.

[sigurd]

some are very happy with cork as a deck material. Some of them are mixed with rubber. Sounds very nice.

[sigurd]

What about aramid mat. I reckon it skould be about as puncture and shock resistant, in a laminate, as woven aramid? You think?

[robherc]

I don't think the mat will be as ABRASION resistant as the woven aramid. I'm quite sure it'll still be better than e-glass, though, whether woven, or mat. So, if you can find the mat for significantly less, it may be just the ticket for you...all depends on where your price/durability trade-off makes you the happiest. As far as puncture/shock resistance, I think any decent-weight glass OR aramid cloth should fare pretty well there; they do NOT tear easily...especially not when they're encased in a couple coats of good, strong epoxy.

[sigurd]

Someone said "starspan" is based on aramid. it is 40gsm mat and 3.75 UK quid per m2. That is comparable to the 50gsm woven glass I can get here. It is going under the outer ply so only puncture and shock resistance is important.

The other places I have found aramid mat:
up to 32gsm, no price http://www.hollingsworth-vose.com/pr...osite_roll.htm
up to .4oz, expensive: http://www.acp-composites.com/home.php?cat=252

I think it is used in electrical insulation films and such.

So far, this is the cheapest woven aramid I have found: http://www.discountcomposite.com/

[robherc]

I think that as long as you're putting it underneath the plywood, fiberglass "woven roving" will give you the best puncture & shock resistance per quid...kevlar will be a good bit lighter, but a LOT more expensive too. I actually found some 18oz "woven roving" on http://www.fiberglasssupply.com for cheaper than any of their other fiberglass, as low as $2.19(US)/yard (100yd roll)!

The main reason I was recommending Kevlar earlier is for ABRASION resistance. If that's not important, and you can afford a little more weight, then I think glass will offer you substantial money savings, and I remember that was your big catch with the Kevlar at the beginning.