planking material for river canoe

Hi there,
To keep costs low for approx. 5 mt.long X 0.8 mt. wide canoe if I use in infusion molding (female mold) following layers:
1st gelcoat
2nd biaxial fiberglass fabric 450gr.
3rd balsa core 10mm.?
4th biaxial fiber glass fabric 450gr
+ extra layer of biaxial fiberglass fabric 450gr for the bottom
what kind of downsides would anybody know or guess?
Would be, the same process but without balsa core, at some extend acceptable?
Appreciate any comments
Adriano

 

Do you intend to line the entire canoe with balsa or just the transom? If there are any breaks in the seal, the balsa will get saturated with water which will add weight and ruin the wood. Do you have any illustrations to help us understand exactly what you want to do? Over here we make the canoe hulls with just fiberglass skin totaling about 3-4 mm thick with flotation at the ends and aluminum extruded moldings.

 

Thanks Hoyt,
It's simply matter of the old us traditional river canoe. There is no trasom, both ends are same.
Also my concern was about the fact that balsa would absorb water like a sponge whenever e leak accurs. This might be real reason for not using it!
So in case I go only for fiberglass/epoxy vacuum infusion, would two layers 450gr. only acceptable plus gealcoat? Certainly at both ends floating chambers have to be built in.
Are you processing in vacuum infusion also or hand lay-up?
Thanks
Adriano

 

I only do hand lay up on wood. I don't build many boats and for a powered vessel I like that extra thickness in case of bumping a rock or debris in the water. Most wood canoes are made of cedar because it is so light in weight. Thicker parts like gunwales or stems and sterns are sometimes made of ash wood because of its flexible strength.

 

You may be doing it the hard way if you only intend one or two or three boats. Just use a strip built hull and glass the inside and outside. Cedar or similar wood is probably better than balsa. Particularly if you are minding the build budget. Strippers are strong and light and durable.

The cost of a female mold will be signifigant. First you'll need to build a plug.......More cost. Then there is the cost of the resin and glass for the mold, to say nothing of the gel coat and all that. Balsa will suck up a lot of resin during the build, a lot more than cedar, white pine, or similar wood.

OK if you anticipate a large number of copies, then the female mold is the way to go.

 

Thanks Messabout,
Definitely the plan is to produce several units that's why using female mold and vaccum infusion, which needs of course some investments.
Although the balsa core would be pretty well mummified have some doubts in using it.

Now my main question is, if I would use only fiberglass fabric without core what could be the minimum recommended thickness?
two layers 450 gr, biaxial + additional layer on the bottom
one layer 300gr covering the inside surface
At both ends floating chambers would have to be built in!
Would be this scantling/weight acceptable?
Thanks for any advice
Adriano

 

Adriano. 10 mm balsa with 450 gr and 300 gr glass is far too much. Besides it will be pretty hard to take the shapes in the mold and requires lot of filling.
A ordinary strip plank canoe is cedar 6.5 mm, 1 layer outside and inside glass 6 to 10 oz. (around 220 gr), plus some more if needed. A 40 feet racing catamaran in 1987 was 9 mm cedar and one layer of 220 gr carbon each side plus a 165gr glass outside...
A mold is interesting is you plan to make more than 3 canoes as it's pretty expensive to make.
As you plan to mold, a coremat 3 mm in one or 2 layers, or 5mm in one layer is an acceptable alternative. Infusion is expensive in materials (bleeders, peel ply etc) and tooling and technical system with a steep learning curve.
I'm not sure it's worth to spend so much on a simple small boat like a canoe. The weight savings will be minimal compared to a careful hand lay up as the surfaces are small, but the expense will be surely maximal.
For such a small boat 450 gr stitched biaxial is not the best, you may have problems of wrinkles and bubbles in the tight curves. I would buy a light and very flat UD around 120 gr, put in layers with the desired angles 0, +45, -45 maybe 90, and 6 oz 165 gr satin cloth, and make the bulk (or core) with a good coremat or similar which has a density soaked of resin of 600 kg m3, does not rot, withstand pretty well stresses ans can be treated as monolithic about engineering, holes, screws and rivets.
I do smell that a total thickness of 4 to 5 mm will be largely enough for an already a bit heavy compared to a wood strip but rather strong canoe. I would engineer for a 3 to 3.5 mm skin (with 2 mm coremat) of glass UD, some carbon reinforcements and an epoxy, hand layed
Foams in slim (less than 12 mm, worst in 6mm) sheets absorb a lot of resin and filling, so the gain in weight is not so evident.
Too complicated is not always the best, many times a simpler technique well mastered give better results.

 

Thanks somuch Ilan,

Glad to hear that thickness/weight can go down quite a lot. Definitely I'll try to avoid Balsa core for sure at least the 10 mm.!.
Basically the goal would be to produce this canoe in serie, it doesn't need to be a high end product but safe and not expensive.
Due to the traditional inward curved ends if I go for female mold, most probabily the best would be using two halves which can at same time speed up the production, at least I think so if any better option available. Yes! Coremat I believe could be a good option for rigidity, have to find a source over here.
I think that vacuum infusion would speed up production and minimize the resin
I know that it's not that simple but have to check I've good workers coming from the
wind mill blade manufacturing who are skilled in that construction method.
Thanks for any further comments/ suggestions
Adriano

 

A safe and low cost build pretty much requires the use of inexpensive materials, as little 'glass and goo as practical and of course something quick to assemble so labor costs can be controlled. Maybe a strip planked female mold with a disposable internal plastic sheath (shrink wrap?), that's pulled after each hull. Saves the bother of a plug and sticking in the mold issues are reduced.

 

Hi Paul,
I guess the female mold as to be as smooth as glass on which we apply realise wax and gelcot and so on?!
Adriano

 

Adriano, Just to put things in perspective, An aquainteance of mine in the Keys was a retired RIB builder. He decided to keep is hand in and had a couple dingy molds in his garage. When he had an order for boats, his day went something like this.

1. Get up, back the car out and trundle the molds onto the floor. Spray the gel, lay in the precut prepregs, set up the vacuum system, and compress.

2. Go eat breakfast, and go put in five hours volunteer time at the local animal shelter.

3. Come home, pull the two boats, get two more cooking, and spend ten minutes installing fittings on the morning boats. All totalled, he had about 40 minutes in to each boat, could build four per day and still park his car in the garage at night. But he spent 30 years developing the processes.

It's hard to compete with that. You may need to clear a couple of grand on each boat just to cover the mold depreciation and infusion equipment. I'd go with prepregs, not infusion. The trend is to get labor out of the picture. Better to be consuming a $1000 of materials every hour and make 5% than to try to save on materials in an effort to increase the percentage of labor.

A clamshell mold such as you described is a very expensive proposition. The entire center seam has to be dressed each time, or a preformed keel cap installed over the seam that becomes part of the boat. It is very difficult to get that to work right. That is why nearly all molded canoes have gone away from the tumblehome bows.

 

Thanks Phil,
I do appreiate all yr advices of which somehow am awere of, nevertheless it's good to be remined.
In my case definitely it will be not a side job but the plan is to set up a production line once the market is requiring it. I am just guessing possible construction alternatives to obtain best result under "due circumstances". I know, nothing is easy in this world you have to work hard to get something going allover this planet.
I've access to red Cedar "Toona Ciliata" not quite as Western Red Cedar" butwith same properties just a little heavier, at good rate. I'll also use it also.
Although here the skilled labour cost is average approx $200, - a month it's always good advice not to have unnecessary too many of them under one roof!
So if I want achieve a certain production at lowest cost I do not have anyother choise but
go for half female mold at least for tumblehome bow canoe (which I do not want change!), gelcoat, fiber glass, resin, probabily coremat type and fiberglass in vacuum infusion construction. I am checking the option to use prepregs and see the effective advanges under due circumstances.
Beside that, as already mentioned, I can hire few skilled persons from the wind mill blade
manufacturing, so some big initial headaches could be avoided. At least hope so!
Thanks again
Adriano

 

This is the BIG problem.

How are you going to compete with the roto-moulded products ?

The first thing I would be doing is getting a rendered illustration of your product on Ebay etc, and seeing if there is any demand for it.

 

Thanks RWatson,

Ebay could be also a good idea but first have to rely on close-by potential customers,
whom I already contacted. Price point is always a big selling factor which can makes a difference in volume. This I am working on.
Roto molded you mean plastic closed molding? I do not think I should fear that competition, my product will be different and make sure that it is!. Anyhow there are also many other factors which make differences in the marketplace.By far I am not aiming to compete with Chineese type of products! if this is in the back of yr mind.
Adriano