working with composite canoes!

[Blue Viking]

This is all new to me...soo here goes.. This cut off "Chipewyan" composite canoe has had one end cut off...Having no experience with this kind of material, my question and your recommendations is whether I can make a wooden transom, and secure it safely to the material so that it wouldnt leak. Or am I just thinking it can be saved! Its wide, deep, un-used, and looks like it would make a nice square stern salmon canoe.
Thanks in advance for any suggested approaches to saving it.

 

[john hupfield]

Sure.Seal with 5200 and use some kind of mechanical fastener,screws backed with washers,maybe ring nails.Transom should be at least 3/4 inch as people tend to mount motors on them.
John

 

[Benson Gray]

What you do really depends on how you want to use it. You can simply cut a wooden transom, add some caulking around the edge, and put some screws through the outside of the hull into the transom to get something that will float. If you plan to use a motor then additional bracing along the rails and in the bottom would be a good idea along with some skid plate material as shown at https://crab.secure-host.com/extrasport/oldtowncanoe/catalog.php?fr_sw=0&section_id=4 along the transom's edge.

Benson

 

[Todd Bradshaw]

Yes, some sort of small knees connecting the transom to the gunwale structure would be a good idea. Oltonar (Royalex) has a vinyl skin, inside and out over ABS structural layers and these all sandwich a foam core. Though extremely tough, it doesn't hold mechanical fasteners very well compared to denser materials, like wood. Fasteners with a fairly small shank and a pretty big head (or washer) will resist pulling through much better than something like a countersunk wood screw. 5200 will probably stick to it (it sticks to just about anything). You can also make fiberglass joints (like a stitch-and-glue plywood boat) but you generally have to use a specific type of epoxy since most regular boat epoxy products don't stick very well to the material. Old Town probably still sells this epoxy for repairs and skid plate applications, but I'll bet it's damned expensive. Mad River might also sell it.

You sand the area to rough-up the vinyl and then quickly run a torch flame over it. You are not trying to heat it or melt it, the flame is said to polarize the plastic and improve the bond. Apply the cloth and resin and sand it smooth once it's cured. OT used to also sell matching spray paint for covering repairs and blending them in. Don't know whether they still do.

Be aware that you are creating a pretty big stress riser when you attach a stiff transom to a rather floppy hull material (run over river rock - hull flexes until rock gets to transon - stiff transom doesn't flex - hull wears badly, or can even break where floppy meets stiff). Benson's suggestion of using skid plate Kevlar wrapped around the transom/hull joint is a good one. It's just about the most durable way to strengthen that joint and beef up the stress area. The Kevlar felt would be applied the same way fiberglass cloth would or a skid plate would be added to a canoe stem. However, unlike fiberglass the cured Kevlar is almost impossible to sand (it just gets fuzzy) so you want to make your application as neat and smooth as possible. You can buy Kevlar felt cheaper from these guys (style 4580 Kevlar) than from most canoe manufacturers:
http://sweetcomposites.com/Kevlar.html

 

[Blue Viking]

Thanks for all this support!....I will be going back to Millinocket and take some measurements as I believe I have seats and some thwarts that have been salvaged from canoes that were not worth saving...This project will be a "pro bono" task for a gentleman who is the Pastor of the I Care Ministry in Millinockett, and operates the only Food Bank in that area...He is an avid fly fisherman and while I am not a member of his congregation, I have a great admiration for the help he is giving in that area.
Many thanks,
Blue Viking

 

[Greg Nolan]

Kevlar & Royalex -- Sweet Composites

Here's my experience gluing Kevlar to Royalex --

Last year I made skid plates for my Royalex canoe from the Kevlar bias tape that Sweet Composites sells. The tape is thinner than felt, and to my eye, makes a more attractive skid plate, while providing what I expect will be ample protection. I used West system epoxy to glue it on, after sanding and torching as Todd describes above. I mixed graphite into the epoxy for the filler coats, largely as an aesthetic matter -- I didn't figure I was going to be able to match the red of the hull very well, so I chose to go with a contrasting color, black. But I doubt that the graphite makes much friction difference when the skid plate is skidding. So far, the Kevlar has remained stuck on to the vinyl quite well. If I were making a structural joint, however, I would investigate whether some other epoxy might be more appropriate than the West stuff.

I don't know if the felt would be structurally superior when used to support a transom -- being thicker, it might well be, but I expect it would also hold more epoxy, and so might weigh a bit more. The Kevlar tape is difficult to cut, and I imagine that the Kevlar felt would be at least as difficult.

Sweet Composites was the only place I found Kevlar tape. They have lots of different glass and Kevlar materials. They were very pleasant to deal with, even though my order was small. And as Todd notes, their prices were good.

 

[Todd Bradshaw]

Kevlar felt is easier to cut with sissors than Kevlar tape or woven fabric. I don't believe felt is woven at all (be it Kevlar felt or the finest beaver fur felt) so you don't have to cut through a lot of long fiber bundles. It does absorb a lot more resin (and resin weight) than the tape though, because it is much thicker. It looks like double-thickness chamois-shirt fabric. This thickness and extra weight does, however, make it incredibly durable with tremendous abrasion resistance. I suspect a felt skid plate would probably outlast a tape one by a factor of at least five to one.

 

[Greg Nolan]

Todd -- I expect you are right about the relative durability of felt/woven tape. But I take more or less reasonable care when landing the canoe -- but it is a plastic boat and does sometimesget rough treatment, much rougher than a w/c boat should get. This canoe is about 25-30 years old, and the red vinyl surface of both stems was worn away when I bought it (after one year of use by a canoe rental operation where you can imagine how it was treated). It was not until last year that the foam layer of the Royalex failed, making repair necessary. I think that a felt skid pad would be useful for a livery canoe, but I expect the tape skid pad to last as long as the rest of the boat -- assuming the epoxy continues to stick.

For the structural use of fastening a transom to a hull, though, I would wonder about the suitability of felt as opposed to a lay-up of woven fabric. I have no well-founded opinion as to which would be better (being completely ignorant on that score) but my uninformed speculation is that a lay-up might be better.

 

[Todd Bradshaw]

If we're looking for something to stiffen and reinforce the transom/hull joint on a square stern, as well as provide the best abrasion resistance for an area that is vulnerable to high amounts of concentrated abrasion anyway and which may get even more because of the stress riser situation we've created, I think the felt is going to be a better bet. If we had a situation where some force was trying to rip the transom off of the hull, making tensile strength the main issue, then an equal weight of woven fabric would certainly be stronger. Unless you're in the habit of swiftly motoring away from the dock while forgetting that the transom is still tied to it though, I doubt tensile strenth is going to be the key issue.

If it happened to be a metal reinforcement, for example, a layer or two of woven Kevlar might be thought of like a thin titanium reinforcement - offering lots of strength with a minimum of added weight and bulk. The kevlar felt would be more like attaching a 1/4" steel plate to the hull - maybe not pretty, somewhat heavier and thicker, but when it comes to bashing it on rocks, it is clearly more durable by a longshot.