Thread: Info for Quick Canoe (formally Disposable Canoe) builders - plan change.

An email from Perttu

Originally Posted by Perttu

I start building my quick canoe. I made bottom ion 6 and siden from 4mm ply.
I used polyester resin and have some problem with duck tape. Tape hold nicely when I started aplying resin, but
when it started cure the tape loosed grip and and both ends started to get loose. I have quite panic while aplying new tape and run out
of tape - so I hit some nails where I could - while the resin cured.

I didn´t manage to get wery smooth curve to shine. Maby it don´t look too bad -if not looking too close. Have to put "some" putty to worst parts.

It was nice sanding weather -20c

The polyester resin and the solvents might have damaged the duct tape or its glue. It might be worth taking some precautions if using epoxy too.

I would recommend that after taping the boat together as in the plan that some plasterboard/drywall screws be used at the ends of the boat (I don't think they are needed along the longitudinal joins) to make sure the two sides don't come apart at the bow. Alternatively the ends could be stitched with copper wire or electrical cable ties.

Drill four small holes through both sheets of ply approximately 6mm (1/4") in from the edge. Hold the two pieces of ply together with hand pressure as the drilling and screwing is done.

Put some duct tape over the sharp screw ends so nobody will hurt themselves.

When the resin is cured the screws can be removed - use a fingernail to see if the glue is cured - it should feel like a rock. If the glues get stuck use the method of heating them in the appendices.

If they were stitched the stitches can simply be cut off on the outside of the boat flush with the plywood surface.

Michael

I have found that the duct tape (or gaffers tape) loses its adhesion at very low temps. I had to move my canoe inside to get the tape to stay stuck. Also, I had big troubles getting the polyester resin to 'kick' below 10c. I ended up heating it up with a heat gun to start the chemical reaction.
I also used fiberglass reinforced autobody filler for the inside fillet, so I did not have a really viscous material such as resin trying to work against the adhesives on the tape. I wonder if that may have caused some of Perttu's issues as well, but I suspect it was a temperature thing.
I think that a Finnish winter and a Canadian winter are similar, and if someone was to be building one of these fine crafts in more pleasant temps, the tape would stick just fine.
Rick.

I think Perttu managed to get the temp in his workspace up to 37F.

I also used fiberglass reinforced autobody filler for the inside fillet, so I did not have a really viscous material such as resin trying to work against the adhesives on the tape. I wonder if that may have caused some of Perttu's issues as well, but I suspect it was a temperature thing.

Many years ago, I used Diatomaceous earth as a thickener for polyester resin with excellent result. It sanded easily and was pretty hard wearing. I used it to build up the bottom of Hobie cats which had been worn away from years of being dragged up and down the beaches - which was so successful that I ended up fixing 2 or 3 boats a week for the local boat shop in the evenings.

I have used it as a filler for seams then applied resin and fiberglass tape over with very good results. It is also much lighter than autobody filler and easier to use as the thickness can be controlled as if using micro balloons. Google shows that it is now being used as a natural pesticide so can probably be obtained at the local garden shop if not available at a pool shop.

I have not tried this with epoxy resins.

The reason I went with the fiberglass reinforced body filler was because the joint/fillet is actually structural, and I needed to rely on the fiberglass bits for strength. The product you are suggesting would make a good filler because of the weight, but I would have my concerns about it having any structural integrity.
Rick.

Where there is a sandwich type structure you can almost get away with any type of material in the fillet.

When I say sandwich - the fillet has structural material on all sides - the underside has plywood on both faces then the glass tape on the other face.

Diatomacious Earth, talc, wheat flour that are sometimes suggested as fillers for resin are very weak (particulate in form) in comparison with the gluing/filleting fillers (fibrous in form) sold by the epoxy companies. The closest simple material that can be used to make fillets is very fine wood flour - which also tends to be fibrous.

Using a weak material is fine in fillets that are going to be glassed. However for those who have a bit more money and want to save a lot of time and end up with a neat result a epoxy fillet with the appropriate filler powder is hard to beat.

The whole boat can be filleted in an hour and if done neatly there is no follow up work as there is with the glass tape over fillet method.

Best wishes
Michael

Using a weak material is fine in fillets that are going to be glassed. However for those who have a bit more money and want to save a lot of time and end up with a neat result a epoxy fillet with the appropriate filler powder is hard to beat.

.

I do agree with Michael - my point (not very clearly made ) is that if using polyester resin, the diatomacious earth option WITH glass tape over is an easy, and very strong alternative to using glass reinforced body filler (particularly where cost and availability are concerned).

Just put the fillet in, sand all smooth, vacuum the dust out then put in the glass tape. The radius of the fillet results in the glass tape not being "folded" at a sharp angle making a very strong joint.

Were epoxy is readily available this is all academic.

Howdy Boddies,

I wasn't putting down your info. Just filling in the whole picture for those who might read this later.

Also to circumvent the idea that the polyester and diatomacious earth is adequate without the glass tape. You had covered the practical side nicely - I wanted to explain the why.

Best wishes
Michael

MIK