Please also see the FAQ - Wooden Boats page for additional questions and answers about woden boats generally.
Your building instructions say to use polyester resin for glass taping the joints. Can I use epoxy resin instead?
Yes, you can use epoxy resin for the taped joints if you want. It will cost more and will make a stronger boat but there is a change in procedure that will be needed.
Joints with glass/polyester joints on the inside are flexible enough to allow the hull to be flexed to shape when fitting the seat risers/bulkheads. Epoxy resin sets very hard and stiff, so this required flexing will not be possible. Instead of fitting the seat risers/bulkheads after taping the joints, fit them first then tape the joints later.
Work resin into the joints under the bulkheads with a brush to seal the plywood, then glass tape the joints between bulkheads.
You specify copper wire ties for the joints. Can I use plastic cable ties instead?
I have successfully used cable ties for dinghy building. It makes for quicker assembly and is very convenient.
Don't use the cheapest and lightest ties that you can find. These don't have the holding power to do the job and you will find that many will either break or their teeth will slip and lose the tension. Use ties about 3mm (1/8") wide. They will need slightly larger holes through the plywood than those needed by copper ties. In high load areas even these may slip, in which case use a larger size or copper ties just in that region.
I have read that a stitch & glue boat can be built using body filler to hold the joints together. Can I do this instead of using glass tape and resin?
Don't do this!!
Polyester auto body filler does not have the strength, flexibility nor holding power to do the job. You can use it as a filleting material to smooth the inside surface of the joint before applying the glass tape but it must have the glass tape to reinforce it.
Can I sheathe the hull with fiberglass cloth in polyester resin?
Fibreglass sheathing will hold the surface together if it is bad plywood and will also make a tougher surface so that the hull can take more knocks.
You should sheathe before you fit the sheer strakes, so that the strakes hold the edges of the glass. If not, a peeling problem can occur with the glass. This is because polyester resin shrinks as it cures and it tries to shrink itself off the plywood. The peeling stresses that result can cause delamination to start at the edges. You can improve adhesion by brushing on a coat of resin thinned with styrene monomer before you start the layup. This thinned coat will penetrate into the surface grain to bond it more securely to the timber.
Lap the glass about 25mm (1") wide around all hard corners (chines, transom and bow) to give a double thickness. When applying the glass sheathing, use a squeegee to remove all excess resin from the cloth. If you don't it will come out lumpy and give you a bad finish. The glass texture must show through when you do the first layer. You can fill in the texture of the fabric with follow-up coats of resin to get a smooth finish for sanding to take paint.
If you do want to sheathe your boat, it is better to do it with epoxy resin. Epoxy does not shrink the way that polyester does, so it has a better bond onto the plywood so will not peel. It is also stronger and more waterproof than polyester, so your boat will last longer.
Must I paint over the sheathing or can I leave it as a clear finish?
Sheathing done with polyester resin can be left unpainted but it is better if protected by paint. It will go yellow from sunlight and become ugly with age, so paint will keep her looking pretty for longer.
Don't leave epoxy unpainted because it will powder off in sunlight. There are UV-resistant epoxies but they will also disappear with time. A coating of paint will protect you investment.
Do I need to do any lofting with your dinghy plans? I have read that lofting is beyond an amateur boatbuilder and that the plans should be sufficient by themselves.
No, lofting is not needed for our dinghy designs. Lofting is something that is sometimes needed for larger boat that are built over a framework. It does not apply to these boats, where you will be marking out panels from fully dimensioned diagrams that even show how the various panels fit onto the plywood sheets. See our articles section, which has an article on lofting, if you are interested in reading on the subject.