The lines of a 6' 3" pram

Pekka Huhta — Mon, 01 Oct 2007 11:12:19 +0000

I was looking for plans to a very small pram. Since I wasn't able to find exactly what I was looking for, I had to try something else. I found a few promising pictures and even a quite close lines drawing (although several feet too long and too narrow in the bow area) and ended up drawing it by myself. The original lines were just shown as 300 x 150 pixel image so the drawing was merely a guideline. I made a 1:10 model out of the plans and seemed to have the lines quite accurately in place.

The drawings were not too difficult although I had to improvise a few areas in the bow and transom, so the drawing is in no ways perfect what comes to draughtmanship. It was quite easy to scetch the lines with AutoCAD after I figured out how the different perspectives affected each other. Then it was almost too easy to print the drawing out with 1:10 scale and transfer the lines from the print to a building jig. I am certain that the jig (not to talk about the final model) is off by one or two millimeters here and there but the model is symmetrical and looks quite good. Only the sheerline in the model leaves a lot to be desired since I didn't have wide enough planks to get enough curve in it. It has been a problem with all of my models, 20 mm wide planks just aren't wide enough for a 1:10 or 1:15 model.

The plans...

... and the pram.

It's easy to practice with such a small project. Even building the model (with 1 mm planking) didn't take more than two afternoons.

Above you see the drawings, a building jig and the finished model.

Hopefully I find some time to build the pram. We have only a few months to the start of the boating season and I still have four wooden boats to tar, paint, varnish and fix before that. But at least I have my first design on my bookshelf...

A few other images of my sketch models

An imaginative racing gaffer built just by eye

Two very different approaches to modelmaking. At top an unfinished model built from a kit and at bottom yet another link in the long chain of finding the"real" boat for me.

A model of one of our own boats, Manta (the whole story of the real boat can be found from the link). The model was held together just by rivets and a drop of glue on each end of the plank. As you can see the sheerline has similar problems as the pram, the planks just aren't wide enough to get a sweet curve.

The use of epoxy in wooden boat building

Pekka Huhta — Mon, 01 Oct 2007 09:44:35 +0000

To build a new wooden boat, you can use epoxy for ease of use and performance. Or then use the traditional methods which don't require using epoxy at all. If one has thick enough and good enough lumber I can't see a reason to use epoxy on a small boat. Everything can be done without glue, and if the boat is done without glue it's always easier to repair or replace a damaged piece when you don't have to fight with glued seams.That was the idea with classics: when something was broken you could pull the broken piece out and replace it. It just doesn't do with epoxied structures.

Of course using epoxy is not out of the question. It just shouldn't be the default or "essential boatbuilding material". There is no actual need to use epoxy on the maintenance of a basically sound wooden boat which has been built without it. Restoring or bigger repairs are always a different case.

In restoring a classic wooden boat, you should use traditional materials in a traditional manner. This is even more important if you are doing major reparations or a complete rebuild. New material and new building techniques will leave nothing of the original, new material with original techniques will fit in much better. The only exeptions to this should be allowed if the desired strenght of the structure cannot be achieved without epoxygluing.

Using epoxy is sometimes handy and may save you from taking too much of the original apart. There are places that can be quite easily repaired with epoxy. Doing things "the traditional way" can require taking down much more of the original structures. If something is rotten, it is absolutely wrong to try to substitute the rotten wood with epoxy or a plastic putty. The only right way is to repair it with new wood.

Oils and epoxy shouldn't be used together. If something is to be glued with epoxy, oil impregnation should be done afterwards, not before gluing. Epoxy might not bond properly on a previously oil-treated surface, so in case you have to use epoxy, clean the surface with acetone or such.

When doing a repair on a classic boat you should avoid using epoxy as a sealer. Excluding the fact that on a real classic you will ruin some of its historical value, you are more likely creating just pockets where the water gets in but can't get out. Epoxy encapsulation works, but it should be used only if the encapsulation is done while building the boat. It is almost impossible to encapsulate a ready structure reliably and that will result to a situation where there is water trapped inside the wood and it can't evaporate. And that means that the wet wood freezes at the wintertime and it is destroyed in a few years.

In restoration work epoxy is a great glue, but it shouldn't be used to bond together things that should be able to move. The original designer has designed the boat accepting the fact that the structure will move some, and depending on it. Now when you stiffen part of the structure with epoxy, something else will break.

Wood movement, UV light, scratchs and knocks may break the epoxy surface. So, it's not as "service-free" as one would think. You have to keep the surface in perfect condition to keep the water out.

Covering the whole boat with epoxy and/or fiberglass should be reserved to the most hopeless cases of rotting fish traps. The trick which may extend the life of a wreck for a few years may as well turn a reasonably sound boat into an un-repairable and quite worthless junk that has very little value. After fiberglassing the hull there is not much left to do. The process can't be reversed.

Otherwise there is no general rules in salvaging those absolutely hopeless cases. You can use ethylene glycol, fiberglass, anything you can think of, but only if you are absolutely sure that there is no other options.

I saw a great little motorboat last year, and found an article about it in a Finnish wooden boat magazine. The boat was very thoroughly restored: in fact only thing there was left of the old construction was the keel, five planks and a few parts of the small cabin. It just shows that some poor fool can find a boat where everyone else sees a just hopeless wreck.

I wouldn't have put so much effort on such a wreck. But the owner is more than happy with it. Don't consider your wooden boat a wreck before asking someone who knows.

Sihistin - Wooden boats

The lines of a 6' 3" pram

A few other images of my sketch models

The use of epoxy in wooden boat building