Some food for thought, when building model boats and their construction techniques following the full scale subject being modeled.

A lot can be learned from studying the construction of their real life full scale counterparts and mimicking their construction in scale model building. Everything from building a strip planked canoe, or a double planked mahogany runabout, to stitch and glue dee vee cruiser or utility, can be produced in scale model form and produce results faithful to the original subject.

Another feature of following the original build procedures is you come to realize that the techniques used in the past full size builds offer some amazing results in scale model form in both strength and weight reduction of the model.

One such model build would be of the PT boat hull build. The original PT boat was built using double planking, with the first planking running diagonally from frame to frame and the second layer of planking running longitude along the length of the hull. Using the same practice as the full size boat in scale down size along with a different choice of materials such a Balsa wood sheet for planking can deliver a hull with the same strength as a ply wood hull with far less weight.

Another advantage to the balsa wood sheeting is the ability of the wood to assume bending in two directions where as ply wood offers resistance to double bending and would require the builder to make slit cuts in the plywood to relive the stress on the sheet. Double planking a hull with 3/32” balsa sheet will offer more strength to the hull than using 1/8” plywood planking and produce a much lighter hull if both hulls are finished in the same manner, ie. (fiber glassing or epoxy coating).

just to add some photo proof to frank's post,, builds fast, needs very little sanding, very very strong hull..

Thanks for good building tips

All true! Except... the final planking layer on PTs was also diagonal... which is even easier than running longitudinally... and still very strong.

One thing that isn't obvious about longitudinal planks (until you pull one OFF a real boat), is that they aren't straight. They can be J or even S shaped, and have to be cut from a much wider board. This funny shape is developed through "spiling", and allows the plank to wrap onto the hull without twisting it or trying to bend it sideways. It's a skill that I haven't mastered, but after trying it, I appreciate the skills of real boat builders even more.

And dang TGHS, I thought I was looking at one of my own hulls! When you going to show us the rest of that beauty?

https://www.rcgroups.com/forums/show...ight=whaleback,, still not finished, it's the boat that you did some of the shapeways parts for..

PAT- You are correct in that the full scale PT’s were diagonal plank in both direction, forward to aft from frame to frame chine to shear and then from shear to chine on the same two frames.

On the scale model of up to 3’ in length running the first diagonal set of planks from chine to shear, and then planking longitudinal with the balsa planks from chine to shear, will save the modeler from waste of material in applying the second set of planking. Since the model will be epoxy coated and painted, no harm, no foul will be committed in the accuracy of the model since the first set of diagonal planking will visible on the interior of the hull.

The main point of the exercise is that due to the fact that the wood grain of the two sets of planking on the hull are crossing each other, the strength of the hull to impact is more than double that of two planks stacked on ton top of the other with the grain running the same direction. Also since the impact of an object’s force will be dispersed over a greater area of the hull sheeting.

The main reason I mentioned this is that the DUMAS 33’ PT boat 109, which was original planked with plywood, is now planked with PVC sheet which some builders are not happy with. By substituting 3/32” balsa and double planking the hull, you will wind up with a much stronger hull and at a lighter weight.

Sounds great!
Another building tip: EDGE-glue the planks in the first layer, to make a stiff "membrane". This can then be rough-sanded before applying the 2nd layer, without individual "proud" planks springing down.

first layer.. pre-flex the plank for fitment if needed..medium superglue on the frames, stringers, deck edge or keel and the last mounted plank edge.. good spray kicker on the plank,, slide it in place quickly and correctly.. maybe a spring clamp.. do plank on other side, repeat repeat.. second layer same as the first but pins in place of clamps.. if your framework was correct and fared well it's amazing how fast it goes.. (well ventilated space required)

On a lot of my double planked balsa wood hulls I will mix a batch of thinned out epoxy ( a little thicker than water) and use it as a penetrating resin before I glue my second set of planks on to the hull.

I do the same thing on my double planked Mahogany over Balsa planked hulls. Adds a lot of strength to the planking as well water proofing the wood in the hull build.