Maybe the most important part of the KEP's T2-21 build and the most different to other outrigger designs are the symmetrical shaped sponsons. Make sure you have read the previous articles and you have got some Divinycell H60 structural foam cores. If not, search on... These sponsons need to be made with that type of foam. If not Divinycell H60 - search for a equivalent such as Airex C70.55. Not as super-good as Divinycell but it will work...
Some have suggested that you could use balsa wood as core material, and yes, you could. But there are some things you should know before using that. Firstly, balsa soaks moisture like nothing else... And because it's a boat that means water of course! You might think that painting them will seal them for good but that is hardly the case. If you race your boat you will most likely get in contact with other boats and stuff and that could brake the "skin" so to speak and the water soaking could start well before you even have noticed it. Then the laminating epoxy you will use to seal the wood is most likely not water resistant either. The product we use for that is the C+C chemical resistant one from R&G that also is said to be water resistant and it has worked awesome for us.
Anecdote: I have a German friend that bought a rigger from the US that had balsa cored sponsons. The boat worked good right out of the box and my friend used it like that for a while. Then it started behaving strangely and he couldn't figure out what the problem was until he noticed it was heavier on one side. He removed the sponsons and one of them was much heavier then the other! He put them in the water boiler heating room in his house for it to dry out and he measured the weight every day. If I remember it correctly it took a couple of weeks for the moisture soaked sponson to get down to the same weight as the other. After that he re-painted the boat and it ran good again... With a correctly built Divinycell H60 cored sponson that would hardly happen.
So find a source for Divinycell H60 as I do believe that's the optimal core material for this application! :)
KEP's T2 .21 Presentation
KEP's T2 .21 Freebie
KEP's T2 .21 Build Series #1
KEP's T2 .21 Build Series #2
KEP's T2 .21 Build Series #3
KEP's T2 .21 "Inspirational" Article
KEP's T2 .21 Build Series #4
KEP's T2 .21 Build Series #5
KEP's T2 .21 Build Series #6
KEP's T2 .21 Build Series #7
After that use a pen and a straight edge and mark the centerline on the top part of the sponson cores. Then use your top-view sponson template and mark one half of the sponson outline. Use the centerline to align it.
Then start sawing the sponson shape out. Take your time and go slow. Look at what you are doing. I saw just about in the center line of the marked out pen-line as that saves sanding. But depending on how good you are and how careful you where when making sure that the sawing board and blade was at 90 deg you might saw a little outside the line... Here is a recommendation also: extend the rearward elliptical shape to a point so to speak. That will be sawed off later on but it's good that it's extended at its max at this stage. Also to the front part of the ellipse I don't saw it exactly as the template as that would make it hard to cover with plywood. I flare it out slightly so it becomes a little pointy. That will also be sawed off later on and the nose-block will be sanded round.
Cut-out a 1 mm plywood sheet that has the same dimensions as the H60 core. Sand it slightly. Spray CA glue activator/kicker on the complete surface of the plywood to be glued to the Divinycell H60 core and place it on top of the concave cut-off part of the foam core. DON'T use kicker on the foam!
Note, you must use a fan that is quite close to your glue-station set to max! You wont be able to breath when the kicker starts to react other wise and your eyes will water up instantly. Trust me. Been there, done that. It's not fun when you forget to start the fan! It's also good advice to cover your build table with thin food wrap plastic at this time. Also use suitable build-clothes and throw-away protective gloves.
Note that I have marked out where the front sponson tube will be approximately. That will be used when the side view template needs to be aligned to make the side profile.
Now you have the basic elliptical shape of the sponsons. Be proud of yourself! :)
Sand it flat and repeat the gluing process of the "transom/trailing edge" of the sponson - a process that you should be quite familiar with at this point... ;)
After that you can do the complete sponson. Make sure that the parts closest to the water has a bit more sharp corners. At least the front rear step that you can see in this picture above.
Note, no-one can be 100% accurate when building a wood outrigger. There will always be some differences even when I build them and that can make each boat slightly different of course.
Next: KEP's T2 .21 Build Series #9