Need Custom Sponson advice

Jhucke. If you haven't realized by now I do over complicate everything. :D

Bigkuhuna, I will look over the entire thread when I have a little more time. It is interesting that they are mixing matte with epoxy. That is a no no with most brands matte. I think it was just a filler, but again I sped trough it.
Hey all
I finally finished the sponson install (it took forever)! Ironically, I think it may have been faster to start from The sponsons weren’t an exact fit, were a little asymmetrical and without a backing I felt that I had to revise them to create a sound install. I used epoxy for the bulk of the structural bits, and as it cures so slow it really drags the project on. As they are bolted on, I probably could have gone with polyester products for most areas and been fine. I am outlining e the install as promised in hope it may help someone else. I have been busy with work, so all of the time spent on this project was done at night under a head flashlight. Sorry for the lousy cell phone photography.

These first photos are of the backing molded off the sides of the ski.


Once cured, I positioned the sponsons on the ski over the backing layup, measured and held them on temporarily with hot glue. I then popped the assemblies off the ski, cut access openings and glassed the two parts together from the inside before melting out the glue from the previous step.

I then beefed up the laminate of the outer inside where the bolts would go with 4ish layers of biax which would give me the thickness to countersink the screw heads so they wouldn’t show when finished. I then used a paper straw that was exactly ¼ inch OD that I placed in a hole drilled from a press that was flush with the backing. Once the straw was inserted, I spun glass cloth around it so when cured & I drilled the straw back out, it would create a strong bushing for the attaching bolts. I then puttied around the straw with a cabosil mix, just in case I left a pinhole which I couldn’t see. Photo is before I cleaned it up.


I then filled the gaps left on the outside between sponson and backing, sanded, filled, sanded exec then gelcoated. My gelcoat supplier left me with gel that was old and too stiff to spray (even with a 3.0 nozzle or dump gun). As it was windy from a nearby hurricane, I decided to brush it on, sand, brush, sand, sand, sand, and finally buff. . I’ll never do that again!!IMG_20201109_134700631_HDR.jpgIMG_20201109_195746413.jpgIMG_20201109_200008964.jpg

Once complete I test fit. They now fit amazing! Even before gluing/bolting them down (used 3 bolts each), I couldn’t slide a piece of paper under them from any point. I then used 4200 along with the bolts for the install, so let's hope when I go for a test run tomorrow I like them. Lol.

Final photos are of them installed and new graphics which were waiting to hug the ski since I started the sponsons!

Awesome work!

funny, fall of 2001 I saw that Chris Lawrence had these front sponsons on his 2001 SJ on tour. I went home got some 1/2” mahogany wood and screwed them on like a wider hull for 36”. Played a little with radius’s. They worked until they came out with RD front sponsons that winter.
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