UHMW usage on a jetjon, thoughts/advice needed

[Wood_Duck]

I'm in the process of building a jet jon which will involve me grafting part of the jetski into a new alumacraft hull. The rivers I will be running will have some rocks and boulders, nothing giant, but while the boat is going to be flipped doing the graft I was considering ordering some 1/8-1/4" UHMW to glue on the hull. Partially to maybe distribute impacts better along the thin hull and also to help slide on the rocks. Do you guys think this would be a good idea and what would be the best method to actually attach it? And if a feasible idea what would be the best source to get sheets of it? Would I only space it between the ribs, and how would it need to be cut around the intake to work properly?

 

[CedarRiverScooter]

PSG1 had a good idea to weld studs to the bottom to attach the plastic with.

I think adding the material is a big investment in money & time. It's something you can do later.

I've gone over a few rocks & they didn't leave any damage, maybe I'm lucky.

 

[Wood_Duck]

I may be completely wrong but seems like going with 1/8" itd be fairly easy to work with and for a 1436 hull not too terribly expensive. I'm just thinking if it's worth adding I'd rather do it before putting the motor and everything in the boat while it'd still be easy to flip and work with since I have no help.

 

[PSG-1]

I'm not sure how much protection 1/8" would provide, other than from simple abrasion. But it would most definitely be easier to form and work with than thicker stuff.

As for my idea of welding threaded inserts, I still believe that is the best route, even if it is more time consuming. Bolting the UHMW into threaded inserts with blind threads (hole doesn't pass all the way thru) eliminates the issues of having to seal every bolt, as well as the potential of bolts loosening and causing leaks. If I were going to do it, the threaded inserts would be the same length as the height of the ribs of the boat. This way, you could drill the hole through the boat, and the rib, and weld both ends, for max. strength.

 

[Scottinva]

For what it's worth, by UHMW is screwed to my hull. There is no sealant on the screws and the hull has never leaked. My hull is 3/16 thick with 3/8 UHMW.

Scott

 

[Wood_Duck]

any pics of the studs welded on? If i were to attach with hardware then I may go 1/4", but I would prefer to glue on and thats why I was thinking 1/8th would be easier to work with.

 

[Wood_Duck]

Well given the thin hull i think I do want to do UHMW. If I go with 1/4" how much hardware should I use to attach it? Just between the ribs? Also any good source to buy the UHMW from?

 

[CedarRiverScooter]

WD - A low cost compromise would be to add aluminum sheet to the inside of your hull. I did this next to my engine installation to stiffen things up. Obviously you can't go under the braces, but can go in between them. I glued the alum down with roof sealant Locktite S30.

 

[Wood_Duck]

could be an idea for stiffness and I'll look into it especially around the area of the graft, however it wouldnt offer that much in impact protection to prevent punctures though.

 

[PSG-1]

I concur with cedar river scooter about reinforcing the engine well with heavier aluminum plate. I did the same with my boat, using 1/4" plate in the engine well. Especially in my case, with that heavy 4 stroke, as repeatedly hitting waves, etc would probably cause the boat to have a 'belly' where the engine is, due to the weight causing the hull to warp over time and use.

As for pictures of the studs.....sorry, I don't have any....just a visual image in my head of what it looks like. But if you can imagine taking 2" lengths of some 3/4" solid aluminum round stock, then boring and tapping blind threads (where the hole does not pass all the way through) Then you would drill through the top of each rib, and though the bottom of the boat, where these studs would be installed. Weld from the top side of the rib, and then on the bottom of the boat, seal weld each one of the studs.

At that point, you would install the UHMW, using countersunk bolts to attach it to the mounting points.

 

[Wood_Duck]

5 layers of fiberglass in the engine well from side to side and for the length of the graft should suffice in place of adding aluminum plate wouldnt it?

 

[PSG-1]

I would think that would be adequate to support the weight. As long as it's tied in correctly to the hull, it should be good to go.

 

[CedarRiverScooter]

You might want to apply the fiberglass such that you can remove the jet tunnel at some time in the future.

I tore mine apart after the 1st season to make improvements.

 

[Wood_Duck]

You might want to apply the fiberglass such that you can remove the jet tunnel at some time in the future.

I tore mine apart after the 1st season to make improvements.

What improvements did you make over your initial setup out of curiosity?

 

[CedarRiverScooter]

For initial build, I was overly concerned with shallow draft. Ended up with the tunnel too shallow & had cavitation issues. Any more than 1 inch of chop & it would just suck air. I tried about 5 variations of a 'spoon' with only partial improvement. So now I have taken the tunnel insert back out (the 3M 5200 was hard to cut, BTW). It is currently in pcs upside down on the trailer, waiting it's turn in my garage project lineup. I will remount the insert about 1.5 inch deeper - will require some aluminum forming to taper the leading edge back to hull.

My buddy went thru same type of trial & error with his jet jon, this is why I suggest keeping future revisions possible. A year ago I was convinced mine would perform perfectly.