Need Input from the jet Jon gurus

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CTilton
Posts: 28
Joined: 23 Nov 2018, 20:28

Need Input from the jet Jon gurus

Post by CTilton » 10 Jan 2019, 11:17

I found a very nice 2010 Grizzly 1648 , I have a late 90's Seadoo 787 and pump to mate to it. I have fab skills and access to equipment to build it and would love to not use the seadoo belly but stay with all aluminum. I know you have to build a spoon to make the water flow properly, just want the "what is the best route" consensus. I plan to eliminate the rt side steering console and go the center stick steer to increase the size of the casting deck. I spent my fishing tournament life in Basscats and then in Xpress's becoming more and more a backwater and river guy. I opened a business 3 years ago, so my bass fishing stopped but things are loosening up enough I can start fishing again. I will run a Fortrex 80 on it so I can use two batteries and will crank off one of the trollers. I can put the fuel tank and batteries anywhere for balance. Any input would be appreciated!

Chris

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CedarRiverScooter
Posts: 910
Joined: 13 Nov 2014, 08:01

Need Input from the jet Jon gurus

Post by CedarRiverScooter » 10 Jan 2019, 13:13

I am not a guru but visit Tinboats almost every day, so here goes . . .

I have rebuilt my jet jon twice now, & have been thinking of yet another tweak to make it better.

I have the plastic tunnel-motor mount glued & screwed in; it is set to be the low point of the hull.

In front of that,I have a tapered panel that extends about 4 foot fwd (It is actually the drop out from the big hole I cut for the tunnel).

I still get some cavitation when in a chop over about 2 or 3 inches It can depend on whether you are going into vs. with wind.

I am now contemplating adding a keel pad to extend farther fwd; the intention is to push the air farther to the sides. I also have a porposing issue above 30 mph, which I think is partly caused by the tapered panel being right at the planing break.

I am thinking of using UMHW plastic for this new keel pad, but most likely will prototype it with a fiberglassed panel 1st (as I could be way off-base).

I wish there was someone with software that could run simulations for these 1 off designs.

Edit - getting back to your question on spoons, I tried making one but it wasn't very effective. If I could have bought something like that already formed, it might have worked better for me. YMMV

Good luck on your build - post some photos!

CTilton
Posts: 28
Joined: 23 Nov 2018, 20:28

Need Input from the jet Jon gurus

Post by CTilton » 10 Jan 2019, 14:02

Ok , good input. We get some wind here so I want to avoid cavitation as much as possible. I can use a customers press setup to punch out a spoon to weld in if I can get a design to him run through his tooling guys.

Do you think that 787 seadoo would push it 30 mph or no ? Will float boxes help porpoising ?

CedarRiverScooter
Posts: 910
Joined: 13 Nov 2014, 08:01

Need Input from the jet Jon gurus

Post by CedarRiverScooter » 10 Jan 2019, 18:25

Yes on both those questions.

I made large trim tabs & that helped porpoising, along with making bow heavy. Those were band-aids though.

A big factor is the thrust angle of the pump nozzle.

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