spoon design for jetboats wanted

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brianb2247
Posts: 113
Joined: 02 May 2014, 23:35

spoon design for jetboats wanted

Post by brianb2247 » 29 Jun 2016, 16:50

look some of you guys have great ideas on this forum and when a question is asked you usually redirect to someones build could some one pose me a pic or two for spooning the underside of an inboard jet if you could provide measurements or little tricks to install one please need help with cavitation .

Xtremeboats
Bx10
Posts: 17
Joined: 30 Nov 2015, 23:25
Location: jarretsville md

spoon design for jetboats wanted

Post by Bx10 » 29 Jun 2016, 21:25

I have just starred to make a spoon for my jet jon after having some pretty bad cavitation problems. I don't know If my design is the right way of doing it or not
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20160629_205051.jpg

Bx10
Posts: 17
Joined: 30 Nov 2015, 23:25
Location: jarretsville md

spoon design for jetboats wanted

Post by Bx10 » 29 Jun 2016, 21:31

I started with a 4ft × 2ft .90 thick pice of aluminum made the top a hair wider then my intake 6 1/4in. Then I clamped one side of sheet all the across on a table and bent 3 3/4in to slope my sides down to a angle I was happy with

Bx10
Posts: 17
Joined: 30 Nov 2015, 23:25
Location: jarretsville md

spoon design for jetboats wanted

Post by Bx10 » 29 Jun 2016, 21:37

I still need to finish the front ramp part of my spoon. Having a hard time finding a perfect way to get a nice gradual front slope along with having being a spoon shape in the front
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20160629_204721.jpg

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brianb2247
Posts: 113
Joined: 02 May 2014, 23:35

spoon design for jetboats wanted

Post by brianb2247 » 30 Jun 2016, 17:00

looks good i was kind of thinking the same thing just wasnt sure how long to make it

CedarRiverScooter
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Joined: 13 Nov 2014, 08:01

spoon design for jetboats wanted

Post by CedarRiverScooter » 30 Jun 2016, 17:36

I too had cavitation problems with jet ski insert flush with jon boat hull.

I dropped the jet ski insert to about 1-1/2 inches below hull. It is level along it's length.

For the transition, I used the material that was cut out of jon boat (for insert).

It is about 4 foot long, so it has a gentle taper. Since my old mig welder hates feeding aluminum wire, I just tack welded it in (at least 100 tacks!)). I used epoxy resin & fiberglass cloth to seal it up. So far, leak free.

Performance wise, I can run in 2 inch chop & no cavitation, so it was worth all the work.

Edit: I also re-shimmed the pump mount. so as to keep the thrust angle similar to before. (this was no small task either).
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Bx10
Posts: 17
Joined: 30 Nov 2015, 23:25
Location: jarretsville md

spoon design for jetboats wanted

Post by Bx10 » 04 Jul 2016, 18:58

I was able to some work making my spoon I was wondering what you guys thinks so far if I'm heading in the right direction
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20160704_175200.jpg

Bx10
Posts: 17
Joined: 30 Nov 2015, 23:25
Location: jarretsville md

spoon design for jetboats wanted

Post by Bx10 » 04 Jul 2016, 19:03

I only have one side of intake tac in right now still have a lot of work with smoothing everything out
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20160704_175114.jpg

CedarRiverScooter
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spoon design for jetboats wanted

Post by CedarRiverScooter » 04 Jul 2016, 22:15

Bx - Your spoon looks much like the one I built. Should work great. Hope you have a good welder, those are long weld joints!

BTW, the steering response on my JJ is now heavier than before. Probably shouldn't be a surprise. It's not terrible, but definitely not as fast of response compared with the flush intake.

Bx10
Posts: 17
Joined: 30 Nov 2015, 23:25
Location: jarretsville md

spoon design for jetboats wanted

Post by Bx10 » 04 Jul 2016, 23:05

I have a 200 miller spool gun welds pretty nice I was definitely going to weld the whole front down and grind it smooth for a nice transition I was thinking about laying a couple 3inch welds down the sides and flex sealing rest of the sides less welding less chance of having leaks also I'm worryed about the angle of intake seems to be a little steep ( not angle of the spoon intake ) I was never able to get my boat to go over a quarter throttle before it spin the pump or lose prime which I found my jet unit was leaking outside boat which means it must been sucking air sence it wasn't totally sealed

Bx10
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Joined: 30 Nov 2015, 23:25
Location: jarretsville md

spoon design for jetboats wanted

Post by Bx10 » 04 Jul 2016, 23:12

I made my aluminum intake almost exactly like the fiberglass tigershark intake
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20151229_210941.jpg

Bx10
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Joined: 30 Nov 2015, 23:25
Location: jarretsville md

spoon design for jetboats wanted

Post by Bx10 » 04 Jul 2016, 23:18

Kinda hard to see in this picture my jet is level coming out of the boat and I also have a trim nozzle
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20151230_174406.jpg

CedarRiverScooter
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spoon design for jetboats wanted

Post by CedarRiverScooter » 05 Jul 2016, 13:03

I se what your intake up-angle concern is & I think it valid. If not too late, i would start the transition much earlier. If you could put a radius on the spoon (sideways) that would be a bonus. The water wants to follow a curve.

I did most of the forming of my spoon with stacked/screwed together lumber & bouncing on the sheet to get it to form. I also fab'd a brake press, but it was limited to short section.

Bx10
Posts: 17
Joined: 30 Nov 2015, 23:25
Location: jarretsville md

spoon design for jetboats wanted

Post by Bx10 » 05 Jul 2016, 15:08

Now if my boat runs and moves at like a 1/8 thottle with out cavaition does that still mean my intake ramp my be a little to much of a angle or is that all air bubbles getting into pump related. It loses all prime when it seems to get ready to get on plain

Bx10
Posts: 17
Joined: 30 Nov 2015, 23:25
Location: jarretsville md

spoon design for jetboats wanted

Post by Bx10 » 10 Aug 2016, 19:16

I have some more time to work on my spoon design
and I almost got done
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20160810_190934.jpg

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