spoon design for jetboats wanted

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

spoon design for jetboats wanted

Post by Bx10 » 10 Aug 2016, 19:19

Tired to get the nicest transition I could but it's kinda hard leaving the center joint in
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Xtremeboats
Jonjet
Posts: 4
Joined: 27 Mar 2011, 11:04

spoon design for jetboats wanted

Post by Jonjet » 28 Feb 2017, 01:24

By looking at all these 'spooning' hulls I've been looking at all over, doesn't the end of the 'spoon' shape
have to end right at the intake of the pump?
Or from what I'm seeing here is that the Spoon sticks out a bit all the way to the input.?

This isn't sounding right.
When I look at the hull of my 'ski', it curves down and then up slightly and flattens out.
So when the water follows the curve (or hull) downward it follows rearward and actually pushes up a bit into the impeller
opening?
I'm at work and can't add any pics or renditions.

thanks E

CedarRiverScooter
Posts: 930
Joined: 13 Nov 2014, 08:01

spoon design for jetboats wanted

Post by CedarRiverScooter » 28 Feb 2017, 20:51

Hey Jon - You are right, a true spoon is convex & wraps back up to feed the pump.

Mine doesn't follow a curve, it just is a straight taper, but it only grows 2 inches over 4 foot.

I think the most important factor is not to have any 'steps' that create turbulence.

Smooth shape all the way to the pump!

IkeCarlson
Posts: 15
Joined: 22 Aug 2017, 16:03

spoon design for jetboats wanted

Post by IkeCarlson » 24 Aug 2017, 17:52

Older thread, I know, but had to speak up. What I am seeing for "spoons" here resemble deflector more than spoons. A spoon is very shallow and is not always the answer. The angle if the leading edge on your intake is very inportant. Too sudden or too steep will cause loss of suction and cavitation. You should not be able to feel any transitions in the hull forward of the intake. These will make turbulance. A keel is normally ok, as long as it tapers out smoothly at least a foot before the intake. The key here is to make it smooth and gentle. If you can taper it out over about a foot, great. If you are making your own intake, be prepared to spent a lot of time getting it right. You will be working with progressive duplex curves. This is not easy to do and get it right. The trailing edge of the intake needs to be smooth/rounded. This can be a bigger problem then the leading edge when trying to get out of the hole because the impeller is pulling lots of water and the boat is not going very fast to push water into the intake to the suction can pull air under the transom from the rear in some cases.

A deeper keel will improve steering, but will tend to cavitate more in turns.

IkeCarlson
Posts: 15
Joined: 22 Aug 2017, 16:03

spoon design for jetboats wanted

Post by IkeCarlson » 06 Dec 2017, 18:51

I can’t count the number of people asking for spoon or ventilation problems on the internet.

The best answer is to build your boat differently. I use the jet ski hull as a “pad” when I build.
It works great and is not too hard to do.
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CedarRiverScooter
Posts: 930
Joined: 13 Nov 2014, 08:01

spoon design for jetboats wanted

Post by CedarRiverScooter » 07 Dec 2017, 21:52

That is best in class!

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