Sponson Design

[Brian MAhoney]

I'm drawing up plans for my latest sport 20 hydro and was wandering what the pros and cons are of having some anti trip built into the righthand sponson.

I have two sponson designs I am considering for the righthand sponson running surface.

The first has the running surface horizontal right to left, the second slopes up 1 in 12 mirroring the lefthand sponson. Hopefully I have attached a picture that should make this clear.

What are the pros and cons of the sponson designs?

Brian

 

[Mark Anderson]

My latest boats have no conventional non trips. The sponson sides are vertical. the left has a 45 degree cut about 1/2 inch tall to act as a non trip. We don't turn left and if the fin is big enough it won't be sliding when turning right. I like my sponson bottoms flat with no diehedral. there are different schools of thought and some probably have very technical reasons why you need some very precise angle but flat is what works for me. I tune the pad width to soften the ride in chop.

Mark

 

[Russ Nachtweih]

Brian,

Use the Flat one!

Russ

 

[Eric Perez]

My latest boats have no conventional non trips. The sponson sides are vertical. the left has a 45 degree cut about 1/2 inch tall to act as a non trip. We don't turn left and if the fin is big enough it won't be sliding when turning right. I like my sponson bottoms flat with no diehedral. there are different schools of thought and some probably have very technical reasons why you need some very precise angle but flat is what works for me. I tune the pad width to soften the ride in chop.
Mark

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How tall or thick do you make this ride pads? What's a ball park width? Has anyone figured out how to make these pads removable -either for prototyping or for tunning (setup) purposes?

I've never used add-on ride pads, I'm interested in learning more about their use.

 

[Don Templeton]

Eric,

My ride pads are 1/16" ply on my 12 and are 1"wide on a 1-1/2" bottom with a 2.5 degree diehedral. I have always used diehedral because I also think it cushions the ride in race water. I have heard that some of the electric boaters have used a plastic strip (like Plastistruct) or something like that and put it on with double sided scotch tape so they can remove it. I I, really think that would work for some testing. Brian, I still don't see why you would worry about sideways trip on the right sponson. Left I can see but your right should be glued down with the turn fin.

Don

 

[Brian MAhoney]

                                                                                                                      Brian, I still don't see why you would worry about sideways trip on the right sponson. Left I can see but your right should be glued down with the turn fin.

Don 

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Looks like I have my terminology wrong it's the dihedral I am concerned about.

Brian

 

[Don Templeton]

Well I don't know much about sport hydros but I would guess that with all the lift generated under the hull compared to an outrigger you might want some deihedral on both sponsons to let some air out on both sides and to give you some non trip on the left at the same time.

Just my thoughts. Better answered by someone who runs sport hydros.

Don

 

[Brian Blazer]

Keep the left sponson as is, keep the right either flat, or add 2 degrees anhedral. Since the boat is so light, I would keep it just like the plans call out for, and that is flat.

I have done a lot of testing with the gas sport hydro, dihedral, flat, or anhedral on the right side. Anhedral works the best. Because the boat is heavy, it lets the boat slide better without grabing the inside sponson like a tunnel.

Brian

 

[Brian MAhoney]

Keep the left sponson as is, keep the right either flat, or add 2 degrees anhedral. Since the boat is so light, I would keep it just like the plans call out for, and that is flat.
I have done a lot of testing with the gas sport hydro, dihedral, flat, or anhedral on the right side. Anhedral works the best. Because the boat is heavy, it lets the boat slide better without grabing the inside sponson like a tunnel.

Brian

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Thanks I'll build this one flat.

Brian

 

[Mark Anderson]

If it's sliding it needs a bigger fin!!

Mark

 

[Aaron Lavigne]

Trying to get a picture of how the rigger will be "tipping" in a right hand turn. Is anhedral used on the right so during a turn the right sponson lifts and then converts to dihedral?

 

[Jim Dorcy]

way way way old post here fella

It your right sponson lifts its game over in a right hand turn. the boat will blow off

What Brian Blazer was saying I think was the anhedral allows the boat to slide left in a right hand turn ( understeer)

without the inside edge catching as much (reduced angle)

I have found flat works for me but I sharpen the edges

 

[lohring]

Take a look at the sponsons on Mark Anderson's last Sport 40 design.

Lohring Miller

 

[dwilfong]

 

[Aaron Lavigne]

So flat or a degree anhedral on right sponson and 1 or 2 degrees dihedral on left sponson would be fundamental?

 

[anthony_marquart]

On my sport 20 and 40 design there are only flat running surfaces. The outside of the sponsons are at about a 10deg angle. No non trip or dihedral. Use a fin a bit bigger than the traditional sport boat and you will not have any issues. Runs fast, turns real well.

 

[Grimracer]

[SIZE=10.5pt]Brain might have the best testing on this.[/SIZE]

[SIZE=medium]Anhedral[/SIZE][SIZE=10.5pt] is "lift" as the boat slides. [/SIZE]

[SIZE=10.5pt]Dont matter how large the fin they all slide "some"..[/SIZE]

[SIZE=10.5pt]If you dont want to "plant the sponson hard" in the corner [/SIZE][SIZE=medium]anhedral[/SIZE][SIZE=10.5pt] is a good thing to help carry the fin, boat weight and torque.[/SIZE]

[SIZE=10.5pt]Grim[/SIZE]

 

[Aaron Lavigne]

I think I understand anhedral now about how it would ride on the outside rather than hook on the inside of the sponson.

If the sponson bottom was flat, but the outside bottom has about 2 degree anhedral- I guess you could conside that "segmented"? Would that work just to have the bottom warped like that?

 

[anthony_marquart]

Anhedral is opposite of dihedral. Helps keep the tf sponson from grabbing in the turn. I've been working on getting the slide out of my sport boats. It's more comfortable for me to drive like that