Need Custom Sponson advice

When I say sponsons I am reffering to those things that rhyme with hubbies. Oh,heck, I'll just say it Tubbies. We call our superjets Jetskis not waverunners anyway! (Now you know I'm really old lol) I think I have searched all the threads I could possibly read on the topic, but before I dive in would like some help as I'm sure custom designs have evolved over the years.

I have a SN superjet. As far as drive-train-- currently installed is a stock 650, but on my bench is a 701 limited (another post) that will eventually go in, stock 144 pump , ss impeller (not sure pitch) jet dynamics ride plate and a pretty rare (as I couldn't find much info on it) ultrac toploader grate (it does stay loaded quite well)

I have left over epoxy and rolls of various glass from other projects (did a lot of race car part molds for a car that I built a while back) , and just enough divinycell left for the project. I was originally going to buy pre-made, but now realize that the small outfit guys that made these are no longer and I can't justify the $400 for destroyers, and heck I have the materials anyway.

I will be riding in flattish water and small Florida gulf surf. Every now and then will travel to West Palm Beach (lived there 15 years ago) for better waves. l also windsurf, so on the heavy wind really rough days I will be on a board, not ski. The glass smooth days, I will probably just fish off a waverunner (the kind you sit on). So, the flat water in my area isn't really flat. as it is pretty open and usually I see 1.5-2 footish chop on a typical day. My current setup stays hooked up well and shows no porpoising at any speed in these conditions. I would like surf slashability, to carve well, and still be able to ride in the chop at wfo. I'm o.k. with wondering (chine walk) as long it doesn't throw me off in a straight line.

What I have gathered so far is:

1. I probably need to make them quite wide in the very front (thinking like 1-1.5 inch) and carry that width the first quarter. I saw this from another thread on here - sorry forgot the name
2. Porb. need to be quite long (40 inch ish)
3. Not sure if I should lip the front (raised sponson- a gunnel as some are calling it)
4. Not sure if the rails should be soft or sharp(hard) ( the rail is the outside lower edge that first enters the water on a turn). If I had to guess I would say a 1/4 inch radius along the front would work.

I know everything is a compromise, so looking for design advice. I mainly ride alone and have never been on a ski with Hubbies (or tubbies).
 
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I have a set of new glass on sponsons for sale. $160 shipped.






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Very tempting! When you say glass-on do you mean that they are contoured to the superjet hull? Which sponsons are they closest to in design. Are they more surf oriented or race oriented? Can I see a some photos of other angles including the backside?
 
When I say sponsons I am reffering to those things that rhyme with hubbies. Oh,heck, I'll just say it Tubbies. We call our superjets Jetskis not waverunners anyway! (Now you know I'm really old lol) I think I have searched all the threads I could possibly read on the topic, but before I dive in would like some help as I'm sure custom designs have evolved over the years.

I have a SN superjet. As far as drive-train-- currently installed is a stock 650, but on my bench is a 701 limited (another post) that will eventually go in, stock 144 pump , ss impeller (not sure pitch) jet dynamics ride plate and a pretty rare (as I couldn't find much info on it) ultrac toploader grate (it does stay loaded quite well)

I have left over epoxy and rolls of various glass from other projects (did a lot of race car part molds for a car that I built a while back) , and just enough divinycell left for the project. I was originally going to buy pre-made, but now realize that the small outfit guys that made these are no longer and I can't justify the $400 for destroyers, and heck I have the materials anyway.

I will be riding in flattish water and small Florida gulf surf. Every now and then will travel to West Palm Beach (lived there 15 years ago) for better waves. l also windsurf, so on the heavy wind really rough days I will be on a board, not ski. The glass smooth days, I will probably just fish off a waverunner (the kind you sit on). So, the flat water in my area isn't really flat. as it is pretty open and usually I see 1.5-2 footish chop on a typical day. My current setup stays hooked up well and shows no porpoising at any speed in these conditions. I would like surf slashability, to carve well, and still be able to ride in the chop at wfo. I'm o.k. with wondering (chine walk) as long it doesn't throw me off in a straight line.

What I have gathered so far is:

1. I probably need to make them quite wide in the very front (thinking like 1-1.5 inch) and carry that width the first quarter. I saw this from another thread on here - sorry forgot the name
2. Porb. need to be quite long (40 inch ish)
3. Not sure if I should lip the front (raised sponson- a gunnel as some are calling it)
4. Not sure if the rails should be soft or sharp(hard) ( the rail is the outside lower edge that first enters the water on a turn). If I had to guess I would say a 1/4 inch radius along the front would work.

I know everything is a compromise, so looking for design advice. I mainly ride alone and have never been on a ski with Hubbies (or tubbies).
Design advice: buy a set that has already been proven to work, time is money, there is 0 reason to reinvent the wheel here.
 
Not sure if that fully classifies as design advice. lI'm sure it's good advice non the less. lol. :)

However, I think I could fabricate them (one off no mold) in the same time it takes to install the typical ones. It would most definately take a few extra hours sanding painting, but some time would be saved most likely by eliminating the need for screwing through the hull . If I go big, I could always shave down and reshape later. (more sanding--ugghh)
One of the inspirations for a homebrew is the post I read from 221 (found it) . His are wayyy wider up front than the typical off the shelf. Also a lot of the tubbies are generic (universal to all/diferent brand skis). I figure that I might be able to flow better with the orig superjet hull design. That said, if I found a resonable set of sponsons that will meet my above criteria ill go that route. Was originally hoping for Tom21's, but they aren't available. Also I am unsure as what to really expect with sponsons as I have never been on a ski that had them.
 
Purchasing them is probably good advice. Probably it's also good advice to not buy a jet ski, so at some point "I want to do it" is a perfectly reasonable reason to do something.

So I say if you want to do it go for it. I dunno what shape they should be though!
 
Not sure if that fully classifies as design advice. lI'm sure it's good advice non the less. lol. :)

However, I think I could fabricate them (one off no mold) in the same time it takes to install the typical ones. It would most definately take a few extra hours sanding painting, but some time would be saved most likely by eliminating the need for screwing through the hull . If I go big, I could always shave down and reshape later. (more sanding--ugghh)
One of the inspirations for a homebrew is the post I read from 221 (found it) . His are wayyy wider up front than the typical off the shelf. Also a lot of the tubbies are generic (universal to all/diferent brand skis). I figure that I might be able to flow better with the orig superjet hull design. That said, if I found a resonable set of sponsons that will meet my above criteria ill go that route. Was originally hoping for Tom21's, but they aren't available. Also I am unsure as what to really expect with sponsons as I have never been on a ski that had them.
Since you have no experience with a ski with tubbies and (wild guess) you are not running CFD on your design, what evidence do you have that wayyy wider than off the shelf is better? Also, prowatercraft are the only tubbies that I know of that are a generic shape. If you're planning on just gluing these to the side of the hull, you're gonna have a bad time.
 
Very tempting! When you say glass-on do you mean that they are contoured to the superjet hull? Which sponsons are they closest to in design. Are they more surf oriented or race oriented? Can I see a some photos of other angles including the backside?
Yes they're contoured to the SJ hull and only need a little pressing down on the ends to sit flush. I was told they were made by CarterB but I haven't seen any sponsons by him. They look like the ones Zero made. I haven't really heard of a surf vs race sponson but I imagine they're for surf / freeride. They're gelcoated white and about 3/16" thick. All glass on sponsons will need to be epoxied on and temporarily held in place by rivets or screws. Remove the screws, then come back and bodywork the edges with thickened epoxy.
 

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Yes, was not planning on using any software, 3d printing, or cnc, just old fashioned hand shaping. (thats part of the fun) . I just found 221'sugestion impelling that he liked his for surf.
If I scuffed the surface enough, added some concave divits, and applied a layer of cloth on ski before divinycell and shaping, I think they would be plenty stout. Then again , we are talking about laying up on smc. I gotta laugh at those that try to reinforce smc hulls with polyester carbon over it.
 

Big Kahuna

Administrator
Not sure if that fully classifies as design advice. lI'm sure it's good advice non the less. lol. :)

However, I think I could fabricate them (one off no mold) in the same time it takes to install the typical ones. It would most definately take a few extra hours sanding painting, but some time would be saved most likely by eliminating the need for screwing through the hull . If I go big, I could always shave down and reshape later. (more sanding--ugghh)
One of the inspirations for a homebrew is the post I read from 221 (found it) . His are wayyy wider up front than the typical off the shelf. Also a lot of the tubbies are generic (universal to all/diferent brand skis). I figure that I might be able to flow better with the orig superjet hull design. That said, if I found a resonable set of sponsons that will meet my above criteria ill go that route. Was originally hoping for Tom21's, but they aren't available. Also I am unsure as what to really expect with sponsons as I have never been on a ski that had them.
Making 1 sponson might not take to long to come up with the shape, make a mold of it. Lay it up... The problem you will run into is the fact that you have to make and exact copy for the other side......... This is where it becomes difficult. Now you get them installed (You will need to install them temporarily so you can remove them when you figure out you need to change something (But What? Trailing Edge, Leading Edge, Width, Vertical Placement, Horizontal Placement.?) Then your going to test again...... remove and start over............................... I would say around 30-40 hours till you had something that worked.
 
Carrera911, Interesting. I'm not sure I could ever get those to adhere to the hull right if they are just attached at the edges. I was thinking they would be more of a sandwich construction. Maybe I just assumed that most that were professionally made with two part molds and vacum bagging. They would none the less reduce shape time. I might j have to fabricate a much better type of adhesion system though. When I get off work I will PM you.
 
Big kuhuna you have some great points. It seems that most people are kind of guessing where they place these though. In a high speed straight line if one was not the same exactly as the other would prob not be as critical in a straight line. It might make turning one direction a little different than the other, but heck i turn left better anyway. maybe it will even me out :D I do hear all this advice though. I always tell my wife that whatever time I estimate to design something, is 1/3 the time it will actually take. You are right 30-40 hours, is prob actual time.
 

Big Kahuna

Administrator
If they are off, even in straight line, water pressure hitting them a different times could cause the nose to start hunting.
 
True, and in chop, it would prob be even more pronounced.

Here is the thread that got me thinking DIY. 227 version is 2/3 down this 2rd page . I have never ridden with him and no idea if he is an authority in surf anyway and the post date was 10 years ago.

 
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I am considering Carrera's sponsons, but at a loss to how I would mount them securely. I wouldn't have any concerns if our skis were glass like the blasters and early raiders, but on smc??? Only ideas I am coming up with are
1. molding them, molding the flat of the ski, and creating a two pice mold so I have a proper backing.
2. molding off the flat of the ski and then cut 6 or so rectangle notches in the sponsons where I could get into and adhere the back and then adhere whole thing to ski
3. Install many bulkheads in the sponson flush with hull side and mount to the ski with fingers crossed
4. Cut sponsons in half lengthwise glass the bottom to a backing then attach top then mount.
5. most obvious, but dread. Screw or bolt on and just refinish

Maybe I am brain dead today, but any other way and I can't imaging a permanent crackless install . I will also be applying a vinyl wrap over these and don't want there to be any movement.
 

Big Kahuna

Administrator
 
I am considering Carrera's sponsons, but at a loss to how I would mount them securely. I wouldn't have any concerns if our skis were glass like the blasters and early raiders, but on smc??? Only ideas I am coming up with are
1. molding them, molding the flat of the ski, and creating a two pice mold so I have a proper backing.
2. molding off the flat of the ski and then cut 6 or so rectangle notches in the sponsons where I could get into and adhere the back and then adhere whole thing to ski
3. Install many bulkheads in the sponson flush with hull side and mount to the ski with fingers crossed
4. Cut sponsons in half lengthwise glass the bottom to a backing then attach top then mount.
5. most obvious, but dread. Screw or bolt on and just refinish

Maybe I am brain dead today, but any other way and I can't imaging a permanent crackless install . I will also be applying a vinyl wrap over these and don't want there to be any movement.

What’s the dread? Screw the damn things on and be done. Don’t over complicate it, you’re just asking for additional headaches glassing them into the hull. I don’t recommend it at all.
 
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