Hollow Sponsons

Hammerhead · Mar 17, 2015

Anyone still building sponsons without foam cores?

It has been almost 20 years since I have. I'm building a new .12 rigger at the moment, and I didn't want to go out and spend 25 bucks on a 2 'x 8' piece of blue foam for some tiny little sponsons.

Anyway, I started building old school.

I remember, I used to have a small hole that I covered with radio box tape. This would keep the sponsons from cracking in hot weather and also worked for dumping any water out that got in.

Any comments welcome,

Marty

Kevin Krogness · Mar 17, 2015

Has anyone ever done sponsons similar to a I beam shape? No sides? That's something I would like to try next. Of course carbon fiber

Hammerhead · Mar 17, 2015

Hey Kevin,

Long time no blog : ) How have you been?

I seem to remember a kit way back in the day that had those. The boat was a dog, though.

Marty

Chris Wood · Mar 17, 2015

Kevin Krogness said:
Has anyone ever done sponsons similar to a I beam shape? No sides? That's something I would like to try next. Of course carbon fiber

Yes I did

Flexed a lot and not enough material to keep the nose of the boat above the water to float

Kevin Krogness · Mar 17, 2015

Hey Marty just a lot of work and some more work about 2,000 hours in 7 months.... Took last year off from boating and just played a lot of golf when I could. I miss the smell of NITRO so I'm back tinkering

I remember seeing a thread someplace about the hollow sponsons, maybe it was RCU... I'll see if I cant find it...

Chris did you every try maybe the first 1/3 of the sponson solid? The flex is the first thing that came to mind especially on the turn fin side. also what material did you use? Thanks

Chris Wood · Mar 17, 2015

No Kevin

The I beam was 3/8 thick

Run surface was 1/16

And yes fin side flex was bad real bad

Hammerhead · Mar 18, 2015

Well, I've jumped in too far to just throw them out and start over. I never really had problems with them back in the day, other than them just being a pain in the your know what to build.

DON MAHER · Mar 18, 2015

Hollow sponsons work as well as any other type of sponson & are a lot faster and easier to build,"if" you keep the design simple!!! My gas rigger with hollow sponsons holds the namba 2 lap record! Made the sponsons in one day, ready to paint.

Don

Jerry Betke · Mar 18, 2015

Go to where they are building new houses and ask the builder for some "scrap" foam!!!!! I have built more sponsons then I care to think about. I found using some material for a core that many more shapes are possible and I was able to hold dimensional integrity. I would recommend using wood block inserts for the sponson tubes when using foam. The alternative would be to use a balsa for the core. Use light weight balsa, especially on a 12 boat.

Kevin Krogness · Mar 18, 2015

The biggest thing I would look at is can they take a hit and still race or turn into open holes?

Hammerhead · Mar 18, 2015

Here they are, Goin' hollow! I'm all in.

Hammerhead · Mar 18, 2015

This is what they look like with what I have done on the tub.

Marty

Kevin Krogness · Mar 18, 2015

uh oh you cut the one too short!! Just kidding looking good

57fairlane500 · Mar 19, 2015

Looking good Marty. Are you going to be able to come to the fun run at Twin Lakes this weekend?

Next time you need foam call me, I always have some around.

Hammerhead · Mar 19, 2015

I'm going to try to stop by a little afternoon. When do you guys figure you will be wrapping up?

Hammerhead · Mar 20, 2015

57fairlane500 said:
Looking good Marty. Are you going to be able to come to the fun run at Twin Lakes this weekend?

Next time you need foam call me, I always have some around.

I don't know if you noticed or not Kelly, but I flared the tips of the sponsons. So, hopefully the next time I t-bone your rigger, it will deflect off without any damage

RaceMechaniX · Mar 20, 2015

I copied Don and routered out the inside of mine to shave a little weight. Then I just add 1/64 outer skins.

Plenty stiff with the center rib section and Divinycell on either side.

They go pretty fast too.

TG

57fairlane500 · Mar 20, 2015

Hammerhead said:
57fairlane500 said:

Looking good Marty. Are you going to be able to come to the fun run at Twin Lakes this weekend?

Next time you need foam call me, I always have some around.

Click to expand...

I don't know if you noticed or not Kelly, but I flared the tips of the sponsons. So, hopefully the next time I t-bone your rigger, it will deflect off without any damage

Yea, I noticed. When Brian handed me the molds for the new boat he said to build it Marty proof so it's a vacuum bagged carbon boat.

It depends on the weather and how many people show up Saturday, but I would guess we will be there at least until 3.

Those look great Tyler. I need to find some good competition balsa, the stuff around here is too heavy.

Hammerhead · Mar 23, 2015

It was nice seeing you on Saturday Kelly.

Here is another in progress pick.

Kevin Krogness · Mar 23, 2015

Looking good Marty, are you running the new 12 or the old reliable?

Hollow Sponsons

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