Widening Sponson Riding Surface

[Ray Barnes]

I had a suggestion to widen the riding surface of my sponsons to about 3 inches. The ones on the Newton plans seem to be a little narrow for scale boats. I would like to do this but not sure how. I was going to eliminate the inside angle just extend the bottom surface to meet the sponson sides. My concern is that one side would run deeper in the water than the other side. The angles for the bottom pads are different angles. I did measure the deepest point from the bottom of the hull to the bottom most point on the rear sponsons. The dimesions are the same but in different locations. If you look at the pictures in my gallery you can see the differences. I would have to cut new sponsons sides and they would not be symetrically opposite. A friend has seen guys doing this in Florida. He says it doesn't sound like a bad idea. I'm just not sure exactly how to set this up. I'm still in the framing stage of this build so cutting new pieces is becoming my new hobby. Has anyone here set thier boat up like this?

Here is a shot of the profile now.https://www.intlwaters.com/gallery/thumbnails.php?album=652

 

[Brian Blazer]

I have a different theory on RC sponsons than most people. I would rather have them as narrow as I can get them and still get the boat to launch. Also, I hate traping air under the boat as I feel this makes the setup very critical, as well as makes the boat flighty.

Unlimiteds weigh aprox. 6700lbs, have 2650 hp, and go 200mph

RC's weigh aprox 12lbs, have 6 hp and go 60mph

We have a more HP to weight ratio and the speed ratio is crazy. You don't need the air to lift the boat.

I have a '68 bardahl that has only been over backwards 2 times in 4 years. It won the 2002 IMPBA District 2 championship, only attending the minimum of 8 races. I finished 1st or 2nd in aprox. 80% of the heats I was in. With that being said, My right sponson (torque side) is 2-1/8" wide. My left sponson is 1-1/2" wide. The right side inside sponson is vertical with the left having a 3/4" notch to relieve air.

In your case, I would not go wider. Where the inside sponson are chamfered, I would make them go straight up. You have anhedral on the right which is good. Should be about 3 dihedral on the left. I like an angle of attack at about 2.7 to 3 degrees. Any more, you are just scrubbing speed.

Turn fin! Turn fin! Turn fin! I don't see too many scale boats that turn the way they should. I love big, hooked fins. When setup properly, your scale boat should turn extremely fast and never hop.

My 2 cents

Brian Blazer

 

[Ray Barnes]

Thanks Brian. I was asking about the new boat I'm building, but your reply on my Bardahl is valuable. Would you happen to have a picture of your hull. I'm just a little confused. I was told by some one that had seen my Bardahl boat run in the past that at high speeds it tends to want to tip toe from one side to another. The possible fix was to widen the sponsons a little.Thanks again.

 

[Brian Blazer]

Thanks Brian. I was asking about the new boat I'm building, but your reply on my Bardahl is valuable. Would you happen to have a picture of your hull. I'm just a little confused. I was told by some one that had seen my Bardahl boat run in the past that at high speeds it tends to want to tip toe from one side to another. The possible fix was to widen the sponsons a little.Thanks again.

I would do the same on your new boat. If you widen the sponsons, in my opinion, you will make the boat flighty. It is rocking because you are trapping air and the boat is releasing the air. The rock will go away if you find a way to not trap as much air.

Brian

 

[Hydro Junkie]

Thanks Brian. I was asking about the new boat I'm building, but your reply on my Bardahl is valuable. Would you happen to have a picture of your hull. I'm just a little confused. I was told by some one that had seen my Bardahl boat run in the past that at high speeds it tends to want to tip toe from one side to another. The possible fix was to widen the sponsons a little.Thanks again.

I would do the same on your new boat. If you widen the sponsons, in my opinion, you will make the boat flighty. It is rocking because you are trapping air and the boat is releasing the air. The rock will go away if you find a way to not trap as much air.

Brian

I have to agree with Brian about not widening the sponsons. Wetted area means drag. The more wetted area from wider sponsons, the more drag you get. The more drag you have, the less speed you get . That is one reason the big boats went to ride pads and narrow runners on the bottom of the sponsons.