Simon, here are some pictures and a quote from Intlwaters regarding our discussions related to packed air under the sponsons (using side rails) and another thought about what they refer to as "shingles".
Tunnel_Sponsons_010.jpg Tunnel_Sponsons_008.jpg
Posted by: Mark Bullard
"Well I have not borrowed this design from anyone. I have saw the cutouts in the ride pads of offshore cats for some time. Never given them much thought. We were in Evansville 2006 for the Internats and stay for the big races on Sunday. I notice the cutouts on the rear pads of one the boats on the hook going into the water. A light when off and the idea of what I wanted to do came from that. I have seen all kind of tunnel traps myself and tried a few also but never saw a great improvement. The shingles I have been working with have shown the most promise. It has done two things. One it has made the boats run very light on the water or like they are running on ball bearings, two they have stop the spoon problem that everyone was talking about at the time. Twins have a bad problem of falling in holes in rough water what makes it look like they are putting on the brakes in the straighaways and I do believe that it was the spoon principle that was causing this. It shows worse in Twins than single boats because of the weight of the boats and this problem has all but went away. But it has also shown me another problem that has plague me for years. And this was why I always had to run more angle of attack in all of my boats than all of the other boats causing the boats to start getting to loose in rough water. I have follow some things I have saw over the years that I thought were good ideas. I got this from Don Pickert when I got my first twin 20 plus years ago and have done it on all of my boats ever since. This was to have the ride pad wider about 3" or so in front of the trailing edge and tapper back to the width that I wanted for the trailing edge. This was always about a 1/4" on Twins. Here again with this type of bottom made the spoon principle kick in in a differant way by suck the sponson down in the water and making the boat run wet. The only way to correct this was by increasing the AOA as much as 2 degrees more than the 4 degrees I wanted. My first twin I got from Don had these type of sponsons and when I question him he said it was to help the boat at slower speeds to hold it up. Sound good to me and the idea stuck all of these years but remember that was in my early years of boating and I do feel that Don is still the grandfather of the outrigger. The problem did show it's self at that time and the correction was to 1/8" tunnel traps on the bottom the help the boat. On my boats of the pasted the problem was not always the same but I do feel that it was the differant dimenions of the bottoms over the years and sometimes I used tunnel traps to correct it. I have notice that my sport boats have not had that problem because I did not do this on them.
This has all came to light after the last race I went to in Charleston. And all templets for the bottoms of sponsons have been changed for my new boats and the shingles will stay."
Thought you'd like to know in case you haven't heard of it before.
Edit More:
"All Mike Bontoft's SAW hydros, from the 3.5cc outboard hudro (81.6 mph) to the GX1 gas rigger (109.2 mph), use air trap sponsons. They were good for a 3 mph speed increase in the 100 mph area. They made the boats track straighter and handle rough water better as well. I'm working on a design for heat racing since the SAW boats trip badly when turned at speed.
Lohring Miller"
Another concept picture: sponsonbott2.jpg
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Originally Posted by andym
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