Hinge Pin Angle - Progressive Mechanical "Power Trim"

[nuzum]

The way it's been taught to me is the "deadrise" is the angle between the boat and the ground if it were on stands and usually measured at the transom and/or mid-ship.

The greater the angle the better it will cut through rough waters under power. The less the angle the more stable it will be at rest (drifting or on the hook)

 

[Carl Van Houten]

Sorry...some refer to it as dihedral but dead-rise in a tunnel hull is the angle measured at the rear of the sponson since the transom is inset on most R/C O/B tunnels. When I change the dead-rise I start at the rear and decide how much I am going to change that angle, then depending on how the boat was responding to my driving style, I run this angle forward and begin to twist it out until it winds up horizontal or close to horizontal to the waters surface at the nose.

This can be tricky as a lot of characteristics are gained or lost in the twist. It is a trade off. You can look at my 1985 model tunnel boat and see that I was twisting the dihedral even back then. You can quickly take it too far. You can't fix everything with one change. A tunnel hull is too complicated for that. There is a lot of things working together when you see a really fast Lynx running right.

The same fix for one boat may not help another much. I guess it depends on how far off you are with your overall design to start with.

-Carl

 

[nuzum]

Carl do u fool with tunnel compression much??

 

[Carl Van Houten]

I fool with all of it. You have to. The compression is something that can be close and still work as long as it is on the positive side. If you have just a little too much compression you can always add a little over-all weight to deal with it. Take the 3.5cc mod class, If you have to add more than 2 ounces in the front of the control box (not the nose of the boat) and 2 -3 ounces on the C/G to finish a race, I would say you need to think about lowering your tunnel compression a little. But as long as you don't go over that your compression is probably ok.

It is relative to what class you are running too. Using that same boat (same compression) in the sport / stock 3.5cc class you would need to run a bit less weight than that. A boat that is weight sensitive and will not carry any weight without getting stupid probably doesn't have enough compression to even fly the weight of the hull.

So actually you would always want a little too much tunnel compression so that your setup is more versatile as long as you don't get too far out of the window.

-Carl

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