i am going to make a 20 inch long ,single piston (comes from kiekhafer underwater flaps),aluminum tunnel flap for 28 skater.

pros advice needed
-shall i try something exactly same with tunnels shape? or use a simple form like a square?

-is one piston enough?

-how thick the aluminum should be?i am thinking 10mm

I just made one from 3/8in.(approx.10mm,9.525mm) it is 28" wide x 24" has twin rams w/ merc pump. Up 30 deg. down 25 deg. Tim my cat has a taller tunnel height, you don't want the tab to tag the water after you are up on plane( stay parallel to the hull, to full out maximum in chop, the tab is mainly for flat water to change the aperture of the tunnel to roll your c/g forward and blow the air out where you want it!) although it has to be strong enough to be loaded at takeoff and off plane.. Be sure it is 6061 aluminum or better, as it has a high ksi loading capability(yield/bending) that you need. Look at Dana Marine Products, or Papke tabs from Prorock Offshore for ideas. I have a Cad model of mine that I can send you plus pix. Hope I helped you......... But be sure to consult the expert racers/riggers on this board.......... Chime in you all!!!!!!! The boat looks great 'T' it has a great attitude in the water........ See Ya ,Bill

thnx for info .
its running better everyday..

jolley : i would be pleased if you send me pics.
thnx too much

Tim, at the 106 mph, what are the details, RPM? prop pitch? I thought you said the gears are 1:36 ? right? why are you doing the tunnel tab? just to get the 70mph lope out of the boat? you are going to carry quite a bit of weight and mass , be very careful with the tab in turns! please let me know the details of the 106, which props are you running?

Philip

Tim I am in the process of completeing a tunnel for my motion. I started with a set of Dana marine HP1000. It is 42''x 26''

Another view
6061 T6 1/4'' thick

Philip How is it goin, is your boat ready to go? Have you had it wet yet? Other then the rain I mean.

Hi Mike, No not been in the water yet, sitting in the rack at Smitty's. I had another gear case with a casting problem, new one is on now, but not run yet. If it keeps raining, I will have to take a boat to get to work. I see you are building a tab, looks great, better quality then you can buy from a ready made. Have you run in a boat with one yet?

Philip

Philip I had my boat out once for about 20min. I did not know that would the last clear day. No I have not run a cat with a flap. Any advice? I will try to get it out to the power coater this week. I am also trying to go to the races in Brick this weekend. Where are the pits and the best place to view the races? Maybe we can hook up.
Michael