building my own tunnel flaps
 

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, what are the details?
 

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:drool:

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

http://www.offshoreonly.com/forums/s...threadid=50758

Mike, this is the thread with all of the info for this weekend, I am not sure if I will be down for the races, I know quite a few boats will be at Smitty's marine in bricktown, rt 70 north, Is the tab to take out the lope at 70 or so? be careful, turnning the boat can be a handfull, the water gets on top of the tab in a hard corner, and instead of letting the boat slide a little, it tends to trip, and the turn, If you are going to Skaterfest, talk to Doug Lewis, or T2x, both have quite a bit of exp. with tunnel tabs. If I go to the races this weekend, i will give you my cell.

Philip

Philip Yea you know what that tab is for. Porpoise is between 60-80mph right at cruise speed. Have to trim out at 80 to smooth out. Too fast for most days on the bay. I don't know if it will help at top speed, that would be nice but is not my purpose. Thanks for the head up. talk later
Michael

Cad file pix, almost finished with 'em pix yo follow

more

next

last

1:36 gears
30 props (three blade -harder to plane comparing to my 28 4 blade bravo1's)
5600-5800rpm
-will receive 32 4 blades soon.will post the results.

jolley thnx for the pics.

mmwalters : thank you too ,i already had your tab-pics ;)

Sparky at Vicious Marine on St.Clair is rerigging my cat...... He just posted the pix of my tab install, coming along nice!!!!!!!!.......:D :D :D

:D

nice !
;)

I finally was able to run my boat with new tunnel tab. Good results all around. At cruise speed 60-70mph with tab down no porpise at all. Added bonus at top speed with 4 blade props gained about 2mph. Could feel the entire boat lift. With 3blade did not see any speed gain. I only ran about 1hr , with a little more time I may learn some more. One tip When I put tab full down to get on plane The boat was bow steering so much I almost crashed.:drool:

thnx for info mmwalters.
i think i will try mine in two weeks.
will post results


*Actually i am expecting more top speed gain. like 4-5 mph.Cause my boat is quite heavy,specially back side of it.do you think its possible?