MadDogDan

Need some help with my DaVette "flatty". I just moved to WI and the ponds have finally thawed. Took my flat bottomed DaVette out for it's first voyage and encountered a strange problem. I got the hull used and it came with a turn fin on the left side only. Since this is a straight line drag boat and a flat bottomed hull to boot, I really wasn't sure why the turn fin. I put a full race mod stroker 29.5cc in it and now I think I know why the fin. It has so much torque off the line the fin keeps the hull from rolling on it's right side.The problem is when I let off the gas at the end of the run. It immediately flips over on it's left side because the turn fin does it's job when the prop torque is eliminated. If I didn't have the capsule/cowl mounted it would end up upside down but luckily the hull would correct itself. This happens every time I abruptly let off the gas so I have to ease it down which is not easy if I am at the end of a run and too close to the bank.Possible fix: What if I take the turn fin off and put the longest trip tabs I can find on both sides. With the proper adjustments I am thinking the right fin will counteract the torque and the left tab will keep the hull from rolling over on it's side when letting off the gas. I wanted to find out what you all think before I go drilling holes for the tabs in my nice hull.MadDog

Hesco Racing

I know it is not a hydro but 2 weeks back helped a guy setup a hydro and it had the weirdest thing it would run fine half throttle and when I would open it up the steering would be so sensitive to the point that it would spin with the slightest of rudder input. After 2 hours of eliminating things like rudder throw and EPA etc the chap said all he changed was the strut. Old one no skegg new one skegg. Right there at the dam we hacked off the skegg with a leatherman and what a difference. Suddenly you could steer no problem boat ran like a dream. Well I had never setup a hydro and did not know they will not run with a skeged strut. Using that thinking maybe the strut is more the problem??


Here is thread of Dana setup on his boat and one thing is clear things are far behind the transom compared to yours.

http://www.rcuniverse.com/forum/m_57...tm.htm#5792179


Cobus

KENDOG689

First off,thats a nice looking DaVette you have.Dana has tried all the options except working cavitaion plates.He will let you know the scoop on how to set it up.

Dana W

Long trim tabs wouldn't be a bad idea . The left turn fin is needed if you want to make a left turn . No need for a right turn fin as it has no problem tuning right because of the engine torque . I have my rudder mounted on the left side of the strut to help keep the boat going straight . Similar to a cracker box set up . I now also run without a skeg mounted on the strut instead I have my skeg mounted at the balancing point ( about under the engine ) Flat bottoms & runner bottoms are both temperamental if you ask me . Each boat has to be fine turned depending on the HP you put into it .

mistycreekboats

My Feedback: (1)

Seeing these two makes want to try mine with a prop as still having problem with Jet stuff getting here I don't understand how that turn fin would not act more like a second rudder ??? ........................By looks of depth and angle looks like they would cause issues ................ I was thinking I would try mine (maybe next weekend if I have enough time and parts) but I will try to go close with rudder 2 5/8" - extended round bottom strut (move prop back some) - trim tabs and no turn fin ....................................Dana have you ever tried a inline strut rudder (like a Bonzi) ? Or a skeg strut with no turn fin ? ................. I think it needs trim tabs to control torque roll then it will turn better .........................Nice boats by the way

KENDOG689

Flatbottoms are very unpredictable,the bigger the HP the more control they need.A center skeg is a must as Dana pointed out,but the biggest thing that controls the launch are the plates.They need to be active and not static.They will in conjunction with the skeg keep the boat from doing funny things.Step 1 plates down,gas it step 2 slowly raise the plates,step 3 have the plates set for a nice plane and step 4 never just let off the gas,it has to be done slowly or the boat will act up.This is not from r/c knowledge it is from 1/1 knowledge over the years,also keep as much of the dead weight to the left and as far back as possible.Just my 2 cents.

KENDOG689

http://www.performanceboats.com/atta...1368228695Here are some pics of flats that did not have the boat planted with the plates off the line.

Dana W

Yeah I think trim tabs would be a good idea . The left turn fin helped turn to the left much better . Without it left turns are pretty wide . Also keep in mind I was only really interested in going straight for drag racing . I off set the strut to the right 1/4" , the rudder and turn fin on the left of the strut caused alittle needed drag . The left turn fin was sharpened on the left and the center skeg was sharpened on the right . All these things helped it go straight . As far as it wanting to roll I didn't have that issue probably because I didn't have the HP that these guys are putting in it now .

I tested it with a Piranha skeg strut once and it did pretty well but I was still in testing stages to see what worked best .

Dana

KENDOG689

Cavition plates really make these things work.A true flatbottom turnes on a dime.Runner bottoms not so much.LOL Adjustiple pitch on the plates will cure the behavior if done right.

KENDOG689

<iframe width="640" height="360" src="http://www.youtube.com/embed/A4ewqh0Ddwo?feature=player_embedded" frameborder="0" allowfullscreen></iframe>Watch the boat plow the nose before adding power,this is a real old video but kinda shows how to launch a flattie.Sorry tied to post a video of a launch.