Flip over problem

[sash]

Hi Guys

I keep flipping this thing over and over again. I cant seem to get the right balance.COG is 36 %.
Should i go beyond 2 deg negative on the prop angle. I've been told this is too much something else is wrong. Any suggestions ????????????
36 inch hull, Leopard 4082 1600 kv, 180 amp Seaking, X452 octura prop, Turnigy 45-90 c 5000mah 6S, Temps 86 deg, max speed on 5 and 6s 51.69 mph before flip over.1.jpg2.jpg3.jpg

[jcald2000]

Prop looks like it is on backward in #3.

[sash]

lol its not detongued

[boater57]

Maybe try a piece of corner protecter between the sponsons, on the flat to disrupt airflow.

[1945dave]

When does this flip occur? Going straight or does it happen when introducing rudder? 51 mph is fast enough for the air to lift the bow of the boat. If the prop is too deep then the prop will keep driving under the lifted bow and flip it over backwards. So I would not worry so much about negative prop thrust and start raising the prop/strut depth. In my opinion you can never get the prop too high as long as cavitation does not become a real problem. Also what some guys have done for this problem looks kind of goofy but add trim plates to the rear of the sponsons. Longer plates or tabs are preferred. 2 inch long as a minimum 3 inch better. Mount them 1/8th of an inch above the bottom edge of the sponsons and then they become something like a wheelie bar for drag racers. The idea being as the bow lifts the trim plates hit the water and kick the bow back down.

Good luck, let us know how you make out. I see mid 50's in your future.

Dave

[rc2266]

Any vids of said flip?

[JIM MARCUM]

When does this flip occur? Going straight or does it happen when introducing rudder? 51 mph is fast enough for the air to lift the bow of the boat. If the prop is too deep then the prop will keep driving under the lifted bow and flip it over backwards. So I would not worry so much about negative prop thrust and start raising the prop/strut depth. In my opinion you can never get the prop too high as long as cavitation does not become a real problem. Also what some guys have done for this problem looks kind of goofy but add trim plates to the rear of the sponsons. Longer plates or tabs are preferred. 2 inch long as a minimum 3 inch better. Mount them 1/8th of an inch above the bottom edge of the sponsons and then they become something like a wheelie bar for drag racers. The idea being as the bow lifts the trim plates hit the water and kick the bow back down.

Good luck, let us know how you make out. I see mid 50's in your future.

Dave

Dave knows his stuff. JIM

[sash]

Dave it flips over on a sraight line. My prop height is centered level with the bottom of the sponsons. I've tried raising by 1/4" but it made the problem worse losing thrust and flipping over at 42 mph @ 3/4 throttle. I cant give this boat full throttle for any more than 1 sec and its driving me crazy.
I thought this set up would get me to 60 mph + on 6S.

[1945dave]

Interesting! At the moment it sounds like we are trying to shove the nose down forcefully and the water is bouncing the nose back up. Are you porposing on the straights. In other words is the boat riding nice and smooth or kind of hobby horsing down the straights? If you don't mind I would like to approach this from the beginning and ask that you not be offended if I seem to make comments that seem beneath your skill level.

First I would like the very bottom of the strut tube even with the bottom of the sponsons. I don't want the center of the prop shaft at this point, I want the very bottom of the strut at this point with the center of the prop shaft slightly higher. This can be done on the kitchen table. Is by chance the stuffing tube lower than that? Meaning is the stuffing tube itself below the sponsons at any point? Hopefully the answer is no.

Next I want the line of thrust dead level, no negative no positive, just dead level straight ahead as the boat sits on a table. We may at some point tweak this alignment but for starters I want it dead level. Remember the outboard tunnel hulls are shorter and exceed your current speed routinely with an outboard hanging on the back. There is virtually no reason to not expect mid 50's and perhaps even 60's if we take it slow and determined with small adjustments one at a time. By that I am old school in the belief we must address one possible corrective adjustment and evaluate that before doing something else impatiently. In our local club we have been known to ask the owner of a problem boat to take a walk or go home and come back later. We pretend that the boat was never run and approach the boat as new without any known problems. Most of the time whatever the problem it is simple and easily corrected just most of the time over-looked. By starting at the beginning we sometimes never duplicate the original problem.

Do you have any 4S batteries? I would think you can run around 50 mph with 4S power. I also want to know if you have anyother props? I would like to drop down to a X442 maybe even a X440. If you can take these baby steps I think between Jim Marcum and some of us older farts we can fix this. Relax it will happen, enjoy it. After doing the above try it and let us know how your boat reacted.

Dave

[CatMan]

I can solve your problem! I'll trade you motors for my stock genesis motor. then your boat won't go fast enough to flip.... problem solved. be happy to give you my address.
I'll be waiting by the mailbox......heheheee

[JIM MARCUM]

Do you have any 4S batteries? I would think you can run around 50 mph with 4S power. I also want to know if you have anyother props? I would like to drop down to a X442 maybe even a X440. If you can take these baby steps I think between Jim Marcum and some of us older farts we can fix this. Relax it will happen, enjoy it. After doing the above try it and let us know how your boat reacted.

Dave

Proud to be in the same boat with you. JIM

[sash]

Catman your funny. But if you want i can trade hulls with you I've seen 82 mph out of those beasts. Maybe you can get this thing to go.

[sash]

Dave no offence taken, I am a noob and you can call me anything you want. It all staretd here if you have a chance http://forums.offshoreelectrics.com/...t+enough+speed
Basically I've learnt props must be balaced and sharpened to spin those rpms. The boat is porposing with 2 deg negative pitch and Iv'e have tried all of the above as you suggested and per Howard Lee on his post http://forums.offshoreelectrics.com/...ot-hotr-90-mph
The x445 too slow but stable. Pranther 230 better but still porposing and slower than X452. With those settings you and Howard suggested, it pulls a wheelie across the water with the nose 4 " above the water and eventually flipping on 3/4 to full throttle. But no porposing. This is why I am asking the question about negative pitch. I have bought the trim tabs as you suggested and will try to fit those tonight and then negative 5 deg strut angle if that does not work.
If this fails I'll be contacting Catman to see if he wants to swap hulls!!!!! lol
Any suggestions on a better hull ???

Cheers Dave

[jcald2000]

Air Dam at the very front of the tunnel.

[CatMan]

My next idea was similar to jcald2000's, except mine was to add an elevator/ canard up front and a 3rd ch. on remote, and if it rolls while airborne, little winglets with ailerons,
before long it will look like some burt rutan designed craft. and if you keep this up with that hull, the moderator might have to move your threads to the FE plane page.
( then you can complain that your plane won't stay in the air and keeps getting wet) so decide what you want now... a boat or a plane?
and I flip enough in my kayak! don't want a boat that flips better than me. Maybe it's one of those airhog's flying boat thing, that's been repainted to resemble a normal boat, and the previous owner didn't tell you?