porpoising - need help to stop it!
 

I've just bought my son a Proboat Sundancer and the thing was quicker than I thought it would be. That's always a nice surprise. Well the thing was losing it's bite on turns almost sounded like the shaft came lose from the motor - then would grab and be off again. I put the 4 AA battery pack as far to the front as possible and that helped with the grip problem but it's still porpoising - I guess that's the term when the boat is bouncing up and down as it goes. And this is on a perfectly calm pond.
Any ideas - fins?? If so, where should the be mounted and how big and where should I get them?

RE: porpoising - need help to stop it!
 

You could try some trim tabs...they'd probably solve your problem.
They look like these here, but minus the part that goes down. [link=http://www.offshoreelectrics.com/rc_boats/triton_boat/triton3.jpeg]trim tab pic[/link]

That is a pic of a trim tab/turn fin combo piece. Yours would just look like an "L" from the side. You can make them yourself for under $2. Go to your LHS and pick up a small sheet of aluminum, and cut out a piece that's about 1'' X 1'' and bend it in half. Drill your holes, and mount it to the trailing edge of your transom (the bottom edge where it meets the bottom of the hull) and your done.

Good luck, let us know how it performs!

RE: porpoising - need help to stop it!
 

Here's another pic to give you an example. This one is a little bit larger, and has water pickups with them:[link=http://www.rcuniverse.com/forum/upfiles/54861/Rw58985.jpg]another example[/link]

RE: porpoising - need help to stop it!
 

In you other pic of the back of your boat - what's that yellow looking tubing over your shaft. I installed a drivedog and joint and it came with these little gromets that are too small to go over the bone and I don't know where they go. I sure they are to help it from sliping out but I can't figure it out. I'm thinking of using something like that yellow tubing to go over both joints to keep the presure on it so the bone doesn't fall out - what is that and what should I use?

I'm attaching a pic of the back of the boat and let me know where you think I should attach the fins because the back is different from any boat I have.

RE: porpoising - need help to stop it!
 

The trimtabs on the drying rack are proper ones, the fins on he Triton Cat need to come off, or the boat won't be able to make a narrow turn if your life depended on it, I know, I had them on..

For testing purposes you can tape a piece of plastic card onto the bottom of the hull, let it stick out behind the transom, a credit card cut in half if about the right size (no, not the gold one!). If the boat runs better/well, glue them on permanent, after sanding off the ink, making them white to go with the hull. A little(!) heat will bend them downward if need be.
The added drag is negigible.

Regards, Jan.

RE: porpoising - need help to stop it!
 

Jan - thanks - as usual. Different subject - drive dog and joints - i remember some forum someone was talking about either drivedog and joints or flex couplers - you and I emailed on this subject a couple of weeks ago with my shaft rubbing problem . Here's my question - someone covered there flex coupler or drivedog with a tube or something so that when it blew apart they would be able to make it back to shore. Well I put a drive dog and joint in my stinger with the bent shaft - (replaced) and the bone won't stay in and there were 2 tiny gromets but I don't know what they attach to - there are the same size as the bones ears but it won't fit in the joint and the ears aren't long enogh to have these fit outside the joints - any ideas about that ? The rubber tube over the whole thing should keep the bone in but don't know what I should look for. Something that expand back anf forth like a rubberbank to keep it together - but what?

RE: porpoising - need help to stop it!
 

Jan - was that to me and the Sundancer? I don't get that? Where should be placed to solve porpoising - close to the rudder or where?

RE: porpoising - need help to stop it!
 

Here's an example, click [link=http://www.rcpics.net/img/37319]HERE[/link]

It's something you'll probably have to play with a little bit, but I think that location, mirrored on both sides would be a good place to start.

RE: porpoising - need help to stop it!
 

hellomynameisdookie - thanks for taking the time to do that on my pic. How do you do this so it's not Permanent so it can be changed ujntil you got it right where it works the best?

RE: porpoising - need help to stop it!
 

Tape them in place with double sided tape, for testing that should work.

Regards, Jan.

RE: porpoising - need help to stop it!
 

Hey man no problem. Let us know if that works out for you!