32" Imex Cat

[tiqueman]

Some of you have been following this on RCU, but its time to call in the big guns of the FE and get some help. Heres what I got....

Long story short, the stuffing tube is junk on the Imex boats. Three runs in and the shaft was already about to snap, probably due to the configuration on the stock stuffing tube and how it put a kink right at the strut. I tore it all out and did a normal brass tube etc etc. Also at the time of reconstruction, I added about 20 inches or so (about 10) of pool noodle flotation on each side down in the sponsons. I wouldnt have thought this would have destroyed my already not right COG, but maybe it did more than I think. Before, it handled pretty well. With ease through a turn it would hook up quite nicely at full throttle and come out clean. Now, as soon as you go into the turn, within the first 1/8. it hooks and spins out. Also, while letting off from full throttle it wants to hook and pull, usually to the left.

What happened??? My strut depth and angle are exactly as I had if with the stock set up. Same prop as well. The only difference under the hull, is that with the old stuffing tube, it was like if you tied a piece of string to the motor shaft and then tied it to the struts nose. That caused a kink at the strut and the premature wear. Now that it is bent as it should be, is it trying to ride on the stuffing tube???

Oh and the stuffing tube/ strut is about 1/32 lower than the bottom edge of the sponsons.

[domwilson]

Can you raise the strut a get a little more positive angle on it?

[tiqueman]

Ive got some positive angle now. Heres a pic. I may be able to tweak it a bit more without any taking things apart and re-bending. And like I said, its the same depth and angle as it was before and it ran quite well. I would spin it occasionally, 2/3 or more through the turn, but now its every time and instantly.

[domwilson]

Is the rudder pointed straight down? Is the whole drive alignment straight?

[785boats]

As domwilson said raise the strut a bit more but keep it at about the same angle in your last pic. The bottom of the strut 1/16" above the bottom of the sponsons is where I run mine. motor temps dropped quite a bit when I raised the strut up just 3/32" to that height.
Also I believe that the rudder is not long enough. There is no blade in fresh water. The prop wash makes the rudder more sensitive. A longer blade would help stop spinning out. The blade also needs to be vertical or the toe even angled slightly forward. With the blade angled back, lift is created in the turns & will cause the boat to spin out as the hull lifts off the water. With the COG too far forward this effect is amplified somewhat.
Here's a pic of the rudder on mine & I still have spinout problems at full speed.

[tiqueman]

The rudder does have a slight angle to it. Bottom being further away than the top. To correct that, Id have to shim the top of the mount, or see if I can do some playing with the mounts holes from the blade to the mount itself. And yes, the shaft is alignment is straight. I glassed in the new stuffing tube with everything installed. The new strut I used is installed into the existing bracket, so that placement did not change in the swap out.

I was able to get a bit more angle on it, in doing so, raised the strut about 1/8". I may be able to get it wet again tonight.

Also, I do not have in my possesion a 3/16 thrust bearing. I had a standard washer I put on there which has an outside diameter probably about 1/32 greater than the strut itself. Not even being the correct piece, I removed it. Perhaps it was contributing to the handling? I dunno. Coming from the gas side of boating, I see set up a bit different. I saw that there is a thrust bearing you can install at the motor. With this set up, are you not installing one between the strut and the drive dog? Or is it in both locations? On my gassers, its only at the strut/ drive dog...

[tiqueman]

I was thinking this one....

http://www.offshoreelectrics.com/pro...rod=tfl-502b20

I felt from purchase that the factory rudder seemed too small. I think its more the "up to 20" or maybe 25 inch range.

[tiqueman]

I think Ive done all I can do now, for 315 on a Sunday....

I was able to remove the rudder from its bracket and file the upper hole towards the rear which allowed me to straighten the rudder blade. I went a bit more to give it maybe 1 degree of "toe in". Couple hours and I should be able to hit the lake again.

[785boats]

That rudder looks like it will do the job. But who knows, changing the angle of the rudder as you have may do the trick.
Getting the COG right is pretty important though. The easiest way is to get two 3s packs of the same capacity & C rating, place one in each sponson towards the rear & connect them in parallel NOT series, & adjust them fore & aft.
I feel for you man. I had the same problem setting my 32" cat up too.
Another thing. You want to leave a 1/8" gap between the drive dog & the strut to allaow the flex shaft to wind up under load. You will reduce the load on the power system & possibly gain a bit of speed. Do it before you go to the lake today.
Cheers.
Paul.

[domwilson]

Yes the rudder does look too small. But I think the angle of the rudder would affect it more. Especially being that the rudder is steering essentially prop wash.

[NorthernBoater]

If the bottom screw is not a brass screw replace it with either a brass, plastic or remove it and tighten the top one down so you can not move the rudder with your hand. With a steel screw the first time you hit something it could potentially tear your rudder off.

[tiqueman]

I love this site... you get such a wealth of info so quickly!

Alright, um... not a good beginning to the run. I couldnt even get it to take off without it immediately trying to turn .... to the left I think? So, I lowered the strut to lower than I originally had it, by about a heavy 1/16. It got better in the take off and on the straight line it didnt pull as bad if I let off the throttle. Still spins like a top though.

NorthernBoater, I thought about the brass screw (or plastic) yesterday and forgot to grab it while in the hardware store. Im going to grab a few tomorrow.

Paul, wiring 2 3s packs in parallel, thats going to keep me at 11.1 and with 2 4500 packs, it will put my mah to 9000, correct? With that said, and being new to all this brushless stuff, will speed controls take any amount of mah? Is it just the voltage you have to worry about? Or do you have to consider both?


So forgive me for this. I shot a video, by myself, and I had to run in the narrow part of the pond as the wind shifted, duckweed has taken over the larger area. This mornings run I had a lot more space. Starts out kind... well, lame, as I was trying to figure out how to look at the screen on the camera and watch the boat. Let alone drive w/ one hand.... the first turn around I completely let off the throttle which Im sure only helped the spin out. Im not sure what you will tell from this, but what the heck.

http://www.youtube.com/watch?v=5LLqYJG8Wow

I think maybe tomorrow I will remove the 442 and try the 440 again? Maybe its prop walking too much. Actually, I think before I do that, now dont laugh at me, Maybe I will make batt trays in the sponsons as low as possible, run it off my 3s 4500, BUT, I will put one of my 2s's in it (not hooked up) just to try and keep it balanced. Then I can start playing with COG. It can be my $100.00 ballast

[Rumdog]

I would say, that after seeing your pics and vid that your rudder is way too short.vIt is long enough to initiate the turn but not long enough to hold it in the turn.

[tiqueman]

Do I have to make batt trays or can I just velcro them to the hull?

[tiqueman]

Rumdog, What I dont get is it handled so much better before the stuffing tube and strut swap...??? I may order a rudder tomorrow.