Twin 6S rigger - Done!

[Fluid]

Frankly I'd toss the new fin, free or not. With CR props the boat wants to run straight, hence the poor-low speed turning. At high speed you are relying on centrifugal force to push the transom out - plus your rudder appears to be on the small side, further hindering turning and the probable reason your rigger didn't like non-CR props. Since the old fin works and you could turn in a 60-foot diameter circle at 80 mph, put everything back the way it was - you're there.



.

[mm123521]

Chris,
First, thanks for your expert help!

Yes the hopping (and video) is with 447 right and left.
I started with the turnfin lifting the right sponson (only at high speeds), so I know it was angled up slightly.
Then I moved the tip of the fin rearward by a few degrees and made a run.
Then I have made several, slight moves forward trying to "feel" for the neutral position of the turn fin.

Ok, next run will be with the strut neutral and the turnfin in its origional position (where it was lifting the right sponson at high speeds) -- this will be my "baseline". Then I'll move the turn fin back just a little. Maybe on tuesday after work.

Thanks!!
Mark

[mm123521]

Frankly I'd toss the new fin, free or not. With CR props the boat wants to run straight, hence the poor-low speed turning. At high speed you are relying on centrifugal force to push the transom out - plus your rudder appears to be on the small side, further hindering turning and the probable reason your rigger didn't like non-CR props. Since the old fin works and you could turn in a 60-foot diameter circle at 80 mph, put everything back the way it was - you're there.


.

The old turnfin actually was bent when I removed it , It was not stiff enough (1/16 stainless steel).
The new turnfin GREATLY improved the handling, it turns good at low speed and very good at high speed.
There may be a middle ground between the two turnfins.
The big turnfin is huge and thick, with a 90 degree roll -- it may be excessive.

I was reading on the internet that some people constructed turnfins out of tool steel in order to make them both rigid and thin.
Yesterday, I was looking at a $33, 4inch X 36 inch X 1/16 piece of O-1 tool steel AND I actually have a heat treat oven in my basement!

The boat turned so well with the new turnfin, I built a new rudder blade, 1/2 inch shorter than the one pictured.
Maybe a better plan is to build a longer rudder, and a smaller turnfin.

P.S.
I just got done thinning out the lower end of the turnfin.
In the process, I may have found some of the lost speed - the turnfin had a concave spot.
I know concave spots on running surfaces is a real speed killer.
I sanded both sides of the fin flat and parallel to the waterline -- bet that recovers some speed.

Put the struts back to neutral.
I would be out running, if there wasnt a lightning storm.

Mark

[Chris Harris]

Well if you do make your own you definitley want to copy the one that you found to work the best, just make it out of better mterial like you said. You can spend a huge
amount of time testing turnfin shapes and sizes to find the best design for your boat, so when you land on something that works
duplicate it if for nothing else use it for a spare.

Chris

[mm123521]

100_0263.jpgSUCCESS! -- HIT 83.9 MPH!!!!
Made a bunch of changes to the turnfin -- thinning, wedging it, and polishing -- that made a few MPH increase

Slotted the struts and raised the props .25 inch --- the hop is now GONE!
Biggest gain came from fine adjustment of the turnfin angle. 83.9 MPH puts me at about 14% slip -- I think there's a little more here - people are telling me 10% is obtainable.

This is all with 447 counter-rotating props and half discharged batteries (hit the sweet spot on the turnfin adjustment on the second half of the charge).
It will do head snapping turns at WOT. Handling is smooth and predictable.

Motors, and ESC's, come back cool -- not even warm. batteries are just a little warm.

Next step is a little more adjustment on the turn fin, as I have not seen the right sponson lift yet.
After that, the Prop Shop props should get me to 90 MPH.
I think there is a lot more speed available in this hull, but I'am gonna take small steps untill I get a little more practice driving at these speeds.

Will try for a video -- Sunday, our club has a race, so tomorrow there will be plenty of people to run the camera.

Thanks All for the advice, support and tips!

Mark

[Brushless55]

Killer man!
we cannot wait for the video of this sucker!!

[Grazacind]

Any new video of this beast.

[mm123521]

Andrew, & Brushless,

Finally got a video.

http://www.youtube.com/watch?v=iJWa2fwHaCs

Trying out a new turnfin for the first time.
Its running 70+ MPH in this video -- a little slow -- needs a little adjustment of the turnfin angle.

Turn up the volume and listen to the twin "whine" on the first pass.

Mark

[carlcisneros]

Very nice!!!!!!!!!!!!!!!!!!

[mm123521]

Carlcisneros ,

Thanks!


Mark