JaayTeee

With all the dinkin I've done
with switching prop rotation
on different boats, the best I've
seen is a little over 1 MPH.
And like Gary said, they handle
like crap around the dock,
( reverse seems less effective)
So, IMO, the 1 MPH or less,
isn't worth the pain and suffering
of poor docking maneuverability

my .02
jt

Gary Anderson

OK, here's the theory as I understand it.
Turning in digs the stern in deeper, raising the bow.
Less trim is therefore needed to raise the bow.
Higher X dimensions can then be used = faster.
Digging the stern in deeper can result in more wetted area = slower. Especially at lower speeds, and possibly at cruise speed.
UNLESS, you have A LOT of hp to get the whole boat out of the water.
OR, you are running a box to move the center of gravity and bouyancy back more resulting in less wetted area.
Anyone buy that?
BTW, I do know a 38 Top Gun, no steps, that got about 5 mph top end turning in. But he's running Vs, boxes, and a pair of 950s.
Gary

JaayTeee

Gary,
I 'm with you on the "dig" theory.

What do you think causes the
poor docking maneuverability ???,
It seems to me, that whichever
drive is in reverse, has very little
thrust.

Is it the thrust being pushed
upward towards the transom,
( Keel side of drives)
the thrust of the inside swing
is the prop being, basically
cancelled out.

Do you buy that theory ???

jt

RMPRam

I have a 1984 Cigarette 38' flat deck, with twin 1100hp. PSI supercharged engines. I notched the transom 12" and have # 5 SSM drives on Stelling's box's.
Up until this summer I had the drives turing out. I talked to Tres Martin about the mid-range porpoising that I was having. He suggested 1) Turn the drive in 2) run 5 bbl props 3) put a "wedge" at the back of the lifting strakes 16" long and .125" high at the transom.
I turned the drives in, and spent $2500 getting the whole bottom " true'd " and the wedges glassed in. I havn't gone to 5 bbl. props yet, still running my 17.5x31 4bbl. props.
I put the boat in the h2o 3 days ago and it seems to porpoise worse than before. I'm going to play with drive height, as the bullet is now 1/2" above the bottom and I have 1" & 2" spacers that I can try.
The boat ran 101 mph on GPS, turning the drives in, before all these modifications, with 3" of spacers in ea. drive and 260 gal. of fuel on board, and the 950hp. pulleys on the blowers. I have 2 sets of upper pulleys that I can change to, to raise the boost aka. hp.
The boat has a full interior and is not a " cover-girl" Cigarette. If anyone has any suggestions- I'm open to listen and try.
I'm also running the 380 trim tabs, which will take out the porpoising, but wastes energy. If tucking the drives in and using the tabs is the only way to get rid of the mid-range porpoising- so be it.
Top end is fine, as the boat rides bow up at anything over 60-70 mph.

JaayTeee

G.K.,
I take it you haven't ran it with the
drives turning out, since the bottom
work ??
Might be worth a try,
That should add back some stern lift.

jt