Porpoise and prop rotation?
 

Has anybody noticed a difference in the porpoise on a straight bottom top gun depending on if the props were turning in or out? Thanks for any info.

Tank on here, used wings or sometimes called whale tails, by max machine works, that mount on drives. Seems they worked well on his cafe. He might chime in. Might be worth trying, assuming you have a bravo boat.

I had a 89 Cafe with TRS drives. When I switched the drives to spin in it helped some of the problem of porpoising

Well I have a 38 straight bottom. Last 10' of bottom of boat has been blueprinted . With 3A's on transom spinning out it porpoised between 35 and 60, with four blade wheels. The previous owner indicated that with five blade wheels it took allot of the porpoising out. Went to 5 drives on transom spinning in, with four blade wheels. Still porpoises between 35 and 55, but less aggressively. Added cup to all wheels. I am thinking it is going to porpoise. Below 60 I run tabs 1 click below parallel to bottom.

Every straight bottom cigarette I’ve ever been on (and there’s been a lot) has porpoised. Straight bottom boats in general porpoise in calm water. That’s all there is to it. Our gun with 3a’s porpoised, our cafe will porpoise. Theres a a sweet spot in straight cigs whether it’s a 35, 38 or 42 where you drag a hair of tab and kick the drives out just far enough, and you’ll feel the boats transom lift up run flat and let go. With that said, I’ve always tuned props out. Props in brings the bow up and causes poor docking manners that I never wanted to deal with to get 1 or 2 MPH.

I will say this, as Curt pointed out, Max Machine Works put wings on my bravo drives at Barrett’s request. When I first saw them I was like WTF? I have now just gotten back from running the boat for past 12 days and holy crap! The difference is insane. Our cafe is a non notched bravo / XR boat. The props are 26’s 4 blades but it’s under propped right now. Gonna try some 5 blades and 4 blade 28’s and see what it does.

as it is, I can put the tabs all the way up, drives in and the boat pops right up on plane effortlessly. Then I can either run neutral tab or tabs up and kick the drives out and the boat runs flat! I couldn’t believe the difference. It’s crazy.

i haven’t been able to run it in big water in the ocean yet but am looking forward to seeing how it will run there. It was windy as sh!t a couple days and threw some white caps and same driving manners. It was also dead flat several times and again flat and smooth no tabs.


https://cimg6.ibsrv.net/gimg/www.off...d7cbc4801.jpeg
https://cimg9.ibsrv.net/gimg/www.off...7c8b3eb4b.jpeg

Those things are cool Tank !
Is that something they sell? for SSM drives?

I did not like how my boat handled with drives spinning in.. drove like a school bus. Didn`t run it long enough to pay attention to porpoise.

My porpoise was helped by the "wedge" I put in the hull , basically a hook, that helped quote a bit

Few weeks ago I tried a set of ROLLA 5 blades . 18x26 These things got me on plane at 2500rpm like a bass boat , I was blown away. They grabbed so hard (would die) during docking the motors needed a different tune.
The made the boat fly straight as an arrow, cut thru waves and handle like it never has before. I was amazed how nice it ran . trim hardly did anything .. I could trim to 8 and still no porpoise at any speed.

I had em scanned and the cup was thru the roof. I think it just carries the bow easily due to the cupping.
Taking into account the cup the real pitch was closer to 32ish .
Rolla makes props geared towards diesels with high TQ , these things are THICK. (so they will never be a fast prop)

Now the bad , they loaded the engines quite a bit and I could only get 4500@75mph (WOT) also hard on drives.
The engines and drives did not like them.

but the boat rides like a dream with them on .. so I had FJ do some work on em . They look fantastic but there was no difference in rpm even with smaller pulleys and more boost.
The issue FJ believes, is that in the meantime I put in 2" spacers
So I`ll take the spacers out and try again.

Long story short , (too late) I think prop selection is key to how the boat handles.


FJ in LOTO made em look real pretty .




https://cimg6.ibsrv.net/gimg/www.off...5b8920c72c.jpg

turning in om my 42 tiger made all the diff in the world, docking is easy once you know what to do, just need a little more throttle. i carries the bow much better... i think its all personal preference. as ive said before, every boat will have a porpoise at some point, its just physics.

Dayum! Those are pretty!

Yes, they machine them and sell them. I would imagine they could do something for a SSM. Give 'em a call say you saw the ones on the Cafe Barrett did and want some more info. They'll know what you're talking about.

https://www.maxmachineworx.com/

I’m currently running 26p 4 blade props on bravo xr’s spinning in. I’m slowly learning the backing characteristics with them spinning in. I was hoping there was a sure fire way to take some porpoise out. Other than that I like how the boat handles and performs. Although like everybody I’m chasing that last mph. In the spring I’ll probably try them spinning out and see how it acts.

Tank were they very expensive and how are they when turning?