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?

I haven't seen the bill for that exact part yet :hitfan:

The boat turns like it's on rails. Did a few pretty high speed, very tight turns. Buddy that owns a 30 American Offshore cat commented, "I miss how sharp Vee's turn" :D I saw only benifit to the wings and ZERO negative attributes.

I might be interested in trying those next season. I'm really disappointed at how bad my tiger porpoises. Raising the drives even 1-2 notches can cause it so you end up running with the drives BURIED way too often. I just don't find a comfortable, low-drag cruise speed like I used to be able to on my Cafe. At least on my Cafe you could pull the drives out 5-6 notches and gain a lot of speed, then if it porpoises the smallest drop on the drives cured it. I don't know - I just find myself praying for 1-2' waves.....

Is your tiger an SSM boat or bravo boat?

I can tell you, from my experience Tigers are SUPER sensitive to bow weight. Even and anchor up in the bow can cause major porpoise. If you are storing anything heavy you front pull it out of there.

**** - I forgot to try that theory out on my last run. I've got a ton of crap up there - beach chairs, umbrellas, a huge box fan, etc..... There is probably 200 of stuff up there (no exaggeration). It was all up there when I bought it. I've got to remember that next season.....

I wonder how they would work on a 28 Pantera with Trs drives.

That’ll do it! We dumped a buddies #6 Tiger in Miami and ran to key west. Put our luggage way up front, holy cr*p! Could get the boat to stop hopping without dragging a lot of tab. Pulled the luggage back, problem solved. Put a big anchor and bunch of chain in the very forward storage of our gun a few years back and same thing, hopped all over. And that was a 3A boat. It’s exaggerated with bravo boats because straight bottom cigs CG was designed for transmission, not to have the motors so far back. But weight in the bow will mess with either.

turn in and it will carry the bow

i watched a max WORX YouTube video

$289-389 each


can you comment how much it helped with the top gun porpoise? Ours is bad..to the point where we have to drag a ton of tab. So much that it looks like we have a rooster tail.

it sucks sacrificing so much speed to keep the nose down. If we gradually let off the tab can feel the nose rise and speed pick way up. It’s like dragging a parachute.

I know not a Cigarette but I might try these on my Formula. I've battled porpoise issues since I've had the boat. I'm sure that I need to remove some weight from the bow too (tools, floats, etc). I'm shaving a lot of weight off the stern this off-season and hoping I won't be making it worse.

Has anybody done a back to back run with and without those plates to see if they scrub speed?

They don`t make em for SSM drive so i`ll have to make my own and give it a shot

I didn't run these on our Gun. We had 3As and transmissions so the porpoise wasn't as bad as a bravo boat. I'd run just a hair down on tab and kick the drives out a bit (not a lot) and that was the sweet spot I was referring to above.

If you're trimming the drives up to show a rooster, there's something wrong. The CG is off. Again, are you carrying weight up in the bow? Trimming the drives out that much is HORRIBLE for them. Super hard on the gears.

I'm still working out speeds on the Cafe. Gotta try a couple different props so I don't know if they scrubbed any speed. But if I had to guess I'd say no. They are horizontal to the running surface so no down drag from them. I don't see how they would reduce speed.

Did you ask if they would / could? They have all the machine parts to do it. I guess all they'd really need to get it done is a #3 / #5 drive to line up the measurements to machine them. I'd be really interested to see how they work on a 3 or 5. I bet it would make a huge difference. Look at #6's and that LOOOONG cav plate. Same affect.

let me clarify. The rooster tail is not from the drives...it’s from the tabs!!!! HAHAHAHAHA

:lolhit:

Ah! HAHAHA. Good!

Still, you shouldn't have to run THAT much tab.

Tank , they said not enough interest. Well I`m interested .

Jeez. I wouldn't think it would be that big of a deal to cut and fab up a couple pieces. I bet you take the pics of them to any fabricator you can get it done. Shoot, Dave (riverdave) in the video above is a machinist by trade and has all the means to do it. Get ahold of him. I'd bet he'd make a couple.

Ya, they`re already making them, I guess the 30 minutes to change the dimensions is just too much to ask. No problem, other places will take my money . They have enough I guess.

There are a number of products made that resemble that drive trim plate. I used them on a twin engine C.C. for years to reduce porpoise. This isn't anything new, they basically lift the stern and help hold the bow down.
They're all variations of this
https://www.basspro.com/shop/en/se-s...B&gclsrc=aw.ds

Oh, for sure. As Curt said they were always called "Whales Tails" when I was a kid using them on outboards. But kind've different to see on a large performance boat. And I'm very interested to see what it would do to a SSM 3 or 5. Don't think it would matter on a 6 because of the large cavitation plate they already have.

I spoke to them a little while ago,about one for a Trs he’s not sure he’s going to check and get back to me.

Looks like Imco has a bravo cav plate available for much less $150.

So, even though my TG was a #6 boat, I've got a bunch of seat time in Bravo TG's. The only time that any of them have porpoised (sp) was when too much trim was being run for the speed that the boat was going. They just don't like trim under 50 mph or so..... Just my 2 cents! ;)

Just loaded this video from a couple weeks ago. Running in the river. This is zero tab down. Drives kicked out a bit (like to 5 on the heads up indicators). Runs flat.

Video is private...

Fixed

She used to run hoppy:




Now she runs happy :


2" spacer and lowered boxes an extra inch.

3" below bottom now, she seems to like it deep

:479:

Dan, my boat had aluminum Cav plates on it when I bought it. They eventually broke, was a noticeable difference getting on plane without them. Had some SS plates made up & had them made about 2 inches longer, big difference. Just a straight plate makes a nice difference. Plus it's nice covering up the top of the props, getting in & out of the boat. On your drives don't the props come up past the lower into the front of the upper?

https://cimg2.ibsrv.net/gimg/www.off...ed2001ad57.jpg


Ya , Can`t attach to cav plate ...I would have to make a plate that fits between the lower and upper. That means machining the grooves for the o rings. Dammit

Are those 5's? I've never noticed the props com up above like that.