torque roll
 

Is torque roll effected by prop set up or drive height? or a combo of both?

I would think drive depth and pitch would be major contributors .

Back in the early eighties I briefly ran around with a guy who had just taken delivery of the 1st factory Big block Donzi 18 , 370 horse thru a Trs.

You could lay that thing right up on the rub rail from 20 to 40 mph if you mashed the throttle hard enough, same with getting out of it too fast.

thats what im getting, have to give it a &^*& load of trim up for it to break loose and sit flat

I had a over powered 272 baja, ran a best of 99.5 gps, in my quest for speed I treid various props. At one point I tried a 5 blade maximus prop and boat would roll onto nits side everytime you leaned on throttle, It was 100% undrivable, I feel its prop more than anything, was fine with a 4 bladelabbed, did it a little with a std prop. My friend had one of those narrow 24 foot sunsations, he could only run 3 blades or boat tq rolled rel evil fwiw, Smitty

i think im to heavy for a 3 blade, my slip would be nuts but worth a shot. wonder if a prop with a ton of bow lift would mitigate it by getting the boat out of the water

I got one of them narrow 24 sunsations and can confirm a 4 blade makes it roll like hell. But a 3 blade blows out too easy for some reason.

So what is the solution to the torque roll it you have to run a 4 blade prop on a stepped hull single engine boat? Trimming up too high is not a good answer if you have to turn the boat:)

Ultraboy,

I have found that a touch of trim tab on the "downhill side" works to settle torque roll and chine walk when I'm leaning on the throttle.

Thanks. Brad.
(937)545-8991

are your tabs flat or do they follow the hull?

LTZCrew,

Assuming you're asking me....

My tabs are all but level with the bottom of the boat, only slightly elevated, while cruising. When I lean into the throttle, I don't think the tabs are really doing much, and it starts to chine walk above about 72-73MPH. I will tap a couple times on the left tab "bow down" button, just enough for the next indicator light to come on, and the chine walk goes away and the boat runs level, assuming passenger load is pretty evenly distributed. If I don't lift the left tab after coming back down to cruising speed, I notice the boat will lean to the right a bit until I do.

I am running a PQ 280, 496HO, M1 ProCharger, through a stock Bravo1 drive with a stock Bravo28 4B.

Thanks. Brad.
(937)545-8991

Check300's old boat (30' Checkmate) with Twin Turbo & north of 1,500 HP.
Ran a Left Hand Rotation #6 drive. (single)

Purposely set up this way to counter Torque Roll

Cougerman,

How would reversing direction counter torque roll in a single? Wouldn't it just reverse the torque roll? Genuinely curious.....

Thanks. Brad.
(937)545-8991

My understanding when shared .... was the engine was rolling opposite direction of the LH Rotation of the propeller for a neutral point.
(Or Counter it at Best)

Cougarman,

I don't mean to be argumentative, and if anybody wants to correct me, please do, but....

I don't think the rotation of the engine imparts any torque upon the boat except through the prop against the water... I guess I could see, MAYBE, SOME counter-torque during acceleration, but not while running.

I'm genuinely curious if anybody has any data to support this theory.

Thanks. Brad.
(937)545-8991

(I don't have a dog in this race, its just what was shared with me)

I will say Check300's boat ran extremely well for Silly Power Single Engine Boat

Cougarman,

Oh, I'm not doubting that. I know Kunkel's 300 CM ran 110-120 with a monster blower motor of some sort. I'm just curious about the counter-torque effect of running the prop LH. The physics don't seem to hold up.

Thanks. Brad.
(937)545-8991

https://cimg3.ibsrv.net/gimg/www.off...afbea6a388.jpg
https://cimg4.ibsrv.net/gimg/www.off...2e5d9990e9.jpg
https://cimg5.ibsrv.net/gimg/www.off...c04c43fe98.jpg

Prop was a Dennis Cavanaugh Special, Bret @ BBlades knows the particulars


BBLADES - A Tribute To Legendary Prop Designer Dennis Cavanaugh

Cougarman,

What a sweet set-up. That is awesome.

Thanks. Brad.
(937)545-8991

No Torque Roll :-)
Brains / Tom Earhart

Also the very First #6 Extension Box (Also Tom Earhart) Transmission is in the box.
Napkin Sketch for BAM Marine, which Contracted Stelling's to build it for Tom & Bill.

Now you know the rest of the story... on how Stelling's Extension back came to be...

Hell, my boat leans revving it in neutral. you have spinning inertial mass. if you swap the prop rotation, it counters it.

Try running an engine on an engine stand.

It will roll right over if it's not supported... so there are definitely "forces at play" inside the boat before the prop even touches water.

Phragle,

Mine does, too. I'd bet about any big block does. But, if you were to stay in it, it returns to level as soon as the acceleration was done.

Torque roll is prop torque, not engine torque. The engine it is inducing torque on the hull, but it's contained withing the hull, between the engine and the outdrive. The prop, however, is inducing torque on the hull, but it's doing so against the water, which is not contained within the mechanism.

I don't think the physics are there for the reasoning in question. I'm not denying the success in the set-up. Just doubting the methods credited to the success. I'm guessing there's more to the prop than it just being left-hand. I'm betting its sharper than a deli slicer on the leading edges.

Thanks. Brad.
(937)545-8991

Not uncommon for the racing teams with Twins to also run one of the Engines with Counter Rotation & Firing order too.
(At least in the past, not sure if still a practice especially if running factory M Power)

Cougarman,

Completely understandable, as those are opposing forces that can be utilized to an advantage. The last thing you'd want is for acceleration torque to be imparted on the hull when the throttles are dumped while the boat is clear of the water. You use any counteracting forces available when you can. But that's twins....

If it were as simple as rotating the prop opposite the engine to counter prop torque, what's keeping Merc from doing so in all their drive packages? Why isn't engine rotation translated into torque roll with a DuoProp drive, where actual prop torque is already countered? Watch a V-drive torque roll when they hammer the throttle; they already run the engine opposite the prop.

I know the single most effective work that can be done to a prop for a V-hull model boat is to sharpen and thin the leading edge to reduce the resistance the prop experiences as it is forced through the water. The second is to reduce the progression of pitch, but that opens an entirely difference can of worms, greatly affecting engine load respective to average effective pitch.

I'm convinced there's more to the story than, "We run a left-hand prop. Wasn't that easy....?" The key to enjoying the same benefits they gained is to understand what that "more" is, and it ain't in the low hanging fruit.

Thanks. Brad.
(937)545-8991

For years we were told we Turbo's didn't work in boats too, Then Mercury came to the table with Turbo's
Now they work

Cougarman,

OK.... And....?

Merc didn't reinvent the wheel. Turbos have always worked under the right conditions. The boats got large enough we don't expect them to come on plane very quickly, and we stand on them pretty hard to get them there. That's where turbos shine. That's also why we don't see turbos on Top Fuel engines. And we still have issues with the one problem with turbos that can't be easily mitigated: Heat. Larger boats have much larger engine compartments that can be exploited to dissipate vent the heat better. Besides....

What does that have to do with torque roll? The question was asked about what causes torque roll. The answer lies in the dynamics involved in the prop in the water. I just think there's more to it than just the rotation of the prop, and the questions and examples I posed support that. I'm hoping some physics guru will chime in and tell us yea or nay on the theory of it. I've got a buddy working on it who excelled in physics in high school and minored in it in college. He's pretty much the smartest guy in the room, whichever room he walks into. I'm hoping he can come up with a visual representation that explains it one way or the other.

I'm not doubting the success story here. The proof's in the pudding. But the recipe is usually a secret.

Thanks. Brad.
(937)545-8991

I am not a physics guru, but did talk to the Powerquest dealer at LOTO about the “torque roll”, or the likelihood of the single engine, single step (Powerquest) boat to lean towards the port side. His solution was to run a left-handed prop.

I also heard this is the solution on the 29 fountains with single engines.

My Powerquest 280 definitely leans to the port side even when there is a relatively equal weight distribution side to side.

good reads

that checkmate looks killer, super sweet sleeper!
i wonder if a turbo motor would exhibit less torque roll at lower loads due to less boost over a blower motor?

I tried a left hand prop. had read about fountain doing it and hoped that would be my fix. sadly it just leaned the other way. haha. i was thinking the same thing about drive rotation offsetting Eng. rotation. but no dice

i don't get any chine walk and i don't touch the tabs at speed - only use for sub 60's to off set loading and such. . they hit like letting a parachute out on anything faster.
thinking maybe some deeper single step V's just want a &^(( of trim?. going to try sending a prop out to add some bite to keep the slip down when its trimmed sky high or see if i can get my hands on a 29" 5 blade.

Turbo's do ok...

https://cimg5.ibsrv.net/gimg/www.off...d4c3180a40.jpg

LTZ,

This is pretty much the consensus from anybody I've spoken with who understands physics. The engine imparts torque against the hull, seen as twist in the frame of a drag car, for example, but not seen in a boat, since there is essentially no separation between the engine and outdrive, while the prop imparts torque against the water, which is the cause of our "torque roll". Running a LH prop will only impart that torque the other way, all other factors aside. Pretty much the only thing that will actually counter prop torque is an opposing force imparted against the water; a trim tab, for example, or hull work, like exaggerated strakes on one side. One could also reduce the amount of torque imparted to the water with prop work, such as sharpening, thinning, or pitch progression. I've also seen a few struts on model boat V-hulls that were machined so that the prop shaft was set on an angle relative to the direction of travel, but the strut body was straight, that was done specifically to counter prop torque. It seems to work. I don't know if this would prove effective, but it would be a LOT of work to test in our full-size boats. My guess is that there was a lot more done to the boat/drive/prop, that has not been divulged, that went into the success of the Checkmate in question. It wouldn't surprise me at all if they tossed out the "We run a left-handed prop" as a way of warding off any further questions, while keeping the remaining efforts close to their chests.

Thanks. Brad.
(937)545-8991

Ton's of Guru's on OSO if ya keep your ears on, then entire reason OSO was started was sharing.
Real Life Experience is usually your greatest teacher.

Cougarman,

Real life experiences led us all to believe that waxing the bottom of our boats made them faster. I can also remember hearing my dad and his friends discussing that conventional wisdom was that the deeper the outboard, the more stable the boat. Turns out, once the physics was explained, we'd been wrong all along. We often perceive what we are seeking in results that aren't there.

As I asked before.... Why are the V-drive guys still using a trim-plate to counter torque roll? They are already running their props opposite the engine. How is it the boats with duo-prop drives aren't slammed to one side, given that the prop torque is already mitigated by the counter rotating props, with the supposed torque imposed by the engine not mitigated? And how is it that Merc hasn't figured this "secret" out yet, given the uncountable hours they commit to R&D every year? The answer is that engine torque is absorbed within the mechanism, and not rendered by torque roll of the hull. The next question is, "How did Check300 ACTUALLY mitigate prop torque?" There are those who would like to know, and not have to waste a bunch of money on a new prop and drive work, only to find their boats leaning the other way.

I understand there are many great minds here on OSO. So far, the only reply here with any actual first-hand real-world empirical evidence, guru or not, has stated the only effect of running a LH prop on a single engine boat was that the boat prop rolled the other way.

Thanks. Brad.
(937)545-8991