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Buddy Benedict

Buddy Benedict

Well-Known Member
Joined
Feb 3, 2004
Messages
537
A friend and I were discussing this today so I thought I would ask everybody here. I am building a scale that has an offset engine bay. Should the strut be centered in the engine bay and not in the center of the air trap OR center the strut in the air trap and be in the center of the ride surfaces of the sponsons?

What do you think?

Buddy
 
How much is the engine well offset to the inside? (right) If only 1/2 inch I would just run it down the center of the engine well, so the shaft wont have big bends in it.
 
The offset is an inch and right now I have the strut in the center of the boat and have a "S" bend in the drive line.

Buddy
 
I also offset my strut to the left but set it at 1deg angle to port as well. (Sport and scale boats only).. well for the most part.

What I have found is that with this setup and the right amount of weight over the left sponson the offset and angle help control torque as well as drive the boat through the corner. I have also found that the boat has a tendency to pivot more easily on the fin and has more aggressive cornering control.

The two VERY BEST full body hydros I have ever drove have both had offset struts with 1deg angle to port.

Grim
 
I think you are dealing with two different issues with strut and engine offset. Offsetting the engine to the left and putting weight in the left sponson helps counteract rolling from the engine's torque. Offsetting the strut to the right gives asymmetrical thrust that counteracts the boat's tendency to turn right from the paddle wheel effect of the prop. This can also be done by angling the strut. The question is what results in the most thrust and the least drag. Joerg's 140 mph hydro used strut offset. Our 110 mph hydro used a lot of strut angle. I've seen a study that showed that a small strut angle with a surface piercing prop directs the thrust along the axis of the boat, giving more thrust. The only thing I can say is that correcting with rudder angle creates more drag than the other methods.

Lohring Miller
 
I had a hull once I bought from someone else that had a left offset tub. Left as if looking at it from the transom. The strut was center of the tub rather than center of the hull or airtrap. It was I think almost 1/2 to 5/8 off center of the hull. I always had to do all kinds of trim to get it to run right. Finally I got pissed and cut the stuffing tube out and reset it center of the trap and made a custom motor mount to bring the motor more in line with the strut. With one sweeping bend rather than an S it fixed a lot of issues. Then it was just all about balancing out the boat laterally to fix the weight issue of having the tub and cowl the opposite side from the way we race. I've seen people make it work offset to the left but it seems to bleed HP with having to do all kinds of tricks to make it work. Just my 2 cents.
 
Mike.. I have had some boats that are harder to set hardware under then others as well..

For me its all about lap times and not boat speed. I could give a rats hinder less about SAW speed.. Unless the boat is just completely off in speed its just not something I hunt for..

Not everybody is as driven as I am to get lower lap times.. some just get off on seeing her SCREAM down the straights!! .. heck that’s fun too.. YE-HAW

Its really hard to turn screaming SAW speed into lower laps times.. I guess my point is I have had MUCH better luck lower lap times with the strut offset and angled... just me maybe and the way I drive.. all willie-nilley..lol

Grim
 
I am building an 82 Dumas Atlas Van Lines. Would I be better off centering my strut under the hull or using the offset in their plans ? If looking at the transom it shows a 1/4" offset to the right.
 
mark couty said:
I am building an 82 Dumas Atlas Van Lines. Would I be better off centering my strut under the hull or using the offset in their plans ? If looking at the transom it shows a 1/4" offset to the right.
Click to expand...
Grim you are on the money That is how it works!!! Doug
 
Grimracer said:
Mike.. I have had some boats that are harder to set hardware under then others as well..

For me its all about lap times and not boat speed. I could give a rats hinder less about SAW speed.. Unless the boat is just completely off in speed its just not something I hunt for..

Not everybody is as driven as I am to get lower lap times.. some just get off on seeing her SCREAM down the straights!! .. heck that's fun too.. YE-HAW

Its really hard to turn screaming SAW speed into lower laps times.. I guess my point is I have had MUCH better luck lower lap times with the strut offset and angled... just me maybe and the way I drive.. all willie-nilley..lol

Grim
Click to expand...
uh..races are won in the turns..

:p
 
Grimracer said:
Mike.. I have had some boats that are harder to set hardware under then others as well..

For me its all about lap times and not boat speed. I could give a rats hinder less about SAW speed.. Unless the boat is just completely off in speed its just not something I hunt for..

Not everybody is as driven as I am to get lower lap times.. some just get off on seeing her SCREAM down the straights!! .. heck that’s fun too.. YE-HAW

Its really hard to turn screaming SAW speed into lower laps times.. I guess my point is I have had MUCH better luck lower lap times with the strut offset and angled... just me maybe and the way I drive.. all willie-nilley..lol

Grim
Click to expand...
Oh I'm with you on lap times. I had to fix this boat just so it would turn better and track down the straights without fighting itself. I ended up changing all the hardware and it not only turned better but it would go almost exactly straight even if you took your hand off the wheel. It do have angle in the strut but ever so slight.
 
Yea Mike.. its amazing how little it can take to upset one of these animals.

I had a boat once that would loose the rudder in the corners.. i went over that rudder with a fine tooth comb and never really got it to work well.. Just for grins .. I put on the same kind.. SHORTER.. and BINGO.. lol

To this day I have not gotten that one figured out..

ROCKET AND ROLL!

Grim
 
For what its worth,

My PICO hull, may she RIP, had the driveline/strut down the center of the engine well and it was offset.

You guys know how she ran. you be the judge. She was a US-1 winner

Its all about the corners!!

Brian
 
Brian Schymik said:
For what its worth,

My PICO hull, may she RIP, had the driveline/strut down the center of the engine well and it was offset.

You guys know how she ran. you be the judge. She was a US-1 winner

Its all about the corners!!

Brian
Click to expand...
Maybe I need to work the retrieve boat this spring and start looking under some of those scale boats. NAh just need to scrub those bouys eh Chuckie!!
 

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