turn fin tuning

[Diesel6401]

Diesel here is the post I saw on the rigger, the data was logged by Eagle tree system



http://www.rumrunnerracing.com/fefor...&highlight=JAE

Sweet, cool info

[Diesel6401]

yep and they all bend under hard cornering. in my opinion they flex to much to give precise cornering.

Tim you could add some bracing like in this pic, and attach it to the side of the hull.

I dont hit the turns that hard. Don't race, normally runs fast straights and soft turns, I'm sure even though I'm letting off the throttle a lot in the turns theirs some flexing going on.

[rc_speed]

I did some research (google is a wonderful thing).

let's assume the boat is going 40mph around the corner.
The Namba nationals shows the radius of the corner to be 35 ft.
So we will assume we are all expert drivers and take the inside line at a constant radius.

40mph = 58.666 ft/sec
A (lateral acceleration) = v(velocity)^2/r(radius) = (58.666^2)/35 = 98.333ft/sec

g-forces = A/gravity = 98.333/32 = 3.07 g's

a boat going 45mph around this same corner will generate 3.89g's
a boat going 50mph will be at 4.8g's

now this is all based on running a smooth line. If a boat turns sharper around one of the corners, the g forces will go up. For instance, the boat has to make a sudden turn to avoid another boat. If you are going 40mph and turn a corner that has a 15ft radius, you would generate 7 g's.
what if you are running a boat with a hotter motor than the stock UL-1 and are going 50mph and need to make the sudden jog to avoid that idiot that flipped in front of you? (NOTE: it is always the other guy who is the idiot. Me/you the driver never makes any mistakes. LOL) You will generate 11.2 g's of force on the boat.


I hope this makes sense. It sounds about right. It has been a LONG time since I have had to deal with this type of physics.

tim

[Capt. Crash]

I don't see the issue here?

I run the stock, old, thinner fin, hammer all the way down, through the turns and one of the turns is a hairpin 180. I have never had a bent fin or even flipped my boat in a turn. This is entering the corners at 50mph never letting off. It hugs the water like an ole time slot car. It's the same with all the UL-1's I've seen at my pond. The only issue is after a turtle strike and having to reset the fin and resharpen the leading edge if it gets messed up.

Why the need for another fin? I'm I missing something?

[rc_speed]

I don't like the thought that the turn fin is flexing while I am cornering. It is a personal thing for me. The boat runs fine in stock form, though.

The other thing for me is that I am thinking of using a hotter motor to run in the P-mono class. This would make the boat faster and thus more g's on the turn fin. I don't want to lose a race because the turn fin bends and changes the handling. I am trying to prevent a problem before it actually becomes a problem.

[Diesel6401]

I just want to try the straight fin out and compare to the stock in my 7xl set-up, I am having a hard time keeping the front in the water. I think the straight may also help with chine walk in my set-up. Just testing and seeing whats better. So far my best luck has been strut 1" l40x57 prop and strut neutral. Still wants to get airborne. If straight fin doesnt work Ill try a airdam. I like testing new things, but if I dont make in progress with this boat I will dump the 7xl set-up and attempt a ammo 2300.

[longballlumber]

If he doesnt take it I will. I want to try it on my 7xl setup.

Sorry, rc_speed got it.

Thanks
Mike

[Diesel6401]

Sorry, rc_speed got it.

Thanks
Mike

Cool no prob, good pick up RC_Speed.

[detox]

Just testing and seeing whats better. So far my best luck has been strut 1" l40x57 prop and strut neutral.

Lowering your strut to 1 1/8" or 1 3/16" will help your UL-1 run tighter. Neutral is not the way to go. Strut needs to be tilted downward in the back roughly 2 degrees. Simply lowering strut will achieve that angle because of the stiff 1/4" stuffing tube. Grimracer turnfin is a verygood fin and if tilted correctly will reduce chine walk. Please read your UL-1 manual.

PS...adding a little more weight to bow will also help.


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[Diesel6401]

Lowering your strut to 1 1/8" or 1 3/16" will help your UL-1 run tighter. Neutral is not the way to go. Strut needs to be tilted downward in the back roughly 2 degrees. Simply lowering strut will achieve that angle because of the stiff 1/4" stuffing tube. Grimracer turnfin is a verygood fin and if tilted correctly will reduce chine walk. Please read your UL-1 manual.

PS...adding a little more weight to bow will also help.


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Yea I have played with different turnfin adjustemnt (straight up & down, swepted), I didnt like how it ran swept and up & down seem like too much lift. I will add a little down tilt on the strut, that will prob bring the front end down enough to stop the occasional blow over. Splayed battery config I like, chine walk is a lot better that way, I could do your aoa mod detox but for now I'm going to keep playing around with the spayed batts. I'll keep testing away, all part of the fun (manual is in my bathroom, so it gets read A LOT )

[Jeepers]

Lowering your strut to 1 1/8" or 1 3/16" will help your UL-1 run tighter. Neutral is not the way to go. Strut needs to be tilted downward in the back roughly 2 degrees. Simply lowering strut will achieve that angle because of the stiff 1/4" stuffing tube. Grimracer turnfin is a verygood fin and if tilted correctly will reduce chine walk. Please read your UL-1 manual.

PS...adding a little more weight to bow will also help.


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Don't forget he is using a much hotter motor than the stock UL1 (7XL).

[Jeepers]

Grimracer turnfin is a verygood fin,
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it is a good design just to soft,

I bent one going hard into a corner, hammer down hard right rudder, bent the fin 90 degrees to the hull, couldn't even get the boat back in it would just go in circles. I am not the only one in our club that has done this. most of us now make our own.

[ncornacchi]

I run the Kintec straight fin on the UL, swept all the way up....Runs like a charm, got less lift than the stock one....Diesel, got 57mph on my 7XL this week (M445), looking to move up to the M447, and will really push the limits to a M645.....Lots of power, finally got it trimmed in nice.....strut is at 7/8".....Norm

[Diesel6401]

I run the Kintec straight fin on the UL, swept all the way up....Runs like a charm, got less lift than the stock one....Diesel, got 57mph on my 7XL this week (M445), looking to move up to the M447, and will really push the limits to a M645.....Lots of power, finally got it trimmed in nice.....strut is at 7/8".....Norm

cool, good info buddy

[detox]

I have never folded my UL1 turnfin. Maybe some batches were made using softer aluminum.

With L40 x 57 prop do not be afraid to go deeper on the strut. I went deep using my Nue1515 1y combo. Larger props may need shallower strut setting


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