sport 40 blow over

[david cox]

I have an AC Sport 40 II that is running too light in the bow at full speed. This is what I have tried so far to prevent the boat from blowing over:

1) Lower strut

2) Angle prop thrust downward (although too much angle will make the boat "hop")

3) Move weight (tanks,batteries, etc) as far forward as possible, even added about 6 oz of weight to the bow.

4) Experiment with turn fin to make sure it is not causing the problem.

All of these items above have given a small improvement, but the boat is still too unstable at full speed. Here are 3 other experiments that I have thought about, but not yet tried:

1) try a lifting prop (maybe 1400 series) that will push the transom up and help give a negative angle of attack. I am currently using a X452 prop.

2) kick the rudder back slightly to also help lift the transom

3) modify the bottom of the hull somehow to try to reduce the amount of air that is being trapped under the hull.

Has anyone tried these suggestions? Anything else that I should try?

 

[Russell Bear]

The 1455/3 is a hot prop and would help. Last resort would be to add a small "spoiler" on the bottom. I think the prop will help.

 

[Duck899]

If you are running an X-452/2 then I can only assume you are using a 'torquey' engine? (CMB or Picco?). If so, the 1455/3 or even a 1455/2 would be a good prop to try. You may have to reduce the lift somewhat though.

I ran an octura X-646/3 on my older versions of the AC pro 40 with a K&B 7.5 in the early 1990's and then switched to Mac's. The Mac would really sing with that X-646/3 and, I don't recall ever blowing over in a race.

The older versions did have a different front sponson design though....and I think were a bit faster than Andy's newer versions.

 

[Jerry Wyss]

Never liked the 452, couldn't make it work wortha hoot. For lesser torque engine the 450 would be better, not many engines will turn the 1455 nowadays. I like the Prather 240 for medium torque engines,

and try sticking about 4oz of lead on the left sponson and give'r a try.

 

[Wesleys Custom Graphics]

I have an AC Sport 40 II that is running too light in the bow at full speed. This is what I have tried so far to prevent the boat from blowing over:

1) Lower strut

2) Angle prop thrust downward (although too much angle will make the boat "hop")

3) Move weight (tanks,batteries, etc) as far forward as possible, even added about 6 oz of weight to the bow.

4) Experiment with turn fin to make sure it is not causing the problem.

All of these items above have given a small improvement, but the boat is still too unstable at full speed. Here are 3 other experiments that I have thought about, but not yet tried:

1) try a lifting prop (maybe 1400 series) that will push the transom up and help give a negative angle of attack. I am currently using a X452 prop.

2) kick the rudder back slightly to also help lift the transom

3) modify the bottom of the hull somehow to try to reduce the amount of air that is being trapped under the hull.

Has anyone tried these suggestions? Anything else that I should try?

Strut depth is critical in a sport 40. 1/8" can mean the difference in a perfect boat and one that blows off evert time you throw it in the water. Set it too deep and it will "drag " the front sponsons so hard the motor will not get on the pipe. Just my 2 cents worth.

 

[user 115]

For what it's worth, I've run this boat with a geraghty modified, CMB CAM 45 motor and a 1455/3. The engine pulled the prop without any problems.. Strut depth is huge on this boat. If I remember right, bottom of the strut should be 1" from bottom of the boat.. I also believe the strut was flat.

Are you using the AC turn fin?

Thanks,

Charley

 

[Lay26]

david, i got my AC running much better this year since we raced last at elmira. few things i did, i change the Stock fin to a Blazer fin and i set the strut @ 1" to the center of the shaft hole, my stock cmb 45 is set up now with a parablic pipe@ 9.5". i can pull from 447/3 to 1455/3 but i love a special X450 that i have and also a 450/3 i'll see you in elmira at the next race, i wasn't able to make it last weekend.

 

[david cox]

Ron:

I am running a modified OPS disc engine with brown parabolic set at 9-5/8". I have never had much luck with 3 blade props on this boat, so I will give the 1455/2 prop a try.

Jerry:

The 4 oz of lead on the left sponson is a good suggestion, as the prop torque tends to lift this sponson.

Wesley:

Strut is set at 1-1/8" at the leading edge of the centre of the drive dog, to the bottom of the boat. I will try setting it about 1/8" deep to see what happens.

Charley:

My strut is no where near flat. Don't have my digital angle finder right now, but I bet its about 2 degrees. I am using turn fin from Rocket city- actually modified it slightly by reducing its depth a bit. Have a Dick Tyndal fin on order as I would like to try a different fin to see what happens.

Lay 26:

Hope to see you again at a race sometime!

 

[El Zorro]

David, email me at "[email protected]" please.

Dick Tyndall

 

[J_Moore]

Ron:

I am running a modified OPS disc engine with brown parabolic set at 9-5/8". I have never had much luck with 3 blade props on this boat, so I will give the 1455/2 prop a try.

Jerry:

The 4 oz of lead on the left sponson is a good suggestion, as the prop torque tends to lift this sponson.

Wesley:

Strut is set at 1-1/8" at the leading edge of the centre of the drive dog, to the bottom of the boat. I will try setting it about 1/8" deep to see what happens.

Charley:

My strut is no where near flat. Don't have my digital angle finder right now, but I bet its about 2 degrees. I am using turn fin from Rocket city- actually modified it slightly by reducing its depth a bit. Have a Dick Tyndal fin on order as I would like to try a different fin to see what happens.

Lay 26:

Hope to see you again at a race sometime!

Hey David

I would try about a brick or two on the nose of the boat and try to sink that peace of crap or the next time your at a race join in on the riggger burning and through that heap on the fire. Ohhh Ohh ohh that ring of fire.

 

[david cox]

Hi Jeff:

I think the brick is a little too light-maybe I will try an anvil!!!!!!!!!!!! Could I use your Crapshooter for kindling?

-David

 

[J_Moore]

Hi Jeff:

I think the brick is a little too light-maybe I will try an anvil!!!!!!!!!!!! Could I use your Crapshooter for kindling?

-David

Hell do something but save the motor. I'm kind of fond of it. C shooters already on fire. No need to relight a flame.

 

[Lay26]

david, i'll be at the next elmira race

 

[david cox]

Hi Folks:

I tried the 1455 prop this evening. Seemed to help prevent the boat from blowing over, however the left sponson was lifting badly. Didn't have a chance to play with strut depth or angle, and so I don't know if this will help. Will try to experiment with different setups next time. Boat had no problem turning the 1455 two blade.

Thanks, David

 

[Jerry Wyss]

Hi Folks:

I tried the 1455 prop this evening. Seemed to help prevent the boat from blowing over, however the left sponson was lifting badly. Didn't have a chance to play with strut depth or angle, and so I don't know if this will help. Will try to experiment with different setups next time. Boat had no problem turning the 1455 two blade.

Thanks, David

I have 5 1/2 oz of lead on left sponson of my PT SS45 to keep it down.

Mostly so I can correct steer "Left" now and then so it don't turn into a "flying tuna".

 

[Duck899]

Hi Folks:

I tried the 1455 prop this evening. Seemed to help prevent the boat from blowing over, however the left sponson was lifting badly. Didn't have a chance to play with strut depth or angle, and so I don't know if this will help. Will try to experiment with different setups next time. Boat had no problem turning the 1455 two blade.

Thanks, David

David....Have you checked if your turn-fin is straight? Parallel to the bottom? The ac boats are not dead straight on the backs of the sponsons where the turn fin mounts.....might be your problem....

 

[RaceCraftBearings]

David, I would suggest that you use pipe insulation for floatation and cut it the length of the boat from tip of sponson to transom. Put a tie wrap around the pipe insulation at the sponson tip end about an 1" or so from the end and insert 3 oz's of lead stick weight wrapped in duct tape behind the tie wrap, then tie wrap aft of the weight. Now install the insulation into the hull doing this for both sides. The weight will be as far forward as you can get it. Run the boat and see how it does. If its still flighty then add more if it looks nose heavy then take a little out until you get it they way you want it.

Ron

 

[rocketcity]

Hi Dave,

Give me a call at 407-913-0590 and I'll help answer some questions about the boat.

Regarding the turn fin.. If you notice the sponsons have multiple angles built into them. So you will need to shim the mounting bracket about .023" on one side. This is why the left sponson is lifting. You do not need any weight added to the boat if it is set up properly.

Brian Watts

Rocket City Racing

Hi Folks:

I tried the 1455 prop this evening. Seemed to help prevent the boat from blowing over, however the left sponson was lifting badly. Didn't have a chance to play with strut depth or angle, and so I don't know if this will help. Will try to experiment with different setups next time. Boat had no problem turning the 1455 two blade.

Thanks, David

David....Have you checked if your turn-fin is straight? Parallel to the bottom? The ac boats are not dead straight on the backs of the sponsons where the turn fin mounts.....might be your problem....

 

[david cox]

Duck899:

The turn fin is as straight and parallel as I can seem to get it. I have clamped a piece of 36" aluminum angle iron to the side of the fin to make sure it is parallel to the centre line of the hull. I check to see if it is parallel by removing the prop, and laying the boat on a flat surface that has a cut-out for the turn fin. I make sure the fin is parallel to the boat at it rests on the strut and bottom of the fron sponsons.

Ron:

Thanks for the suggestion of adding weight- I will consider giving it a try, I was hoping there was a way of setting up the hull without adding weight.

Brian:

I will give you a call about the fin. I have had to shim the fin in order to get it parallel as mentioned above.

Thanks again fellas for all of the suggestions so far!!!!!!!That is what I love about this forum!