rigger pulling to the right ?

[speakerboy]

I am running the twister hydro for a couple of months now . its a Gas motor powered hydro and the speed is going up .. after i passed the 75 mph limit i found that the rigger is staring to pull to the right a bit . now in full speed passes at 82till 85 mph its very difficult to keep it straight . i have been reading a lot on Jims and on IW and i have read some like "your not going fast enough if your rigger isnt pulling to the right " ... good statment , but here i am with a rigger that is pulling .. good thing is i can make 80 mph turns in oval racing without any problem .. bad thing is .. a small correction to the left with speed higher than 70 mph is deadly , it will blow off real easy .

some setup hints .

i run a razor sharp rudder blade on the right side of the boat .

i run a razor sharp prop .

all edges of the tub and sponsons are sharp .

i have a virginia crafman turnfin ..

the turnfin is stock . i didnt touched it .. it looks pretty scharp in stock form , but not like a knife ore so ..

could it be that i have to sharpen te turnfin ?

is the speed in a level that i have to find a shorter thinner turnfin (built for saw ) .. ?

Jeroen

 

[steve wood]

try shimming the right side of the strut bracket,1/2 mm or so, which will put some angle in the strut. we do this on our 67/80 crapshooters to help the pulling to the right. make sure you have enough servo power, also and use 5 cell packs

 

[Preston_Hall]

The feathered edge on the TF will cause it to pull some. CMD uses something like a 45 degree angle on the LE of the TF. That seems to solve the problem, however, I found it to be slower than a feathered (blended) edge. So I would leave that alone but I thought I would throw it out there.

Try decreasing the angle of attack on the left sponson. Or increase the AOA on the right.

 

[Matthew Hughes]

First there is no hydro that will turn left at high speed. So stop turning left. I don't remember anyone putting left turns out on the course anyway...... The back of the boat is being lifted and moved to the left everytime the prop goes around. You can shim the strut. You can also shim the turn fin. Both with effect how the boat tracks when going slower. By adjusting it to track straight at high speed it will be easier to drive and helps with your over turning the corner. At slower speeds you will have to drive the boat because it does not track straight. This is much easier to do at those speeds. Oh yeah did I mention stop turning left!!!! Unless you have a boat go dead right in front of you. At full song my 90 rigger will stop within 10' or so after I give it hard left. Saved mine and others boat twice. Works great.

Mike

PS If you have one of those fancy computer radios, you could mix the steering with the throtle. Giving you some left rudder input at full throtle and none at 3/4.

 

[Kelly Miller]

Jeroen, I was looking at the photos of the boat on the other thread. What is the sponson offset measurement. It looks in the picture like the right sponson is farther from the tub than the left. Great looking boat.

Kelly

 

[Nigtmare]

Try to run 1/16" toe in on the right sponson

Nick

 

[dr gary turner]

Put a shim under the left back boom tube. Start with 1/32". GTT

 

[Buckshot]

I am running the twister hydro for a couple of months now . its a Gas motor powered hydro and the speed is going up .. after i passed the 75 mph limit i found that the rigger is staring to pull to the right a bit . now in full speed passes at 82till 85 mph its very difficult to keep it straight . i have been reading a lot on Jims and on IW and i have read some like "your not going fast enough if your rigger isnt pulling to the right " ... good statment , but here i am with a rigger that is pulling .. good thing is i can make 80 mph turns in oval racing without any problem .. bad thing is .. a small correction to the left with speed higher than 70 mph is deadly , it will blow off real easy .
some setup hints .

i run a razor sharp rudder blade on the right side of the boat .

i run a razor sharp prop .

all edges of the tub and sponsons are sharp .

i have a virginia crafman turnfin ..

the turnfin is stock . i didnt touched it .. it looks pretty scharp in stock form , but not like a knife ore so ..

could it be that i have to sharpen te turnfin ?

is the speed in a level that i have to find a shorter thinner turnfin (built for saw ) .. ?

Jeroen

Hello Jeroen,

I had a similar issue with my twin earlier this year. It would pull hard right after reaching speeds anywhere over 85mph. I did some asking around on here and I then I got an answer from A. Brown. I had tried shimming the struts and this did help the problem but then I started to have hooking issues exiting the corners at high speeds. I was told to square up the struts with the transom, run a little deeper rudder blade, Flatten out the strut angle, and add some AOA to the right front sponson. All of this is of course along with the "standard" rigger set up of sharp edges, straight lines, ect.

Mr. Hall has a good point about the CMDi style turn fin and I think that it would be better suited to your application.

Please PM if you have any question.

Regards,

-Buck-

 

[speakerboy]

Guys , thank you for replying , realy appriciated , there are some good tips and tricks here ..

Steve, i can shimm the strutt , i do run 5 cells pack and i have a massive strong servo , so this is an option .. thanx

Preston , i think i understand what you mean .. i do have the A.brown turnfin here , but by the looks i liked the Virginia crafman much better and started with that one . i am thinking on rising the AOA a bit .. i will come back about that later .. thanx

Mike .. i must have wrote that down with other intentions . i am not steering left to make a turn .. i only steer a tiny to the left to make a small correction , for example : making a turn and go in the straight after bouy 3 .. what i do is let the boat go wide by it self and becouse the boat turns right a little by it self i ended up at bouy 4 perfectly . the water is wide behind the oval couse so no problem there . now making the turn from bouy 4 to bouy 6 .. no problem there but getting out of the turn right at bouy 6 i have to head straight to bouy 1 . the water here is narrow to the shoreline becouse the oval is close to the shoreline .. i can't let it run wide at bouy 6 so i will never reach bouy 1 without making a correction to the left ! and there you have it , i have to steer a bit to the left . at 80 mph you dont want that .. just a tiny to much and the boat is in a majure water splash ... ended up like driftwood ....

i do have sucha fancy radio so i will play with that ! thanx for your answer .

Kelly thanx for the good eye .. i will show the details below ..

Nick ..if i toe in the right sponson , i will change the angle of the turnfin aswell ? thats what you want ? so the boat might track more straight ? does make sense. but what are the side effects ?

Gary , that will make my AOA on the left sponson more flat right ?

Buck , i do run a flat strutt (bottom) i also have a sharp strut leading and trailing edge , why do you think the A brown turnfin will work better ?

some more info ... i have pics of the rigger at : jeroentune find "my boats " and scroll down for the pics of the rigger ..

i did some messurments of the sponsons to the tub to make sure what we are talking about :

front left sponsons boom to the tub is : 5 1/4 inch

rear left sponons boom to the tub is : 5 5/16 inch !

front right sponsons boom to the tub is : 5 11/32 inch

rear right sponsons boom to the tub is : 5 5/16 inch

messured that . i must say that Kelly has great eyes .. ! conclusion is that my left sponon has a to in from 1/16 inch , and my right sponson has a toe OUT , a very small one but its a toe out !

the AOA on both sponsons is 3 1/2 degrees . i dont have any water comming from the sponsons in top speed .. i do see somewater spray at the front of the rear sponsons .

again i like this turnfin in oval racing it hold amazing and i can make full speed turns , with a 13 pound boat at 80 mph .. i find that impressive ! i will see if it need some sharpning .

i dont eant to do some more angle of attack on the sponons ..i have a pair of new ones comming with a AOA af 6 degrees .. just to test ..

so whats the best to do with the sponsons ?

Jeroen

 

[Nigtmare]

Jeroen, that's exactly what the 1/16 " will do. It will put the turn fin angled a bit and it will track the boat to the left, with no other effects. By the sounds of it, your toe out on the right and toe in on the left. So i would say that's where your problem is. Make your left parallel to the tub and give 1/16 " toe in on the right . Or even try making both parallel with a little less AOA on the left backside.

 

[Matthew Hughes]

Yeah gotta get the fin at least parallel with the boat. You might want to check to make sure it is not bent also. That 1/16 does not sound like a lot but it will put the fin out by .5 degree or so. This at speed with the prop walk will cause problems. I would go with a little toe in to start with.

Mike

 

[speakerboy]

Guys , thanx so much for your comments ..

i will change the Toe in on the left sponson to parralel , and change the right sponson from Toe out a Toe in with 1/16 inch ..

than i will test again ...

Jeroen

 

[Tom v.d Brink]

Jeroen,

could have just called me but anyway,

steering left without throttling down is a real no-no with any rigger as has been said before.

turnfin is as said before angled on outside only at 45degree sharp edge. (sharpness, as long as not ridiculously blunt, is not that much of a factor at those speeds)

then for setup:

- adjust your sponsons to run parallel to the tub.

- don't run any toe in or out on them.

- make sure they are spaced equally from the tub

- run the strut straight from the back no angle, no offset.

- correct front sponson angles: dip the left sponson angle a tiny bit compared to the right.

it is like that on my boat and on the setup instructions.

 

[John Finch]

All the tips are right on. What prop are you running?

 

[Don Ferrette]

I am running the twister hydro for a couple of months now . its a Gas motor powered hydro and the speed is going up .. after i passed the 75 mph limit i found that the rigger is staring to pull to the right a bit . now in full speed passes at 82 till 85 mph its very difficult to keep it straight .

How much of the rudder blade is in the water?? What worked at 75 might not be enough to get it done over 80. Often people forget that a rudder is not just for turning. Try the same style rudder blade but 1/2" deeper, a easy test you can do back to back to see the differences.

 

[steve wood]

i have had flat bottom struts cause a bad pull. switched to round and problem went away

 

[Buckshot]

Buck , i do run a flat strutt (bottom) i also have a sharp strut leading and trailing edge , why do you think the A brown turnfin will work better ?

I was referring to the strut angle. I would suggest a round bottom strut for any hydro not flat bottom.

-Buck-

 

[speakerboy]

Guys thanx again for pointing me in the right direction ,

mr Finch .. the prop is a 2716/3 cupped . i have found that this prop works great on this boat . right now i will fix up several of this moddels , all with different pitch ,and cup .

Tom , your right .. i could have called you ore send you a mail , but its good to hear and see so much info like this aswell .

Don , the blade is in the water for about 3 inches .

Steve , it might be that the flat bottom stutt has to much lift ..

i have found some pictures that Andre Abtmeyer made from the rigger last sunday .

first pic is the Twister running in a straight line at almost top speed .

second pic is the twister in a pass but with a little "to the left "correction . result is a lifting rigger ..

Third pic is a passing by pic and i cant say if this is a moment short ore a bad ride additute , the boat is running real loose at the rear

funny part is ..i have changed the stutt some times for better handling and hopping . the boat is not hopping at all , i will start with the sponsons first and than with the strutt ..

Great that i get so many help to get this thing going even more straight and hopefully a little faster ! but i am allready pleases with the speed i got out her now .

thanx again ..

Jeroen

 

[Nigtmare]

Jeroen Nice looking boat!!! One thing I don't see is the water discharge from the engine :blink: :unsure:

Nick

 

[Terry Keeley]

I'd say by looking at those pix your hull is trimmed (rides) very nicely. The "boat is running real loose at the rear" is really what you want IMHO and that's about where most high pitched props want to run, only the bottom half of the bottom blade in the water:

I'd go over the alignment of the sponsons, strut and rudder as suggested and make sure everything is straight.

From there I'd make sure the LE of the prop is very sharp and is blended smoothly to the TE, I'd go with the turn fin that has a wedge on the outside vs. smooth blending, and I'd make sure the rudder is not sloppy and that the linkage is strong (1/8" wire) and tight.

If all those are right then you have to try other things like angling the turn fin (toe FR), shimming the strut etc.