Strut offset

[Kez]

I know this topic must have been discussed before but I could not find any old thread....

On a sport hydro, I have seen strut installed down the centerline. I have seen offset to the left, to the right and in combination with angling the strut to the left (view from the stern). Can you share what works for you and why?

I have found that with no offset, prop walk would pull the boat to the right. Evreyone knows this. For me, angling the strut 2 to 3 degrees to the left halp make the boat track straight with neutral rudder.

I have also tried offsetting to the right about 1/4". Theoretically, this would put the thrust line to the right of the CG thereby pushing the boat to the left. In practice, I have found that this effect is much less than angling the strut on a sport hydro. However, it works quite well on a vee and a mono.

Thanks for sharing your experience.

 

[Hydro Junkie]

IN THEORY, offsetting the strut slightly to the left and angling the strut toward the left is supposed to help you drive through a corner. Dumas even included offsetting the strut 1/8" in the instructions of the 30" Pay'N Pak years ago. Since I never achieved anywhere close to racing speeds with my Pak, I don't know if it actually does help or not as I haven't done it since. That being said, whether or not it actually works or not is for someone with more design knowledge than me to answer on.

 

[BobGutsell]

IN THEORY, offsetting the strut slightly to the left and angling the strut toward the left is supposed to help you drive through a corner. Dumas even included offsetting the strut 1/8" in the instructions of the 30" Pay'N Pak years ago. Since I never achieved anywhere close to racing speeds with my Pak, I don't know if it actually does help or not as I haven't done it since. That being said, whether or not it actually works or not is for someone with more design knowledge than me to answer on.

Sloppy workmanship on my part has my strut angling about 2° to the left and boat tracks fine. The centreline of strut is the centreline of the hull.

 

[Kez]

IN THEORY, offsetting the strut slightly to the left and angling the strut toward the left is supposed to help you drive through a corner. Dumas even included offsetting the strut 1/8" in the instructions of the 30" Pay'N Pak years ago. Since I never achieved anywhere close to racing speeds with my Pak, I don't know if it actually does help or not as I haven't done it since. That being said, whether or not it actually works or not is for someone with more design knowledge than me to answer on.

HJ,

Dumas is not consistent in their recommendation. They suggested offsetting the strut to the LEFT on their 3" Pay'N Pak and on the 36" Atlas van lines but they suggested offsetting to the RIGHT on their 1/8" scale Atlas.

If you think about it, offsetting to the right will help prevent prop walk since we are placing the thrust line to the right of the CG. But offsetting to the left may help turning.

One observation: Of all they full sized hydro I have seen, there is eiher no offset of they offset to the left (inside the turn. I have not seen too many full sized hydros so there may be some that offset to the right?

Bob, I have found that angling the strut to the left is more effective than offseting the strut. I have found that a couple of degrees is all it takes to make the boat track straight.

 

[Hydro Junkie]

I may be missing something, but it seems to me that if you angle the strut to the right it would increase the prop walking problem as the prop tries to push the rear of the boat to the left already. By offsetting the prop to the right, it would seem to me to that it would intensify the problem as it would be pushing the boat's transom even more to the left requiring even more left rudder to compensate than running the shaft right down the middle of the hull with no offsetting either way

 

[dschigoda]

I may be missing something, but it seems to me that if you angle the strut to the right it would increase the prop walking problem as the prop tries to push the rear of the boat to the left already. By offsetting the prop to the right, it would seem to me to that it would intensify the problem as it would be pushing the boat's transom even more to the left requiring even more left rudder to compensate than running the shaft right down the middle of the hull with no offsetting either way

I think we need to be more descriptive when we say "offset". Is it offset and parallel to the hull centerline, or is it offset on an angle to the hull centerline, or both?

 

[Kez]

I may be missing something, but it seems to me that if you angle the strut to the right it would increase the prop walking problem as the prop tries to push the rear of the boat to the left already. By offsetting the prop to the right, it would seem to me to that it would intensify the problem as it would be pushing the boat's transom even more to the left requiring even more left rudder to compensate than running the shaft right down the middle of the hull with no offsetting either way

I think we need to be more descriptive when we say "offset". Is it offset and parallel to the hull centerline, or is it offset on an angle to the hull centerline, or both?

By Offset, I refer to having the strut moved to one side with the stut running parallel to the centerline.

By angling the strut, I refer to turning the strut at an angle.

Simply offseting the strut to the right should push the boat to the left; provided that the drag on both side of the hull is equal. This should be quite intuitive. Example, if you push a shopping cart on the right side, it will track to the left.

In reality, I find that offsetting the strut to the right is less effective than angling the strut to the left a couple of degrees. I have also found that offsetting the strut is more effective on a mono or vee hull.

I can not think of a reason to move the strut to the left other than helping the boat drive through the turn better.

 

[shann harrison]

I offset my strut on my scale boats 3/8 to 1/4 just to keep the left sponson glued to the water rather then carry the left sponson in the turns and straights,at full speed.Plus I have noticed it also helps with tracking straight.It really doesnt matter your still going to have to have some trim setting one way or the other to help with trackin due to many things turn fin,prop your using,rudder placement,and etc.Off setting is up to the individual builder.The other thing you could do if still unsure is mount it with the center line run the boat and watch what it does,if you still not happy,Place a screw driver in the back of the strut and bend the whole strut one way or the other 1/16 in any direction is all you need.I due this trick on my 45 hydros.hope this helps.Shann