Right shift engine intallation.

ikaros · 22 November 2014, 19:41

Hi Guys.

I want kindly to ask if somebody there can explain how the right shift installation of the engine affect to the tension which the boat has to leaning to the left,due to the torque of the engine.

Thanks in advance.
Kostas.

Pikey Dave · 22 November 2014, 22:14

Offsetting the engine to one side, effectively shifts the centre line of the boat, this makes one side of the boat "heavier" than the opposite side & counterbalances the torque of the prop. The amount of offset depends on boat/engine combination.

Maximus · 23 November 2014, 09:14

Quote:

Originally Posted by Pikey Dave

Offsetting the engine to one side, effectively shifts the centre line of the boat, this makes one side of the boat "heavier" than the opposite side & counterbalances the torque of the prop. The amount of offset depends on boat/engine combination.

Which is fine in theory,indeed I always thought this was the concensus.
I hear now the Racing boys don't bother,and it's largely a thing of the past.....??

C-NUMB · 23 November 2014, 10:27

Guess a boat can be correctly rigged both ways, centered or shifted to the right. Some talks strongly for the moving right and others to keep it centered, advice depend on whom you talking to. Propellers also makes a big difference, as the height. Think a lot o ribs have been successfully set up with the engine offset.

On my own the previous owner moved it back to the center and told it was better that way, for me its fine and that's anyway how my boats usually have been rigged.

I believe tho idea regarding offsetting is not only shifting the weight but also that thus the boat have two "balance points" that are not in a straight line making it slightly more stable, might be wrong though.

chris.moody · 23 November 2014, 10:31

Some of the Seariders (SR4 and SR4.7) have the console and jockey seat offset as well. I have always presumed that was to counteract the turning effect of the prop.

Maximus · 23 November 2014, 11:01

Quote:

Originally Posted by chris.moody

Some of the Seariders (SR4 and SR4.7) have the console and jockey seat offset as well. I have always presumed that was to counteract the turning effect of the prop.

That would be a bit drastic on a small Boat...because they're pretty narrow,more to do with load/casualty carrying capability I hear Chris.

chris.moody · 23 November 2014, 11:09

Makes sense, you could lie a casualty down the port side.

ikaros · 23 November 2014, 11:15

I agree with C-NUMB,and also regards to the weight shifting.

Also I think that when we move the engine from the center,-to the right-we extend the arm from the center,with result to have bigger moments at the center line,and maybe make the phenomenon -leaning to the left-worst. arm x weight(force)=moments.

Mine (XS-550) with opti125 has a right shift,and leaning a little to the left at cruise,and with all the loads at the center.

ikaros · 23 November 2014, 11:45

I agree with C-NUMB,and also regards to the weight shifting.

Also I think that when we move the engine from the center,-to the right-we extend the arm from the center,with result to have bigger moments at the center line,and maybe make the phenomenon -leaning to the left-worst. arm x weight(force)=moments.

Mine (XS-550) with opti125 has a right shift,and leaning a little to the left at cruise,and with all the loads at the center.

9D280 · 24 November 2014, 13:41

My Merc is set dead centre, and she travels flat & straight.

RIB-Teccie · 24 November 2014, 18:56

I've seen a small Fletcher speedboat have the Port side nearly go under because of being dead centre. When it was moved an inch to Starboard it was perfect.

I've seen a 6m Searider run with its port sponson permanently in the water. Raising the engine an inch sorted the problem.

Rule of thumb is try a smaller pitch prop and ensure your not overevving by doing so. Then lift the engine an inch. Lastly move the engine or engines to Port.

I was taught that the SR5.4 had an offset console for more room on deck and a place to put a casualty. The ones with the speedboat layouts didn't really suffer by not being offset.

ikaros · 24 November 2014, 20:00

Quote:

Originally Posted by RIB-Teccie

I've seen a small Fletcher speedboat have the Port side nearly go under because of being dead centre. When it was moved an inch to Starboard it was perfect.

I've seen a 6m Searider run with its port sponson permanently in the water. Raising the engine an inch sorted the problem.

Rule of thumb is try a smaller pitch prop and ensure your not overevving by doing so. Then lift the engine an inch. Lastly move the engine or engines to Port.

I was taught that the SR5.4 had an offset console for more room on deck and a place to put a casualty. The ones with the speedboat layouts didn't really suffer by not being offset.

So,I think that another reason my boat (XS 550) leaning a little to the left,
is the asymmetry vpad at the transom as you can see at the photos.
I wonder why it's less from the left,that mean for me less lift from the left.
http://www.rib.net/forum/f8/xs-550-transom-65212.html
As I mentioned before, the engine (opti 125) has right shift installation,and despite I lift the engine one hole,and trying some other props I had the
same results.
So,i plan to try another option,making the asymmetry vpad just symmetry.
Already I have construct a wooden mold,which I plan to fit with sika just to see what would happen.
If it will work I will make a permanent fiber construction.

Your opinion please.

ikaros · 24 November 2014, 20:02

http://www.rib.net/forum/f8/xs-550-transom-65212.html

RIB-Teccie · 24 November 2014, 21:28

Sorry, but of brain fade in my comment. If you need to you should move the engine to Starboard, not Port as I said earlier. DOH!

ikaros · 24 November 2014, 22:14

Quote:

Originally Posted by RIB-Teccie

Sorry, but of brain fade in my comment. If you need to you should move the engine to Starboard, not Port as I said earlier. DOH!

Any opinion regard to
the asymmetry transom?