Broaching tendency - correction possible?

[tom28571]

Originally Posted by Mr Efficiency

I have seen outboard powered flattish-bottomed planing hulls that had broaching tendencies modified with skegs on both sides, maybe 3" or so deep, over the last 3 feet of the hull approx., halfway between the centreline and the chine. That avoids interfering with the water flow into the prop that may occur by deepening the central keel. Moving fixed weights aft may not be that helpful, as the "lever arm" working to broach your boat will be lengthened by it. Dragging the centre of lateral resistance back by increasing the underwater profile aft will dampen broaching.

Skegs near the longitudinal position of the prop is going to give ventilation problems in turns whether on center or to the sides. There is a reason that skegs are cut away forward of the transom.

[Mr Efficiency]

I wasn't talking near the propellor, Tom, "halfway to the chine" is nearly 2 feet, would be a crazy sort of turn to interfere.....and give cavitation or ventilation problems, with a shortish length skeg out there. It would result in additional drag though, and has to be seen as an original design flaw if added as a result of unsatisfactory handling.

[tom28571]

Originally Posted by Mr Efficiency

I wasn't talking near the propellor, Tom, "halfway to the chine" is nearly 2 feet, would be a crazy sort of turn to interfere.....and give cavitation or ventilation problems, with a shortish length skeg out there. It would result in additional drag though, and has to be seen as an original design flaw if added as a result of unsatisfactory handling.

Not sure we are on the same page here. I think, although I have not tried it, that a significantly deep skeg all the way to the transom will still cause turn ventilation problems even if it is 2' off center. In a turn, it will still be in front of the prop as the stern moves sideways.

[skypoke]

Eli,Yep, I still have the cat, it's worked out really well. We've had it out 100+ miles and it's handled anything thrown at it. After several years service the nyalic finish is shot, I need to either renew it or let the hull go "natural." Lots of fish have met their ends on its deck...

Chuck

[daiquiri]

Skypoke, was the broaching issue resolved?

[cyclops2]

Unofficial N A solution.

Put in a VERY DEEP keel. Full length . Stop the keel far enough foward of the engine in the STANDARD location. There is NO SENSE to putting in a keel that causes a loss of control when in broaching seas. Nothing accomplished.
Keeping the engine in the original location should pay for the cost of the full length.

Lets see.
No keel in the bow causes the bow to be pushed around by waves easily.
No keel in the stern causes the stern to be pushed around by waves easily.

What modification will correct both dangerous conditions with very little steering effort ?

Rich

[michael pierzga]

Well...best to slow down or bring the bow up. I cant see any benefit to addition skegs. The added lateral resistance just causes tripping.

[cyclops2]

We should have not gone out or came in sooner.

Rich

[michael pierzga]

And as far as the bow biting into the back of a wave , slowing the boat down causing the stern to catch the bow. This happens to all craft. An alert throttle man is required to work the wave trains.