Sliding in turns -PLANING HULLS

[eightwgt]

I have a questrion for the experianced designers here. What are your thoughts about reducing a planing hulls sliding thru a turn. I am reffering to small hulls 14-18' with an almost flat bottom.

What can be done to minimize this ?

Rounding the chine ?
Strakes ?
'Reverse strakes' at the chine ?


????

Thanks - I look forward to input.

[FranklinRatliff]

Originally Posted by eightwgt

I have a questrion for the experianced designers here. What are your thoughts about reducing a planing hulls sliding thru a turn. I am reffering to small hulls 14-18' with an almost flat bottom.

What can be done to minimize this ?

Rounding the chine ?
Strakes ?
'Reverse strakes' at the chine ?


????

Thanks - I look forward to input.

It's called a skid fin. Unlimited hydroplanes have been using them for decades.

[eightwgt]

I should have addressed that - "No skid fins"

I am reffering to a typical recreation boat-think fiberglass Jon boat - not a performance hull such as a hydro...

Thanks - I appreciate the input -

[FranklinRatliff]

If you're going fast enough to be sliding in a turn, you're going fast enough to be thinking about a skid fin.

[eightwgt]

Franklin

Thanks - I agree, however I am looking for other ideas

[kach22i]

You might get a little insight if you read this whole thread.

http://boatdesign.net/forums/showthread.php?t=11121

jehardiman; At most planing boat speeds, side velocity due to a turn is negligable compared to ahead velocity. While a jet boat can achieve significant side velocity in a turn , it is unlikely that a propeller driven craft can. But Yes, if you somehow managed to break a conventional powerboat into a sideslip without flipping it, then the prop will provide significantly less thrust due to inflow AOA effects. I mentioned it because it is a common proplem in auzimuthing pods. Turn the pod at right angles while going fast and you don't get the response you expect

[tom28571]

To stop sliding in a turn, you must have some lateral resistance. Messing with the chines is not the best way. Strakes near the centerline of the bottom like a keel will do the job. One strip on center will be most efficient but two off center is easier on dragging the boat around on the beach. You need to make trials to determine how deep they/it need to be. Stop the strakes well short of the transom (14" or more) or the prop will ventilate on turns. Strakes on the chine can flip you over on a flat bottom boat. The easiest solution is a skid fin but they can get in the way.

The long keel or strakes may also help in making the boat bank inward in a turn.

The worse thing is to have the boat slip in the first part of the turn and then suddenly grab hold. Better have on a good life jacket. Done that on a speedy flats boat and cracked ribs are no fun.

[eightwgt]

Tom

Interesting reply.....

A flats boat huh ? Which one if ya dont minf me asking ? You can send a private reply if you prefer also...

The hull Im working on I know will have sideslip due to the nature of the hullform.... I was simply looking into ideas to safely limit it if possible.

[buckknekkid]

Originally Posted by tom28571

To stop sliding in a turn, you must have some lateral resistance. Messing with the chines is not the best way. Strakes near the centerline of the bottom like a keel will do the job. One strip on center will be most efficient but two off center is easier on dragging the boat around on the beach. You need to make trials to determine how deep they/it need to be. Stop the strakes well short of the transom (14" or more) or the prop will ventilate on turns. Strakes on the chine can flip you over on a flat bottom boat. The easiest solution is a skid fin but they can get in the way.

The long keel or strakes may also help in making the boat bank inward in a turn.

The worse thing is to have the boat slip in the first part of the turn and then suddenly grab hold. Better have on a good life jacket. Done that on a speedy flats boat and cracked ribs are no fun.

bin there done that many times. I throttle so its my fault.

[tom28571]

This particular boat was designed and beautifully built by John Martin of Charleston, SC. He was experimenting with skegs to control the unnerving skids and had installed two parallel ones off center. We were running pretty fast, how fast I don't know but d***m fast and showing off a bit after a big fast boat tried to outrun him. He went into a full bore turn and everything was OK for a while although the boat was skidding quite a bit when it suddenly dug in and I catapulted across the boat. Non tripping chines would have helped too and the lack of them may have been the major fault in this situation.

Maybe I was only bruised rather than busted but a strong lesson anyway.

"Good judgement comes from experience.
Experience comes from bad judgement."

[eightwgt]

Tom

What do you define as a "non-tripping" chine ? I am not sure I understand what type of chine you are reffering.

Thanks again

[tom28571]

Looking at the boat from aft, the bottom will have a portion of the width turned up near the edge. This keeps the chine from digging in when the stern slides sideways in a turn. Don't forget that the stern of boats with the propeller in the stern always slide sideways in a turn.

[eightwgt]

Tom

How much of a turn up ? Do you have an example I can look at ? This sounds like a good idea to incorporate into my project.

Thanks once again - it is appreciated

Tom

[tom28571]

I don't know of a fixed number but you can look at the link below. The view of the stern gives an idea of how it was done on this boat.

http://www.woodwindyachts.com/Restor...orpedoRest.htm

[eightwgt]

Interesting..... Thanks.

Take a look at my example.... A-B-C-D "A" being 'standard'....