need help in correcting a tender cruiser

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Psuedomonas
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Location: Murfreesboro, Tn

need help in correcting a tender cruiser

Post by Psuedomonas »

http://im1.shutterfly.com/media/47a0d93 ... /ry%3D400/

well I tried to enter a picture



So here's the transom of the cruiser I built a few years ago. Its a flying bridge 23' cruiser. The bridge is constructed as light weight as possible using foam impregnated with epoxy. The tankage is positioned as low as possible amidship. It uses a sterndrive so there is no strut, shaft and rudder. There are also no keel, skeg or bilge keels. I built it that way for speed.

But out on the lake on a busy Sunday, I was suddenly aware that this was a tender boat. It rolled in every wake and I had the feeling that I could turn it over in a tight power turn.

So, whats to do. I could add trim tabs, bilge keels, a good sized keel, lifting strakes. How about some informed opinion on the best solution, including dimension and placement.

Thanks in advance guys- I can always count on you.

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X23
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Re: need help in correcting a tender cruiser

Post by X23 »

Before you spend a lot of time on a fix, get a copy of Dave Gerr's book "The Nature of Boats" and read what he has to say about initial stability versus ultimate stability. Particularly with the V bottom you have. Some library systems have it, as does Amazon.

I am very interested in your technique, since I was planning on an Escapade build & was thinking of the same composite flybridge & cabin top for the same reasons.

And the picture works fine, just copy the URL & paste into a new browser window. Would be nice to see more pictures of her, side view & more.

Jack

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Bill Edmundson
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Re: need help in correcting a tender cruiser

Post by Bill Edmundson »

Now it works.

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
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Psuedomonas
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Re: need help in correcting a tender cruiser

Post by Psuedomonas »

well let me be a little more clear. She is quite stable at rest. But at 3000 rpms (sorry no speedo) and with one person on the bridge, she heels a little too much dealing with wakes and such. This is with the sterndrive full down. Would anyone council chine flats, a full external keel, bilge keels?

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raymacke
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Re: need help in correcting a tender cruiser

Post by raymacke »

What does the beam measure?
So Many Rivers,
So Little Time....

Psuedomonas
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Re: need help in correcting a tender cruiser

Post by Psuedomonas »

He beam is 92".

Brian Eager
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Re: need help in correcting a tender cruiser

Post by Brian Eager »

Prior post deleted by author, who realizes he is way out of his depth to try to advise on conditions of stability.
Last edited by Brian Eager on Thu Aug 01, 2013 4:28 am, edited 2 times in total.
Noah was a first-time boatbuilder

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billy c
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Re: need help in correcting a tender cruiser

Post by billy c »

Image
(insert Witty phrase here)
Billy's Belle Isle website

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raymacke
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Re: need help in correcting a tender cruiser

Post by raymacke »

When I was considering designs for my last build I was set on having a flying bridge. The True Grit came as close to fitting my other criterion but lacked that one important feature. I figured if I could keep it light it would be workable. But before I made the decision I decided to talk with the designer, Ken Hankinson when I was ordering the plans (this was shortly before he retired). I explained my thoughts on keeping it light with minimal structure - actually just enough to allow mounting of the steering system. I planned to trim it out adding a front and sides of canvas and tubing similar to what they are now doing with the Ranger R-31. http://www.rangertugs.com/R-31

Ken was extremely adamant this should not be done. He explained even a minimal structure along with the weight of an operator that high above the center of gravity (may have been the C.O.B.) would create an highly unsafe condition. He said there was just no way to safely accomplish it on the TG's shallow draft hull with only an 102" beam. He added at best it would roll severely in most anything but flat water and if rough conditions were encountered there was a good chance it could roll. I dearly wanted a fly bridge but he convinced me this would be a mistake.

Since then I have seen a few 8.5' beamed boats with a flying bridge but everyone was a deep V. The Ranger 31 does have a fairly shallow hull that planes and a fly bridge but it has a 10' beam. Still as you can see they fought to keep the bridge very light. They make smaller versions but none with an 8' 6" beam has a flying bridge. From the photos it looks like your hull is a fairly shallow V like mine. Sitting still it may be reasonably stable but when you bring it up on plane you are raising the center of gravity higher off the water and you have less hull in the water. To me it would be logical when the wetted area is reduced and the C.G. is raised it could become less stable particularly since you beam is 10" narrower than mine and the 4' shorter hull has less mass.

In your first post you asked for an "informed opinion". Well, this isn't. No real expertise here just passing along information as it was presented to me accompanied with a few thoughts. I am sure there are much better informed builders out there.
So Many Rivers,
So Little Time....

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raymacke
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Re: need help in correcting a tender cruiser

Post by raymacke »

With a little more thought on the subject I remembered a section in Dave Gerr's book "The Nature of Boats" that discusses stability. I went back and looked and there is some information there that might help sorting through the problem. Chapter 15 deals with stability and on page 114 he explains how to run a test, "Roll Timing", that will indicate your level of stability. I would recommend you read the chapter and do the test. I think it will give you a better understanding of the situation which will help guide your choices for possible solutions.
So Many Rivers,
So Little Time....

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