rather unstable boat

T

tangerine

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Joined
2 Jan 2008
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209
Location
hampshire uk
www.normanwhite.co.uk
Took delivery of my Colvic sunquest 29 and brought her back from Brighton to Southampton a couple of weeks ago on a pretty smooth sea. Boat felt quite unstable,and since arriving at my berth, have had some seasoned experts look over her. General opinion is she is too light in the water, and would benefit from some ballast. Anyone had a similar experience, and can anyone offer any further advise. Powered by two Volvo Penta AD31 diesels on outdrives. I should point out I am fresh back on the water after 30 years. Im not sure I had all the advantage of correct trim etc.
 
Depends a lot on what you are used to. I drove a 38' 15 ton semi displacement workboat for 10 years then bought a 26' cruiser not unlike yours. My boat feels as tender as anything compared to the big one... but having driven many boats since this is a fairly common theme. I think sometimes stability is sacrificed for speed. If you ballast her you will most likely just slow her down and waste fuel without making her much more stable. You may ned up having to do what I do which is accept that a fast planing boat will always feel a bit unstable compared to a heavy displacement or semi displacement boat... cheers Iain
 
Thanks Ian. Trouble is Im not used to much at all as I have been away from the water for 30 years. Luckily a couple of the experienced guys at my berth are going to come out with me. I guess I will get a clearer picture then.
 
Please describe 'unstable'.

If you mean that she rolled like a pig, whipping back and forth, then she is too stable, if she rolled slowly and barely stopped before she rolled over then she may be unstable.

We discussed this near the end of last year IIRC.

Tom
 
If your previous experience is of a boat with a long keel then you will find that the shallow draft/planing type hull takes more in the way of correction. After a while you get used to it (or fit an auto pilot).

As regards stability, I think it would be difficult to make a modern motor boat unstable when you think of the weight of the engines etc. low down in the hull. If you are considering adding ballast low down then remember that it is unlikely to reduce the amount of rolling and will probably increase the rate of roll instead.

Adding ballast at deck level may well help but should only be done after careful calculation using the published stability data.

I suspect that your insurance company would also be interested.

Tom
 
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Thanks for message. She seems very light in the water,and I am constantly correcting the steering. In other boats wash, I felt at one time we were going to corkscrew into the water.

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Having the leg trims too far in causes the nose to twitch about a lot especially when on the plane. Having them too far out when in displacement can have a similar effect....
 
"I am constantly correcting the steering. In other boats wash, I felt at one time we were going to corkscrew into the water"

Welcome to the world of outdrives /forums/images/graemlins/grin.gif
You do get used to it after a few trips.
 
Me thinks you need to play about with the drive trim.
My boat seems to prefer being trimmed all the way in, only trimmong out to "Zero" when up on the plane and looking for top end speed, trimmed in, bow down seems much more comfortable.
 
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