To Ballast or not???

by Eddie Gregory

Hi Folks.

My 21-ft 60s SeaHawk planing fast fisher (New build) is coming along just fine with me just fitting the glass to the wheelhouse.

My big dilemma now is weight.

I have stuck to the original plans quite well but used slightly thicker oak and fir than shown for the frames, ribs & keel and glassed the whole hull.

I have also altered the wheelhouse slightly in an effort at providing more weather protection.

What I'm worried about is any alteration in weight above the waterline and should I account for it by using ballast?

As a rough guide I think I have added about 100lbs over and above what was in the plans for the wheelhouse with the addition of a wheelhouse rear bulkhead and side perspex windows.

Please have a look at my progress on my wee site at and tell me what you think.

I have had plenty of welcome feedback already from Mike and seek your knowledge and advice.

Am looking forward to the summer and the big launch, but do you think she will float???

All the best for now,


Comments for To Ballast or not???

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Jan 30, 2011
Thanks lads.
by: Eddie from Ireland

Wow! Thanks lads, just the encouragement I'm looking for, I think I am worrying over nothing as indeed she is designed for at least 7 adults!

I will experiment with sandbags until I get her sorted out.

Will keep you all in touch.

Thanks again, what a great site.

Jan 29, 2011
by: Anonymous

No worries,
she will have been designed to carry several people, much more weight than the extra you have added.

On the plane the she will be relying on the hull shape not the ballast.

Jan 29, 2011
by: Mike Duncan

You can try experimenting with bags of gravel or sand until you figure out how ballast and where works best.

Jan 27, 2011
by: Mike

Hi Eddie,

Good to hear from you again and to see how well you are getting on at www.floatyourboat.

I'm afraid this business of working out ballast ratios and the like is way beyond me, I'm sure Naval Architects have some complicated formula for working it out, taking weight, hull shape etc, etc into consideration.

My gut feelings though, (not very scientific) make me think that the extra weight of the hull scantlings will probably cancel themselves out, as this is spread below as well as above the center of gravity.

As for the extra wheelhouse bulkhead, all I can suggest is using some sort of cheap easy to remove again ballast such as polly bags of wet sand.

However, I think that I would be inclined to launch her, see how she floats and feels first.

You might find that she needs some ballast just to get her down to her waterline anyway.

Quite how this will affect her when on the plane is another matter.

Hopefully someone with more experience will chime in and add a comment.

As for this summer’s launch, may the gods bless her and all who sail in her.

And yes of course she will float.

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