Simple question, i think

hello, i was just wanting to find out; is your boat more stable if it has a flatter bottom hull than a steeper dead rise hull? I have a 17ft glass over ply boat and it has quite a flat bottom and a sharp front with big flared sides. Another thing, are there anygood sites about what weights would be suitable for what size boats? Cheers

 

simple answer
at rest your flat boat is much more stable
if you google up freeship and doWnload, you can draw your boat here,AND THIS will answer you load questions, rotton weather in NEW ZILD!!1

 

My first boat was narrow with a vee bottom, pretty but unstable as hell. Not enough stability.

So I went to a flat bottom expecting a big improvement, it stayed upright but still did not feel secure. I ripped out the bottom and jacked out the sides and put in a new bottom about 10% wider, better but felt "wrong" like it wanted me to fall out every time a wave went by. Wrong type of stability, lots of primary, not enough secondary.

I figured the CoG was too high so third time lucky; I reduced the bouyancy with a narrower but still flat bottom, added garboards sloping up to meet the sheerplanks just under where I figured the waterline should be. I got what I wanted at last, just enough primary stability to stay upright with a bit of margin but still allows waves to pass harmlessly by with plenty of secondary stability for when I lean over.

The trick for me was to keep the CoG low with plenty of beam at the waterline. Next time I will increase the rocker to see what happens; my current boat is great but slow in the turns. The rocker should help that and at the same time lower the CoG a tad.

No, it wasn't a simple question. Stability is a bit of a black art. Of course, you can feed the hull dimensions into some software and get numbers, but then you have to interpret them. I'm not an expert.

Maybe if you publish some more dimensions such as beam, height etc and provide an image some of the more knowledgeable guys might give an opinion.