False bottom v on a flat bottom

This is a 12.m Myark barge I built some years ago which was a flat bottom and a V built into the very front part as it was used in rough seas all year round.
Because it floats in 2 inches of water and has a kick up back and front design, when accelerated it rocks back onto the back kick up that becomes level with the water surface and skips along avoiding the water drag.
It had a 115 HP out board and its speed is over 30 knots.

 

I really appreciate this resource but I'm not really looking for a debate on v hull vs flat bottom . I've been researching for a while and realize by now the drawbacks of both and flats seem to have more draw backs than v but I really think this flatty will work well for me , just though I could improve it a little but if you guys think this is a foolish idea that's fine. Also I never see ANY wood boats on our river maybe that's for good reason , maybe we can just fish from the bank a few more years

 

Wow, myark, that self trailer Barg is awesome , similar to what I want just way bigger , could you run a jet on something like that and still steer it? Was just flying down our shallow river today in my friends alumaweld super v and it kinda drove home how important it is to be able to turn quickly

 

Flat bottom high performance jet units have no problems, some are used for drag boat racing.
If you are going to use an inboard motor and want low cost with high performance I would recommend a Tom Kane pivotal drive system.
http://www.boatdesign.net/forums/profile/tom-kane.html

 

I'll check out that tom Kane system , but i was hoping to run an out board jet so I could keep the prop and run it when I go to the coast crabbing in the bay or pulling a tuber around the lake in the summer

 

You know, if you actually use Giggle you will find so many garvey's both flat and V that really, you are wasting your time here. No one here (yet) is really going to add much to your quest; there are an immense amount choices out there. Notice that no one here has said, "Oh yes, I've built 22 V bottomed garvey's!" Here's a good start:

http://www.bateau.com/proddetail.php?prod=GV15#.VUg4DflViko

From there you can find all sorts of helpful friends and people that actually know what they are talking about.

 

Thanks yofish, ya I have found a design already, spira int. 20' garvey dory , I really like it , just thought I might improve it to run a jet better but looks like I might leave well enough alone. I guess I was trying to make a simple boat that can do everything, I should know better , thanks

 

I think you are missing my point. You are obviously stuck on a design: "ya I have found a design already, spira int. 20' garvey dory , I really like it." but are casting around for something better? I pointed to a better design, if what you mean by that is a V bottom. A better design with lots of support to boot. Don't you see that you are wasting everyone's time here by not expending the energy to do the basic research before asking questions? Lots of V bottom garvey's to choose from but you're stuck on one flat bottom design that you want to be a V? Come on, man!

 

The total buoyant force on an object equals the water pressure at it`s floating depth times the area of the object in contact with the water. this means the more area you can give a material,the higher it can ride in the water, where the water pressure is much less.

(briefly) I will say no more on this thread about flat bottoms.

 

Not on planet Earth, Tom !

 

If toms v bottom has the same draft as a flatty she might be a bit tender I think. and now myark thinks flat bottoms make good jet boats.:?: As long as they don't try to turn to much. Now yofish is saying we are stupid and unfriendly on this forum.. Better than watching a soapy.

 

A v bottom can never have the same draft as a flat bottom (for a constant mass)....

 

I think thats what mr e has been alluring to.

 

Ah yes, I hadn't read the rest of the thread....

 

Myark is playing his agenda as usual (generally in every thread he enters), I'm not sure what's up with Yo, but I've built both flat and V as well as put a V on a flat bottom once too. As to Tom's point, he's technically correct, in that it could be a complex subject, if we wanted to split hairs, but really it's a simple thing and easily understood, in terms of the questions the OP has posted.

The flat bottom hull form is the most efficient getting in a full plane regime. It will climb up on plane faster, with less power and at lower speed than a V bottom. It also has the advantage of shoal draft. The flat bottom is also easier to build. This assumes moderate speeds, as the drag associated with the flat bottom will hold her back and generate other issues at high speed. Yes, (as noted) some drag racers use flat bottom boats, but these are class racers and we've all seen what happens to these, if they catch a wave or wake badly. Once you're over say 30 knots in a relatively small flat bottom, the "issues" rise exponentially, not the mention the need for new dental work.

This said and as I mentioned, everything in design work is a set of trade offs. The flat bottom will tend to pound, often unmercifully with any kind of chop. The wise skipper will angle off and take the beating on the forward quarter, plus some heel can postpone the inevitable pounding, but sometimes, you're just married to it. The flat bottom also can become "skittish" once it's pushed hard and will tend to "trip" in hard turns at high speed. You can mitigate some of the discomfort with a particularly stiff bottom.

For this discussions sake, a flat bottom will always displace less than a V, given the same immersed volume. It's simple physics. Now, with a 20' flat bottom, we're only talking about a couple of inches over a relatively shallow warped bottom (V), but to some, this may be what they need.