Round stern vs box stern??

[Deadrise13]

Would a round stern boat (like a cheseapeak bay deadrise) be Faster than a more traditional box stern?? Is there a differance in drag, Or dose it make a differance?? Thanks

[robherc]

Hmmm.... Chesapeak Bay Deadrise..from the photos on Wikipedia, has a box-stern....I'm confused
...what exactly are you looking at? can you draw us a picture?

[Deadrise13]

Thanks for the reply. Check out----- The Albatross fleet of Hatteras NC. ----Sorry I am new here and do not know how to post a picture yet. They have 3 old deadrise boats all of them are round stern. I grew up fishing on them as a kid with my pop. Thanks again for the input.

Originally Posted by Deadrise13

Thanks for the reply. Check out----- The Albatross fleet of Hatteras NC. ----Sorry I am new here and do not know how to post a picture yet. They have 3 old deadrise boats all of them are round stern. I grew up fishing on them as a kid with my pop. Thanks again for the input.

Go to your post... click edit...go down to the button "go advanced"....
go down to the button "attachments" or "manage attachments"
upload.... smile!
Regards
Richard

[robherc]

OK, that's what I was thinking you were asking, but I wanted to make sure you meant round-stern & not round-bilge

Anywise, the rounded stern will give slightly better efficiency at lower speeds (below planing). The rounding of the stern allows the water to close more smoothly behind the boat, but will actually increase drag on a boat that CAN plane. Since those boats are listed as being 45' boats (hull speed = 8.72kts) & they're showing 18kts cruising speeds on them, I'm wondering why they would have made the trade-off there?
Maybe I'm missing something though...if you wait a couple hours, I'm sure someone else will point out my error.

[Deadrise13]

Thanks to both replys, I should be able to post pix next time. And that is what the old guy that is going to build my new boat said. He thought round may be a little slower. I will see what some of the other guys say. I am trying to get the best speed for the $. I do like the look of that round stern though. Thanks for your time. I knew I could find lots of help here!!

[Roger Moren]

You can have both. Tampered stern at the waterline ( min.stern wave ) and flairing to actually having a stern, providing lift.

[Deadrise13]

So you are saying it is a wash?? If so I would go for the look!!---Thanks---

[PAR]

Are you talking about an elliptical stern? If so the elliptical stern will have little, if anything to do with performance, unless it's immersed, which it most often isn't.

[Deadrise13]

Thanks for all the input, it seems it dose not make that much differance either way. The boats usally are under 25 kts top speed. Just trying to milk every bit of performance I can.

[Leo Lazauskas]

Originally Posted by Deadrise13

Thanks for all the input, it seems it dose not make that much differance either way.

I wouldn't be too quick to leap to that conclusion. None of the replies mentioned any calculations, nor did they point to any experiments supporting their guesses.

[Leo Lazauskas]

Originally Posted by Roger Moren

You can have both. Tampered stern at the waterline ( min.stern wave ) and flairing to actually having a stern, providing lift.

You are guessing. No stern wave can also mean that there is nothing to cancel the bow wave, and therefore wave resistance will be greater.

[robherc]

Deadrise:

There HAS to be some difference made by it, or nobody would make them. The question is: what was their reason for using it?

The most likely possible reasons I can think of off-had are:
Low speed efficiency;
Aesthetics;
Extra deck space.

That doesn't mean that there isn't another reason that I'm missing, or that any of those reasons are necessarily practical/plausible...they're just guesses. Your best resource may be to find someone who designs boats with those stern shapes & ask him why he did it.

[robherc]

Originally Posted by Leo Lazauskas

You are guessing. No stern wave can also mean that there is nothing to cancel the bow wave, and therefore wave resistance will be greater.

I think it's a safe bet that every poster in this thread is guessing.

[Leo Lazauskas]

Originally Posted by robherc

The rounding of the stern allows the water to close more smoothly behind the boat, but will actually increase drag on a boat that CAN plane.

Do you have any support for this guess.
The air cavity behind a transom is vented to atmospheric pressure, and so it cannot sustain a pressure. So how does the shape of this cavity increase or decrease (for example) the wave-making component of resistance?