Looking for D Utility-"ish" 16' Runabout Plans

[Ray Downes]

Ray, while I have you "on the line", can I ask you, does your Raveau have a V bottom, and if so, do you happen to know what the deadrise angle is? Just curious.

Eric

Since the bunk extends past the transom, I couldn't get a physical measurement, and instead used a photograph:



I came up with 12.2 degrees keel to chine.The hull design is more complex that that lone number, as you can see. Sorry, didn't have the means to measure more accurately.

[FlatRacer]

Cool pic, Ray. So it looks like each half of the bottom consists of three longitudinal steps in lieu of a flat surface with strakes. I wonder how much the steps overlap each other.

Eric

[wolfgang]

Based on this and other photos of the Walsted builds, I would guesstimate about 3 inches wide longitudinals in the overlap area. But, to me it appears that the longitudinal steps are the wrong way `round, thereby creating an awful lot of wetted area. Just compare with the spray rails (lift strakes) arrangement on "standard" Vee-bottomed hulls - i.e. bottom outline should be more convex than concave.

[Ray Downes]

FlatRacer, a question for you - have you worked out a materials cost estimate?

[FlatRacer]

to me it appears that the longitudinal steps are the wrong way `round, thereby creating an awful lot of wetted area. Just compare with the spray rails (lift strakes) arrangement on "standard" Vee-bottomed hulls - i.e. bottom outline should be more convex than concave.

Wofgang, I'd have to disagree. Since the purpose of lifting strakes is to provide a (more or less) horizontal planing surface to lift the boat higher out of the water than it would normally be, planing solely on the flat surface of the V shaped bottom, which it does partially by capturing the water and preventing it from "squirting" outward past the chines, I'd say Walwork's overlap design effectively accomplishes that. And bottom concavity is not necessarily a bad thing.

I'm not a Naval architect, but it seems logical to me.

You can also see the overlap design in this shot on page 73 of the Wooden Boat magazine article:
http://www.woodenboat-digital.com/wo...304?pg=82#pg82

Eric

[FlatRacer]

FlatRacer, a question for you - have you worked out a materials cost estimate?

No. I'm toying with different ideas, including having a glass hull laid up onto which I can build a wood deck. Very '60s "SK style."
Whatever I build though, I'm going to have to buy my wife that Wave Runner she's been asking for before I add another boat to the fleet!

Eric

[wolfgang]

Wofgang, I'd have to disagree. Since the purpose of lifting strakes is to provide a (more or less) horizontal planing surface to lift the boat higher out of the water than it would normally be, planing solely on the flat surface of the V shaped bottom, which it does partially by capturing the water and preventing it from "squirting" outward past the chines, I'd say Walwork's overlap design effectively accomplishes that. And bottom concavity is not necessarily a bad thing.

I'm not a Naval architect, but it seems logical to me.

You can also see the overlap design in this shot on page 73 of the Wooden Boat magazine article:
http://www.woodenboat-digital.com/wo...304?pg=82#pg82

Eric

Eric, lifting strakes (among other purposes) are utilised to limit the wetted surface(s) of the hull. The Walsted Vee-bottom appears to propagate the water to the surfaces above the lifting strakes. For detailed theory, refer Renato Levi`s hows to Deltas". Unfortunately, book is still copyrighted. I do not want to highjack this thread with our discussion, so please write me an e-mail - wbarthel@tubular.co.za. rgds

[FlatRacer]

I'll concede that Walwork's design doesn't have what we would think of as "normal" or "traditional" strakes which have both horizontal and vertical elements. But why would the lack of a vertical element result in more wetted surface and consequently less lift? Curious.

Eric

[Ray Downes]

Eric, lifting strakes (among other purposes) are utilised to limit the wetted surface(s) of the hull. The Walsted Vee-bottom appears to propagate the water to the surfaces above the lifting strakes. For detailed theory, refer Renato Levi`s hows to Deltas". Unfortunately, book is still copyrighted. I do not want to highjack this thread with our discussion, so please write me an e-mail - wbarthel@tubular.co.za. rgds

I'm under the impression that cleaner flow (less turbulance and air bubbles) occurs with the z-plane design.

[FlatRacer]

I'm under the impression that cleaner flow (less turbulance and air bubbles) occurs with the z-plane design.

I would have thought so. "Z-Plane" is a good name for it!