I think it Will Float

[ratrace2]

Smooth, Fast, upriver cruising....yea baby

[rwatson]

Is that 'bump' in the keel just behind the bow meant to be there ?

If so - why?

[ratrace2]

Yea, it's part of the knife

[Mild Bill]

Does that have anything to do with the design philosophy of "Trumpet"?

[ratrace2]

Originally Posted by Mild Bill

Does that have anything to do with the design philosophy of "Trumpet"?

Not directly, it started with the "unsailboat", the need for a very shallow draft, and my aesthetic preference for that bow shape.

[EStaggs]

Smooth water or whitewater?

She looks like she will root in waves....

E

[ratrace2]

Originally Posted by EStaggs

Smooth water or whitewater?

She looks like she will root in waves....

E

What makes you say that? Have any analysis you would like to share??

[EStaggs]

My analysis is usage. I have a 22' launch with a fine entry like that and less aft waterplane (its a double wedge hull) than your design. She requires a long skeg underneath because of her fine bow, as when she hits a wave at any sort of an angle, she thinks about rooting off course. Bcause of the skeg, there is plenty of lateral resistance, and she stays straight. If it is a slow boat, I think your golden, but I see what appears to be either a warped plane or a monohedron on the bottom aft sections.

Thats the reason for the question about whitewater or slack water rivers. In a whitewater boat shes a no-go, and as an ocean going boat, She has the right characteristics to cause her to root in waves.

Picture the slender bow in your head, with those knife like features. In a straight line they work to split waves, but load the hull at a slight angle and that side will start to steer the bow of the boat. Once the bow begins to steer her, something aft needs to either compensate or be proactive. A skeg will prevent rooting in substantial sizes, or you can hope that your propulsor will be in charge and bring her in line.

If someone else can explain how im wrong, please do as I would love the learning experience, but thats what I see.

E

[ratrace2]

Actually, that was an excellent answer.
Yes, this is a slow boat. Mostly for the rivers around NY.

[ratrace2]

I think I'm going to run the deadrise to 20 degrees at the transome and eliminate the warp.

[EStaggs]

Actually you can keep the hull shape if you feel its efficient, but just add some lateral resistance (skeg) to it. Id think 30% of the length should be good, but testing seems to always tell the story.

E

[PAR]

20 degrees of deadrise in a monohedron or 20 degrees in a double wedge form will make for a poor low S/L hull shape. The steeper deadrise forms are for higher target S/L's then you're likely anticipating.

If you want a moderate S/L hull form, add more shape to the entry to fatten up the entry, keep the aft sections reasonably flat (assists the low power, lower S/L requirement) and move or reduce the effective planning surface. Many examples of very serviceable double wedge, efficient, moderate S/L hull forms are available at little to no cost. It would be wise to closely adhere to these shapes, until your understanding of what modifications to these shapes will do to the performance envelope you're targeting.

In other words attempting to make a 20 degree deadrise hull form, perform at lower S/L's then intended, will result in a poor handling and fuel sucking beast. Attempting "new" concepts on a tried and true hull form requires a considerable amount of understanding of the concepts and dynamics involved. Until these concepts and dynamics are second nature in your mind, as you develop new shapes, then attempts to do so are literally a shot on the dark.

I say this because of the very dramatic differences, between the distorted warped bottom you've drawn and the 20 degree monohedron you've suggest, as a possibly more suitable revision on the same design brief requirements. No offense, but this shows a clear lack of understanding in the dynamics of planning craft design, in light of your moderate S/L target.

[ratrace2]

Par,
I agree.

Par says: "No offense, but this shows a clear lack of understanding in the dynamics of planning craft design, in light of your moderate S/L target."
... . . . .It sure does, but look at what I learned in the process......

Par says: "Many examples of very serviceable double wedge, efficient, moderate S/L hull forms are available at little to no cost."
. . . . Where?. . .
Still waiting for Amazon.com, Gee they are slow.