Spira Ablemarle 17 and similar boats

Hi all,

I've been on the hunt to build a boat between 18-20 ft that is relatively light (towable by a small suv), powered by a smaller outboard, less than a foot of draft and isn't just a skiff. I plan on using it in a bay (around Sandy Hook NJ area) which I find can get choppy, some days are maybe 1.5-2ft chop, and possible tow it down to Chesapeake. I sort of locked on to Jeff Spira's Ablemarle 17 (Spira International Inc - Ablemarle Wooden Displacement Boat Plans https://spirainternational.com/hp_able.php). I'm still conversing back and forth via email, but so far I understand it can be powered with just a 15hp and 'get around 12 knots' (so maybe 13 mph?), and has around 5-6" draft, while still being more on the side of displacement boats, which I'm hoping will handle the chop more smoothly at speed than a planing skiff might. Before I go all in on this, does anyone see anything wrong with this design for my purposes, or are there better designs for my use case? Jeff says he can lengthen the design to 19ft, but I'm not sure if that will help my use case too much. I've never seen anything more than one picture of the design built, and no videos so it's hard for me to imagine how it handles in the water.
Ideally my envisioned boat might be going as fast as 15-16 mph at top end on flatter days, so I'm not sure if this slightly slower speed will totally fit, which is the biggest draw back. The greatest interest is the hopefully better handling it will have in less than ideal conditions, which seems often.

 

I think you may be better off with a boat that carries the beam further aft. This is a design for low power and speed. Lengthening the design will give you more speed and a better ride.

 

Better ride in what way, could you explain? Do you have any other designs that come to mind? Thanks

 

That appears to be a largish light displacement dinghy that really wouldn't be happy going more than 5 or 6 knots. If you have ambitions to be cruising around at 12 knots, that won't be suitable. You'd expect a pronounced nose-up attitude to develop as you tried to power up past displacement speed, and expose the underbody to waves, I reckon it would be a misery unless backed right off.

 

In a displacement boat more length equates more speed without squatting and porpoising like Mr E points out. Have you browsed through the directory on this website? There are dozens of designs that can give you an idea for other boats.

 

If all other parameters do not change, more length can mean more speed. BUT this can only be affirmed if the other parameters do not change.

 

It should be noted that the designer Spira mentioned specifically that this would not be the case while under way, and that the hull was designed to not squat at the stern. He also mentioned to me that I would likely be better off with a slightly different hull based on the chesapeake deadrise to achieve the greater speeds I am looking for. I did find another design called the Point Comfort 18 (Hylan & Brown) which is basically what I'm looking for performance wise, but I think I want to see what Spira comes up with from the tweaked Ablemarle design, as I think his will likely be easier to build. I'm not sure I have room to build a 19ft though, need to measure it out-- I might have to dolly it out of the shed or garage while working on the ends which does not seem practical.

 

Well, I'd have trouble believing it would maintain a low trim angle underway, when powered to exceed the "hull speed", but I guess seeing one in action might change that perception, which is informed by the rocker and the narrow stern, as revealed in the drawing on the website.