Optimizing Speed on Small Wood Hull

My first post, so go easy on me.

I'm in the initial stages of planning for construction of 4 or more small layout boats to be used for duck hunting. The will be powered by predator engines on a long-tail frame (6.5, 8, 13, or 22hp). I'd like to design the hulls for maximum speed within reason. Somewhere between 10 - 20mph would be ideal.

The hull design I'm looking at is the Kara Hummer, which is originally designed as a displacement hull with no transom. I'd be modifying the hull by carrying the mid-ship lines aft, and extending the length behind the cockpit to increase bouncy and lift. I'll also try to minimize the dead rise as we approach the rear of the boat to increase lift. It would have a rounded chine if I stuck with the original design (I'd like to keep that feature) I am toying with the idea of mounting the engine a foot(ish) forward of the back of the boat to help with balance.

I'm considering an overall length of around 16ft. Vessel-only weight would be around 150lbs. Motor weight could be 65lbs - 140lbs (depending on HP). I'm 180lbs. My dog is 50lbs, and my gear is probably another 50lbs. So total operational weight around 450lbs - 550lbs.

Question: What is the likelihood that the above modifications would allow the boat to plane with one of the noted power plants? Would it be so inefficient at that point that it wouldn't be worth it? I know I'd have to consider hull design and stability at that speed.

Question 2: How do I estimate (or do you have a guess) of the smallest HP that would get me on plane?

One thing I want to avoid is having a hull design and power plant that allows me to lift the bow in the air, but never being able to get it down and on plane.

Modified hull would be designed similar to this:

 

Welcome to the Forum Mel.

Have you seen the wide variety of duck boat plans that are available from Sam Devlin?
There are 12 different boats mentioned at the link below - one of them at least should be suitable for what you want?
Duck Boats | Devlin Designing Boat Builders https://devlinboat.com/shop/duck-boats/

 

Thanks for the welcome and the response!

I did look at the Devlin designs and opted for the Kara Hummer because of the build simplicity and it was closer to the profile I was looking for in a layout boat. One of the most respected boats on the market is based on the Kara; the Four Rivers Refuge Runner. I ordered the Kara plans form Rob Leonard, so hopefully I'll have them soon. But what I'm really focused on now is how to modify the double-ended Kara to best suit my needs.

Thanks for you help.

Mel

 

What are your needs?

Avoid modifying a proven design, it defeats the purpose of a "proven design" concept.

 

My needs are to (1) integrate a transom to attach a long-tail mud motor and (2) increase the speed by incorporating a planing hull into the modifications to meet need #1.

 

But longtails don't "attach" to the transom.
Maybe you meant "accommodate".

Modifying a displacement hull to a planing hull is a major modification.
I would suggest finding a proven design that meets your needs instead.

As for question #2, determining your HP to plane at 10 - 20 MPH.
Tow your completed boat, loaded, and measure the drag at speed.
From that you can calculate your HP needs.

Could you show us your modifications to the existing design?
Drawings, sketches, whatever.

Finally, why four builds? Are you going to sell three or are they going to be gifts?

EDIT: Why not build the Four Rivers Refuge Runner?

 

I posted a reply, but later disagreed with part of my reply.

I would avoid modifying a displacement craft to planing as @BlueBell alludes to..

The SOR needs to be better understood. Is this trailerable or flop in a swamp anywhere?

For a planing hull; it would be better to have sharp chines aft; you can maintain round chines forward for stealth.

To prevent bow lift; you'll need more balance than the boat you pictured. If the boat has a long skinny bow and all the weight is aft, and the boat never comes out of the hole or hops on plane; it's going to run bow up like the aforementioned Refuge Runner at less than planing speeds.

I'm a former duck hunter and never used a layout boat. We hunted lakes from traditional boats. I stopped hunting cuz I was spoiled by eating domestic duck, which I love.

 

Thanks Blue. I don't have the plans yet (they're ordered), but here are some pictures and descriptions:

Here is the "original" Kara Hummer frame. There is no transom, and the frame narrows and rises toward the aft.



Here is an example of the frame on a modified Kara Hummer that someone else built. They carried the dimensions of the mid-ship to the aft and added a transom. This is the approach I plan to take. I'm in the initial stages of planning, so am seeking input here on what considerations I might make to optimize this design. For example, should I extend the length, more/less dead rise, chine shape (I'd like to keep it within the bed radius of the 1/4 ply, but I'm open to reconsidering), etc. This boat works for the owner, I'm just trying to maximize its function to suit my needs.

Because I often hunt with at least one other person, and would like the option of hunting with up to four.

The Four Rivers Refuge Runner only adds a transom to the "original" Kara Hummer. The hull maintains its displacement characteristics. To increase speed, I'd like to design it to plane. So my planned design would differ from the Refuge runner by having a wider and deeper aft all the back to the transom.

Here's the Refuge Runner:

 

Okay, I understand much better, thank you.

It's too big a modification for a displacement hull design.

If you refuse to use an existing design then design from scratch.

 

Thanks Fall,

For the SOR, here are the things I'm hoping to achieve, though there will (of course) be compromises:

Duck hunting vessel that can comfortably hunt 1 person and a dog
powered buy a long-tail mud motor
able to be paddled when needed
able to be powered by a trolling motor as an option
Relatively easy to build
Minimize vertical profile for concealment
Include features to help "brush in" the boat, the hunter, and the dog
Stable hunting platform
Maximize water ingress/egress for dog
Will be trailered, likely with at least one identical boat (perhaps with 4, with second two stacked on a frame, so it would be best if hull [without motor] could be handled to the ground by two adults)
Maximize speed to access hunting locations

Those are the things that come to mind, but I can probably come up with more if prompted

I had hoped top keep the chines within the curve radius of the 1/4 ply for build simplicity, but I'm open to making a relief cut(s) or sharper corners.

Some long-tails have a pivot point that is behind of the engine, so I could work to bring the weight of the motor forward. At worst, it would be balanced on the transom (unlike an outboard hanging off the back). Because the long-tail is operated from a long handle, it will put my body forward, and also require may dog to be in front of me so she doesn't interfere with the handle operation. I can also move other items to the bow (battery, decoys, etc). If that wasn't sufficiently balanced, then I could extend or widen the bow to increase mass and move the SOG forward. I was actually already strongly considering broadening the nose which would put more material in the bow.

I feel this with all my soul. I definitly don't do it because it taste good or because I harvest enough to keep me full

 

So, does the layout boat need to be paddled in reverse?

If not, you can widen the hull aft which will offer more displacement and be more suited to four hunters. But four guys are going to require more displacement than the refuge running shared by BB. When the boat is on plane, a wider forefoot won't matter and when it stops; the added displacement you need it there.

Check out the Flats Stalker 18 by Jacques Mertens. It is more boat than you want, but a move in the right direction as the hull goes.

I'd probably build more of a jon boat or a garvey hull. Instead of plank on frame; stitch n glue will he lighter as well, if you build monocoque.

 

Also, I couldn't help myself from googling. While I'm not ever going to support splashing anyone's plans, tbe Duckboss line of production boats is not to be overlooked. Your plans need to be like them.

 

Thanks for continuing to help!

No, it only needs to be paddled forward.

That's exactly the plan. Except it only needs to cary one hunter. I plan on building 4 replicate boats. The variables I'm still considering are things like extending the aft (for more planing surface), the amount of dead rise, and the shape of the chine.

That's definitely very similar to the overall shape I'm going for with the mods to the Kara Hummer (especially if I went with sharper chines in the aft). We might be miscommunication a bit on load needs, since I'm only talking about 1 hunter + a dog. The ratio of length to width and the form factor of the planing surfaces looks like they could be very similar. I wish there were some pictures of the bottom of the hull. I'll dig more.

I have a 1548 jon boat and am looking for something lower profile (stealthy). I thought about stitch n glue, but there aren't a lot of layout boat plans and I'm think (perhaps incorrectly) that the plank on frame might be a bit more forgiving for my novice experience. The only stitch and glue plan that I've found that comes close is the Devlin Bluebill 13, and it seems considerably more complicated than the Kara Hummer.

I had not seen those! That seems a bit more substantial than my needs would require, but some of the design features are worth incorporating!

 

Stitch n glue will be better, last longer, lighter.

 

Stitch and glue is easier to build than plank on frame. Also lighter, as Fallguy mentioned.

Less deadrise will get the boat on a plane easier. In fact a flat bottom will plane more quickly than an arc or vee bottom. The disadvantage of flat bottoms is that they will pound when in disturbed water. That may be a disadvantage when on the blind. Noise being one of the considerations. Although hard chines may make for easier for planing, they are more likely to cause noise while at rest.

Somewhere in my library there are plans for a Chesapeake sneak box. I will dig around and see if I can find it. It might have been one of the Atkins designs from long ago. It is a curvy low profile boat that could be built as a stripper, be almost silent, and weigh a minimum. If I recall correctly it had a transom to accept a small outboard.