Design idea and help needed

[Englewoodcowboy]

Good day all,
I have been kicking around a design in my head for decades and I finally started putting my thoughts down to see if it can become reality, or is even possible. This design incorporates things and ideas I have had from actual experience over the years. As a kid in SW FL the commercial mullet fishery used a well boat for a clean transom and net deployment. I always liked that design because most of the boats were home built so it attracted my attention as well as they were the original skinny water boats before hydraulic jack plates etc. We also had a 40' sport fish and several CC boats from inboard shamrock to a flats boat. My design idea is taking key things I love about certain boats and trying to meld them together. I love the lines of a Carolina flare and the dry that flare provided. I am including a rendering I made in Fusion, I am not great with this product so the flare is not correct but it lays out a good idea of my concept. It is a step hull hybrid well boat. My idea is the benefits of an outboard and the benefits of an inboard with a clean stern for fishing etc. I am looking for more technical feedback and even help of making this concept a visual reality and potentially building it myself. I would possibly do a stitch and glue but could also do a plug and one off mold for proof of concept. I am including a couple screenshots for the general idea. The engine would be fully concealed by a CC to keep egress and usability for fishing etc. as high as possible. Once the basic overall design is better defined then I can look at adding additional features etc.

I need help in getting the hull correct in a step file so I can continue working on it. I will eventually 3D print is for basic scale testing etc. In my design the hull is 27' OAL by 10' beam. Engine transom is 140" in front of the stern. It is a deep V entry for a 25" shaft and the tunnel in the images is 8" up measured at the chine for exhaust and channeling.I know the skiffs that had a tunnel tended to have better steering control but their engine was fully forward of the centerline. I am wanting to keep the engine behind the centerline so steering characteristics are familiar and not complete opposites however I know this will have its own unique handling by design.

I am not focused on price or economy with this, it is merely a concept I want to explore, looking for knowledge in those areas. Efficiency is almost a joke when I think of any boat as far as fuel consumption etc. but it does play a factor. For power I am thinking somewhere in the 400hp range potentially to perform possibly even the Mercury Verado 600 but that is a very tall engine. It needs to be eye appealing to me so there will be some tradeoffs I know, I just need to better define them.

 

[kapnD]

Looks like a great deal of the weight will be forward, handling will be an issue.

 

[bajansailor]

Welcome to the Forum Englewood.
I would agree with KapnD - I think that a design like this will be very difficult to 'get it right' 100%, and you will have to pay close attention to your weights estimate and the2 hull design - not only to see if you have enough buoyancy, but also where the centre of buoyancy is in relation to the overall centre of gravity.
You might get a lot of turbulence from that long outboard well / tunnel?

Re the link below, this thread is currently ongoing - the OP has managed very well to have an outboard engine near the stern, yet under cover, so it does not interfere with (eg) fishing operations.
Albin 25: Emergency Propulsion/Kicker Motor https://www.boatdesign.net/threads/albin-25-emergency-propulsion-kicker-motor.69697/

 

[Englewoodcowboy]

I don't think weight I going to have as much of an effect as you think. I have been in several well boats with the motor just ahead of center as well as far forward as possible and they had no problem getting on plane empty or loaded other than the time it took to get on plane. I am thinking the fuel tanks will be under the aft deck so it should be closer to balanced in that regard and stern head when full. Right now this is a concept and I am trying to think about all possibilities but without the proper software or short of building it, there is going to be a lot of guessing at this time but all good points to look out for.

 

[bajansailor]

Even though you have modelled it nicely on the computer, you can still learn a lot about your design if you build an actual model. Make it waterproof, and then test it out on the water - see how she floats, with different weights in different positions.
You could even try towing it at different speeds - we have done this in the past using a windsurfer mast as an outrigger (so that it is clean calm water to the side of the tow boat, ie not in the wake), a pulley on the end of the mast, and suitable small line.
If you do towing trials, you do not want to simply attach the tow line to the bow - it should be a bit forward of amidships, forward enough so that the model does not become unstable and want to turn sideways.
If you include one of those little portable spring weighing scales like what fishermen use, then you can measure the resistance in pounds at different speeds.
And if you get to this stage, then we can all help you to calculate what the resistance of the full size boat might be.

 

[Englewoodcowboy]

Even though you have modelled it nicely on the computer, you can still learn a lot about your design if you build an actual model. Make it waterproof, and then test it out on the water - see how she floats, with different weights in different positions.
You could even try towing it at different speeds - we have done this in the past using a windsurfer mast as an outrigger (so that it is clean calm water to the side of the tow boat, ie not in the wake), a pulley on the end of the mast, and suitable small line.
If you do towing trials, you do not want to simply attach the tow line to the bow - it should be a bit forward of amidships, forward enough so that the model does not become unstable and want to turn sideways.
If you include one of those little portable spring weighing scales like what fishermen use, then you can measure the resistance in pounds at different speeds.
And if you get to this stage, then we can all help you to calculate what the resistance of the full size boat might be.

That is very much my plan but I need to get the bow flare right as that will change the displacement in that area. I am at my limits on getting the hull shape correct in this program. I am certain it can be done however I just do not have the know how to make it happen or be accurate.

 

[TANSL]

Hi @Englewoodcowboy, I can help you better define the shapes of your boat, but I only work with Rhino, dwg, iges, or sat formats. If any of these are suitable for you, we can discuss the project, not just its shape, but also stability, buoyancy, and other aspects of a boat design.

 

[kapnD]

Better to carry lead or water as ballast than a variable load like fuel.
Water is good ballast for a trailer boat, as it can be drained for trailering.
Have you looked at “inverted vee” hulls? They channel the water flow more smoothly than a squared off channel.

 

[Eurosnob]

Your hull plan reminds me of a Coble. They were designed to launch and land on a beach and the deep forefoot would cause them to swing the stern around when the sails were dropped.
https://c8.alamy.com/comp/KFH6CF/tr...ewbiggin-by-the-sea-northumberland-KFH6CF.jpg

 

[fallguy]

2nd kapn’s remarks

Not a fan of the well placement for the planing hull and carolina flare. She’s gonna be stern light for you, and run like a bobber with a motor; worse at low speeds. You are going to need to be far more careful with well and engine placement for all the weight for’d. Maybe take up tansl on his offer.

You can strip build or foam core the foredeck to help, but there is still a lot of boat for’d of cog and adding ballast aft defeats all the purpose in a well design afaik. You may find it so bad you cannot even put an anchor on the foredeck.

Sorry, but you have to overcome clear flaws in the hull for the power plant. These are intuitive and easy to see for a casual observer.

Almost all gains in a well design are lost here. The boat will lose top speed, fuel efficiency, good trim and gain a hard helm, bow down attitude, rough ride in most sea states.

 

[fallguy]

ps ~ noone has mentioned, but the Statement of Requirements here has conflict.

You like the well from the mullet boats, but the engine placement had a clear purpose in them.

But your powerplant wishes are in a pretty clear conflict with a well design.