First boat design

[sbeausol]

Hi Everyone-

In my quest to find the perfect boat for my needs, I've decided I would like to try out the newer style power drifter type boats which are part drift boat, part jet sled. However, my location on the eastern part of the US has limited my access to these boats as the only manufacturers are out west. This is what they look like:



Using a few drawings and the specs from these types of boats I grabbed the free version of delftship and tried to recreate the hull with the ultimate goal of exporting the dimensions (DXF file) to have the parts cut at a local CNC shop and welded in my area. The basic specs are 16', 55" at the chines, 75" beam. I would power it with a 40/30 or 60/40 jet. Bottom will be .125 or .188 5086 and the sides will be .125 5086 aluminum. Here is what I was able to create:





This is a pretty simple design so I can't imagine there are any major pitfalls, but I'd like to hear what more experienced designers might have for input. Have I simplified this process too much and headed down a more difficult road than it seems?

Any input is appreciated!

[alidesigner]

Nice effort for first time around.

Just make sure that the surfaces are developable. I dont know anything about delftship but have a look in the help files for the word developable or ruling lines and make sure your surfaces will develop from the cut parts into the shape you want.

Good luck!

[Guest625101138]

You can produce cut files from FreeShip. I am not sure if the free version of Delftship allows you to develop plates. Also I am not sure the free version of Delftship will allow DXF export.

I expect you intend to have the boat plane. In this case the run aft at the keel should not curve upwards as you have it.

There seems to be some pinching of the plate low down at the bow. If you post your file I will have a look at this bit.

The flat bottom will tend to pump. It is extra work but a slight 'V' will stiffen the bottom.

The angle of the transom seems too far off vertical for typical outboard trim range - should be about 12 degrees.

Rick W

[sbeausol]

Thanks for the input, I will check into both things. I've attached the files, one is the standard file format and one is the dxf file.

As far as getting up on the plane, one of the goals for this boat is to power upstream against up to class II rapids, so yes it will need to be able to plane, and it also will need to be able to 'get on step' quickly. Although I agree that a slight v would increase its performance under power, the primary goal for this boat is to provide a stable fishing platform while drifting. The slight rocker in the back is meant to allow the boat to anchor or be held back in current without too much effort. My understanding is that this will have a negative effect under power, since it will cause the bow to raise up, but I believe is this is a necessary compromise?

Thanks again for the input, let me know if the files are the right format.

[Guest625101138]

I have modified to reduce the plate torture at the bow. The curvature images show the difference. I also included the plate developments from Delftship. You can get plot files for these direct from Delftship.


I guess you transom angle does not matter if you are using a jet.

The curve in the keel line will reduce planing efficiency. I expect not much. It will also stiffen the bottom plate in a similar way to forming a slight "V". I doubt that it will help flow from astern unless you can get the transom clear of the surface by shifting weight forward.

Rick W

[Fanie]

Hi sbeausol,

Do have at a cathedral hull or semi cathedral hull as well. They are very stable and make excellent stable boats for their small size.

[sbeausol]

Rick-

Thanks for the help I've downloaded your attachment and it looks great. I appreciate the input and the tweaks. I have a little more tweaking to do in terms of figuring out the appropriate side height and also the appropriate transom height such that it is right for the motor I will run which will likely be a long shaft. I also need to decide if i want a tunnel for the jet, although from somethings i've read, I'm not sure those always produce as expected and often cause cavitation issues.

[Gilbert]

Hi,
Take a look at this link to check out a really exceptionally good design that is very similar to yours. I especially recommend the bow shape over yours. I am not saying your bow shape is bad, but I think this one is a much better all around bow.
http://www.smallboatforum.com/PDFfil...icCityDory.pdf