need advice please.....Phantom Build

Designs for inboard or outboard power

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need advice please.....Phantom Build

Post by Musicman » Sat Sep 24, 2016 9:43 pm

Hey All,

So I've taken onboard all the advice given about the aussie timber issues I was having but have discovered another more pressing issue.

The phantom has been designed for either V drive or stern drive engines. Using a few online tools to give me a very rough idea of what horse power i would need to be able to easily get moving between 20-30kts max AND keeping it under the 1800lb weight limit, I have found that once I put the floor in (Using the smallest 300hp inboard I can find) I'm left with about 30" on the sides. I'd originally planned to build this boat to go fishing out off the shelf but this motor issue isn't really allowing for it. The sides of most larger boats come up to waist height but this, so far, is below the knees.

So my questions are as follows;

1. Given certain aspects of designs can be safely changed, would I be able to give the sides a bit more meat and extend the frames by no more then 1ft?
2. Those of you who have built flybridge power boats, What inboard/s did you use, does the boat plane well and how far out would you safely take it?
3. Considering that both V and Stern drive engines are accepted, is there any reason to think I couldn't do either of the following?
3(a) Pod Mount a couple of large outboards.
3(b) Build an extra frame between frames 7 and 8 and build a motor well into the stern to accommodate outboards.
The image is an idea i had to make things work. Half of it is from the plans, the level is around where the floor would be to fit the engine flush under it without sacrificing deck space for more important things such as fishing. Frames are 35" apart so considering raising the stern plus preceeding 3 frames and transfering material that would be used for the cabin between frames 2 and 3 down lower to give more freeboard.
The only thing i'm wondering is on the extended version, where i've notched for the original sheer clamp, will it still be strong enough?


Considering keeping the same deck height right through to the helm then dropping down for sleeping areas and having under floor storage as well as doing away with the flybridge but utilising that height for the cabin area to be able to stand up. So in short it will still be the same width and height, just the stern sides and the floor will be raised.

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Joined: Sun Apr 10, 2016 9:25 am
Location: Melbourne, FL

Re: need advice please.....Phantom Build

Post by riplash » Sun Oct 09, 2016 10:56 am

Hello Musicman,

I am looking at the Phantom, Catalina Express, and Calypso plans. (They have the same hulls, just different superstructures). I am working on combining ideas from all three designs to make it more like a modern dual console boat like a Sailfish 270 DC or a Boston Whaler advantage 270. I am drawing my changes on autocad and making a 1/10 scale model from wood, but it is a long slow process and going slowly.

I think all of your options that you listed are possible. But extending the height of the frames and sides aft of the cabin seems like the best Idea to me. I don't think there will be too much of a weight penalty. Another Idea would be to build a "dog house" cover for the motor and make the floor lower. Similiar to modern ski boats with direct drive or v-drive. Plus all of the boats that I personally like have deeper cockpits and I like that.

I am planning on using a V-drive and a 350 on my boat. I like to waterski, Snorkel, hopefully scuba dive in the future, and go fishing offshore and inshore. So one of the goals for my design changes is to have it be really versatile. Plus I don't know what decade it will actually be finished.


P.S. it is nice to know someone else it working on a phantom.

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