New Dingy design . Want some inputs

[mydauphin]

I am design a dingy for my boat. This is not your average dingy.
MY SOR is coming. Here are some very rough sketches to discuss some concepts.

[mydauphin]

SOR for dingy.

Dingy will fit into my boat sideways into/unto transom so dimensions are going to be critical. It will also have to be symmetrical.

So dimensions are:
Length: 15 feet
Width: 6 feet
Height: 1.5 feet

To be made from Aluminum.
Faceted look like Wally Boat
As light as possible
Driven by either outboard that is removable or perhaps small diesel jet drive.
Capable of being used as a dinghy, small flats fishing boat or for crossing a small bay.
Possibility of being used as lifeboat.
There will be flotation compartments and removable fuel tank.
Should be able to carry 6 adults in displacement mode
or at least 2 adults and some cargo in planing mode.
Outboard probably something like a 25hp two stroke

Anything else you guys might think about. I have about 6 months before I start serious on it. So starting to talk about it now.

[tunnels]

Originally Posted by mydauphin

I am design a dingy for my boat. This is not your average dingy.
MY SOR is coming. Here are some very rough sketches to discuss some concepts. Attachment 48235

Attachment 48236

Attachment 48237

Attachment 48238

Put a little concave in the bottom fore and aft direction will help with going in a straight line ! also the very aft end of the bottom have a small 1 inch step 90 degrees all way across the bottom to break the surface of the water as it gets on the plane or it could suck the back down as the speed increases

[mydauphin]

Originally Posted by tunnels

Put a little concave in the bottom fore and aft direction will help with going in a straight line ! also the very aft end of the bottom have a small 1 inch step 90 degrees all way across the bottom to break the surface of the water as it gets on the plane or it could suck the back down as the speed increases

Two good points - thanks

[PAR]

Stop by the local Lowe's/Depot and pick up their largest concrete mixing tub, install a deck and call it a day.

[FAST FRED]

Every operator of this may not be highly skilled .

I would round the sharp corners , and pad them well.

FF

[mydauphin]

Originally Posted by FAST FRED

Every operator of this may not be highly skilled .

I would round the sharp corners , and pad them well.

FF

Of course, this is just a sharp rough draft. thanks

[mydauphin]

Originally Posted by PAR

Stop by the local Lowe's/Depot and pick up their largest concrete mixing tub, install a deck and call it a day.

Built a boat similar to this before to use as workboat to stucco seawall, and it was a giant mixing tub. It would carry about 20 bags of concrete. The transon was square on it and sides vertical but the basic box was 8x4 plywood with an extended nose. We used it or 3 years and actually ran pretty good with with a 5hp engine.


I want to see you guys opinion on its performance. Being a double ender, with the engine inside the transom. What do you all think of ruby hull shape. Come on guys, I was expecting greater critiques. How would I calculate displacement on this?

[mydauphin]

I had strakes on bottom of my last tub, would those help here.

[lewisboats]

As to the displacement...divide it into 3 parts...the box middle and the two triangular ends. Find the displacement of the box then find the volume of the box created by the vertical edge of the box times the waterline length to the junction of the angle and the waterline and the width of the boat then divide by 2.



edited...oops I didn't re-look before and now I see it has flare too. Simple...just a bit more work. Find the vol of the triangular sections of the flare the same way as you would the ends.

[PAR]

I see no advantage to the steep rake on the ends. You could nearly double the displacement speed by taking advantage of her length. The volume of a shape like this is fairly easy to calculate. Preform an accurate weights estimate and see where she comes out.

[idkfa]

The sides are set at 45deg? beam at deck 6', at bottom 3'?! That makes standing on the gunwales or ends of thwarts very unstable.

Given that there will be no obvious reason for the slant, she'll look weird at best.

[mydauphin]

Originally Posted by idkfa

The sides are set at 45deg? beam at deck 6', at bottom 3'?! That makes standing on the gunwales or ends of thwarts very unstable.

Given that there will be no obvious reason for the slant, she'll look weird at best.

Perhaps that is a little extreme. I will change to a less pronounce amount.

[PAR]

Let your desires and design goals establish the size and shape of the hull form.

[mydauphin]

The problem with this boat is that it has to fit against my transom. I will try to draw picture of it.