Scaling designs for mini boat

Builder's Forum
1

I am new to this and way out my depth (pun intended) in designing plans for a small boat.  I have a CNC design and intermediate build experience on other projects (never any watercraft) but looking to start a new project based on this idea:

http://rapidwhale.com/mini-boat.php

Since this is meant for kids I want to make sure the design is solid in terms of stability but I'd also like to merge it with this kind of design to improve on the asthetic appeal (it's on a lake of wooden boat affiicianados!):

https://www.boatdesigns.com/Barrelback-19/products/721/

Any advice on either finding some help getting a good design done or any advice on scaling designs to something of about 6'?  I do know you can't scale any design based on a flat % and make it sea worthy and I don't want to risk that anyway.

I'll take any advice as a complete newbie here.

 

thanks!

Chuck

2

Hi Chuck,

If this is your first ever boat project, scaling an existing design is probably one of the worst ways to approach it. That's the kind of thing that you really need some experience for. Instead, you should be looking at finding designs that meet your requirements. 

So far, your explicit requirements are:

1. Small, in the vicinity of 6' long

2. Stable

3. Safe for kids

4. Good looking

5. Suitable for first-time build

6. Protected fresh water use

Those are a good start, but you need to supply more details to help us help you.

a. How close to 6'? A little longer OK?

b. Power (gas, electric, steam?), sail, paddle, pedal, row, other, some or all of above?

c. Are the kids experienced in watercraft or is this their first time with a boat?

d. Trailer, cartop or docked?

e. How much does weight matter?

Even without your answers, there are some designs here that might fit your needs. First, the 6' Eastport Ultralight Dinghy.

As you can see, it has a good capacity and stability, you could add a trolling motor and battery for propulsion and the oars will let someone get home when the battery dies in the middle of the lake.

Then, there's its 8' big brother, the original Eastport Pram:

It'll also take oars and an electric rig, but can additionally have a sail. As you can see, it's plenty stable and has classic good looks.

And if you want a small gasoline power boat, there's the Cocktail Racer:

At 8' long, it's small enough for kids to drive.

So, let us know a few more details and maybe we can help you out with finding designs that you won't have to scale.

Laszlo

 

 

3

thanks Laszlo,

sure- the cocktail racer is pretty close but even a bit longer than I'd hoped.  I was hoping to get to a size that is portable enough even for one adult to pull out of the water with a small ramp or other.  8' feels slightly too big.  7' maybe doable, but since this would be powered with an electric trolling motor and 12V battery that already adds a lot of weight.

In addition to the weight of the motor and 12v battery (which should be around 40 lbs total) I was designing for 1 adult and one child seating or two children 6-12 years old for a total weight of no more than 400 lbs (our sample of kids weighs between 40-80lbs and I would not expect adults over 250 lbs to be able to fit in this boat at all.)  We have a little Whaler for other folks and older kids.

- kids will have some experience with basics like canoes, paddleboats but not power boats per se.

-definitely for freshwater use only

-per above weight kind of matters so that one adult can get it out of the water failry easily.  We might add a mini trailer for it but ideally it would alternatively fit in the back of a large SUV with the rear seats all folded down which gives about 6'-7' clearance max.

Hope that helps - let me know what else I can answer- thanks!

4

cosmetically speaking, this is the profile I was hoping to get close to - the cocktail class is very similar :

https://www.woodyboater.com/wp-content/uploads/2011/12/Copy_of_IMG_20111216_1144511.jpg

One issue with this design however is a low riding bow which I know will be an issue with any boat this size, but I would want to try to give it some ability to weather large wakes it might have to from wake surfering boats.  Hopefully it could have some ability to repel an average wake of that size.

5

 this is exactly what I had in mind although from the photo it looks even smaller than I was thinking so this scaled up very slightly to hold the weights described above.