Kids runabout design

Hi all,

First post
(Just typed a very long post and when I tried to add media the whole thing disappeared so this is a somewhat shorter version of what I had originally intended to post)

I'm designing a small runabout for the kids. I looked around online but the existing kids boats were all a bit too clunky for my taste, so I decided to dive into DelftShip and try and do it myself.

To bring some method to the madness a few sort-of-ish SOR/design principle list
- Small, max length of sections is limited by a sheet of plywood (2.44m)
- Will be built in fibreglass over plywood (hull)
- Planing hull
- Electric propulsion (under hull waterproof inrunner BLDC)
- No need for planing speeds in the beginning, but I'd really like it to be able to in a later stage (hence the planing hull design)
- Classic looks
- 2 kids or 1 adult (~100kg)

After a few initial designs and reading up on lots of literature online, standard designs (hull series 62 etc) I came to the following design. It took quite a while to get the bow to develop nicely, have to redo the transom so don't look there . This is also my first attempt at 3d design.

It's basically a bit of classic wooden runabout transom mixed in with parts riva like flared bow, a bit of modernism in the straight upper stern (not sure about that yet). I know the waterline ratio for planing hulls is (way) off, more like 2:1 in stead of 3:1, but if I look at ie the Glen-L squirt they are also nowhere near that ratio (guestimate from a million online pictures).

Wonder what you guys are thinking
I'll try and keep this thread updated with progress.

(edit - I'll add pictures when they are approved, first post for me so I guess the mods need to make sure I'm a relatively sane individual).

 

[QUOTE="
I guess the mods need to make sure I'm a relatively sane individual).[/QUOTE]

Im going to ramble a bit off topic here.
A sane approach might be to find a used boat similar to the one you proposed, clamp on an outboard, and spend the time on the water with your kids, rather than wasting valuable bonding time alone in the shop.
I’m speaking from experience here, your kids are only young once, and it’s way too easy to get involved in your own passions while doing projects “for them” rather than “with them.” They won’t appreciate boatbuilding like you do.

 

True. Very true. Luckily I'm blessed with a job that allows me to plan my work more or less anytime that suits me so I'm free to pickup the kids from school and spend my afternoons with them. I'm quite an early bird, so often days I finish work around 3pm. Like most of my previous projects (ao. building copper/stainless stills, developing still electronics, distilling, building a plethora of loudspeakers, restoring espresso machines and lots, lots more) this will be an after-kids-bedtime project. I'm not in a rush, if it takes me a year or more to finish it, that's fine. From my loudspeaker building days I learned not to underestimate woodworking cost, effort and duration.

Having said that, there's of course always the potential of getting overabsorbed in a project. I'm equally lucky/blessed with a wife who knows me quite well and I've learned to heed her "advice" (heaving learned the hard way, years ago).







This way is easier than getting an album filled I guess.

Was a major pita to get the bow section stress-free and to develop nicely, have to redo the transom. Have to do the deck aswell, learning as I go. Need to find out how intersects work as currently it's just an extruded, curved surface and that'll never work with plywood.

Odd thing btw, If I add a control point on the upper straight edge of the bow (without moving it anywhere) the gaussian view paints the whole front red.

 

At the length you want, that design is not going to work. Unless they are already experienced, you will have to start by being in the boat with them to teach them boat handling. The boat will be very cramped and hard to trim properly. If you really want to build instead of buying, a jon boat can be built in one day. That will also allow you to get the kids involved in the build. It would be a nice weekend project.

 

^ KapnD Has the best of advice.

 

As you have the current shape, this hull cannot be built in plywood. To avoid the double curvature zone at the stern, marked in red in the picture, you should give the transom more height and give the sheerline a smaller width at the stern.

 

Thanks for the comments.

I live in the Netherlands, and over here you need a "vaarbewijs" (boating license?) if your boat is able to go faster than 20km/h, which you can only get when you're older than 18. So, for the kids it will be a non-planing boat and >handling is less of an issue. With the short waterline it won't be fast (2m waterline > ~6km/h hull speed) which will be good enough for them to cruise the small canals around our house.

I know the aft section needs to be redone, thanks for the heads up, will post back when I have something that works. I may even do away with the double curve completely if I can't make it work.

So why build a boat and not, as suggested, just buy one? Well, I need something to keep my head and hands busy after hours. I don't like hanging in front of the TV watching stupid movies. I like the process of making stuff. Design, learn, redesign, learn more, make and learn even more etc. And then, why a design like this? Well, it's not too big, will touch all aspects of boat building and I can make it relatively cheap or decide to take it a step further if I'm happy with the results. A jon-like boat doesn't tick the "needs to look nice" box for me

Maybe even build a hull from cheap interior plywood first, slap on some cheap epoxy and see how it handles and decide from there.

Although marine grade plywood and epoxy is expensive stuff, the major cost components are bound to be motorisation and the shiny blingy stuff. If I can keep cost down to ~2k for a bare, working boat (ie. marine plywood, epoxy/fibre, other base materials) and a small-ish electric motor + battery that lasts for an hour (or two) and at the same time satisfy my "diy urges" for the upcoming year (or two), that would be great.

Maybe I should've give the thread a different name - "Keep me busy runabout"?

 

It seems like a boat for the kids is less important than you having a hobby. There is nothing wrong with that, but the goals are different. I doubt your kids would see much of a difference in their adventures on the water as long as the boat floats and moves. If you build a work of art, the impulse to hover over your kids as they scratch and dent it, may ruin their experience.

 

The day after I finished my last set of subwoofers (speaker drivers facing upwards) I found my cat sleeping in/on the left speaker driver. Build cost was about 700€ each. Piano like high gloss black. Took me 6 months to build them. That was about 4 years ago.

Still have the cat, still sleeps in the same speaker driver.

 

In that case, you may be looking at several years to finish the boat. I was not criticizing if your main goal was a hobby designing and building a goal. My suggestion is that the hobby and taking your kids out on the water are not compatible.

 

Boat Builders Central has a 12' runabout , scale down 10% in length and call it good , or do a little redesign .

 

True. Taking the kids out on the water is something we do regularly with the boat we already have, and they love it. Maxum 1800SR runabout, so officially they can't drive it, but my son loves to drive sitting on my lap.

Anyway, a bit of tweaking and it ends up like this. Everything develops nicely. Flat deck. All panels fit within a 2.44m sheet of plywood, so i'll need 3.



Might be nothing special for you guys, but for me it's the first time i did something like this. Now, on to the chines and bulkheads.

 

Good job, congrats.

 

Actually, designing something with developable panels is a challenge. Congratualtions. You can test is with a carboard model to see if they fit as expected.