Maslow Home Maslow Community Garden Newsletter

Boat build(free online Dinghy plans turned to Gcode)

Had my Maslow for a couple weeks now and tinkered with it and got it pretty dialed in. I already have cut some things from other files I found, including a paddle board frame. Today I was able to turn paper plans(free online) into proper Gcode and cut out all the pieces and was pleasantly surprised that everything actually fit! The dinghy is an Apple Pie dinghy and the plans are free online so I think it’s ok to convert them to digital files. I’m not an expert on the legality of what I did but I’d be happy to share the files. Attached are some pictures of the cuts and loosely stitched together to verify sizes

2 Likes

Pretty cool, are you using marine grade ply?

I didn’t use marine ply. I didn’t know if my paper to sketchup to gcode would work so I used cheap stuff. I’m going to cover it in epoxy and fiberglass so I’m thinking it should be OK anyway. For as much as it will actually be in the water I think it might be OK.

2 Likes

This is so neat!

I’m working on getting a “project of the month” contest going again and you’ve got my vote so far for sure! I can’t wait to see the finished version

2 Likes

I will be interested to see how it goes, I have been toying with the idea of doing some boat building for fun for years, but the cost of marine ply stopped me in my tracks. I have thought many times that a person should be able to make regular ply work fine, especially in cases where it is not left in the water all the time. So I wish you success and will be watching with interest, please let us know how it goes.

can you link to the original plans?
I’m curious as to which design software that they used to model the curved surfaces and then “lay them flat”.
I can’t figure out how to get Fusion360 to do that kind of thing.

Its the “apple pie” dinghy. I printed out the paper plans and used sketchup to make each panel. I don’t know how to do anything other than that.

Marine plywood has better glue, and “guarantees” that all voids are filled. I believe exterior-grade plywood uses the same glue (or very similar), but voids aren’t filled. Interior-grade plywood will delaminate on its own after a season in the elements.

I guess it comes down to the expected lifetime of the thing you’re building. If you’re building boats just for fun, and your fun is actually in building them, a boat made from cheapo plywood would definitely work for at least a season, probably longer if you protect it really well (fiberglass + good paint). If your goal is just having a boat, investing in quality materials would be worth it.

One thing to note here, is that epoxy & fiberglass is not cheap, so “wasting” it on cheap plywood could be a nonsense.

I’ve also wanted to get into boat building for a long time (it was the original reason for my interest in the Maslow), but I think I’ll practice on a few cheap plywood boards before going in on the good stuff.

You’re not wrong. But I can build 2 boats for the cost of 1 sheet of bs1088 okoume shipped to my house(since I can’t get it locally). Covered in epoxy they seem to last pretty long. They get worn out from abuse before the plywood delaminates on me.

Unless you’ve built 5 boats. I’d build the first several with super cheap wood because you’ll build each one better than the last. I don’t think it’s a waste to use epoxy on cheap wood. It’s still a learned skill that you’ll be better at when you’re ready to build your heirloom Whitehall rowboat.

3 Likes

That’s a very good data-point, thank you.

I agree, it also doesn’t make sense to do prototyping or experimenting with the expensive stuff.

Here’s the complete boat! Finished and out in the wild.

11 Likes

You will need 3 8x4" panels of marine ply max only, right? I strongly recommend using marine ply for this project.

I didn’t use marine ply and I wouldn’t use it next time either. The sides and bottom are .25 inch luan and the front and back are .25 baltic birch. The rear seat was built with baltic birch and the front seat is .75 baltic birch. All coated in epoxy.

The meranti or okoume plywood costs more in shipping than this whole thing cost me. Standard marine grade plywood that I’ve seen would need a lot of sanding. 2 coats of epoxy should keep it nicely sealed.

3 Likes

That looks fantastic!

A word of caution about epoxy and the elements:
Epoxy is great from a water-penetration standpoint.
Epoxy is not great from a UV and sun damage standpoint. (or at least most epoxies. some have UV inhibitors mixed in, if you specifically go get those, but most don’t have any UV inhibitors at all)
It will first yellow, then start to crack and then it won’t work very well keeping water out.
The parts that you have painted will solve that: it keeps the UV from damaging the epoxy.

I think you mentioned that you went from paper-drawings to G-code.
Do you mind giving us some flavor of how you did that?
I see that you mentioned sketchup, but could you talk us through the process? I’ve had no luck getting anything out of sketchup in a way that I could turn into g-code. :frowning:

-M

The comments about epoxy are spot on. I agree that using cheap ply is a great way to make a short-term boat (3 to 5 years) if used regularly. If its is covered religiously with decent paint and stored under cover and the water is kept out of the ply who knows how long it might last.
An observation about marine ply: fir is decent stuff but be diligent about paying attention to micro cracks in whatever you use to sheath it. Fir has a tendency to make small “checks” or micro cracks as it ages due I think to temperature changes between night and day during boating season. These checks can telegraph thru the outer coating after a while and let in a bit of moisture.
If you are building a boat that is more complex and you want it to last it is false economy to not use epoxy. Regular Fiberglass resin (polyester) is a cohesive and does not have as great a bonding strength as Epoxy which is an Adhesive.
Marine plywood is pricey but there are different species that are less expensive than Occume, Meranti being one at about 2/3rds the price/$ . There are different gradings of the ply also: BS1088 is graded for its no flaw surfaces and interior plies, BS6566 Does allow for some face veneer and inner plies to have repairs and some minor putty fills. It is not as pretty but just as durable for all practical purposes. Oh, the BS stands for British Standard, not what you might think. Many of the plywoods have 5 layers of veneers in a 1/4" (6 mm) thickness. It is pretty tough stuff. I am building some parts for an i550 sailboat for myself.

I always thought the biggest difference between standard off the shelf plywood and the more expensive marine grade had to do with voids in the hidden layers. That is, the standard stuff might have holes punched in some of the layers because of knots. The marine grade has those holes filled back in. The marine label is used because you really don’t want those hidden voids causing weak spots in the plywood. Water can put a lot of pressure on the walls and might force a large hole or break to form.

I have a sheet of marine grade fir (special ordered through local lumberyard), seems to have a lot more Dutchman in it, which I believe are harder than the surrounding plywood, but however it’s made, it resists even bending, which if you are making a curved bottoms or sides is not what you need, fine for bulkheads though, and splinters galore.
Have a few sheets of Aquatek, no Dutchman, even plies, just as heavy, no splinters, machines nicely, bends evenly. I love this compared to the marine fir. Although I’m not terribly experienced with woodworking, so take this with a grain of salt.
I’ve used Meranti once in the past I believe, similar to the Aquatek.
Had a class build of stitch and glue kayaks using Okoume, but these were precut via CNC, so all I could say they were light and bent nicely.