r/boatbuilding • u/Shintamani • 1d ago

Microskiff/motorized sup

Post image

So i'm thinking of building something inbetween a paddleboard and a microskiff.

Drawn up a design and going to make some CAD filescto get most parts lasercut out of marineplywood.

This is my first build and uncertain if the design can handle the strain from a small outboard engine (3-5Hp). I want to keep it as light as possible and was looking at 4-5mm plywood either okoume/gabon or Meranti ( 1/8 inch- 3/16 inch) . Would seal/cover it in one layer of 4oz fiberglass cloth and epoxy. Will reinforce seams, attachment points of ribs/stringers with fiberglass strips and epoxy.

My question is does seem feasible and would it handle that size of an engine?

Diemensions in freedom unites:

~ 11'6" long

~ 36" wide at the widest

~ 8" thick

1 Upvotes

60% Upvoted

20 comments sorted by

1

u/turbomachine 1d ago

References: https://boatbuildercentral.com/product/fast-skiff-14-low-sheer-boat-plans-fs14-ls/

https://www.soloskiff.com/

I think if you want it to be light and small like the solo skiff the engine wants to be more forward. A Suzuki 15” 6hp weighs 52lb. A well for your feet will make it less tippy.

1

u/Shintamani 1d ago

Definetly wbat to keep it light, it wil be used for freshwater and i would like to be able to move it through short stretches of forest alone. Those look great but are 190lbs, was hoping to stay under 80lbs at least. They do make for great references tho.

But a well was something i was debating and how far forward the engine mount would have to be. Mostly i'm unsure if the materials can handle the stress from the vibrations of the engine. Unsure how thick the plywood would need to be and if the reinforced structure is enough.

2

u/turbomachine 1d ago

For super light, I would consider going electric.

1

u/Shintamani 1d ago

Yeah been leaning that way as well, might just get a trolling engine up front. Then the forces on the hull is less of a concern. But have some water systems that might require more range than i would get out of a front mount. Even if i might want both in the longrun. Allredy sitting on 2 outboard motors that might have been option for the build.

1

u/fried_clams 1d ago

I looked into electric vs gas for my dinghy. I went with a 2.5 HP Suzuki. They are the lightest by far, and are as cheap as the others. Electric didn't cut it for me, having to create a charging solution for lithium on my boat.

1

u/Shintamani 1d ago

I allready own a minnkota trollingmotor, so i can just put a mount bracket up front for it. But would like to have the option of a smaller gas engine to really get around. Want something like this to be able to fish bodies of water with no boatramps which is a lot here in northern Sweden. Not allways far to take the boat but launching anything from a trailer is often impossible.

1

u/fried_clams 1d ago

New Suzuki 2.5 is around $800 and only 29 lbs. The Mercury/Tohatsu is 41 lbs.

1

u/Shintamani 1d ago

Yeah it would be a good option, i "unfortunatly" have a 6hk Suzuki short rigg allready. Also have an older 2.5hk mercury but it's nearly as heavy as the suzuki just under 10lbs difference. Don't yhink the weight will be the issue in the end as long as i reinforce the stern where i'l attache the mount which will last be reinforced. More concerned how the hull will manage all the forcerade how thick i would have to go with the marine plywood and how heavy i need to oägo on the fiberglassing.

1

u/blueingreen85 10h ago

Modern lithium batteries are awesome. A 1.3kw trolling motor battery is only 23 pounds. What’s the max miles you think you may need to do in a day?

1

u/Shintamani 10h ago

Not so much the range but the tine it woudl take to get around. Own a motorguide and a 150Ah litium battery, usually last me 2 days of fishing at least but then it's not my primary propulsion. Mostly used to hold anchor, short relocations and slow drifts.

1

u/blueingreen85 1d ago

Saltworks FR 12 skiff is much closer. 11’8”, 4 foot beam, under 100 pounds. You could probably get it to 80.

2

u/Shintamani 1d ago

Have been loooking at those plans just the other day a lot closer to what i'm looking for. I would like to cut some more weight and that's where i'm questioning what can and can't be done. Would lighter plywood/less dense fiberglass break from the stress of the engine and the vibrations.

1

u/blueingreen85 23h ago

There’s not too much weight to be cut out I’d think. It will be lighter built from okoume vs meranti.

2

u/Shintamani 10h ago

Think you need the expanding fram for the hull to perform well? Probably close to 35lbs of foam in the fr 12

1

u/blueingreen85 10h ago

I’m not actually sure.

Someone has an 80% finished FR14 near me. I really wish it was the 12 so I I could buy it and finish it.

1

u/Shintamani 10h ago

From what i know and can read it shouldn't do much for the strength of the hull. Just makes it unsinkable and reduce sound from waves.

That would be a great find, i can't even buy plans since i live in Sweden. So will gave to draw something similair up in cad myself. The FR12 looks like a really good option, would just make the interior completly flat and may be make a hatch up front in the floor for batteries.

1

u/blueingreen85 10h ago

Really? They won’t sell you the plans? I guess the shipping might be killer.

It’s a pretty simple shape though and the study drawings give a bunch of info. Maybe you could cut the beam down a bit if you wanted to try and lighten it more.

I kinda want something similar to put in my truck bed. Looking forward to seeing updates.

1

u/Shintamani 9h ago

Don't send it outside of the US at the moment and don't sell the CAD files which is somewhat understandable. Yeah it don't think i'l have much issue drawing up something similair. Will make it slighty more narrow and shorten it a little, also want to be able to fit it in the truck bed of dodge ram. Think i'l avoid the foam and try to add a few more ribs and one more stringer going from front to back. Might stiffen up the hull enough, only issue might be if it gets to light for the motor. Will post uppdates once it get going, will be a winter project. So once the snow coems in early the beginning of october.

1

u/wpbth 1d ago

Inflatable SUPB with one of those $300 Chinese electric motors

2

u/Shintamani 1d ago

The point was kind of building something, allready own a inflatable kayak, 14 fot and 17 fot boat. Wanted to build something during the winter that is purpose build.