Jon boat design and materal help

Discussion in 'Boat Design' started by Heynow999, Jun 23, 2020.

  1. Heynow999
    Joined: Jun 2020
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    Location: Toronto

    Heynow999 Junior Member



    I want to build a Jon boat approximately 11 ft long that will sit upside down on the top of an 8 x 4 utility trailer. I have a 9 foot fiberglass boat that I have adapted to fit on the trailer but the problem is that it is very heavy and the top of the trailer is about 4' high so it takes several people to remove it. I am hoping to build a boat that would be less than 100 lbs so it can be easily managed by 2 people and maybe on in a pinch. While my trailer is 8 feet, I have measured that I can overhang the front by 2' and 1' off the back for a total of 11'. The actual width of the trailer is 54" so if I do 15 degree sides, at 16" tall that would make my bottom a little less than 48 ". I have some fiberglass matt and epoxy resin that I bought for another project so I will use that as required to make it stronger. The boat will be used in small fresh water lakes and not spend more than a few days at a time in the water.


    Lightweight- I was thinking 1/4 marine plywood for the bottom and sides. Could I go for 1/8 for the sides?

    What wood should I use for the frame of the boat, with lightweight being the goal?

    Fiberglass- should I plan to fiberglass the whole boat, the outside, or just the bottom, or some other combination? Where can I find tips on lightweight fiberglass methods

    Construction-I wanted to use Titebond 2 (supposedly waterproof) and stainless brad nails for speed and ease of construction. ( I already have this on hand)

    I was thinking of buying plans from Uncle as a guide. They claim 70- to 80 lbs for a boat

    For propulsion, I know this is unconventional, but I have a 5 hp electric motor as well as a torqeedo propeller that I tried to size for the output of the motor. I would like to try a tunnel drive where the propellor would be half in the tunnel and half hanging below the bottom of the boat. I know this would reduce the utility of the boat, but I'm willing to live with that as again, I already have most of the parts. I imagine a 3 foot shaft at about 6 degrees
    Last edited: Jun 23, 2020
  2. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    At that size you can use 3/16 with no problem. Do not use Titebond. It is ok for furniture or other uses in humid locations. Gorilla glue or epoxy are a much better choice. You can cut the sides and add 1x2 on the edges. Glue/screw the bow and stem panels. Bend the sides to shape and glue/screw the bottom plywood to the edges. I usually use a few sticks to hold the sides in place. With 3/16 plywood, add t 2 or 3 1x2 to the bottom lengthwise to stiffen it. I assume there will be one seat somewhere at the middle. I add a 1x2 almost the width of the bottom under it and a post to the seat. It creates a girder and stiffens the seat and the bottom. You should be able to be under 70 lb. I have build many and fiberglassed only the seams with mat and polyester.
  3. Squidly-Diddly
    Joined: Sep 2007
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    Location: SF bay

    Squidly-Diddly Senior Member

    why upside down? I know its the default way to carry a boat, but if right side up you got extra space for big lightweight items and maybe keep all the boat stuff in the boat.

    See my recent threads about car-top storage-pod/boat, and better ways to get semi-heavy boats on and off vehicle roof-tops.

    I'm trying to design a lightweight minimalist camping/utility trailer based on Harbor Freight style 4x8 (might add extra axle), and part of it would be built in ability to hoist boats on and off.
  4. Heynow999
    Joined: Jun 2020
    Posts: 7
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    Location: Toronto

    Heynow999 Junior Member

    Thanks for that input Gonzo. I need some time to absorb it but I will have follow up questions.

    Squidly, I managed to post a picture. You can see what I am doing. What we do is put our bikes under the boat, as well as the motor and other stuff. Its a pretty good trailer with nice hwy tires, not those crappy little 13" ones, so I might as well build a vice boat and keep the setup for a while.

    The Tesla takes about a %35 hit on range, but one day I will own a Cybertruck with 500 miles range, but that is another story... not to get sidetracked
  5. gruntled
    Joined: Jun 2020
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    Location: Fl

    gruntled New Member

    Sounds very much like the construction method shown in this video

  6. Heynow999
    Joined: Jun 2020
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    Location: Toronto

    Heynow999 Junior Member

    So I jumped right in and started building. I am using Gorilla glue as reccommeded. I found blemished 6mm (1/4inch) marine plywood that I am using for the bottom and sides and 9mm (3/8) for the transom, bow plate and seats. I used some 3/8 oak strip flooring for the gunwales. I plasced it on the trailer and after some difficulty managed to glue the bottom on

    With lightness in mind, I was thinking I would use 60" 60z cloth and cover the bottom and about 5 inches up the sides? I want to fillet the inside joints and coved with 4" fiberglass tape ??

    Then coat everything with epoxy, and finish with a coat of paint.

    I appreciate suggestions, comments as I am a novice boat builder


    boat.jpg [​IMG]

  7. Heynow999
    Joined: Jun 2020
    Posts: 7
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    Location: Toronto

    Heynow999 Junior Member

    IMG_20200720_172939960 (1).jpg IMG_20200726_162328620.jpg IMG_20200714_111958006.jpg IMG_20200720_172939960 (1).jpg IMG_20200726_171653961.jpg IMG_20200726_171722915.jpg IMG_20200726_172145155.jpg

    Progress Pictures. I tried to load them in order but it got all messed up!

    Bottom glued on, Boat is pretty much complete. I still need to attach the seats and there will be wood decks at the front and back as defined by the 1x1 cross pieces

    Cut the hole for the tunnel

    Tunnel in place. I used birch plywood. It will be entirely encapsulated in epoxy

    Tunnel from the outside

    Mock up with propellor. Its a torqueedo propellor

    Angle of tunnel is 21 degrees. I was aiming for 17 degress as per a plan I saw on this forum, but this wont be a speed boat so Im not too worried.

    I am really happy the way it looks so far. A potential problem I see it the boat will only sit about 2 inches deep, so the tunnel may be half out of the water! Im thinking that with myself (220 lbs ) and the battery It will sit lower in the back so the pro should be underwater. I have a ~5 HP electric motor to power it
    Last edited: Jul 27, 2020
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