(Another) Newbie Jon Boat Design

Discussion in 'Boat Design' started by JeepDVL45, May 8, 2009.

  1. JeepDVL45
    Joined: May 2009
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    JeepDVL45 Junior Member

    I was wondering if someone could help and tell me if this design is reasonable, make suggestions for possible improvements, and maybe some tips or hints in the building process.

    I decided a few weeks ago that I wanted to build a Jon Boat as a small project for the summer (or at least for a weekend or two). I was going to buy a kit, but I am slightly delusional and think that I could do a pretty good job designing my own (and I think it would be ALOT more fun). So thats what I did. Before going into the design:

    It will be mainly used for fishing on small lakes (and large ponds) with relatively calm water (the occasional speed boat with a water skier will pass by). It will primarily be used by me(6', 200#) and my dad (6' 230#) or my g/f's dad (6', 275#). So a combined passenger weight of about 500lbs and then our gear. I want to keep it small as possible but still be comfortable ( I was thinking 12' by 4' to keep it more stable)

    I was going to pick up a 20-40 ft lb trolling motor to move myself around the lake. ( I don't need to go fast just move me faster then I could row).

    So I think thats all the background info anyone would need to help me out. I have the design on paper but a quick run down if what you will see...

    (Bear with me, I'm not great with the terminolgy, but if YOU use them, I can figure it out, I just can pull them out of the air when I talk)

    12 feet long by 4 feet wide by 18 inches deep. It will be a flat bottomed boat, but will have a bit of a curve to help it move. all the straight lines you see in the birds-eye-view along the length of the boat will actually be curved. The side walls of the boat will be totally verticle and so will the transom. There will be two boxed bench seats for storage and there will be a small compartment at the front of the boat for storage as well. The hull will also have a rounded shape along the length of the boat. The bow will be squared off like in the picture.

    I was going to use 1/4" plywood for the entire boat, I would use 1/2" for the 'ribs' and the seats, but I'm not sure if this would be strong enough. After It is pieced together, I will fiberglass all the joinds inside and out, and then fiberglass the outside of the boat with two layres of fiberglass. Then I will add some runners (1X2s) to the bottom to take the abuse of the rocks when I drop it in the water (or the tree stumps I hit while fishing) I will also mount a Gunwal in the same fassion (the reason I will fiberglass before is so I can replace them if I need to) Then I will seal up the interior with several coats of poly, and coat the bottom with epoxy. Then I will paint the interior as well as exterior with marine grade paint.

    So, If anyone actually made it this far, does this sound like a reasonable plan? Will the 1/4" plywood be strong enough with the runners on the bottom?
    Is there something I am missing? Any tips? Anything someone would change?
     

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  2. lewisboats
    Joined: Oct 2002
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    lewisboats Obsessed Member

    I did up a bit of a sketch using as much info as I could glean from the scan. I think I saw... 36" bow, 40" stern, 48" max beam, 9" from shear to bottom of bow, 16" from shear to bottom of transom, 12' LOA and the max beam at 5'6" aft of the front transom. Your displacement needs will necessitate the transom being raised on the bottom to about 13" from the shear. This will allow a draft of up to 5" and a displacement of up to 700 lbs total.

    You probably won't need so much fiberglass...one layer on the bottom should be fine. I would use 1/4" for the sides and front transom, 3/8" for the bottom and 3/4" (doubled 3/8") for the rear transom. 1X runners on the bottom will work well. You can use 1/4" for the seats and fill the space with styrofoam as flotation. 1 good coat of epoxy on the inside will seal the wood. This boat will weight 150 or better so you will probably need a trailer to haul it.

    Steve


    [​IMG]
     
  3. Guest625101138

    Guest625101138 Previous Member

    Apart from the fact that you cannot add up you have it just about right for what you want to do. Adding the proposed crew I get 700lb not 500lb. Add 200lb for the boat, motor and a bit more for gear and you have 900lb.

    The attached shows the waterline. It will be quite stable unless you all stand at once. One-up it might be a bit skittish for standing and casting but once you add seated "ballast" it will be fine.

    You have not mentioned the weight of cloth. A couple of layers of 6oz cloth will add tremendously to the strength if placed well. You need to soften the edges (chine) so it wraps firmly. It is nice if you fill the internal edges with epoxy filler to give them a curve as well before glassing.

    The hull will tend to twist unless you have a solid gunwale or keel to take any torsional load between the bow and transom.

    The only other suggestion is to take a look at the second hand market as you might get something at a giveaway price.

    You could also search here for "jon". There are other threads like this one:
    http://www.boatdesign.net/forums/wo...ombody-post-building-jon-boat-pram-26934.html

    Rick W
     

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  4. lewisboats
    Joined: Oct 2002
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    lewisboats Obsessed Member

    he said "or" not "and" ... so only two people at a time. The boxed seats should provide a bunch of torsional rigidity by dividing the boat into smaller open areas. A sturdy gunwale and the bottom skids will tie things together.

    Steve
     
  5. Guest625101138

    Guest625101138 Previous Member

    Missed that important little word. Just saw the numbers. Will still carry the three but the transom will drag of course

    Rick W
     
  6. JeepDVL45
    Joined: May 2009
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    JeepDVL45 Junior Member

    Thanks guys! I really appreciate the help. I knew I would probaly need to go with a trailer for it, but its more then likely going to be stored right on the water, or if we go for a trip, we might try and throw it in the back of a pick-up. And thanks for the tip with the size plywood that I would need. I can't wait to start the project. I'll post pics when it is finished (hopefully by the end of the month)

    Thanks again!
     
  7. lewisboats
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    lewisboats Obsessed Member

    We'll hold you to that! ( I mean the pictures...not the timetable).
     
  8. thudpucker
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    thudpucker Senior Member

    Lewisboats,
    send me the Sketch/Drawing of the one you did for me so I can make a model.
    I'd make a model for this one too.
    Thud.
    PS: I cant seem to get into your website.
     
  9. lewisboats
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    lewisboats Obsessed Member

    PM me with your email address and I'll send a larger picture and a picture of the panel shaped. You can enlarge it and trace them to help with your model.
     
  10. thudpucker
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    thudpucker Senior Member

    Awww your a good man. No matter what your old girlfriends are saying about you.
    Thud.
     
  11. JeepDVL45
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    JeepDVL45 Junior Member

    Alright, I'm picking up posterboard/cardboard this week to make the patterns for the plywood! I should be starting this weekend, I'll probably just cut (but measure 2X or even 3X first) the pieces I need. I'll probably wait until next weekend to assemble the boat and start fiberglassing.
     
  12. thudpucker
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    thudpucker Senior Member

    I used 2" Celophane tape to put my Cardboard pieces together. (to make bigger pieces)
    For my model, I'm just going to use scrap hard board that comes in packaging.
    I might shellac it for stiffness.
    I want to make all the little pieces, gussets, sisters etc in my model.
     
  13. JeepDVL45
    Joined: May 2009
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    JeepDVL45 Junior Member

    Alright, I have slightly modified my design to make it a bit easier to build, but I do have a couple quick questions. I'm getting ready to buy my plywood this weekend to get underway, but I have a question about it. I know that the marine vs. exterior question has been asked 10000Xs don't worry that’s not what I am asking.

    I'm not entirely sure where to buy marine grade plywood around the Western Mass area, (real western mass -- Pittsfield to be exact -- not just somewhere west of Boston), but I’ll find it. I've been checking the internet and I've come across Fir and Birch plywood (both marine grade)

    Is there an advantage of one over the other?

    I would prefer to keep it a little on the lighter side, but if I can add a significant amount of extra strength with a little extra weight, then I can deal. Also I'm not too worried about rot (at least I don't think I am) because I'm going seal the entire boat.

    Also, I’m going to fill the boxes with foam for a little extra rigidity and buoyancy:

    What should I get (or what is it called) and where do I get it?
    Advantages over pour in vs. blocks vs. spray in (if they make it))

    I think that’s everything….or at least everything for now.
    Thanks again everyone.
     
  14. lewisboats
    Joined: Oct 2002
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    lewisboats Obsessed Member

    Massachusetts

    * Gloucester - Essex Bay Boat Co, 15 Rocky Neck Ave, 01930 617/281 2189 - L, V, PW (Okoume)
    * Hanson - Churchill Forest Prod, 91 Franklin St, 02341 617/293 3577 - PW, L
    * Newbury - Pert Lowell Co, Lane's End, 01951 617/462 7409 - PW, L
    * Newburyport - Keiver-Willard Lumber Corp, 11-13 Graf Rd, 01950 617/462 7193 - PW, L
    * Rowley - Yankee Pine Corp, Rt 1, 01969 617/948 7356 - PW, L
    * Salem - Yachtcraft, 94 Ocean Ave, 01970 617/744 3180 - PW, L
    * Somerville - Boulter Plywood Corp, 24 Broadway, 02145 617/666 1340 - PW, L
    * Somerville - Atlantic Plywood - 617/933 3830 - PW (Okoume)
    * Shelburne - Thomson Canoe Works, 323 Shelburne Ctr Rd, 01370, 413-625-8555 - L (northern white cedar, and other long lengths of hardwoods and spruce.

    Borrowed from GlenL's site. Hope this helps...

    You want a closed cell foam...pour in is ok but you have to be careful you don't use too much and spring your planking around the cavity. Sheets you can cut into blocks would probably be better but plain airspace is the best. It allows you to check things, doesn't trap moisture between the foam and the surrounding wood and lets you air things out. Check with Duckworks magazine...they have some nice sealable inspection ports.

    Steve
     

  15. thudpucker
    Joined: Jul 2007
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    thudpucker Senior Member

    I just went through the Marine Plywood dance yesterday. None here unless you order it.
    About (with Tax) $83 a sheet. 1/2" and 3/4" only and 4x8 only.
    That's gonna make my little wooden Jon boat about a $430 dollar job with the paint screws glue and some etcetera!

    I was shocked. But when I think back on all the money I've spent on boats, and this might be my last boat, the shock lessend quite a bit.

    I'm going to make a box in the middle of my Jon. I'm putting the Sliding Rolling Rowing seat on the box. The box opens from both ends, two compartments divided in the middle. Maybe I'll patent that idea eh?

    I still dont know where to put any floatation, but I do want some!

    C'mon plans!
     
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