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Noob building 9 foot jon boat. A few questions


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  #1 tacojon

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Posted 14 June 2012 - 11:52 PM

Hello all. (sorry for the long post in advance)


Next summer, or perhaps this winter, I'll be building a variation of a Jon boat. To be honest, I don't even know if it is technically considered a Jon boat, but I'll do my best at describing exactly what I'm trying to do. I'm new to the world of boating, so please excuse my lack of correct terminology.


I live on a small man-made lake in Buena Park, CA, and I want to build a small row boat to get some exercise and relaxation. I've never built or designed a boat before, but I have some experience with carpentry and believe I have some basic skills to build a very simple boat. I've come up with a basic design and I have a few questions about it. The boat will have two plywood side panels, one bottom panel and a front and rear transom. It will be about 9 ft long, 36" wide at the beam sheer and 30" at the beam chine. The rear transom will be 24" at the sheer and about 18-20" at the chine. The main reason I think it might be considered a flat Jon boat it because I want to put a narrow rectangular transom at the front to allow for a steeper front angle without requiring too much flex of the overall shape. Also, I figured it would let me build the boat a bit wider without as many issues with bending the sides. The bow transom will be about 1 foot wide at both the sheer and chine and the angle of the bow transom will have about a 30 degree rake above the water line. The gunwales will be 12-14" tall. I am planning on putting chines and gunnels both on the inside and outside to increase the strength. One of the main goals of the design was to keep the inside as open as possible without requiring an additional deck. I'm planning on putting 3 1x4 keels on the bottom to increase the rigidity and as far as the frame goes, I was hoping to have about 6 frame ribs made from 2x4's that come all the way down the sides and end about 6 inches from the bottom corners to keep the hull as open as possible (I did this in hopes of putting in a sleeping pad that i can put in the bottom and take a nap on) I was planning on making the sides from 1/4 plywood and the bottom from 1/2 inch plywood and fiberglassing the entire outside of the hull to increase rigidity and improve the seal. I was thinking of building a bench at the bow and aft and perhaps having them double as sponsons if need be (I like to overbuild things, so I'm estimating this boat may be as heavy as 60-80 pounds) As far as propulsion, I will be building a forward facing rowing system similar to the EZrow and i will put a removable slide seat track down the middle of the hull (It'll be removable so i can put in the sleeping pad when I'm not rowing). The seat track will be a glue lam made of 3 stacked 1x4's to match the slight curvature of the hull. I may eventually put a little minn kota endura c2 30 but I'll worry about that later



Questions:


1. Does the design seem feasible/sensible?


2. Is 80 pounds too heavy for a 9 foot boat?


3. Will I need spreaders or will the framing I am planning suffice?


4. Will I need to make the benches double as sponsons? If yes, both benches? or just the aft one?


I would greatly appreciate any other advice anyone may have with regards to my project.


Thanks for your time

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  #2 176inches

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Posted 20 June 2012 - 01:14 PM

The design sounds feasible but you may be over-designing this boat quite a bit. For this size boat 3/8 inch plywood should be sufficient for the bottom, and if there's any curvature in the bottom 1/2 inch ply is very hard to bend. Fiberglassing is unnecessary in my opinion and only adds weight and cost, unless you expect a lot of scraping, but the three 1X4 keels should protect the bottom. I would suggest hardwood for those, and I've found 3/4 by 1 inch oak (actual dimensions) to be good. Ditto with chines on the outside: probably unnecessary. Can't really picture the ribs but once again 2x4s are excessive. Nothing wrong with over-designing but I personally prefer economy of means...

As long as there is curvature and flare in the sides, you do need spreaders until the glue sets.

What are youg going to use the sponsons for?

  #3 176inches

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Posted 20 June 2012 - 01:24 PM

Another thing: don't mean to complicate your life but you will find that a flat-bottomed boat with a blunt bow is sluggish at rowing and will not track well. For good rowing preformance you'd want a narrow, sharp-bowed one with a v-bottom and a skeg; but of course that kind would be hard to build and to nap in. Boat design, like life, is full of compromises...

  #4 Howard

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Posted 28 June 2012 - 10:09 AM

What you describe sounds like either a pram, or in traditional terms, a punt (do a google search for punt boat and view the images). What we call jon boats are very similar in design to punts. Built as you describe, my guess is you will be closer to 100+ pounds vs. the 60 to 80.

Unless you would prefer to re-invent the wheel (can be fun) there are any number of plans already available. One source you can view is here:

http://www.duckworksbbs.com/plans.htm

Gobs and bunches of boat designs there. There are a couple other versions similar to what you describe that are intended for sail........Puddle Duck Racers (PDR's). The duckworks site has information on those. Look under designer Storer and you will find something similar called Oz Racers and a simple punt.


If nothing else, you can view what people who design for a living have come up with and go from there.

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