What wood for shell

I am building a small Jon-boat but do not know what would be the best wood to cover the frame in. I have the frame of it built, I just need the shell of it and do not know what would be the best type of wood to use. I am currently in college and do not have a lot of money, so the cheapest suggestion would be most helpful

 

Best and Cheapest don't really match.
Get the best plywood (exterior glue) you can afford and paint it well with oil based house paint.

Did you do it from plans?

 

I didn't get the plans from the internet, I just kinda sat down and designed them one day

 

Go to Home Depot or Menard's and get underlayment for wet locations. Well painted will last for years. If you need thicker, #1 exposure starts at 3/8" to 3/4".

 

If you use "Exposure 1" construction grade plywood, it'll delaminate, but if you use "Exterior" construction grade plywood, it will stay together. Exposure 1 grade is designed to tolerate an occasion rain shower, before the house wrap goes on, but not a soaking, while Exterior will tolerate a good soak.

Assuming the typical sizes for a jon boat, you'll use 1/2" on the bottom and 1/4" or 3/8" on the sides. If your frame spacing is tight (less than 16" on center), you can use 3/8" on the bottom and 1/4" on the sides. What size and spacing are the frames? A small jon boat will use 1x3's or tapered 1x4's.

 

My dinghy is made of 3/16 underlayment. After a year outside it still has no delamination. the sides are 1/2" pine. No epoxy, only painted with leftover house paint.

 

I've seen "underlayment" done both ways, but "Exposure 1" isn't built as well as underlayment. Most underlayment is red shora (lauan) and has a WBP adhesive. APA Exposure 1 is Douglas fir and maybe it'll have WBP adhesive, but the defects, voids and repairs counts will be much higher with this grade.

 

Menards sells underlayment that shows no voids in the center laminate. I agree it is not the same quality as true marine plywood, but it sells for $7.50 a sheet.