60ft flat bottomed barge new build

Hi we are in the process of planking our wooden barge we are planking the hull in 50mm x 225mm strips at 4.8m long at the hull (2 x layers of 50mm) and are putting 1 x layer of 50mm amd 1 x layer of 25mm at the sides(all staggered joints with plenty of glue )my first question is on the best way to seal the wood ie fibreglass,paint the hull or cotton in the joints my second questioon on what would be the best size of engine this vessel to cruise coastal waters and thirdly as our barge is 60ft x 15ft the frames are 75mm x 150mm frames spaced every 900mm apart and has no centre keel what would be the best way to add extra support to the frames

 

Usually you would add a keelson and or girders, riding and well attached to the tops of the floors.
You'd need to post some lines and a target displacement and maybe some pictures for more detailed information, estimation of engine size etc.

 

This doesn't sound like a commercial design - are you making it up out of your head ?

Also, what sort of glue and what sort of timber are you using ?