The Incredible Hull

I finished cutting the pieces of the main hull, and began gluing and brad-nailing them together.  Only being 3/8″ plywood, and using normal butt-joints, doesn’t create the strongest joints.  But it turned out to be a really nice fit around the frame… like a glove.

I then did a little research on the best way to strengthen those joints/seams, and it quickly became very obvious what I should do.  It’s a hull. Water tightness or water resistance would be a cool feature.   Sounds a lot like a boat.  So I decided to use fiberglass.  I already had the supplies (2 part fiberglass epoxy) from some past boat repairs, so I just bought some fiberglass cloth, and cut it into strips.  You can buy it already on a roll, but cutting it worked fine for me other than all the extra strings all over the place.  I flipped the hull over, and placed it on the upside down frame.. this way, I know everything will be square and still fit after the fiberglass dries and gives the hull the rigidity I am looking for.

There is apparently a method in boat building called “stitch and glue”.  Where you literally just take adjoining pieces of plywood, and drill little holes and stitch them together with wire (or zip ties).  Then you “glue” the seams with an epoxy, or fiberglass tape and epoxy.  Then you cut the stitches and do another layer to fill your holes.   For the seams that were not easily wood glued and nailed, I decided to try my hand at this stitch and glue method.  Turned out to be really cool and was easy to do.  It’s a little ugly now, but fiberglass appearance shouldn’t be judged until after some sanding, and more coats of epoxy and sometimes more cloth.   Also note that in these pictures, where you can see white colored cloth, the epoxy has not yet soaked the cloth completely.

So far I am so pleased with the fiberglass method, I am pretty sure now that the main tank body later on will be made of thin plywood, with fiberglassed seams.  It’s light, strong, waterproof, and easily fixable if it has issues.  You can still easily cut it, drill it, or add more fiberglass to it.  And of course, it can be painted.   Stay tuned for the completion of the hull!

Back to building… finally.

Sorry for the HUGE time off since my last post.  I’ve just been super busy with about a million other projects, including even having to go through and clean and organize my shop work space.

Also, I scrapped the whole sheet metal hull idea.  I started to do it, but the metal was just SO thin my welder wasn’t working great, and it was just really hard to work with.  I decided using pretty thin plywood would be much easier to work with, easier to attach stuff to, and easier to modify later if I need to.  It may add a little weight, but I think the trade-off is well worth it.  I mean, it is a tank after all, not an ultralight plane.

I started by cutting the bottom pieces, using 3/8″ plywood:

Then I cut the sides:

So I guess my next steps are to just cut a couple more pieces for the front and back, and start joining them all together to make a solid hull that will be bolted to the frame.   And of course, once that is complete, I will finally be able to finish the bogies, and begin attaching them to make a rolling chassis.