Tee Bee

Here's the boats my dad and I built last year. We took them to the pond today for some Cox-powered airboat action. These are powered by stock Cox .049 Surestart engines and 3-bladed pusher props. After a lot of searching for web videos of these boats with Cox engines I couldn't find much, so I made my own so others can see how much fun these simple boats can be. Wide-open, rudder-only running. Old-fashioned simple model fun.

Turn up the sound for that sweet Cox noise.

http://www.youtube.com/watch?v=n-lxYyCqy_E

fastkat

Pretty Cool. Try a .10 instead, they really move[8D]

rcairboater

Nice! What fuel are you using and can you post some pics?

controlliner

Did you use the pusher surestarts with the brass prop drive?

Tee Bee

We built these as designed with the .049s to keep them simple and to put to use some of the Cox engines I had lying around. I'm pretty heavy into 1/2A RC planes and have a lot of Cox engines and parts available. We're pretty happy with them as they are.

For running Cox engines, I usually use Sig Champion 25% nitro(1/2 castor oil and 1/2 synthetic blend) with about 1.5oz extra castor added to each quart bottle. It has worked on my .010s, .020s, .049s, and .09s for years with good results.

rcairboater

Thanks TEE BEE. Your post has inspired me to build a lil swamp buggy.
Thanks for the pics as well. Is the sure start a pusher engine or did you just
use a regular .049 and add a pusher prop? Feel free to add additional pics and vid.

Tee Bee

Our engines are stock Surestarts w/5x3.5" pusher props. The engines and props are available here: http://coxengines.ca/ Bernie is a good fella to do business with and is the distributor for the remaining Cox inventory of engines and parts. I see he's now selling the version with the brass prop driver. That would probably be the best option for a pusher, though I'm using the plain aluminum one with a phenolic washer and it seems to be doing just fine so far.

This is a simple boat to build but does take a little time. Our Dumas kits were cut very crudely and the joints didn't fit well, so we just used lots of epoxy to join everything. Everything must be sealed well from the water. I used epoxy for most of the construction and coated everything with finishing resin before painting it. We used leftover Sullivan Gold-n-Rod pushrods for the rudder and made custom fuel tank shelves out of 1/16" plywood to fit the Sullivan 1oz tanks. Placed foam underneath the tanks to dampen the vibes. If this thread inspires just 1 person to build one of these and run it in a traditional manner with a Cox engine, then my efforts here were worthwhile. Hope this info helps. Some Lil Swamp Buggy project pics:

Argess

Here's my Lil Swamp Buggy I built back in the early 70's. Used a Cox 049 and a Pixie "one-button" radio:

rcairboater

Thanks TEE BEE. I just ordered the lil swamp buggy. What size servo did you use on your lil swamp
buggy?

Tee Bee

standard servo, nothing special

rcairboater

Arges, Nice looking airboat. Do you still run?
What set up is your lil swamp buggy?

Argess

Not sure what you're asking about "set-up", but it's a Cox 049 Babe Bee with a pusher 2-bladed prop. The engine was originally in a control-line PT-19, so its run-time is sort of limited by the small fuel tank.

I got the radio used. All it would do was oeprate a relay in the Rcvr when a button on the transmitter was held down. So I made a little box that looks like a servo using brass Meccano Gears. I was only about 14 when I did all this, so I used what I had. Here's a pic of the partially dismantled "servo":



So basically, if I made left turn, and then went straight, I couldn't turn left again unless I cycled through a right turn first, but it did give me some control. Later on someone gave me an actual servo, but I never investigated enough to make it work any differently than the home-made one I had. Here it is installed in the boat:



I havn't used it for a long, long time. The existing electronics, plus a 9 VDC battery for the Rcvr, and some AAs for the servo make it a bit heavy. I think I'll upgrade to a small car radio Rcvr and servo. I also have another 049 with an extended fuel tank. I think it will fit without hitting the rudder, so I might do some sort of swap there.

Oh, I did run it on snow once. After it got moving, it would really fly, but the crusty snow did tend to strip off the urethane varnish off the little keel ribs, so I didn't try it again.

coriolan

You don't really need a pusher prop with Cox reedy engines, they run the same either way.

Argess

True, but a pusher prop makes using a standard one of these easier:

coriolan

Cox used to have a reverse rotation starter spring available, don't know if Cox International has it too. Personally I use an Astroflight 1/2A starter so running either way is just a matter of switching the plugs.
There is a lot more choice in tractor props than pusher and Cox run real well with MAS 6X3 cut down to 5"

Tee Bee

If it's mounted backward, starter access would be a problem since the rudder is directly behind the prop. There's no law against mounting the engine facing forward, however. Then you could use whatever prop your heart desires. We just decided to build ours pretty much by the plans to keep them somewhat old school and to have the prop blast close to the rudder. The Sullivan 1oz tank with the 3-blade pusher gives good 5 or 6 minute runtime with reserves left. I do not hesitate to recommend this setup to others. If I built another one, I'd be tempted to use a forward facing Medallion .09 for a bit more zip. Would have to be careful not to flip it during tight turns, though.

I can just imagine trying to run the boat in a tight spot with argess's "servo". [X(] Extra pucker for sure.