Hey Bill

Lookin' good! I see you've decided to go with the "Boredoak" .25 as my pilot calls it, for the motivator. Right now, the two props that appear to work the best on that engine are the 8x5 APC sport, and the 7x6 Taipan. Opening the venturi to at least .312" really wakes these things up.
Shutoffs are always a good idea, certainly makes getting the needle setting less agonizing for the pilot.

Let us know how the test flights go...

Cheers, Les

Verrrry Nice

I like how you've done the filler/overflow system. Might have to give that a try!

Les

We flew the new SSR yesterday. It flew well, and went fast. I can't say how fast until after the contest next week, because you never know who's spying! Fully tuned, we could get over 50 laps, so I decided to make a slightly smaller tank just in case. While I'm building it, I took a few pix of how it goes together. The tank body is made of only two pieces. Usually I make a wooden block to form the tank around; this time I was lazy and didn't. The tank is 1 1/4" tall, so I bent the two pieces around a 1 1/4" wide aluminum ruler. The tank is 1 5/8" long, 1 1/8" wide at the front, and 5/8" wide at the back. The bigger tank is 7/8" wide at the back, and all other dimensions are the same as the new tank. A rectangular plate of the same tinplate material is soldered to the inboard side of the tank for mounting. All the tubes stop just inside the tank where they are installed. Since the fill and vent are at the outboard edge of the tank, it is uniflow. It is important that the ends of the fill and vent tubes are above and inboard of the fuel tank to prevent siphoning. The tank can be built bigger or smaller to suit different events. Just as a reminder, one fluid ounce is equal to 1.8 cubic inches, so that's what you need where one ounce is specified.

I wimped out and didn't fly it. It was simply too windy and I didn't want to risk it. That being said, I did fly two other peoples' airplanes without incident, but every takeoff and landing was an opportunity for mishap. For the record, it's running 18.5 to 18.7 with an APC 8x6 and a .320 venturi. We're going to open the venturi a bit more and see how it goes.

I got a chance to race TWO new SSR's for the first time at the Dallas contest today. The black and red airplane above won with a 5:43, with decent, but not perfect pits. (Not a complaint or a shot at my pit man Mike Greb, I think he would agree with that assessment.) The even newer airplane, which I built for Mike's entry, came in second with a 6:02. Again, decent but not perfect pits, but we had no practice time with this airplane. First test flights were Friday afternoon. This airplane uses the "short tank" plumbing design described above, and we used it to good advantage in the race.

Perhaps more interesting about the blue and yellow airplane is the construction. It is built like a slow combat airplane. The foam wings have wooden spars, leading edges, trailing edges, and tips, but no sheeting. The wings are covered with silkspan, then covered with iron-on film. The fuselage and tail were sealed with thinned finish-cure epoxy, then painted with epoxy primer and epoxy paint. This type of construction goes together very quickly, and ended up a couple of ounces lighter than the red and black airplane.

For the gearheads, the Brodak has a .330 venturi, and the ThunderTiger has a .200 venturi. Both used the APC 8x6 sport prop. I don't have exact numbers from today, but I think the Brodak was running in the mid 18's, and the ThunderTiger was running in the mid 19's (airspeed, not RPM).

Doc, send me a message when you're ready to start building one!

An 8"x 12" sheet of 2mm carbon fiber by Great Planes is $55 from Tower Hobbies. If you search the internet you can probably find it cheaper, but it will never be as cheap as plywood!

For maximum stiffness a single thicker doubler on the inboard side is advantageous. It also provides a very firm, crush resistant surface for the blind nuts. Just don't expect to press them in as if the doubler is plywood. You have to drill all the holes for the "teeth" . I use carbon or aluminum pads under the engine lugs as well.

I am just finishing up a fun type aerobatic plane kit from a well known combat flyer and manufacturer.  No plywood on either side of the nose where the engine bearers are.   The balsa is laminated 1/8 balsa that is fairly hard by most standards with the hardwood engine peices full depth of the thickness of the fuse.   Fiberglas and epoxy both sides.   Will be using aluminum engine pads on outboard side.  Did think about a balsa doubler on the inboard side, but that will be the next one if this one doesn't work.