EdwardB and John, thanks for your posts about DA-50-R.

Just called Brian at Desert Air; what a great fellow to work with. Brian gave me more exact measures on the the DA-50-R, which confirm EdwardB's comments above: I'm dead in the water with the DA 50 R. What a shame; The DA is such a beautiful gasser. Here's why:

DA-50-R RULED OUT

1) The DA 50 R length of 6.7 inches from prop washer to back edge of engine mount can be shortened by using 1 and 1/4 inch standoff mounts instead of the standard 2 and 1/4 inch standoffs that come with engine. That would put me at 5.45 inches, within the 5.75 inches EdwardB measured above. Or I could cut down the 2 and 1/4 standoffs to get the exact 5.75 inches. Or, during building, probably could move firewall back in a bit in toward tail.

2) The DA-50-R is 5.5 inches from engine ctr line to top of head, but there is only 5.25 inches available inside the cowl. One could cut the cowl out at the bottom to alow clearance of the head plus the spark plug and plug cap-wire. But there would be at least a half of an inch of head showing, and the spark plug wire. For many, the esthetics of the scale Moth would dictate against this.

3) Initial measurement on the DA-50-R head above was incorrect and oversize, but it is still too much. The widest portion of the DA-50-R head at the top, is 3 and 1/8 inch. With a Pitts Slimline muffler attached to the exhaust flange, one side from cowl center line must be 2.8125, but there really is only 1.75 inches of cowl space on that side available. On the other side, 1.5625 inches is needed, and there is 1.75 inches of cowl space available, which is enough. One could cut the cowl open and make it fit, but there would be at least an inch of slimline muffler hanging outside the cowl on one side.

One idea is to think of the Moth as "sport scale", mount the DA-50-R upright, and showcase the engine at the front of the plane as-is without any cowl instalation. Its a beautiful engine, and the plane would still have that great "antique look". Yet, might as well build a Flair Pt-17 instead if I'm goin' to hang out the entire engine.

Another engine idea for my altitude is the new methanol/nitro YS DZ 160, same weight as the Laser 180, maybe 30% more power than the Laser 150, it's supercharged, has a fuel pump and C and H Ignition's spark could be added. Since a glow driver for idle is needed anyway, maybe a good idea just to add a few needed onces and go all the way with spark. Have to research dimensions...

Rebuilt a YS 120 AC, supercharged, now obsolete, with custom gaskets and a few tweaks, and it flew a quarter scale cub well. About same power as Laser 150, running a Zinger 16 X 8 at 9200 RPM at seal level. But just don't think it would cut it with the Moth up here.

Thanks John for the Laser 180 suggestion. Might consider adding spark to it.

A correction: All the altitude density and relative engine power ratings I posted above are for the true altitude of my flying site at 9350. Above, I mistakenly posted my flying site 400 feet higher than it actually is.

EdwardB, could you post a picture of your laser 150 engine instalation (without cowl) showing how you routed your mufler?

My best, Peter