This is built from the BMJR kit for the Simplex 45 (45" wingspan) for 1/2A Taxaco. I made the test flights yesterday evening and was disappointed with the engine I built. I swapped some parts around this afternoon and went back out with it. Now it turns that Cox grey 7X3.5 merrily for near five minutes. Thermals abounded this afternoon and I got a 20 minute and a 21 minute flight. This airplane came out at 18 ounces but required 2 oz. of nose weight for proper flight trim. I built a Super Sniffer from this series that came out at 14 oz. balanced.

I have a 40" Simplex built from the Aeromodeler plans, its an old model fitted with regular gear and a 1cc diesel weighs23oz but still thermals well, climb is about 80deg and will go OOS if left to climb , fuel load is generally 3mls, best flight is 43 mins
Stewart

Nice model-unfortunately the Simplex dates bacvk to 1941 and ignition engines-and was at its original size of 60" , intended to be built for around $2 worth of materials at the 1941 prices. The catch for us now of course it that it was designed for the then popular igintion 'rack' which comprised the coil and batteries-all the weight up front-accounting for the ludicrously short nose. Scaling it down in size only makes things worse proportionately,unfortunately! Unless you are an unbelievably light builder and use 'blotting paper' balsa for the tail feathers, you'll always be faced with adding quite a lot of lead to the nose to get the CG right. No way round it sadly-its intrinsic to the design if built to plan. Regardless of the size they all seem to fly extremely well. I've seen scaled up ones flown here (NZ) with Enya 4-strokes in R/C vintage classes very competitively.
At 18 oz you're only a couple of ounces over the typical Texaco weight of around 16 oz though. As an alternative you might consider fitting one of the 'heavy hub' 1/2A (Dubro. Goldberg, Harry Higley or Mecoa) brass spinner nuts to the Cox Texaco-this will a) add a bit of flywheel effect, and b) get ballast as far forward as it is physically possible to do on any tractor model-so you may be able to take out a bit of lead, and still get the CG right!

'ffkiwi'

Hi ffkiwi. Thanks for all the info. I did realize what I was getting into and knew about the old FF models having all that weight for engine, coil, and battery. I previously built a 60" R/C version from a plan that Stu Richmond drew up for Model Builder Magazine and powered it with a K&B Sportster .20 engine. I was able to get all the equipment (3 servos, battery, and rx) up against the firewall because the fuselage is so deep up front. It's natural balance was at 50% and flew fine like that. I flew it at a Little Rock SMALL one year and had to sell it to a guy that loves old timers and made an offer I couldn't turn down. On this BMJR version the equipment is behind a bulkhead that is an inch behind the firewall. The plans called for the servos to be further back, I flipped the part they mount into to get them forward. A design change would give a little edge there but I wanted to use the kit parts. I did grade all the 3/16" sticks and used all the lighter material toward the rear. Anyway, the two thermals I hooked yesterday made the whole project worthwhile. FWIW I still don't have it balanced as far forward as BMJR indicates, it's like around 40% and the first few attempts where at 60%. The large horizontal area at the long tail moment helps. It flies with an appreciable amount of down trim in the climb and a slight amount for the glide.