Originally Posted by
sigrun
By O.S. convention, anything FP or LA with an -S suffix was C/L. Without suffix indicates R/C carb version. e.g. FP vs FP-S, LA vs LA-S. Those specs I quoted in a prev post were from the actual spec sheets supplied with engines in their respective boxes at the time BTW.
"S" stood for "standard" IMO.
Back in era of MAX-15 pre suffix other than annotation C/L or R/C , the engines came supplied with two venturies in the box. One for C/L, fitted, (the smaller diam) and a second for FF in a bag. In the era of FP-S they came supplied only with a single venturi intended for C/L. If you wanted a wider throat for FF, it was a purchaseable accessory.
Today in US there are a number of small cottage industry folk with machining tools, can make up a custom venturi either out of plastic or aluminum at reasonable cost. Thus getting a right sized one isn't a problem. Also there are enough NOS NVA's out there that one can match one up a venturi like it was made for it, although may be for another engine. Regarding RC carb engines on CL, have only used Enya plain bearing, but works fine for sport flying. Guess just depends what one wants to do. Fuel, tank placement, feed and props make or break.
I've tried a few engines in Akromasters, Peacemakers & Smousens amongst others in class over the years. Akro would fly on both of those engines above, or even an .09 Rossi, Cipolla and probably even an ENYA too. Just not or up to standard of my expectations in what I want the Akro to do. As per earlier, OMMV. With the right powerplant and built light, it's a fabulous airframe.
Peacemakers have intrigued me, guess that the designer made a change so could be published in mags like Aeromodeler, but the Flite Streak heritage definitely shows through.
Originally Posted by
paw080
Hi Vert, If the ASP .12 is under 3.75ozs , it should keep the wing loading at an acceptable level. The point of all my blabbing is that wing loading is the key factor for changing directions; in essence; the ability for the model to "pop" a tight corner. Airfoil thickness is not the most important factor. I'll just let that point sink in for now.
There was a flier that won a major CL Stunt contest with a Ringmaster here in US last year. It has a thinner airfoil but that didn't stop the winner. I guess no one told him that the thinner wing section couldn't be a winner. No one told the bumble bee that it could not fly.
As for the Fox .15BB being suitable, it is not. The engine is way too heavy and way too thirsty, and all the power that engine delivers is wasted on the Akromaster's small wing area(240 sq"). Before the rule change that restricted venturi intake area; many USA FAI Combat flyers were using modified Fox .15BB with lotsa Nitromethane to be competitive with very high performance European(and Nelsons). Tom Fluker a Texan, used modified Foxes to win the FAI World Combat championship in the late 1980s.
Interesting factoids, Tony.
My Fai Combat models were powered by the Fox .15BB, they had 400 sq" wings, and were capable of 89-93 mph, depending on nitro %. Stock Fox 15BBs would fly the same model design 81-82 mph. So...Lighter engine, a displacement providing adequate power loading; yields a model with a lighter wing loading, easier to meet the proper CG without adding much tail ballast and if a smaller displacement engine is used, then the fuel tank capacity is also smaller. I had to shorten the nose of my scratch built Akromaster because of the smaller fuel tank. Going back to your Fox .15BB, you might have a great flying model if you mount it in a 390 sq" FliteStreak! Top Flite actually showed a suggested engine range of .15 cu" - .35 cu" engines in their early magazine advertising. If you think it cannot possibly work; a no longer with us friend, built and flew a 'Streak with an MVVS .12 cu" plain bearing diesel.
Tony
Fox .15BB then could power a lightened Ringmaster S-1 then without problem, as it also has 400 square inches wing area. I am told that a CL converted K&B .20 Sporster makes a good .35 stunt aircraft engine. Got 2 of those in RC, a modeller on one of the CL forums gave me the name of a the individual who makes venturis for the Sportster. - George