flyncajun
Posts: 400
Score: 105
Joined: 12/26/2006
Last Login: 5/24/2013
From: DENHAM SPRINGS , LA, USA
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Hi Jim
One of the biggest misconceptions is that wings don`t produce lift in the up lines or downlines.
The wings never stop lifting! they just don`t lift quite as much in the up and down lines. but the drag never goes away.
Wings are 70% of all drag on a airplane, a bipe has two wings, 1.5 times the drag of a mono, plus 1.5 times the lift. The dynamics of a Bipe allows for not relying so much on the prop for drag breaking
You are right about the diameter being more effective on braking. I love large diameter props for breaking but, the more diameter you run the less pitch you can use ,this is where the breaking comes in, add pitch to that same prop, and you loose breaking. So the problem you run into is, with too much diameter for the breaking and,on a windy day, you don`t have the pitch or enough rpm to produce the pull needed to fight the wind, and keep up your speed and authority for many of the manuvers.
With a bipe, you increase the lift ( allowing you to fly slower speeds) the drag from the wings helps with the constant speed ( no zooming) and keeps the downlines slow.
The abilty to fly slow with authority gives you the flexibility to run the engine in the lower rpm range, and use the tourqe curve, this is what allows us to use more pitch to couple the torque and not rely on the diameter for breaking even in the downlines. This also gives you the ability to run the higher pitch for limiting the rpm to a specific number thus, enabling you to pass the sound test, but giving you the flexibility needed to fly in all conditions.
I`m not trying to say the prop does not help with the down line breaking is absolutely does,adding just 1/2 " has a dramatic effect on breaking, However the ability to back off diameter and add pitch is a big help with selecting the prop you "want" to run, verses the one you have to run! throttle resolution on the first 1/2 of the rpm range is now more smooth and duplicatable.
I have been whittling on props adding pitch, diameter, Ect for ten years now, I have so many custom props that work and just as many that don`t SO I know a thing or two about getting props matched to the airframe.
Diameter trumps pitch for the most part on Mono`s ,But Bipes are a whole new dynamic. My Bipe is the first one to experiment with this dynamic and take advantage of my theory. most of the bipes available today have the same drag profile as a mono due to flawed thinking.
As far as the fixed gear story, thats one of the Biggest BS lines I` ve ever heard it was told to me first hand many times but, Sorry, you have to disregard common sense to even consider that to be true.
First, the wheel wheels are in a area of the wing that mostly don`t do much, or even see much spiral slip stream (sorry could not help it  )
Retracts are less drag period, I can make stories up about wind tunnels too! We started using fixed gear for drag! not to reduce it , now the story has changed to support the Habit! we are" only"stuck on them for convenience.
Given the opportunity to increase speed ,do you think the pylon guys would rather use fixed gear or retracts?
Why do you think retracts were used in the first place ,not to add drag, but to remove it.
You know It took about ten years for guys to start using my trim methods, after thousands of debates like this I freely give the information but people take offense to facts!, May be I`ll get a ten year head start on bipe designs and bipe trimming too!
Bryan
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Hebert competition designs "Team" YS, Futaba, cool power, Central hobbies, Hyde Mounts, contra, xtreme composites
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All Forums >> RC Airplanes >> Pattern Universe - RC Pattern Flying >> RC Pattern Flying >> RE: F3A Results - SPOILER 
RE: F3A Results - SPOILER - 
and in the trenches. as new schedules change so does the systems to make the podium. it`s why you will see 50% bipes in the finals at the worlds in years to come. 
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