atari7up

Hi guys..i'm a newbie with RC..Flight WM supersport 40 s use Magnum pro se 46..now i used 10 x 6 apc , byron 15%..peak power on the ground is on 13.000 rpm...what size prop i need for got more speed?

Regards,
Atari7up

rmenke

My Feedback: (13)

OK kiddo. First things first. All things are not created equal, and as it always will be, going fast starts with spending money in the proper direction. The Magnum, OS and Thundertiger are all basically sports engines where overall performance is the design the manufacturer shoots for. All run in the 13-14K range with little difference in top end performance. I fly with the Thundertiger pro 46 in T-34 club racing where the 3 choices above are legal, beaten once in a while but still on top for past many seasons. I run10X6 apc, 15% max allowed Power master with 4 oz of castor added. The OS has a little more torque, you may be able to pull a 10 X 7 for a small advantage, maby. Nothing is a sure thing in racing and going fast, honning your flying skills will create more wins in the long run, all else being near equal.

Yes, you can get some reasonable speed out of the clunker sports engines. You must start with a fast airframe something like a Sig Wonder, or a good old Quickee 500 that you can buy or build reasonably. Yes, there is a very slight advantage with the V tail,however many standard tail designs still post the fasttimes. With a decent airframe and sport engine, you can play with props, fuel etc to your hearts content. Intent here is to gain as many mph as possible and a advantage of any sort. Still, the best pilot will probably win even if you have 5-10 mph on him.

There is little available inbetween the sports engine and all out Nelson or Jett racing engines. IMHO, the Jett sport engine is the well woth the bucks in idle, transition (3D) and higher rpm's, 16 to 20K. They sill not stay with the all out quickee or formula racers, but will be much faster than the average. My Jett 35 and 50 are over 6 yers old and still going strong, so overall expense is below the other sports engines in the long hall.The Jett 60L is a 60 in a 40 frame and will give the racing 40 engines fits. Yes, love my Jett engines.

There are a couple of sleepers out there. The Webra 55 speed is a beast, properly broken in will pull a 10 X 10 apc in the 18-20K's.My Jett 60 would burn up with that prop, the Webra 55 just keeps singing away with head temps around 280%. I am told the OS 55 is almost as strong, but I have no first hand knowledge of their performance. I am one of the old hard nosed guys that have never forgiven OS for selling out to Fatuba and producilng sleave pealing junk for a number of years without fulliy backing the product. Won't buy a Cadallac either, but do have one OS 46FX that was given to me, NIB. May actually run it some time.

With over 50 years in the hobby, my best advice to all newbys who want to go fast and race is to find the club go faster guy, carry his gear and help him, and watch and listen closely. There is a art to adjusting the needle for max rpms once in the air and unloaded. There is a art to airframe and transmitter setup. CG should be as far forwardthat will give you a solid feeling at speed, but back far enough to turn well without a lot of drag. Ballance the airframe in all directions so the airframe turns without dropping or increasing altitude. Make sure your engine, wing and tailfeathers are 0-0-0 incidence. A .05% wing positive or negative incidence will requiresomeqhat the same in the elevator to fly streight and level. That means you have a .05% airbrake going on. Keep throws and expo at a setting that is not overall too sensitive. You may be a great 3D pilot, but making a pylon turn is also a art. Gainning or loosing altitude costs you in distance to the next pylon. Too sensitive in aileron can easially cost you the airplane by over rotating the bank and pulling into the ground.When flying 20'
off the ground atabove 100 mph, the time needed to correct a bad turn is frequently not enough, splat.There are a lot of good and fast guys out there. Learn form the best and beat the rest!!!! I rant. Enjoy

MJD

My Feedback: (1)

For now stay with APC sport props, and try a 10-7. Many sport .46 engine and ARF combos respond well to that prop and manage surprising speeds.

You will know right away if you are better off with a 10" or 9" diameter prop by any increase or decrease in performance with the 9" relative to the 10". Test a 9-7 against the 10-7. If it picks up top end speed and the acceleration, climb etc are still satisfactory, then that tells you that the diameter of the prop, 9", is sufficient for the aircraft, and that the system generates enough horsepower to pull the aircraft faster. Perhaps even try a 9-8 if you like what the 9-7 does, nothing to lose except the cost of a prop, but that would be about the limit that might do something useful I think. If nothing interesting happens with a 9-7 relative to the 10-7, then stay with the 10-7 and experiment in the 10" range.

APC sport props are very well designed props, and by sticking with the one type of prop you can mess with variables with a little more overall control of your experiment, and that gives you the best chance of finding what you are looking for and learning a bit in the process. In general for this combo, stick with the 9 and 10" diameters and vary the pitch one inch at a time.

Another thing to consider is an aftermarket muffler, such as a Jettstream, or Nelson Ultrathrust, and there's another one or two I can't recall. They are halfway between a stock expansion can muffler and a tuned pipe - they are "mildly tuned" and often give a nice rpm boost in the rpm ranges you'd be working at, and are not fiddly at all - bolt and fly, but use thought with regards to prop selection. The question of whether the cost is worth the performance boost is subjective and up to you.

MikeD aka MJD
MikesRC

atari7up

@ rmenke , MJD

Thanks a lot for yours attantion and input will try it like u guys told

Regards,

Atari7up

freakingfast

My Feedback: (3)

My two Webra 55s and red Jett tuned muffler are maxed out at 16.3 K spinning a 9X10 APC on 10% fuel and they were correctly broken-in. This was confirmed with two different tachs. I had a wild number years ago with a 9X9 but it turned out to be a bad tach.

A Jett 90LX FIRE on a tuned pipe max's out at 16,300 RPM with a 10X10 on the ground and may even sag a bit in the air when it "hooks up" or un-stalls.

APC may have miss-marked some props or rmenk's engine is indeed an exceptional one and not the norm.
My concern is that someone may relentlessly try this 10X10 prop after break-in and cook their Webra 55 engine in the attempt to replicate the high RPM numbers.

rmenke

My Feedback: (13)

Freeking fastis right on the money in his comments. My tack is good, remote temp. gage is questionable. That Webera 55 is on its secondsearon of club racing with the apc 10 X 10,theoriginal prop and running strong.I also have a Jett 90 LX, but turns a 11 X 9 and seldom doesthe low 16's on a good day, usually 14.4. to 15.6. Its a great running motor, but not impressive in the rpm's.Have had a few exceptional sport engines through the years, but they are rare.Keep your attempts to get more out of the engine to proper needle setting and props, andexhaust systems such as Jettstream and nelson performance mufflers.The best and cheepest improvement in rpm you can bolt on.There are rare exceptions but most stock sport engines will run within a few 100 rpmsof each other.Would have never even tried a 10 X 10 on the Weberawithout therecommended by Chuck at rc country, Sacramento and one of the top german motor builders around, who chimes in here once in a while.It may well be one of those 1 in a 1,000 things, gonna enjoy it while shes strong.