Building Tips and technical articles. > ARF'S
LA 25 in a ARF NOBLER
Brett Buck:
--- Quote from: Al Ferraro on December 08, 2016, 08:30:38 AM ---
The engine will be stock except I will be using the Gardner piston & liner that is timed at the stock spec. I have the stock muffler and a much lighter Mac header to try.
What would you recommend as a base line setup?
Thanks Al
--- End quote ---
Dead stock in all respects, including the muffler, spraybar, etc. Start with an APC 9-4 and be sure to have a selection of 9-4, 10-3, 10-5 and 10-5 props. With the 10-5 you might end up needing 15% nitro or an air filter. As always, adjust the pitch and diameter to get the right level flight speed at a medium 2-stroke, and then evaluate the performance in the maneuvers.
The airplane is mostly OK as is, with the controls replaced of course. Carefully check the alignment of the parts and correct any misalignment in the basic structure. Also, inspect and rebuild the front end as needed. *If it was me*, I would be strongly tempted to lop off the nose and scarf on a new one, I despise the stock arrangement and parts. The stock system will stay together if the glue joints are done correctly (and many are not). Carefully inspect the leading edge, and if it is sharp, peel back the covering and round it off as much as possible, then recover. Cut a rudder loose from the fin, and make provisions to make it adjustable, same with the leadouts and tip weight.
If you were really ambitious, you would probably get a better-flying airplane if you also built an enlarged tail - just scale it up about 25% in area. Also, carve the flap down about 1/2" at the root and 1/4" at the tip. Even more ambitious, build an entire new fuselage with the enlarged tail, conventional engine mount, and increase the tail moment by an inch to ~15 1/2". All that will get you very close to my scaled-down Infinity project (which has been kicking around for about 15 years with very little action).
Brett
Skip Chernoff:
Al I don't have any experience with the LA 25 so I can't say how good that set up can be. However, it would seem to me that you would have to rev the @#$% out of them to get any power for the vertical and overhead stuff. As you know I flew two ARF Noblers this past season,and both were .40 powered. One had an HP 40 the other an OS FSR 40. One plane was 43 oz the other 44oz. Both flew almost identically. The thing that I liked was the "drive" I would get on the "up" portion and overhead portion of the stunts(especially on windy days).
Who knows, maybe the LA25 set up will work ok for you,just wanted to mention my experience with these ARF Noblers....PhillySkip
Brett Buck:
--- Quote from: Skip Chernoff on December 11, 2016, 09:02:58 PM ---Al I don't have any experience with the LA 25 so I can't say how good that set up can be. However, it would seem to me that you would have to rev the @#$% out of them to get any power for the vertical and overhead stuff.
--- End quote ---
You will launch around 13,000 rpm or so. Thats not revving the "@#$%" out of them, it's barely into a 2-stroke with a 9-4 APC, presuming you have a "new" version 25LA.
Chugging around at low revs hasn't been a mainstream competitive approach *for the last 30 years*.
Brett
Dan McEntee:
--- Quote from: Brett Buck on December 11, 2016, 11:50:27 PM --- You will launch around 13,000 rpm or so. Thats not revving the "@#$%" out of them, it's barely into a 2-stroke with a 9-4 APC, presuming you have a "new" version 25LA.
Chugging around at low revs hasn't been a mainstream competitive approach *for the last 30 years*.
Brett
--- End quote ---
Is there any way of identifying the "new" LA.25? Other than it may be the natural finished units that are not blue? Anywhere I can read up on it? I have several of these and think a few are the natural aluminum versions. I also have a ARF Nobler that I can adapt the mounts on and want to try this when spring comes back around. I have flown the LA and FP.25 engines quite a bit in a SIG Primary Force and found them to be just enough power for that airplane and it weighed 43 or 45 ounces at the time, but is a bit smaller and cleaner than the Nobler, in my opinion. I would give the FP. just a slight edge on power, but it ran very similar to the LA and I used the prescribed E2030 muffler. I remember trying the 9-4 APC for one flight and it just wasn't happening for me enough to do a pattern. An APC 10-4 at anywhere from 10,000 to 11,000 RPM did the trick. Neither engine would pull a 10-5. I am MUCH happier with the OS.32 on my P-Force. But I would be willing to try an experiment with the proper LA.25 and a ARF Nobler. If someone has any video of one flying in that configuration, I would be interested in seeing it.
Type at you later,
Dan McEntee
Dane Martin:
--- Quote from: Al Ferraro on December 07, 2016, 11:12:39 AM --- I'm going to try a LA 25 in the ARF Nobler (got the Tower deal) and wanted to know if anyone has done this successfully? After using the Gardner piston and liner in my LA .25 powered combat plane will great results, I thought why not try it in the Nobler? I already mounted the engine by replacing the mounts with 8" long 3/8 by 1/2 maple because the stock mounts were to wide and short. I would like to know prop, tank size, fuel, etc.
Thanks Al
--- End quote ---
My friend dennis flys his noblearf with an OS 25 LA and I fly mine with an OS 40 LA. At first, I was slinging it around at 3.6 sec laps. I dropped down to the 25 la venturi to slow it down. I'd say the os 40 la is nice, but not a necessity. I can't tell much of a difference between flying his and mine. Maybe his is slightly lighter. They are actually pretty light as they come out of the box.
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