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Building Tips and technical articles. => ARF'S => Topic started by: Marvin Denny on May 11, 2010, 08:15:55 PM
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If you "plant an ARF, will little ARFsprout? Do little arfs sprout and grow well on cement?
I guess we will find out as I planted my Brodak Pathfinder ARF today on cement. Comingout of the first pull out of the Reverse Wingover to inverted---- SMACK!!! think it got the engine too. This was the third flight on the plane. First two, it rasponded to turns both ways s if it was terribly nose heavy. But the CG was where it was supposed to be. So for this flight I sealed the hinge lines and really didn't get to do anything. I did a couple of ups and downs and the plane seemed to be responding ok, so I tried the RWO and SPLAT--- IT just felt dead on the lined VERY sluggish as if it was nose heavy. I hvae carbon fiber pushrods and there seemed to be no flexing there.
Ah well---- one less ARF to worry about.
Bigiron
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If you "plant an ARF, will little ARFsprout? Do little arfs sprout and grow well on cement?
Only if you dump some "fertilizer" on it.
Brett
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Which engine did you have on it Marvin?
Let us know if you need parts, after all the people you save engines for with parts from "Ye old junk barrel", I am sure whatever you need will be quickly on its way.
Of course if it was a Fox then we know you probably already have what you need!
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Only if you dump some "fertilizer" on it.
Brett
Brett, as you should already be aware of, there is always an abundance of "fertilizer" around ANY well established model flying field. (G)
Bigiron
Bill the engine WAS an OS LA 46, and I don't think there are enough parts in the world to fix it. At least it was an E-Bay product that I got pretty cheaply.
Bigiron
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Marvin, sorry to hear of your loss. My question is if it was flying like it was nose heavy, why not add tail weight instead of sealing hinge lines. I always thought you sealed hinge lines when the plane does not turn equally both directions. H^^
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i have an arf cardinal that felt the same way. the balance was good as was the line tension, but it was just a dog. the instructions said to set it up as a 1 to 1 flap to elevator travel. i moved the elevator in one hole from where the flaps were and problem solved instatly just by having more elevator travel than flap. a day late and a dollar short, but oh well.
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Marvin, sorry to hear of your loss. My question is if it was flying like it was nose heavy, why not add tail weight instead of sealing hinge lines. I always thought you sealed hinge lines when the plane does not turn equally both directions. H^^
Doc, I did recheck the CG location given in the instruction booklet and wes already behind the recommended position. So that is why I decided to try sealing the hinge lines for the naxt flights. I have several more things I want to check out from the wreckage before I do much else.
Bigiron
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Marvin- an LA .46 huh- too bad. If you want to recoup part of your investment- I need a Venturi - N/V assy to replace the one I "borrowed" from my buddy Tom's .46 in his ARF Nobler. And if it has a good backplate that is always in demand.
Let me know if ya want to seel the venturi stuff.
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well, I finally got up enough gumption to look into the cause of the ARF Tathfinder crash. I have settled on the probable cause as being failure of the elevator hinges. I used the E-Z Hinge types that came with the kit as I didn't want to spent more on the ARF (bad decision)Besides, It SHOULD have sufficient materials to fly adequately. It appears that the coating surface on the hinges separated from the mylar (or whatever the core material is)and the hard "down" elevator pushed the control horn along with the elevators rearward instead of iving down to the elevators. The coatings from the hinges is still in the slots of the stab and the bare ends of the hinges are still attached to the elevators, The stab and elevators were not damaged in the crash, so it appears that the hinges failed before the crash.
Just looking at the wreckage, I think I MAY try to rebuild it. It looks kike the engine, spinner, and tank took most of the brunt of the impact and suffered the most damage. OS LA 46 (E-Bay orphan) bent shaft, Creamed venturi and NVA, skint up head, piston binds in the cylinder near the bottom of the stroke, ---backplate (plastic) appears ok as does the thrust washer. OH yes-- muffler broken off at the lug area.
Concencus--- it goes into the junk barrel annex until further notice.
Bigiron
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Just a thought on hinges pulling out, I always pinned my hinges with round toothpicks, two on each half. Never had a hinge pull out. Easy to do when building the plane. Glue in the hinges, then drill two small holes through the trailing edge/control surface and insert glue coated toothpicks. Let dry, clip off flush, sand and finish with the rest of the plane.
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Yes Dick, I know about the "toothpick" fix for hinges, and I do that on most of the planes that I build myself. BUT--- this was (and I emphacise the WAS) an ARF and I built as closely to the instruction sheets as I could so I could give an honest evaluation of it. Yes, there were some "issues" that I HAD to fix that were not included in the instructions --such as regluing the hinge slots in both the flaps AND the horizontal stab, as the slots that were there had split out diagonally from the slot ends those cracks were two to three inches long at each hinge location. There were 16 items that I HAD to fix before the plane could be flown safely or with any confidence. Apparently I Missed at least one (G).
Bigiron
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G'day Marvin
I lost a Shoestring—built by a friend—when the Klett hinges pulled out. There was little or no glue on them.
However, the hinge slots that you mention may have been cut with a very thin saw blade. That's the way they look on my ARC Vectors. It still means that the slots need gluing/filling but they may not be cracked or split.
Good luck with the repair, Geoff
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Hey Marvin, I have a fuselage for the pathfinder. It has a little bow in it, and Brodak replaced it. I never did try to straighten it. Your welcome to it, iffin ya want.
Lee TGD
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I'm a little confused. You checked the c/g and it was well behind the spot on the plans. I would call that a big problem, myself.
'
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I went to the Brodak web site and found the Pathfinder ARF listings. In those listings he tells us (specifically) that the "C/G is 2 3/4" behind the leading edge". Why does he do that? Do the instructions say something else? On no other listings does he tell us where the C/G is...
Ward-O