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Old Jun 29, 2015, 11:23 PM
CZQ Tom is offline
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United States, CA, Clovis
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Poor quality glue and plywood?

Don't get me wrong because this Stearman is one of my favorite planes and flyers but this is the second EFlite ARF that the motor mount has fallen apart on (1st was the Cub 450). Neither airplane has had any even slightest abuse.

I pulled the Stearman down from its hanger in the garage and discovered that the motor was very loose. I removed the cowl and discovered that the front of the motor mount delaminated or separated from the rear portion of the face. There was some uneven filler ply pieces between the two plies.

No breaks, just came apart. I reassembled with epoxy but worry that the ply quality is very poor and soft. It's very arid here but very hot (central Cal, 100 deg plus days).

Fortunately, I found it before flight unlike my cub where the motor actually came off in normal flight. Just curious, has anyone else experienced this? Both of these planes smell very strong of mildew; this was noticeable during the unboxing but since it didn't see any mold, thought what the heck? A lot of the wood seems to be soft and spongy for plywood.

Still a favorite but I wonder if should come up with another motor mount solution?

Tom
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Last edited by CZQ Tom; Jun 29, 2015 at 11:39 PM.
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Old Yesterday, 07:20 AM
walter3rd is offline
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add some additional triangle stock and epoxy and it should be just fine.
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Old Yesterday, 10:06 AM
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Motor Mount

Every ARF I build gets the motor mount reinforced similar to this. I also go over all the joints and edges with thin CA. I have been flying my Stearman since about 2010 and the motor mount has held up good even after several nose overs.
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Old Yesterday, 10:19 AM
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Lookin' up at the centerline
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Lawrenceville, Georgia
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I too, as a matter of routine, apply thin CA to the edges of light ply and have had no trouble.
My practice comes from buying old '80s kits to build that have ply that wants to separate.
(CA on the edges works good and is easier... correction... Much Much easier than cutting new pieces)
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Old Yesterday, 10:20 AM
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Obsession, not a hobby
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Joined Sep 2013
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I have a 15e and two Cub 450s and they're fine. I go over at least the motor-box, firewall and LG mount with CA or epoxy when new. I tend to go big in the power department so it's automatic. Our weather can get over 115f so it's probably not heat related. About the only thing I notice is I have to shrink covering a few times after new because the Arizona heat just bakes the moisture right out!
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Old Yesterday, 11:13 AM
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I just want to go fly!
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I recieved my stearman after the original owner ripped the nose clean off on his maiden. He gave up and gave it to me. I rebuilt the nose strong but not pretty and its holding up great with generous amounts of wood and epoxy. There is no such thing as too much nose weight for this girl. Lol. Walt
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Old Yesterday, 02:43 PM
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Thanks for the input, guys. I'll add extra triangle strips and a good CA soak and see how that holds up. When I repaired last night I "clamped" all four corners of the forward face with zip ties through the Lightning holes around the mount; think I'll leave those in place as a safety belt for awhile.
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Old Yesterday, 10:01 PM
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United States, MT
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Got some lipos today and got the stearman balanced... wow, added ~9oz of lead to get it balanced and although I felt that was a lot (still do) it seemed like it wanted even more and would still balance just fine. Damn! I hate adding dead weight to a plane but this one seemed completely necessary. Came in around 74oz AUW.
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Old Yesterday, 10:14 PM
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If it flies, I can crash it.
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I maidened my PT-17 today. Three flights, all great.

I mounted a Power 32 motor spinning a Xoar 12x6 wood prop, and flew it on a 4S 3900mAh pack.

After reading through this thread, it was abundantly (brutally) clear that the plane needed a lot of ballast up front to get the CG right. I figured a bigger motor could always be flown at a lower throttle, and was a better choice than dead weight. I wanted to run the Xoar 12x6 because I already have a bunch (I use them on my Dynam Waco which is about the same size as the PT-17 and also flies 4S) and they really look nice. But even with the P32, it was of course still way tail heavy.

I put a HH Brass Spinner nut on it, which still wasn't enough. I thought about tape-a-weights to the inside of the cowl, but I wanted to get my ballast as far forward as I could (and unfortunately, a spinner nut machined from depleted Uranium is outside my budget). I had a bottle of this stuff the model railroad guys use for ballast, it's like really tiny iron shot (like 0.5mm diameter), it flows almost like liquid. It's dense and heavy. I mixed some 5-minute Epoxy and watered it down with some IPA, and then made a slurry of that and a few Oz of this ballast stuff. Then I poured it in to the engine cylinders from the back side of the cowl. Having also read here that the motor was rather fragile, I figured a shot of Epoxy coating the inside couldn't hurt either. The result came out perfect. The plane balanced at the recommended forward CG point with a total of about another 5-6Oz of weight (between the Higley and the slurry not counting the Power 32).

I was foolish to think the motor cylinders were water-tight, they're not. While none of the ballast material leaked out, my Epoxy did. I freaked when I saw what was happening, since I didn't have a lot of time to figure out what to do about it. I decided to just clean up the places where the Epoxy accumulated a blob but let it be every where else. Turns out, it gives the cylinders a "wet" look like oil is leaking out from the motor a little. Scale, in a way. So it turned out to be OK.

With the Power-32 it slows down and flies quite scale like at something maybe a little less than 1/2 throttle. But it has a most un-scale like unlimited vertical at WOT. And on the flat at WOT, it's faster than my FMS 1450mm P-51. Not scale at all. I flew it at moderate to high throttle for 5 minutes and landed and my pack was still at 4.02v/cell (installing telemetry is on the list of things to do), so scale-like flight with a 3900mAh 4S looks like it'll be good for >15 minutes. Sweet.

Now that I know it flies nice, and that I'll like flying it, I plan to rig it with flying lines and install my Mr-RC radial engine sound system in it (will come out of the Waco, which I will retire). And I need a piece of white ribbon for the pilot's scarf...

The only issue I had was that on the second flight the covering on the left side of the fuse started peeling back. Took me a while to realize the left side of the plane didn't look like I thought it should, and why that was. Taped it down with some Scotch Tape for the third flight. Will fix tomorrow (I go back far enough, I have the covering iron and heat gun to do it).
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Old Yesterday, 11:02 PM
walter3rd is offline
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I just want to go fly!
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i hear ya! i installed power 25 and use 3800 3s batts all the way forward plus 1 oz. lead in nose. could use more weight but fly's well. crazy!
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