Author Topic: Thud. Crud. (Read 4327 times)

Tim Wescott · « **on:** May 14, 2011, 06:27:40 PM »

I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
(repeat 97 more times)

Broke the Waiex. Again. Because the engine was a bit too rich. Again. It leans out on launch, so I have to start it below the ideal RPM. So I have to guess it down a bit. I missed, and instead of just doing innumerable really boring laps I waggled it around until I had the engine on the step, then tried a wingover.

The engine sagged.

I lost line tension.

I would have recovered it, but the lines got tangled at the handle when I recovered tension.

I post-holed it. Vertical, into the ground. Fortunately I was flying over dirt -- over pavement, and I'd be looking for a new engine. As it is, I need to clean up the engine ASAP, and decide whether the airframe is salvageable.

I have got to stop doing that -- it's what broke the plane last time. The worst part is, I know know, after back to back flights, that the Waiex flies better than my all-stock Sig Skyray, by a considerable margin.

Bad Dobby (thud). Bad Dobby (thud). Etc.

Garf · « **Reply #1 on:** May 14, 2011, 07:32:51 PM »

Been there, done that. Also, too many times.

Russell Shaffer · « **Reply #2 on:** May 14, 2011, 07:55:09 PM »

Been there. Advice from Dan: " get the engine running right before you maneuver", this after I broke one at Salem last year. He's right, of course. I think I may have finally learned to apply the lesson to myself. See you in Eugene.

Tim Wescott · « **Reply #3 on:** May 14, 2011, 07:57:07 PM »

On inspection, I'm pretty sure that the airframe isn't salvageable. The leading edge is crushed on both sides of the fuselage, and that'll be a pretty hard thing to put back together.

Dang. Now I have no spare airplane.

Mark Scarborough · « **Reply #4 on:** May 14, 2011, 08:28:22 PM »

Tim, I have a slightly spare Fright streak if you need a back up, I can bring it with to Eugene. Get a hold of my

Mark Scarborough · « **Reply #5 on:** May 14, 2011, 08:29:11 PM »

OH and sorry to hear about the Waix, it was a cool plane.

Oh and one other thing,, DONT DO A WINGOVER IF THE ENGINE ISNT RIGHT, especially if its rich,,

Paul Taylor · « **Reply #6 on:** May 14, 2011, 08:34:28 PM »

Tim,
If this is a profile plane, the one thing I do is pinch the fuel line a little to make sure the rpm is going to hold steady. I almost made the same mistake this past week. First flight was launched at 9500 rpm. Second flight I did not touch the needle, started the plane and it was running 8900 rpm. I thought it would speed up after launch. It did not. Started the wing over and the lines went slack. I caught the plane on the other side, recovered and did lazy eights the rest of the flight just to run the tank out. Save the plane for another day. And trust my Tach... if it says 8900 rpm tweak the needle.

I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.
I will not do that first wingover when the engine is not running right.

Peter Nevai · « **Reply #7 on:** May 14, 2011, 08:55:58 PM »

Been there, done that, I have learned since that when that happens, is just to let it continue to inverted rather than try to recover. Then just deal with a inverted landing if necessary.

Tim Wescott · « **Reply #8 on:** May 14, 2011, 09:06:50 PM »

Quote from: Mark Scarborough on May 14, 2011, 08:29:11 PM

OH and sorry to hear about the Waiex, it was a cool plane.

The Waiex is going to get built again -- I already have plans that incorporate the lessons learned from rev 0 (it needs a longer nose, and some other detail changes), and had been planning to build rev 1 over the winter. I just need to accelerate the schedule a bit now.

Clint Ormosen · « **Reply #9 on:** May 14, 2011, 09:41:36 PM »

Tim, avoid guessing rpm. Get a tachometer. Sorry to hear about the mishap.

Steve Helmick · « **Reply #10 on:** May 14, 2011, 10:24:28 PM »

I recall that the Waiex started out with a .25 "S", but not sure if you've changed to a .20/.25FP. The latter need to be set by tachometer.

If you don't have a tach, the Hanger 9 mini tach is the low-buck one to get. In our group, I got one first, demo'd it to Mike Haverly, and next week he had one. My demo was to set it on the asphalt about 18" ahead of the prop. It read the rpm perfectly from there. Daniel Dirt picked one up awhile later and has applied his stamp of approval. They have another that doubles as a digital VOM, but we don't know anything about it. Somebody I know just bought one, but I can't recall who, right now. This is the one we use: http://www.horizonhobby.com/ProdInfo/HAN/250/HAN156-250.jpg It will do 2, 3, or 4 blade props. About $28.

Regarding the "run-up", I like to block off the uniflow vent or pinch the muffler pressure line until the engine leans out to peak and starts to sag. A couple of times, at least, but it depends on the ambient temp. The idea is to get it heated up faster. I think a lot of folks have bad runs because they set the NV with the engine still a bit cold. This is what causes the engine to change as you are hiking out to the handle. Not good.

Steve

Tim Wescott · « **Reply #11 on:** May 14, 2011, 11:48:45 PM »

It's got an FP20 now, and I'm setting it by tachometer. But it tends to lean out in the air, so I have to 'guess' it a little rich. I had been assuming this was happening because it was unloading -- I'll try your "pinch the fuel line" idea next time & see how it goes.

john e. holliday · « **Reply #12 on:** May 15, 2011, 07:30:50 AM »

Hey, been there and done that even with a tach saying RPM was right. Just need to trust the pull of the plane more and listen to the coach. Results of not listening to my own instincts.

Jerry Leuty · « **Reply #13 on:** May 15, 2011, 12:49:51 PM »

In 50+ years of on and off again flying I have never used a tach to set the needle. Hmmmmmm, now I am thinking; "Yeah, why not use a tach?" Now the question is; 'Where do you buy such a gizzmo?' I don't remember ever seeing one advertized in any model magazine. Or else I would of surely bought one by now.

Tim Wescott · « **Reply #14 on:** May 15, 2011, 01:56:05 PM »

Quote from: Jerry Leuty on May 15, 2011, 12:49:51 PM

In 50+ years of on and off again flying I have never used a tach to set the needle. Hmmmmmm, now I am thinking; "Yeah, why not use a tach?" Now the question is; 'Where do you buy such a gizzmo?' I don't remember ever seeing one advertized in any model magazine. Or else I would of surely bought one by now.

At your local hobby shop, or from Tower.

I use the Hanger 9 tach that's been mentioned. It, like most others, uses a photosensor that looks at how often the prop blades pass by and calculates the engine speed from that.

Brett Buck · « **Reply #15 on:** May 15, 2011, 02:29:42 PM »

Quote from: Tim Wescott on May 14, 2011, 07:57:07 PM

On inspection, I'm pretty sure that the airframe isn't salvageable. The leading edge is crushed on both sides of the fuselage, and that'll be a pretty hard thing to put back together.

   I would be very surprised if it wasn't salvageable. One of the rules of crashing is that the pilot doesn't decide if it's fixable or not, at least not in the first week or so. We have pieced airplanes back together that looked like a 500-piece jigsaw puzzle - crashed on the morning warmup flight, and he didn't miss his first-round flight in OTS. With Hot Stuff, 1/64 ply, and packing tape, no built-up airplane is unfixable.

We fixed a Skyray that had the wing and tail knocked off, and the fuselage broken just behind the wing yesterday in about 1/2 hour of actual work. Stood up to 15 MPH winds, won the contest (Beg/Int Profile).

   Brett

Tim Wescott · « **Reply #16 on:** May 15, 2011, 02:49:09 PM »

Quote from: Brett Buck on May 15, 2011, 02:29:42 PM

I would be very surprised if it wasn't salvageable. One of the rules of crashing is that the pilot doesn't decide if it's fixable or not, at least not in the first week or so. We have pieced airplanes back together that looked like a 500-piece jigsaw puzzle - crashed on the morning warmup flight, and he didn't miss his first-round flight in OTS. With Hot Stuff, 1/64 ply, and packing tape, no built-up airplane is unfixable.

We fixed a Skyray that had the wing and tail knocked off, and the fuselage broken just behind the wing yesterday in about 1/2 hour of actual work. Stood up to 15 MPH winds, won the contest (Beg/Int Profile).

Well...

Yes, I have it hanging up now because you never make the final decision until things have cooled off. In a contest situation I'd have pulled the wingtips back toward the tail until the spars were straight, stripped off the relevant covering material, and flooded the crushed areas with hot stuff. Then I'd fly again.

I may do that here, and just declare the plane "ugly for the rest of the season". It may well still fly better than the Skyray, so perhaps that's best.

OTOH, the temptation to stomp it to dust is strong in me right now.

By the way: I searched for the correct launch RPM for an FP20 with the BBTU and couldn't find it. The very secondary problem was that I was launching at the wrong RPM for reliable running, although the real problem is that when the reliable running failed to surface I went and flew anyway.

Brett Buck · « **Reply #17 on:** May 15, 2011, 03:01:51 PM »

Quote from: Tim Wescott on May 15, 2011, 02:49:09 PM

Well...

Yes, I have it hanging up now because you never make the final decision until things have cooled off. In a contest situation I'd have pulled the wingtips back toward the tail until the spars were straight, stripped off the relevant covering material, and flooded the crushed areas with hot stuff. Then I'd fly again.

I may do that here, and just declare the plane "ugly for the rest of the season". It may well still fly better than the Skyray, so perhaps that's best.

OTOH, the temptation to stomp it to dust is strong in me right now.

By the way: I searched for the correct launch RPM for an FP20 with the BBTU and couldn't find it. The very secondary problem was that I was launching at the wrong RPM for reliable running, although the real problem is that when the reliable running failed to surface I went and flew anyway.

I don't use a tach, generally - peaked out, then back off about halfway to a 4-stroke (maybe 6-8 clicks). It depends on your tank and tank vent setup. I am using a relatively narrow tank and suction with muffler pressure on a clunk tank. We were launching Jim's "20-point" Ringmaster yesterday at about 11,200 or a little faster, but the Skyray probably needs more.

Brett

p.s. check this, I haven't changed anything since this was written:

http://www.clstunt.com/htdocs/dc/dcboard.php?az=show_topic&forum=103&topic_id=198043&mesg_id=198043&listing_type=search

Tim Wescott · « **Reply #18 on:** May 15, 2011, 03:12:47 PM »

I tried the "peak and back off 6 clicks" and got very unreliable running -- presumably my ear isn't as good as yours. I had misremembered your launch RPM (I thought I may have), and was launching too fast (which leads, by the way, to an overly-lean run and a long, tense, low-power flight -- thank goodness that ABC motors are resistant to that sort of abuse). So I've been launching at a hair above 11K, which (it turns out) is on the ragged edge of too damn rich. Your cited launch RPM of 11.6 - 11.8 may work well -- the engine seems to want to 'stick' at about 12.4, but I guess that's the FP20 magic working.

The too-rich run was partly an effort to shorten the flight time without short-tanking the plane, as I'm worried about the pickup tube uncovering before airspeed is achieved -- the obvious solution is a smaller tank, which is exactly what the plane will get if I put it back together.

Tim Wescott · « **Reply #19 on:** May 15, 2011, 09:20:49 PM »

Well, Buck kind of pushed me over the edge to saving the plane. Assuming that things hold together (the spar was broken right under the fuselage, where it's darn near impossible to get glue, much less reinforcement material) I'll have a nice flying, if ugly, plane.

And if not, I'll have the Skyray.

I need to treat this like a combat plane & build several airframes, get them set up to just swap in a motor and go. Then as long as I don't shatter the engine, I'll be fine & dandy.

Larry Fernandez · « **Reply #20 on:** May 16, 2011, 07:39:23 PM »

Quote from: Brett Buck on May 15, 2011, 02:29:42 PM

I would be very surprised if it wasn't salvageable. One of the rules of crashing is that the pilot doesn't decide if it's fixable or not, at least not in the first week or so. We have pieced airplanes back together that looked like a 500-piece jigsaw puzzle - crashed on the morning warmup flight, and he didn't miss his first-round flight in OTS. With Hot Stuff, 1/64 ply, and packing tape, no built-up airplane is unfixable.

We fixed a Skyray that had the wing and tail knocked off, and the fuselage broken just behind the wing yesterday in about 1/2 hour of actual work. Stood up to 15 MPH winds, won the contest (Beg/Int Profile).

Brett

And then there was that dork who had his wing fold on his first flight at the 2000 NATs.
Thanks to the support and advice from his flying buddies, the plane was back in the air the next day.
It now has about 1600 flights on it and has been handed down to Brian Baker.

Larry, Buttafucco Stunt Team

Jerry Leuty · « **Reply #21 on:** May 16, 2011, 08:08:31 PM »

Thanks for the info on the tach. I ordered a new tach today from Tower Hobbies for a mere $19.99 plus shipping. It should be here by the weekend. Probably won't make it before I leave to Ring Master Round Up in Houston but that is fine too. In over 50+ years I have never used a tach before. Got some inconsistent engine runs too.

Rafael Gonzalez · « **Reply #22 on:** May 16, 2011, 08:42:23 PM »

WOW... I am amazed at the beauty of this site. Here I am thinking that I am a hack at PA. But realize that we are all humans and are not perfect. I can count the times I've pile-drived a C/L in the pavement or ground by the same reasons... I have to train myself and resist the urge not to do stuff when I am in a bad engine run... It is soooo nerve wrecking to just fly for 8 min...

Steve Helmick · « **Reply #23 on:** May 16, 2011, 08:59:15 PM »

Quote from: Jerry Leuty on May 16, 2011, 08:08:31 PM

Thanks for the info on the tach. I ordered a new tach today from Tower Hobbies for a mere $19.99 plus shipping. It should be here by the weekend. Probably won't make it before I leave to Ring Master Round Up in Houston but that is fine too. In over 50+ years I have never used a tach before. Got some inconsistent engine runs too.

Jeez...the two (or three?) brands of tachs that Tower sells are the WORST you can get. You'll be doing yourself a favor if you send it back unopened and get the Hanger 9 tach that the link in my post leads you to. Honest!

Steve

Brett Buck · « **Reply #24 on:** May 16, 2011, 09:57:08 PM »

Quote from: Tim Wescott on May 15, 2011, 09:20:49 PM

Well, Buck kind of pushed me over the edge to saving the plane. Assuming that things hold together (the spar was broken right under the fuselage, where it's darn near impossible to get glue, much less reinforcement material) I'll have a nice flying, if ugly, plane.

Cut straight down immediately adjacent to the spar, fore and aft of it, with the fine Zona saw. Reach in with an Exacto knife and cut the sheeting away from the spar, and temporarily remove the sheeting and attached bit of fuselage. Then cut some clearance in the sheeting for doublers. Butt-glue the ends of the spar back together - be careful not to mess up the broken ends, they should fit back together almost perfectly. Push them back together and put a drop of thin hot stuff on it. That should hold it. Then make some full-depth doublers out of 3/32 regular ply, about 2" long. Glue one on the front and one on the back of the spar across the break. Then, take a small t-pin, and poke a hole into the spar right at the break. Drip in some more hot stuff. Glue sheeting back on, glue little bit of fuse back on. Fill saw kerf with hot stuff and sawdust. Sand everything even and refinish, better than new.

If you have to cut through the fuse doublers, no problem. When you get the fuselage bits back together, cut some clearance along the inside face of the doublers. Face them off with sandpaper on something stiff, like a steel ruler. Add some backup to span the cuts +1" on each side. Glue them in and fill the gaps, sand it straight, refinish.

The hardest part is convincing yourself to do it. You have absolutely nothing to lose, the alternative is tossing it, so don't futz around, just cut away enough to get clearance, fix it, and put the cut=away parts back. You can pretty much cut anything you want as long as the cuts are all span-wise, without really losing anything strengthwise. If you fill and sand it, there's no reason it even has to show any ill effects.
Brett

Clint Ormosen · « **Reply #25 on:** May 16, 2011, 10:27:33 PM »

Brett forgot to mention that cussing at it under your breath while doing all that repairing seems to help. Just a tip for ya' .

Tim Wescott · « **Reply #26 on:** May 24, 2011, 04:41:35 PM »

I should have listened to Brett even though I already had the wing buttoned up -- I did an inverted landing (some joker moved the earth up five feet during the last of three outside loops) and broke the wing again. It should not have broken from that little of stress. Clearly I didn't get it solid enough the first time.

Sigh. Off to Eugene with the wrong airplane -- but if I'd done it 'right' I wouldn't have gotten it together in time anyway, so I suppose that's life.

There really is enough good plane there that it's not a good idea to stomp it and start over again. But I'm tempted.

Tim Wescott · « **Reply #27 on:** May 24, 2011, 08:10:42 PM »

Whoa. Virtue rewarded. Even though the NW Regionals is this weekend, and I was sure that the spar was broken under the fuselage, I went ahead and ripped into the wing on the Waiex. Turns out the spar was broken about halfway out on the wing and I had missed this fact in the first repair. Not only is this a one or two evening repair (meaning I can maybe fly plane #1 at the regionals!!) but I was able to cut out some of the ugliest crushed and reglued bits, so it'll be prettier and stronger than before.

Now if my flying buddy that offered me the yellow Ultracoat really has some, I'll be all set.

Howard Rush · « **Reply #28 on:** May 24, 2011, 11:15:44 PM »

Goody. We'll see you in Eugene.

FLOYD CARTER · « **Reply #29 on:** May 26, 2011, 05:44:31 PM »

I have a tach, but seldom use it. I've pitted for people who "tach" their engines before takeoff. I watch the tach, and it's jumping all over: from 8900 to 10K. The only thing for sure--the engine is running. In the end, the trained ear works better than a tach.

Floyd