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Jun 03, 2015, 02:17 PM
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time907356's Avatar
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Build Log

Eu1-A #2


EU1-A's are my favorite RC Airplanes, hands down. We're fortunate to have a couple of guys who are kitting them again; one in MO, and one in CA.
I just ordered mine from RCAiir, (frequent flyer on here) in CA and am awaiting delivery. Don has a price list he sends out on request (maybe posted here somewhere) and if you're looking for any retro, classic pattern plane, he's worth a look.
I first saw an EU1-A in Washington DC (DCRC) in about 1983. It was the blue and white one in the picture archives. All I got was the name, and set out to have one, until 1988 when my wife bought me one for Christmas (Aero Composites). Here are a few pics of that lovely bird (both of them)!
10.3Lbs. dry, OS .61 RF ABC -P. 12x10 APC, Macs quiet tuned pipe, Goldberg retracts, Futaba 7-UAF FM radio.
Last edited by time907356; Oct 01, 2015 at 08:11 AM.
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Jun 03, 2015, 10:12 PM
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Glad to see you are getting back to these birds again.
Jun 04, 2015, 06:42 AM
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Hard to think of that as 27 years ago! And that the EU1 is pushing 40!!
Jun 04, 2015, 09:06 AM
JOE MOCERI
Glad to see another EU1A go together and what you come up with on the assembly.
Joe
Jun 04, 2015, 10:44 AM
KM6UBL
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On board. Will be following along.

Are you going to do the lowered stab/andhedral mod as on #1?

Robert
Jun 04, 2015, 12:19 PM
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Yeah...I don't see why not. Maybe this one will be different, but it worked last time and that's what I have to go on. It came from a guy in TN that had built 3 of them, so I figured that was the best rec. I'd come by.
I do remember one thing I screwed up; I aligned the bottom of the fin to the bottom of the fuse before putting that under-tail extension piece on. Rather than dropping the fin and top cap, I just elongated the extension all the way back along the bottom of the fin...looked weird back there. Live and learn! Here's a pic of one I met in a contest that weighed 9.5Lbs: I picked it up - really light! Lots of sanding on the glass went on
Jun 04, 2015, 12:42 PM
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Here's about the best I can do showing the tail of mine. Not sure you can get anything from it, but you can tell it's lower than normal.
Jun 04, 2015, 01:34 PM
KM6UBL
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Quote:
Originally Posted by time907356
Here's about the best I can do showing the tail of mine. Not sure you can get anything from it, but you can tell it's lower than normal.
Thanks for the pic and info. I see a "cut and paste" job for my EU-1A in the near future!

Robert
Jun 04, 2015, 10:07 PM
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Hey Tim its Chris. Glad I found your little thread. Can't wait to see your new EU1 fly. Its going to be EPIC.
Jun 05, 2015, 06:02 AM
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Glad to see you here! I hope after your breif tour on the Persuasion, you'll get the itch. Good calling too; I had someone else try it and they couldn't keep up. Eric said he'd bring his Arrow out next Tuesday for our novice pattern 'gathering' and fly a demo. Hope you can make it.
Jun 05, 2015, 09:09 AM
JOE MOCERI
Time,
I was thinking on the stab placement and leaving it where the plans show.

What about making it a flying stab using a Bob Violet fork system? The incidence is changed by adjusting center. Wouldn't you think this would work to trim out for pull to canopy or belly with the least amount of drag?

May cause other problems on flight trims. Just a thought that has been in my head
Joe
Jun 05, 2015, 09:22 AM
KM6UBL
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Quote:
Originally Posted by JMDESIGNS
Time,
I was thinking on the stab placement and leaving it where the plans show.

What about making it a flying stab using a Bob Violet fork system? The incidence is changed by adjusting center. Wouldn't you think this would work to trim out for pull to canopy or belly with the least amount of drag?

May cause other problems on flight trims. Just a thought that has been in my head
Joe
No. Because if that was the cure, then elevator trim would be all you need. Flying stabs are not the answer to this problem, nor is adjustable stab the solution.

I obviously do not yet have the answer, but I am seeking. The phenomenon that we are chasing is airspeed related. And I mean velocity related, not angle of attack related. If it were AOA related, it would show up in all flight modes. But this specific issue only occurs at low velocity. Changing stab heights is known to affect that. I wish that I could be more articulate in my reasoning.
Here is what I have tried, based upon others experience, as well as my experimentation:
1. CG. No effect. I put the CG so far back that I barely got it down in one piece
2. Thrusr line. Minor effect, but it would require a radical reconfiguration to do more good.
I don't know if there is a definitive solution to the problem. I have been advised by some who are far wiser than I to just accept the EU1-A for what it is- a great rolling airplane that is mediocre in everything else. Maybe they are right. But part of the adventure of modeling is trying to make these things fly better. What do you guys think?

Robert
Jun 05, 2015, 10:16 AM
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Let's step back a minute. If one of you would explain the phenomina in as much detail as you can (as to one who hasn't seen it...) maybe that will lead us differently. I tend to think the fuse design, including profile (flat bottom) and stab / wing / engine location are the culprit.
? Does it happen at only low speeds?
? Does it happen at low/high throttle?
? Does the plan 'fall over' or push while keeping vertical heading?
? Do any other planes do this that you're aware of - like the Brushfire, or Excalibur?
Just want to collect some data. I may have had some tendency, and just not identified it correctly. However, I was able to pull into stall turns without reverse elevator compensation and get through the maneuvers.
I generally agree with the above; flying stabs shouldn't solve the issue. I thought about adding them, but they won't work well with the anhedral, or at least get much more complicated...
Last edited by time907356; Jun 05, 2015 at 10:37 AM.
Jun 05, 2015, 11:21 AM
JOE MOCERI
I have not been behind the sticks on a EU1A nor seen one fly in person. Correct there is a lot of flat surface area under the bird. Until I get mine in the air I can only think of any changes that may improve its flight. Mine is built to the instructions and will see first hand the way it fly's.

I will probably accept the way it fly's and " Fly it like I Stole it" due to my bucket list of planes. LOL

Good discussion thou.
Joe
Jun 05, 2015, 02:27 PM
KM6UBL
Vertigo II's Avatar
Quote:
Originally Posted by time907356
Let's step back a minute. If one of you would explain the phenomina in as much detail as you can (as to one who hasn't seen it...) maybe that will lead us differently. I tend to think the fuse design, including profile (flat bottom) and stab / wing / engine location are the culprit.
? Does it happen at only low speeds?
? Does it happen at low/high throttle?
? Does the plan 'fall over' or push while keeping vertical heading?
? Do any other planes do this that you're aware of - like the Brushfire, or Excalibur?
Just want to collect some data. I may have had some tendency, and just not identified it correctly. However, I was able to pull into stall turns without reverse elevator compensation and get through the maneuvers.
I generally agree with the above; flying stabs shouldn't solve the issue. I thought about adding them, but they won't work well with the anhedral, or at least get much more complicated...
Yes, it happens at low speeds. My EU is strange/different/weird as it was build (not by me) as a taildragger. All I have to do is open the throttle and steer with the rudder as required, and the airplane will lift off the ground and climb by itself. A trike gear version may not lift off by itself, so it may not be obvious to them. Then as it accelerates, or "gets on the plane" it levels out and locks in. When it is locked in, that is the EU1-A that we all love. Slow it back down and it turns to crap.

High throttle required. More accurately, high throttle/low velocity. Power off downlines are not affected. So there is a relationship between the two. This is where adding down thrust has had an effect. But more that a couple of degrees and it starts screwing up the way it does everything else. Jerry Budd used to run 7 degrees (!) down thrust.
But- on approach, as it floats and floats, when you expect to be on the elevator, you are not. Not until you are in need of flair does the elevator get heavy. So the issue is there at idle as well, but only a fraction.

In a vertical, the aircraft will slow way down , and with full down elevator, will still fall over on it's back. Tony F's solution- give it enough power so it does not slow down much. That's why I went with the YS Classic engine. And it did indeed help mitigate the problem.

Other aircraft with a similar problem? I can't say, I do not have any experience with them.

That is my experience as best as I can describe. My experience ssems to line up very well with other EU1-A owners that I have talked with.

I am very close to getting out the Dremel and cutting my stab, and giving it the treatment that you did with yours. Here is why:
1. It seemed to work with your old EU. If it had the pitch problem, you would have known it. It is neither slight or subtle.
2. Subjective- look closely at a T-38 (the EU1-A bears a strong resemblance) or a BAE hawk. Low mounted, low aspect ratio (swept) wings, flat bottom line, LOW STAB. I know that low stabs on supersonic aircraft are low to prevent transonic "pitch-up". Perhaps there is a relationship at lower speeds as well. I am speculating here, as I am not an aerodynamicist. Just a hobbyist. Perhaps the prop blast (high velocity) acts on the horizontal stab at (low air velocity), the net effect is for the tail to act/push down???? That might explain why lowering the tail seems to alleviate the problem. ??????? I guess that I won't know unless I try it.

I will have mine out this weekend at the Classic Pattern Get-Together in Riverside, Ca. I will try to make some worthwhile observations. I don't fly it much, it is more of a hanger queen.

There is an airplane called the Thunderbird. It is supposed a design that was leveraged off of the EU1-A, to cure it's ills. See pic. Note the thrust line/wing/tail line. Other than being butt ugly, it is supposed to fly very well.

Robert


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