Someone help me get this Stearman flying!!  
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Someone help me get this Stearman flying!! - 8/15/2002 5:32:21 AM   
wulf190



Posts: 1112
Joined: 3/31/2002
From: chicago, IL, USA
Status: offline 		I have finally fixed this bad boy and have measured the incidence angles all around. This is my first experience with the incidence meter, so I hope I did it right. I aligned a small level along the main fuse crutch that seems to run down the thrust line of the plane. Making sure as best I could from this level I attached the meter to all of the surfaces. Top wing is about +1.5, bottom wing about +1 and the tail seems to be pretty much zeroed out, which I found hard to believe since I added 1/8 sheet to the stab mounting platform, sanded at an angle to nothing in the back. This should have given the tail more incidence than this, right? I don't plan on ripping the tail off of this thing, but am willing to add some more weight to the nose as it seems to have lots of power with the Homey 30cc.

I ordered a new firewall and cowl from Midwest (it arrived promptly within a couple of days). I didn't change any of the original set up here, but reinforced the landing gear mounts stoutly with plywood and epoxied in 1/16 rods through the blocks and mounts. The firewall couldn't have fit in any better as the old one sheered off pretty cleanly (builder had used thick CA rather than epoxy or pro-bond). I filled in the cracked sheeting, gusseting where it needed and it looks better than it did after I swapped engines and used the old cowl.

I sure don't want to wreck this plane, so I will listen to all advice, be careful with it, and if I am not confident with my abilities here, I will pass it along to someone who might have more experience here.

(in reply to wulf190)
       Post #: 26

Incidentally - 9/3/2002 5:17:41 AM   
E-Challenged



Posts: 242
Joined: 9/3/2002
From: Garden Grove, CA, USA
Status: offline 		My Guillows 28" electric PT17 nearly beat itself to death until I:

1. Removed positive incidence on top wing , now close to zero.
2. Added more down-thrust.
3. Reduced control surface throws ( use dual rates/expo). Plane is very sensitive to rudder, don't have ailerons.
4. Try a smidge of down trim for take off and adjust trim for level cruise.
5. Be ready for pitch up after take off ( keep nose down when at full throttle).
6. I wouldn't mess with elevator incidence, mine is around zero.

Sounds like you have eliminated tail heaviness, make sure it isn't way noseheavy.

I notice that my little PT17 needs elevator trim changes for fast medium or slow flight to fly hands off. Rudder must be at neutral, no right trim for takeoff with right thrust, sometimes needs a little rudder trim after take off. Bipes handle strangely but sure look great in the air and not.

(in reply to wulf190)
       Post #: 27

Stearman are cool - 9/3/2002 8:55:23 PM   
had enough



Posts: 3616
Joined: 1/29/2002
From: From LA to Avon Lake, OH, USA
Status: offline 		OK I thought I'd chime in.
I have a Stearman built from the royal kit ( pic in my gallery)
I had a real bad tail-heavy condition on my first flight. Mostly because I did believe the plans, anyway I got that fixed with about 2 lbs. of lead in the cowl.
I have a ys 120 + this 2 lbs. of lead and mine still only weights 12 lbs. How did your turn out 14.5 -15 lbs?

The incidences' on the plane are critical to smooth flight. Mine has +4 deg in the top & bottom wings, +3 deg in the tail and with the engine at 0-0 deg as per the plans.
I wouldn’t deviate from the plans if I were you
I don’t know if this is going to help or add to the confusion. but these extreme incidences make the plane fly in a scale like manner ( tail high). The 120 is way more power than I need. I was think of going to a 91 fs. When I fly at full throttle the plane doesn’t seam happy and really it doesn’t look scale either. I fly mostly between ¼ and ½ throttle.

lastly on the n-struts, I used the streamline aluminum tubing
After quite a bit of jigging and cutting I got them set up perfectly.
Then the angle connection was made using line for fishing rods and epoxy. the tubes slide over a hard wood piece and are held in place with 4-40 bolts

Good luck with your plane

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< Message edited by scale_only_4_me-RCU -- Sep 3 2002 4:06PM >

_____________________________

Don’t give me your attitude,
I already have one

(in reply to wulf190)
       Post #: 28

Someone help me get this Stearman flying!! - 9/3/2002 10:48:38 PM   
wulf190



Posts: 1112
Joined: 3/31/2002
From: chicago, IL, USA
Status: offline 		Thanks for the input. During reconstruction, I added about 2lbs of nose weight inside of the fuse behind the firewall so that I wouldn't have to put it all out front. I triangulated the CG on the plans downward and found that the plan location is just about exactly at the front of the bottom wing bolt hole. If I balance the plane from the lower wing, the CG is a little rearward of this location. The distance seemed within reason to me until I started adding more nose weight to move it forward. Upon this, I realized how much weight it takes to move it forward even a 1/2" (quite a bit). I immediately became suspicious that I need to move the CG farther ahead. This said, I removed the smoke system and moved the servos two inches farther forward as I knew this would allow me to use less nose weight. I have yet to rebalance since I have done this, but hope that it helps. Looks like my idea about using the TME system on this plane is out the window considering the inability to mount the system in front of the CG and the servos resultant rearward position due to it's mounting. I don't know the rules for how much difference moving the servos forward makes, but given the nature of the plane, I'll bet it helps significantly.

The Midwest plane is built pretty heavy to begin with. The additional weight of the smoke system, Robart struts and the lead up front, resulted in it's greater weight. The weight, however, doesn't seem to be really limiting as the engine has plenty of power and their is a ton of wing area. I don't feel too afraid of adding a little more nose weight. I do think removal of the smoke system and the movement of the servos forward should help keep the weight down a bit better. What should I expect with moving servos forward, big difference?

(in reply to wulf190)
       Post #: 29

servo location - 9/4/2002 12:56:41 AM   
E-Challenged



Posts: 242
Joined: 9/3/2002
From: Garden Grove, CA, USA
Status: offline 		The nose is short and the rear fuselage is long. A small amount of extra weight in the tail requires a large amount of weight in the nose. Did you add a heavy tail wheel assembly with springs and brackets, etc? Lightening stuff in the tail will make a big difference.

The three servos in the fuselage probably weigh around nine ounces and are probably already somewhat near the cg. Moving them to the design cg point will help to some extent. Moving the battery pack to just in back of the firewall will help. A larger heavy battery pack would be better than lead ballast. A heavy prop spinner would help too. A heavier engine would help too.

I once read about a PT17 that lost a prop blade and then the entire radial engine vibrated off. The pilot survived by giving it fill down and landing nearby on a golf course.

(in reply to wulf190)
       Post #: 30

Someone help me get this Stearman flying!! - 9/4/2002 2:14:29 AM   
wulf190



Posts: 1112
Joined: 3/31/2002
From: chicago, IL, USA
Status: offline 		Actually, I used the Klett assembly, opting to use it instead of the 1/8 wire included in the kit. I figured this was lighter, all plastic. I just rebalanced and it took a little shy of 3 pounds to move the CG just ahead of the back of the leading edge of the bottom wing. Total weight is 14.6 pounds, flyable I think. It sure does seem to balance more like it should than I had it before, tempting that nose-over that so many talk of when they speak of this plane. The engine weighs just under 4 pounds, so I get extra weight here as well.

I stiffened up the elevator pushrod, reinforced the interplane strut connectors and decided to stay with the connecting wires from the bottom to top ailerons, seems like it should work all right. I have some confidence that my problem was balance as the CG has been moved substantially farther forward after rehab. We'll know after the weekend if all's well.

(in reply to wulf190)
       Post #: 31

IT FLIES......IT FLIES - 9/30/2002 3:44:20 AM   
wulf190



Posts: 1112
Joined: 3/31/2002
From: chicago, IL, USA
Status: offline 		Finally got the courage to take it up again today, and, IT FLIES! Took all of the down-trim I had and a little more, and full right aileron trim to get it reasonable. I didn't fly too long, just long enough to see determine characteristics and make a few passes. Strong headwind down the runway helped liftoff, but, boy, this thing doesn't need any help slowing down. At a little over 16 1/4 pounds, it's a hog, drops like a stone without throttle, something I learned by squatting it stoutly on the gear when landing, again, cracking the gear mounts, day over. But, I attribute the last to my own error, not making a few more passes, getting the feel of the glide path. All was looking pretty good up to the end though, so I stuck with it, another try or two and I think it should get a little easier. The plane sure does look good in the air though in spite of the weight, and it was very enjoyable to fly. Flies well slowly. I don't think I opened the throttle more than 3/4. When I looked down at the TX quickly to see how much more I had, I couldn't believe I had that much extra power left. I wish I would have pulled it through a loop with it, but it needed trimming badly enough that I thought it wise just to get it back. All in all, I figure a pretty good success, well worth the lab time on the struts! Problem was definitely CG related...I know, I know.............it's called nose heavy, stupid!

(in reply to wulf190)
       Post #: 32

Congtrats!!! - 9/30/2002 8:32:25 AM   
E-Challenged



Posts: 242
Joined: 9/3/2002
From: Garden Grove, CA, USA
Status: offline 		You got it down in one piece, that's the main thing. Your flight was a lot like my first successful flight with my little electric one. I now take off with a little down trim, let it develop plenty of speed keeping it straight with rudder then let it lift off and keep the nose from rising too much then back off the throttle a little when I get at least 75 feet altitude. It always amazes me how much less thrust is needed to maintain altitude once you get some altitude and get it trimmed for level flight. My advice for landings ..there is a lot of drag so leave a fair amount of power on, level wings with rudder, land on the mains and reduce power until the tail settles keeping it straight with rudder. ( land it like a P51)

Much continued good luck.

(in reply to wulf190)
       Post #: 33

Someone help me get this Stearman flying!! - 10/1/2002 4:57:11 PM   
G.F. Reid



Posts: 741
Joined: 12/5/2001
From: Palmetto, GA, USA
Status: offline 		Wulf, first off, I'll admit that I didn't read every word of this thread but from what I gather, you're adding more and more weight to solve your problem which you perceive to be a cg problem. After building five bipes I'll tell you what I've found. The incidence meter is not "helpful"....it's mandatory.
Unless you're just plain lucky, you've got to have it to build a bipe that flies right. Incidence problems on a bipe can mimic a cg problem. I found that almost every one of my bipes flew in a nose up attitude. I thought the first one was tail heavy and adjusted the cg. It still didn't help. Took a ton of down trim and I flew it the rest of it's life like that, which was about five years. I finally lost it due to that fact. In an inverted, downwind, deadstick situation, I suddenly ran out of up elevator, ideas and altitude at the same time. No wonder, I had used just about all the elevator travel there was just to fly level under power. If I had been a little quicker to evaluate the situation, I would have rolled it upright and turned back to the field instead of trying to split 's' it back....but....hindsight
What I came to realize was that the plane flew too well to be a cg problem and if the elevator solved it, that it was an incidence problem instead.
Now, I build all of my bipes with zero incidence on elevator and both wings. If I fly it and it want's to do the nose up thing, I put in 1 degree of down incidence top wing by shimming the rear of the that wing up. Usually, a popsicle stick or something of a similar thickness (washers, scraps of 1/16 ply, etc.) has done the trick.
So far, this has worked well for me and allowed me to reset my elevator trim to neutral.

< Message edited by G.F. Reid -- Oct 1 2002 12:14PM >

(in reply to wulf190)
       Post #: 34

Someone help me get this Stearman flying!! - 10/1/2002 8:54:13 PM   
wulf190



Posts: 1112
Joined: 3/31/2002
From: chicago, IL, USA
Status: offline 		Thanks for the reply. I checked the incidence and all appeared to be within reason of the plans and directions. You might be right about the top wing incidence. It seems like a degree here might correct the trim required. However, their is only a slight deflection downward in the elevator in the trimmed position, and there is definitely plenty of travel in the throws. It does fly quite well considering all, just a heavy glide path. I have only seen the larger Balsa USA version of this plane fly, and it flew just about exactly like this one, heavy. The plane needs to be rolled onto the runway taking up a hundred feet or so on the mains when landed. I had hoped it would lumber in slowly and glide well like many biplanes (mostly lighter ones). But, I think this might sort of be the way that it flies, which isn't really a problem for me. Hey, it just means that I'll build a different bipe that might fit this requirement!

(in reply to wulf190)
       Post #: 35

Good deal - 10/1/2002 10:17:50 PM   
G.F. Reid



Posts: 741
Joined: 12/5/2001
From: Palmetto, GA, USA
Status: offline 		Well, it sounds like you've gotten it sorted out pretty much. Bipes are definitely different alright but once you fly one for a while, you'll never be without at least one from now on. They're really a lot like the fairer sex...they can be troublesome and tempermental at times but I love 'em!
Here's a pic of my latest. I like it so much I built it twice. It was severely damaged a couple of weeks ago due to battery failure but I'm ready to cover second one as of now.

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(in reply to wulf190)
       Post #: 36

Someone help me get this Stearman flying!! - 11/21/2002 7:17:33 PM   
mikeh


 

Posts: 32
Joined: 11/21/2002
From: Oxford, MI, USA
Status: offline 		It seems like you have your problems well under control. I have one more comment. I recently purchased the midwest stearman kit and have completed the building process and am begining the covering process. In my kit was a revision which states that the top wing incidence has been changer to -1 degree for improved flight performance. I hope this is of some help!!!!

(in reply to wulf190)
       Post #: 37

Someone help me get this Stearman flying!! - 11/22/2002 3:40:28 AM   
wulf190



Posts: 1112
Joined: 3/31/2002
From: chicago, IL, USA
Status: offline 		Mike, Thanks, this is very interesting. I do think that mine would fly better with this incidence angle as I needed a bunch of down trim to keep it level. I think the -1 on top would fix this problem. Other than being heavy and without much glide without speed, the plane flies pretty easily and looks great in the air.....worth the effort.

(in reply to wulf190)