RE: Flair 1/4 Scale PT-17 Stearman Review

RE: Flair 1/4 Scale PT-17 Stearman Review
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RE: Flair 1/4 Scale PT-17 Stearman Review - 4/18/2007 2:53:14 PM

jack1933

Posts: 182
Joined: 1/31/2004
From: marietta, OK, USA
Status: offline

Hello Geoardsog Thanks for the input. My only intention was to be positive about the many years of experence Ive had with model airplanes, not full scale. The original Stearman rigging drawings, from boeing, circa 1928-30 called for + 4 deg. in the bottom wing and +3 deg. in the top wing. Actually this has no bearing on a model airplane, except to be a guide to set up our models. Im not getting upset when disagreed with, if only someone with any experence will post solid, tried and true info on the subject will we gain knowledge, and be able to have a good flying plane. As I said many times on this forum, Just trying to help anyone that does not want to have down trim in their elevator. Dont see why this is a bad thing. There is only 1 person that I have had any negative input from, and that person has invited me to stop posting on "his" forum. Well it boils down to this. I will not post any more threads on the forum. Hope you Stearman lovers have great fun with your planes. Regards to all Jack

(in reply to geoardsog5)

Post #: 626

RE: Flair 1/4 Scale PT-17 Stearman Review - 4/18/2007 9:44:01 PM

Cybertom

Posts: 545
Joined: 12/2/2002
From: Streetsboro, OH, USA
Status: offline

ElectRick,

Thanks for your input I couldn't agree more. We have had a great run with this thread since 2003. Lets everyone redouble our efforts to keep the personal stuff out and focus on Stearman. On to business at hand...

I posted a detailed question about incidence and decalage to the "Brain trust" in the Aerodynamics forum. They are starting to post responses. Once they feel they have put this matter to rest I will post a summary of the answers here for everyone to read or you are welcome to read their original responses in their entirety in the Aerodynamics Forum.

< Message edited by Cybertom -- 4/18/2007 10:04:38 PM >

_____________________________

Real airplanes have 2-wings and round engines!

(in reply to ElectRick)

Post #: 627

RE: Flair 1/4 Scale PT-17 Stearman Review - 4/21/2007 1:56:47 AM

Cybertom

Posts: 545
Joined: 12/2/2002
From: Streetsboro, OH, USA
Status: offline

Decalage Incidence Update,

Well the Aerodynamics Brain Trust posted some replies to the incidence / decalage questions I posed. They may feel that they have answered it to their satisfaction because the thread I started has now moved onto unrelated topics. I will give it another week and then summarize their responses here.

_____________________________

Real airplanes have 2-wings and round engines!

(in reply to Cybertom)

Post #: 628

RE: Flair 1/4 Scale PT-17 Stearman Review - 4/21/2007 3:37:46 PM

jack1933

Posts: 182
Joined: 1/31/2004
From: marietta, OK, USA
Status: offline

Hello Rick To answer your item about the positive top wing incedence relative to the bottom wing, Have been over this question with a restorer of many Stearmans, he also sent me the correct rigging manual from Boeing, circa 1927-30, it calls for + 3 degrees in the top wing and +4 degrees in the bottom wing. Did not post it here, whats the use, chas has this info and ill be glad to send it to you, just send me your email address in a private message. If the milatary had set the incedence per the 1944-45 milatary rigging manual, which is not the manufactures info, and a student had stalled the plane just after takeoff he would have chrashed, with the cg being shifted aft, this is just logical, and was told to me by the restorer. If you are reading the " brain trust" forum you will see that the fellows that are actually flying model bipes agree that the top wing should be negative to the bottom wing. This pretty well puts this question to rest, I hope, why not build a bipe of some kind and experiment with the incedence yourself.

(in reply to ElectRick)

Post #: 629

RE: Flair 1/4 Scale PT-17 Stearman Review - 4/21/2007 10:22:14 PM

Cybertom

Posts: 545
Joined: 12/2/2002
From: Streetsboro, OH, USA
Status: offline

quote:

If you are reading the " brain trust" forum you will see that the fellows that are actually flying model bipes agree that the top wing should be negative to the bottom wing. This pretty well puts this question to rest, I hope

Results from the Aerodynamics Forum so far:

1. "When in doubt follow full scale" +1 decalage-Pimmnz
2. "Most biplanes have" -1 decalage-Bax
3. -1.5 decalage-Rodney
4. +2 decalage-Ed Moorman
5. -1.5 decalage-Herb Brown

< Message edited by Cybertom -- 4/22/2007 9:04:36 AM >

_____________________________

Real airplanes have 2-wings and round engines!

(in reply to jack1933)

Post #: 630

RE: Flair 1/4 Scale PT-17 Stearman Review - 4/22/2007 4:18:28 AM

Cybertom

Posts: 545
Joined: 12/2/2002
From: Streetsboro, OH, USA
Status: offline

Geoardsog5,

I cleaned up my last post #637 because you must have taken something the wrong way if I am reading this right.

To clear things up I wasn’t saying that Stearman can't fly acrobatics. I was referring to this quote from the Aerodynamics Forum:

quote:

The Stearman was designed and set up to be a primary trainer, but almost every model builder wants their Stearman to be more aerobatic than the big trainer was. If you want it to be aerobatic, then set it up properly for aerobatics.

Unless someone else here has also had Stearman aerobatic training you are the most qualified to determine if a model Stearman is flying in a scale fashion or has been modified to exceed what is typically expected of full scale. So the question is if we change the incidence in the manner that Jack recommended does it still fly like a Stearman? How do we measure that?

Did I clear things up?

< Message edited by Lightfoot -- 4/27/2007 7:02:26 PM >

_____________________________

Real airplanes have 2-wings and round engines!

(in reply to geoardsog5)

Post #: 631

RE: Flair 1/4 Scale PT-17 Stearman Review - 4/22/2007 4:29:19 AM

geoardsog5

Posts: 25
Joined: 1/8/2005
From: Tinley Park, IL, USA
Status: offline

Cybertom - Anyone who is interested in learning some factual information about Stearmans should obtain a copy of "Wings of Stearman" written by Peter M. Bowers. Flying Books International 1401 KIngs Wood Rd. Eagan, Mn. 55122. For those who don"t know, Bowers is a reknowned aviation writer and historian. Note in chap. 5 that reference is made to modifications required by the military to make the stall characteristics less docile.I really don't think we are going see a full blown NACA wind tunnel test report complete with mathamatical formulas posted to document the decalage possibilities in this thread or the Aerodynamics thread. It may be that the only way to settle this controversy is for everyone to rig their bipes as they see fit, go out, fly and see what happens. If the results are unsatisfactory, small incremental changes can be made without turning the aircraft into an uncontrollable beast.We have some opinions from very knowledgeable modelers based on real life experiences. In light of the lack of hard technical data, I am going to go with that as guidance for my rigging.

< Message edited by geoardsog5 -- 4/22/2007 2:10:17 PM >

(in reply to Cybertom)

Post #: 632

RE: Flair 1/4 Scale PT-17 Stearman Review - 4/22/2007 6:24:16 AM

Cybertom

Posts: 545
Joined: 12/2/2002
From: Streetsboro, OH, USA
Status: offline

Geoardsog5,

So far we have lots of opinions and that's about it. Don't you want to know why a Stearman or any other airplane needs the specific amount of incidence it has and how to figure that out? Isn't that what we all have been asking for? Do you think that question has been adequately answered in any way? Could we design the correct amount of incidence into an new airplane with what has been written here? I rest my case.

PS,
Full Scale Gloster Gladiator incidence settings:
Upper Wing +2.5
Lower Wing +2.5

2.5-2.5=0 degrees decalage

< Message edited by Cybertom -- 4/22/2007 2:40:00 PM >

_____________________________

Real airplanes have 2-wings and round engines!

(in reply to geoardsog5)

Post #: 633

RE: Flair 1/4 Scale PT-17 Stearman Review - 4/22/2007 10:49:06 AM

waldo

Posts: 38
Joined: 4/3/2002
From: Dublin, IRELAND
Status: offline

Hi Tom, I just rechecked the data on the Brian Taylor Gladiator. Firewall/tailplane, 0 deg.
Top wing +2 deg, Lower wing 0 deg. Are designers trying to enhance handling characterstics of models by altering prototype angles. Is pitch stability enhanced for instance by using positive decalage. Can anyone comment on the difference in trim required before and after Flair changed the tail setting. Flair also suggested using some downthrust on the motor if larger engines were used. Any thoughts?

(in reply to Cybertom)

Post #: 634

RE: Flair 1/4 Scale PT-17 Stearman Review - 4/22/2007 2:50:53 PM

Cybertom

Posts: 545
Joined: 12/2/2002
From: Streetsboro, OH, USA
Status: offline

I bought "Stearman A Pictorial History" when I started my project back in 2003. See it in the picture. Excellent book, great from a historical perspective but lacks some of the in depth technical data it should have. Good find. I'm going to see if I can find "Wings of Stearman" for sale anywhere. Sounds like an excellent reference.

I own the book "The Gloster Gladiator" by F. K. Mason. It's the best aviation book I own. Not only does he have the complete history of the Gladiator but he has history about aircraft that lead to its creation. There is ton's of technical information showing what modifications were being made in what year as the plane was developed. Time to climb, landing distance with flaps & without flaps, turning radius, it goes on and on. Unfortunately it's hasn’t been in print since the 60's. I own 2-copies which I bought from book collectors. One I actually use as a reference and the other one is in nice condition which I have on the shelf as a collectable.

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< Message edited by Cybertom -- 4/22/2007 7:39:32 PM >

_____________________________

Real airplanes have 2-wings and round engines!

(in reply to geoardsog5)

Post #: 635

RE: Flair 1/4 Scale PT-17 Stearman Review - 4/22/2007 3:27:21 PM

Cybertom

Posts: 545
Joined: 12/2/2002
From: Streetsboro, OH, USA
Status: offline

Waldo,

Excellent questions Waldo. Wish we had the answers. Fortunately I have lots of friends who are engineers and one of them specializes in fluid dynamics which often used to evaluate air flow. Before I nag him with this I hope to find someone who is actually in the industry and an authority on the subject.
As far as this thread goes it's obvious to me that most here aren't as concerned about the "why" as much as I am. They seem to be satisfied with the information at hand (if I am interpreting this right) and that's not a knock against anyone. It's very practical. With some experimentation they should be able to get things working.

I'm planning on designing my own 1/3rd scale Gladiator. I don't know about you but I would expect the designer to know the answers to these questions for me to respect the body of work. I need to do some investigation on this issue, but the level of detail I am intrested in will probably be outside the scope of this thread. For me personally I need to know why.

As far as me building Flair Stearman #2, I will make sure that I have 3.5 degrees incidence in the stabilizer as recommended on their website. Since the lower wing has 3.5 degrees built-in not much choice there. As far as the upper wing its dependant on what I find out. The good thing is all you have to do is drill another set of holes in the aluminum cabanes, make another set of struts, and redo the rigging. Guys should be able to try just about any upper wing configuration they want. It will be interesting to see if changing the upper wing incidence creates an imbalance with the stabilizer (which is not adjustable). Instead of down trim they might need to carry up trim.

Factory Recommendation Flair Stearman (3.5 - 3.5 = 0 degrees decalage)
Upper Wing=+3.5 degrees
Lower Wing=+3.5 degrees
Stabilizer=+3.5 degrees

I'm guessing some of the guys are going to try this (1.5 - 3.5 = -2 degrees decalage)
Upper Wing=+1.5
Lower Wing=+3.5
Stabilizer=+3.5

PS,
I used a "much larger engine" in my Stearman. 3 degrees down and 3 degrees to the right works out great. Remember that if you measure the actual angle of the surface you created it turns out to be around 4.25 degrees. It took me a while to wrap my head around that one.

< Message edited by Cybertom -- 4/23/2007 4:14:49 AM >

_____________________________

Real airplanes have 2-wings and round engines!

(in reply to waldo)

Post #: 636

RE: Flair 1/4 Scale PT-17 Stearman Review - 4/23/2007 4:35:26 AM

geoardsog5

Posts: 25
Joined: 1/8/2005
From: Tinley Park, IL, USA
Status: offline

Cybertom, Don't be so rigid in your demand for hard technical data to accept the views of others. Have you ever heard of the concept of demonstrated ability? It is quite prevalent in the civil aviation business.Basically, it says that if you can demonstrate a practical knowledge and successfully execute the various aeronautical tasks required of the rating or special priviledges you are requesting, that request will be acknowledged and approved by the regulatory powers that apply. If we carry this concept over to model aviation, and I realize there is no regulatory agency involved, the opinions and accomplishments of guys like Bill Baxter and Jack Strickland carry a lot of weight. I consider it foolhardy to discount their opinions due to a lack of hard technical data. They have essentially been there and done that.
Once again, the answer to this argument is to fly, adjust as necessary , then fly again. Do whatever it takes to engineer wing incidence adjustability into your aircraft, otherwise you will have to settle for whatever you get off of the building board and if you don't get it right, you will be stuck with a poor flyer that you can't do anything about.

< Message edited by geoardsog5 -- 4/24/2007 1:14:58 AM >

(in reply to Cybertom)

Post #: 637

RE: Flair 1/4 Scale PT-17 Stearman Review - 4/24/2007 5:54:41 PM

waldo

Posts: 38
Joined: 4/3/2002
From: Dublin, IRELAND
Status: offline

I thought your use of 3deg of down and right thrust was interesting, now we have some forces acting at different angles to produce a good state of trim. If we can tolerate an unscale thrustline surely we can accept a wing incidence which is proven to work even though not prototypical.
I think the inspiration provided by the various contributers to this thread even though we may not all agree on everything, has been of great help in researching the Flair Stearman build. I've got some great ideas from the generous contributors to the thread and hope that this will continue as various builds progress.

< Message edited by Lightfoot -- 4/27/2007 6:46:17 PM >

(in reply to ElectRick)

Post #: 638

RE: Flair 1/4 Scale PT-17 Stearman Review - 4/26/2007 8:11:44 PM