Stearman build

[Bill Gaylord]

The plastic parts are always good ones to get out of the way. Joining the halves and sanding the seam between all the fins on the cylinder halves was a LOT of work on that model. Fitting the landing gear farings perfectly against the fuse is another interesting task on this one too. Good to see you're back on it.

[davidchoate]

Some progress last night.

[davidchoate]

Started covring, and painting plastic pieces. Uggh. I hate plastic. Too heavy.

[davidchoate]

Just have to invent some spark plugs, and exhaust pipes. I have'nt thought about an intake manifold yet. But every picture of a PT-17 I look up seems to have a different engine hanging on it.Between the Engine, and the Pilot, Mitch should be proud of Me.

[Bill Gaylord]

I noticed that also with the engines. There's a number of variations of the exhausts/intakes are routed. I thought briefly about modeling them, but that would be a real chore!

[davidchoate]

It is. I'm not used to attempting such detail,but I want this plane to look really good. and Fly. Today I took My Hobby Zone Champ (I love that little plane), and My Bird Dog (rubber powered) to the park. I learned how to do loops, and land! I even got down how to flare the Plane just a bit before touching down. A little more practice ,and I'll be confident enough to fly one of My scale Models I built. And I finally Got My Bird Dog trimmed just right, and the right length motor. I only went a couple hundred winds because of the limited space, and trees. As I have no way to steer around them,but That little Bird Dog Flies nice. I got it trimmed to do about 50 yd. diameter circles as it climbs. With more space I would set it up for a larger circle. It only took Me 3 years to accomplish all this. LOL.Rubber power is a lot of fun once you learn how.

[davidchoate]

I'm covering the wings now. I will have to put off covering the fuselage until I get the servos,and pushrods, etc... installed, and adjusted, and placed for balance. Then a little infilling behind the Plastic engine. It appears from photos to be of a solid metal covering to about the landing gears. I am a bit confused, and a little uneasy about the Vinyl wing struts. Not only do they not appear as depicted on the plans, but I don't trust they will adhere good and strong. I have learned the hard way that wing positioning, and straight assembling make a very big difference in the flight Quality of the Plane. I have not assembled a Flying Biplane in 30+ years. Any advice on correct wing alignment, and balancing would help alot. Thanx.

[davidchoate]

I've been on vacation for 10 days now. I guess I'm well rested because I had no problem staying up all night, and finishing covering the wings. I really like the new white tissue better than silkspan. It's very light,and is the only thing so far that woks well with Elmers Glue dope. I used a 50/50 mix with water, and had good results. I plan to paint with Acrylic and brushes. Thats why I chose the elmers. If I spray enamel I use a clearcoat spray paint, and a topcoat of clear. The covered and doped parts are remarkably light. with the large wing area I could see this Plane doing fine on Rubber power, but I would not recommend the scale tail with the added rib thickness. There is an alternate; actually two other alternate. Three altogether tail designs as Mitch would sat "It's a multipurpose kit". I can see though, already, It's gonna take a ton of weight to balance it out. The tissue gets scarily soggy when doping with water based stuff, at first this was a concern, but I have done it a few times, and knew it was gonna come out O.K. Can't wait to paint. Thats the best part. Makes or breaks the thing in My opinion.And I'v decided to not use the vinyl struts. I got plenty of Spruce ply around of all sizes. I know it's pricy, and thats why they dont put it in kits anymore, but I'd rather not have the wings blow off 50 feet up on a Plane I spent a year working on.Not to be critical, I mean I got the kit free from Guillow's last year,and am very grateful ,and Dale did ask for feedback; so I'd rather get a ply firewall, gear support, and struts in the kit rather than a piece of inadequate rubber, a lump of clay ,and a mile and a half of thread. And they could keep the props too. I'd give all that for 6sq. inches of spruce 1/8" ply. Gladly. I got so much clay I could make a life size Gumby Doll.

[davidchoate]

A took alot of photos. I worked on it like 16 hrs straight.

[davidchoate]

Started painting. I bought two of yellow cause I knew two wings would take alot. But I used half of one of them on a Aeronca. I hope It will do it all.I'm not gonna be able to go get more cause of the holiday thing, and I'm running short on vacation time. I don't know if you ever tried to mix acrylics, but they dry a way different color than wet. I only know one Guy who could do it , and he even took a while. As you must mix, and let dry, and check the color. And remix, and repeat that til you get it. Used to be a very good Essay on the whole procedure, but its gone from the file now. I am adding the cardboard wingwalks, and I think the one on the top is a Gas Tank? There is also three bulgy looking things that go on bottom of top wing. Not sure what they do either, but I got a Plenty strong motor for this thing, and a nice big slowflyer prop. So I'm not concerned about weight yet. Its turned out MUCH lighter than expected considering the details. Thats never happened before. And I kind of understand the wingloadind/ power thing, and being a Biplane I think its alot different. Correct ,or enlighten Me please if I'm wrong.

[Bill Gaylord]

Yeah this model turned out much lighter than I expected also. The wing loading is not quite as good as a single, larger wing having the same figure, but the added area helps. I understand there's some loss of efficiency in stacked wings, versus having one large wing of the same area.

[davidchoate]

I'm not a aerospace engineer, but I do what I can, and it seems that, yes alot of drag will happen, but I xpect that it will create more of a low speed lift with two wings. They are two thick wings also.I think that when engines became more powerful in 1930's that enabled higher speeds, and ability to reduce wing area to get lift; therefore cutting air resistance, and getting higher speeds. I think that sounds like a logical progression. Maybe thats what happened. Not 100% on the facts.Where's David Lewis? I need help. I wanted to ask you Bill where did you end up at the best CG? and what size motor? I looked in your thread, saw a nice Castle 9amp ESC. But could,nt make out the motor. Thats some nice gear you usrd. I as well am using a bit better quality on My PY-17. I got all spektrum, and eflite stuff. Except the motor and esc which are not top of the line but not elcheapo I'm just gonna hope it dont quit on me stuff either. I had to keep a budget. I usually put cheap stuff on, but I really put a lot of work, and research in this one. If it gets destroyed in flight. I want only My own inept piloting to blame. The Yellow paint is done for now,and the color is are starting to come out nice. I tested this paint on another plane before,and am not super experienced with acrylic paints, but am learning fast. I was honestly ready to throw the plane I tested the paint on away.I put it to the side and started on something else to take My Mind off yet more disappointment when one Day, I don't know, A week or more later, I happened to look over at it, and saw a perfectly smooth Lemon Yellow finish in front of Me. It was so pretty that it mesmerized Me like a bar of Gold or something.

[PsyberPhlier]

Looking good, David.

[David Lewis]

For a wing strut, or any member that carries axial loads, plywood is not a good choice in my opinion because ply is an isotropic material (equally strong in all directions). That means the laminations where the grain is perpendicular to the load path do not do anything. Half the structural mass is wasted. I believe it's better to use balsa, which is non-isotropic, and also has a higher strength-to-weight ratio.

Make the strut attachment points strong enough, and you should be fine. It's rare for a strut to break before the connection to the wing or fuselage does. A lot of designers are impressed with plywood because of its hardness, strength and durability, and there certainly are applications where ply is ideal, but always consider whether the advantages outweigh ply's drawback of lower strength-to-weight ratio.

The benefit to low wing loading is that stall speed is reduced, which makes the airplane easier to fly, easier to land, and safer; just what you want in a primary trainer. The disadvantage is that cruising speed and top speed are reduced -- not a big deal for a trainer -- but huge disadvantage for a fighter or airliner.

As drag coefficient goes up, the motor has to work harder and the battery won't last quite as long (all other things equal) and the glide ratio will be reduced, but it has no significant effect on stall speed.

[Bill Gaylord]

I can't remember offhand where the CG was located, since the model is now a block away at a WWII veteran's place who used to fly them. I can tell you a few things however. First, I believe it was the plan CG, which looks about right after checking it. The second thing is that some stagger winged biplanes have no tolerance for aft CG, and it also tends to appear to be a bit forward. With the Guillows Camel it flew well at 10mm from the LE of the bottom wing. At 15 it was a completely unflyable tail heavy monster. This plane has a bit better proportions than the Camel, but it's probably in a similar relative placement. Another thing is to make sure that the top wing either has a slight bit more positive incidence, or is equal to the bottom wing. The staggered wing biplanes will go into a horrible tail heavy flight condition, if the bottom wing stalls first. The DR1 was one of my earlier builds, and had this issue. It was flyable, but had a constant roller coaster stall issue due to the problem. I corrected much of it and it flew much better afterward.

I've used ply for struts many times on these models simply because a hard balsa strut with equal strength tends to be somewhat large in cross section. A good grade of 1/16" ply with 2 layers of laminate running lengthwise is quite strong. Obviously not all ply is created equal, where some are made from better wood and laminate adhesives that others. The good stuff is amazingly strong. Another reason for ply struts is that the 1/16" width fits easily fits into the socket base, when built per plan. I always use hard balsa stringers to create the socket base on the wing formers, as well as amply gluing of the struts, since ply does not tend to glue well with only a lick of CA. A full joint with something like BSI gap filling CA has never come apart on me as of yet, although we commonly hear the epoxy is better with ply lectures.

Another advantage of ply is that a nick or surface issue does not tend to cause stress concentration failures as it would with balsa, where the grain runs in one direction. If you took a 1/4"x1/16" balsa strut and nicked it 1/16" deep with a knife, I would be really concerned about it failing in that area. With ply, it would be much less of a concern.