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Old May 15, 2011, 11:49 AM
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Build Log
Guillows Stuka (Flight Video) 16.5" kit 508 with AR6400BL board

It's probably better that I went into the build a bit, before starting the thread. Hopefully I won't drag anyone through the process of changing my mind 1000 times concerning the specs.

General Build Specs:
The plane will have aileron control. I've had success with rudder control on planes this size, but it's always been a bit lacking, and difficult to trim out the correct thrust angle and perfect the wing adjustments. I was tempted to use a BA2.5 servo that I have on hand for the ailerons, but ruled it out, as it is added weight. The same goes for using 1 or 2 Spektrum micro servos for the ailerons. I'm also too broke to buy them. Since I basically never use rudder individually, I decided to link the rudder and ailerons together, using the common Spektrum board rudder servo. It will be equivalent to having them mixed, and the radio is now set to mix the aileron channel with the rudder channel, so that I can control the plane from the aileron channel.

The plane is now powered with a 5gm ELE outrunner and small 2s-200 Full River lipo. The tiny motor was costly at over $30, as it was stocked by my LHS back when they were more costly. Still, the quality is notably better than the low cost AP05 outrunner. The motor comes with a rear mount and screws, which thread into the housing. The shaft is retained with a C-clip, rather a simple press job. My AP05 required removing the bell, crimping it, and then re-pressing the shaft, as it came with a loose shaft. I have a Fly-Zone (similar to Cox) micro prop-spinner setup, that is running within the proper amp range, and seems to have ample thrust from testing.

As for the heavy Guillows balsa: the tail feathers, fuse keels, and some of the wing parts have been re-cut from lighter balsa. Other parts such as fuse formers have been lightened. The overall weight savings is now about 3.5gms, which is considerable for a plane this size.

Aileron linkage:
Time to get creative. This is what separates our builds from ARFs. The ailerons will use .015" music wire, which can be individually adjusted in a common Dubro Micro E-Z link. As for the wire setup, this will be the 7th micro that I have, using the setup. The key is to custom bend the wire such that it moves freely, throughout the needed range of aileron travel. It really is not that difficult to do, as the travel range is small. Obviously all of the linkage should be tweaked to have minimal friction, given the tiny servos. There are photos below showing the linkage setup, which will be Dubro E-Z link adjustable through a small opening in the bottom of the wing center. The overall weight of the setup is less than using a separate BA2.5, or even a Spektrum servo for the ailerons.

Preliminary CG test:
The most difficult thing about a build this small, is trying to hit the CG, with no ballast required. The long nose makes this subject appealing, as I failed before with the micro FW190, by needing an amount of nose ballast that darn near outweighed the plane itself. I've found a good building rule of thumb for warbirds concerning CG. Assemble the fuse, tail feathers, motor/prop, cowl, and fuselage gear-batt, when you reach the point where the fuse and tail feather frames are completed. The fuse should be sheeted for the test at this point, if it is to be sheeted. At this point, somewhere from the leading edge of the wing saddle to a few mm rearward is a good place for the balance point to be. It may seem a bit forward, but consider that the plane will have more covering/paint aft of the CG, than forward of the CG. Much of the wing will contribute to aft weight also, along with it's covering and aileron linkage. Even little things like tail feather control horns will add aft weight. It all adds up. If a plane ever does end up a bit nose heavy, it takes little tail weight to correct it, as it is placed so far rearward.

That writeup was too much like work!
Bill
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Last edited by Onna Vakkation; Jun 05, 2011 at 09:44 PM. Reason: Flight video added to title
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Old May 16, 2011, 11:41 AM
Chad
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United States, CA, Cathedral City
Joined Dec 2010
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i will be watching to see how the aileron linkage is done. I used bead wire on my P-40 for the aileron but I went brushless too and used 2x 2.2g servos 1 for aileron one for elevator.
dont know if i will need rudder but if i do i will just toss this build and start over on one of the 3 i have sitting here.
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Old May 16, 2011, 11:58 AM
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Bill,
These little birds have been grabbing my attention. Having only used Futaba equipment before, I've been trying to research the Spektrum ultra micro stuff and I have a (probably stupid) question. The Ar6400 recievers I've been reading up on say compatible with DSM2technology, but the transmitters all say they are DSMX technology. What's the deal? It looks like the two of them are going to be used together here, but for a simpleton like me, DSM2 and DSMX are two different things.
Wonder why Futaba doesn't catch up with the world and get something like this out there? Sorry to side-track you thread, but I figure you would know.

(You just never know who might be watching, do you?)

David
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Old May 16, 2011, 06:33 PM
Chad
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United States, CA, Cathedral City
Joined Dec 2010
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Yes DSMX transmitters are backwards compatable with DSM2 recievers. some people have had isolated problems that can be fixed by a firmware update but other than that it should work just fine.

found this statement on another site
Spektrum changed the communication protocol, and some aftermarket suppliers werent ready with the software updates. So, when you are trying to connect satellites to FBL units (using it as the bus) it's not talking the right language (the FBL unit).
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Old May 18, 2011, 01:35 AM
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TheOne420 the thin bead wire is nice stuff, that I've used for a number of things. WalMart had some really light bead wire for 2 bucks, that would be good for small apps. I used to to rig my last biplane. Thanks for answering the DSM question also, as I didn't have a clue.

CD now is a better time than ever to use the micro Spektrum gear. I had to go to a good bit of effort to use a BL ESC with 2s lipo, on the older board. Now the new brushless board has it all there. I knew they would come out with one, so I held off on another micro until the released the new board.

I figured that since I have a working rudder, I may as well have a steerable tailwheel. To keep it light, it uses .015" music wire and a very light aluminum sheet "U" clamp, crimped around the pushrod wire with a tiny hole in it, for the steering arm to insert into.

Probably not the easiest way to do this, but I came up with a method to create a flush surface across the cowl-fuse mating joint, with no step. The inset planking is raised where it meets the front firewall, so that it creates a step for the cowl to slip over. When the cowl is installed, the outer surface of the cowl is flush with the front fuse inset planking. Now here's where this is probably not the easiest way to do this: The inset planking gradually fits between the stringers for a flush fit with the outer stringer surfaces, as it runs toward the second fuse former. Remember that at the front fuse, the inset planks are raised slightly above the stringers. Next, small balsa strips are glued above the stringers, to fill the low area between the planking sections. Last, the entire strip planked front fuse is sanded, being careful to not sand away the front cowl mating step, while tapering the outer surface to meet flush with the second fuse former from the front. A bit of work, but I like the sheeted appearance of at least the front fuse area, on a sheetmetal covered warbird. From past experience, I know better than to sheet the entire thing, as much as I'd like to.

Bill
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Old May 21, 2011, 07:10 PM
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Gotta love the Stuka gull wing:
If you enjoy fitting the die-cut parts from hand drawn vintage plans like I do, then the wing construction is a rewarding job. Otherwise, a gull-wing at this size would benefit from CAD drawn, laser cut parts. I spent a good bit of time fitting the wing center parts, for a non-twisted wing. One interesting part of the design, is that whether intentionally or by accident, the wing incidence decreases from the center to the gull bend line, which provides washout. This is accomplished by the design of the wing center framers. From the the center wing section outboard, I continued to add slight washout into the wing build.

The next task will be fitting the ailerons and static flap parts. I'm still deciding whether to step the parts below the wing bottom surface with a gap, or just step them without a gap. Mounting the parts directly, or gapless, would be easier. I'll look at what Tuctronics did with his, as it seems to fly well. Obviously the aileron hinging scheme will need some gap, or the ailerons would not move upward. Custom bending the 0.015" music wire aileron cables will also be interesting. I've used them numerous times on small planes, but the gull shape will add effort to the wire bending/fitting process, for low-friction movement within the travel range.

Bill
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Old May 22, 2011, 12:09 AM
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Looking good, I'm just starting a Guillows 16.5" FW-190 conversion using a Parkzone UM J3 brick powering a Parkzone UM P51 motor/gearbox. Going to do ailerons and elevator for controls. Interested to see your setup! I'll be following your build closely. It's looking great so far!

Dave
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Old May 24, 2011, 09:22 PM
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Quote:
Originally Posted by davewilson View Post
Looking good, I'm just starting a Guillows 16.5" FW-190 conversion using a Parkzone UM J3 brick powering a Parkzone UM P51 motor/gearbox. Going to do ailerons and elevator for controls. Interested to see your setup! I'll be following your build closely. It's looking great so far!

Dave
Hello Dave. Just don't sheet it like I did. I love that little plane, and may build another someday. I used very light sheeting for the fuse, but still needed an unreasonable amount of nose ballast to fly it. It has been done successfully, and I assume that they paid very careful attention to keeping the tail light. The Guillows FW190 is actually an A3, so you can cheat and add a few mm to lengthen the nose and still not look bad, as that would be scale for the A5-A8 models. If I remember correctly, I may have lengthened the fuse formers in front of the wing slightly on mine. The 190 is a favorite though, and my 28" Guillows FW190 is a decent flyer. With needed ballast, mine was actually a decent chuck glider without the battery, but the battery weight killed it.

Stuka:
The plane is moving along well now, and I've started covering parts. Considering that I'm never excited by covering, the tiny size is a welcome break.
I blew a good few hours making another prop adapter, as the last one was off center, and not a smooth as I liked. These 1mm adapters are not generally at the LHS, and I would thus have to order one. While most people would just blow the 5 bucks and buy one, I have to blow yet another entire evening making one. This one worked well, as it was made from the broken portion of a collet adapter stud, that was threaded for a spinner to mount on. It was perfect, since it was already threaded for my spinner mounting screw, and the thread I.D. was about 1mm, which was just what I needed for the motor shaft to fit well. Of course I had to drill and thread set screws, along with all the other spinner fitting-shimming operations to get it all properly mounted on the plane. A lot of time spent on such a little part.

Bill
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Old May 25, 2011, 11:44 PM
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Thanks for the advice! So far I've managed to plan everything out so the motor, board and battery are all ahead of the CoG. I may sheet the lower part of the forward fuselage and wing centre for belly landings but the rest will be all stringers. For the ailerons, I'm adding a 3/8" strip to the back of the wing instead of hinging a portion of the TE, this will add a bit of wing area and move the CoP slightly aft so hopefully that will make things slightly better in the air. I'm also using pull-pull setups for both ailerons and elevator, I'll have to take some photos of that once I finish rigging it up, so far it seems like it's going to work pretty good!

Your Stuka is looking gorgeous already! I can't wait to see the finished product! I'm interested in the aileron control linkage, you said you're using .015" wire and it obviously has to be bent in a few places to make it to the aileron. Is there any slop or "spring" at the control surface because of this?

Dave
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Old May 26, 2011, 12:31 AM
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Quote:
Originally Posted by davewilson View Post
Thanks for the advice! So far I've managed to plan everything out so the motor, board and battery are all ahead of the CoG. I may sheet the lower part of the forward fuselage and wing centre for belly landings but the rest will be all stringers. For the ailerons, I'm adding a 3/8" strip to the back of the wing instead of hinging a portion of the TE, this will add a bit of wing area and move the CoP slightly aft so hopefully that will make things slightly better in the air. I'm also using pull-pull setups for both ailerons and elevator, I'll have to take some photos of that once I finish rigging it up, so far it seems like it's going to work pretty good!

Your Stuka is looking gorgeous already! I can't wait to see the finished product! I'm interested in the aileron control linkage, you said you're using .015" wire and it obviously has to be bent in a few places to make it to the aileron. Is there any slop or "spring" at the control surface because of this?

Dave
Good move, that's what I was thinking. I would put gear as far forward as possible, and then some. I have a Guillows DR1 with tail servos in the cowl. My Guillows Rumpler has the board aligned with the wing LE, balancing and flying with a 5gm motor, with no ballast. The more forward, the better. You'll want to get real creative with that plane. The pull-pull setup can work well also with these planes. If I was doing the 190, I would want the string, as even the tiny music wire weighs. I built a Dumas Peashooter (not the best easy CG setting subject) using the Toki bio-wire servos with Guillows CL string, for pull-pull. I was a bit nervous about the whole thing, but it worked much better than expected. Those servos have very little torque also.
BTW, I have no problem with cheating wing areas a bit. I didn't cheat the Stuka's wing area, but it certainly wouldn't have hurt to cheat the tips a bit. I've seen other kits of it that do.

As for "spring" in the Stuka controls, there would be, if I didn't fit the guide holes well. Not really spring there, but the cable would buck back and forth, and have the same effect. Also, if you hold back on the cable ends, yes they will spring, but not withing the amount of force range needed to move the ailerons. On a larger model, it would have issues. Bending for perfectly smooth motion is one of the keys. I have to have the setup smooth and slop free, as this one will have short control horns, as it loses throw ratio at the aileron bellcrank. It wouldn't work out well, for play to make up 50% of the total throw range.

"For the ailerons, I'm adding a 3/8" strip to the back of the wing instead of hinging a portion of the TE, this will add a bit of wing area and move the CoP slightly aft"
With that thought, I had considered bashing my little Guillows 190 into a 190D. It would definitely help along those lines. I'm not sure what the small airfoil is like offhand, but on the larger Guillows 190, the max camber is far rearward, and looks a bit awkward. It is supposed to help with moving the CP aft. I was less than thrilled with adding noseweight to my 28" 190, and Milesperpound flew his with a CG setting or 47mm if I remember correctly, which is further aft than I would normally think of using. I used his setting to avoid adding more lead, and it worked well. I believe that somewhat verifies the airfoil design, in terms of moving CP rearward, which as you stated doesn't hurt with the short nosed plane.
Bill
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Old May 28, 2011, 07:52 PM
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What are your plans for down thrust and right thrust? I pulled a UM P51 out of the box at my LHS and these small planes seem to have quite a bit of both. Updates? I've been taking a few photos, I've got to start a thread for my FW190!
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Old May 29, 2011, 02:11 AM
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Originally Posted by davewilson View Post
What are your plans for down thrust and right thrust? I pulled a UM P51 out of the box at my LHS and these small planes seem to have quite a bit of both. Updates? I've been taking a few photos, I've got to start a thread for my FW190!
I'll look for the thread. I probably have between 1 to 2 degrees right and down thrust, with a bit more right than down. The down thrust stated is relative to the stab. With rudder and ailerons working, I can always trim, but with just rudder the right thrust needs to be pretty close to what it wants. I also found out in the past, that if you go just a hair too far with right thrust, you get disastrous results, i.e. shut down and glide in, before you lose it. The Stuka will be an experiment, as I slightly reduced the wing to tail incidence, and the wing goes from a reasonable amount of positive incidence in the center, reducing incidence (washout) progressively to the tips. I'll just have to fly it and see, and be ready to throttle down if it climbs too fast.

Well I finally broke down and bought a proper prop adapter. Thanks to all the micro helis, the LHS had several different types of 1mm tail rotor adapters. The prop spins very smoothly now.

Getting the 0.015" music wire aileron cable to work well has required some tweaking. I had to keep tweaking the bends until I got it to work satisfactorily, after test fitting the wing to the plane and testing the ailerons. Good thing that I did this, as it would not have been smart to cover the wing and assemble it later, without ever testing the operation. I honestly wouldn't advise using this setup on a gull wing, unless a person wants to put in some effort with the setup. With straight wings, they have been relatively easy to do in the past. The gull wing really throws an added degree of difficulty into the mix.

Another thing I found testing the ailerons, is that the Spektrum board had a bit of end-to end freeplay, where it was mounted between the fuse formers. Small balsa shims cured this problem. The freeplay caused the entire board to shift slightly when operating the ailerons. The board was held down in place, but had a slight amount of space between the front pcb edge and mating fuse former. Somehow I must have overlooked this, when mounting the board.

Bill
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Old May 30, 2011, 11:44 PM
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Coverite Microlite shrinks really well. That said, some genius decided that they could use a single piece of covering to cover the fuse. It worked out well, but was a bit of effort. The seam is at the fuse top center. Looks like this plane will be finished fairly soon now.

Bill
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Old May 31, 2011, 06:42 PM
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Looking great! nice idea on the hatch! What are your plans for preping and painting the microlite?
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Old May 31, 2011, 07:52 PM
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Nice work. I like the radiator slits, good idea.
Mind if I borrow that idea for my Stuka?
What does it weigh?
Glenn
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