3rd 400 series FW190 rc

[Bill Gaylord]

My second build of this plane is a decent flyer, but I've always wanted to build another with a few afterthoughts included. The laser cut parts was another attraction. This one will have micro retracts and a slight wing incidence change, which gave excellent results with the P51. For rc, these flat bottom wings seem to fly best with the stab at zero degrees to the flat wing bottom. A bit of Phillips entry at the bottom LE probably helps some, which was done on the P51, but I'm convinced the incidence change is the most important.

If Guillows were to make any changes to this kit, my wish list would be a plywood main spar, Phillips entry airfoil LE, and headers included for cut-away aileron fabrication. The kit still includes the die-crunch (literally with nylon) main spar, although I guess it might not work out really well to laser cut that stuff and the ply costs. Since I cut a new 1/16" ply main spar, I figured I'd take a slight bit of dihedral out also, since this will be an aileron flyer. The main spar was moved rearward, to open space for the retractable landing gear. The wheels I plan to use are slightly smaller than the kit wheels, and will just barely clear the LE, without moving the gear legs further rearward than roughly 5mm, which is about as far as I care to go, or I'll end up with a nose-in special. Studying the geometry of the full-scale plane, it appears they can have the gear doors and wheels sweep rearward a bit and still match the wing bottom surface profile when retracted, since the wing bottom is semi-symmetrical and curves upward toward the LE. If this was done with a flat bottom wing, the gear doors and wheels would either not align flush with the flat bottom when retracted, or you would end up with slightly toed-in wheels if the doors and wheels were to align flush with the wing bottom when retracted.

[Mitch]

Bill
Wow, that's plane looks nice. Looking forward to see your new build. I was at a local hobby shop the other day and looking at the new electric motors. Please give us a list of what you put in your plane. I do not know much about the new motors, and other gear. By the way...my 40 yo FW will never fly, if I want I would build a new one with an NOS Cox engine or a NW engine or maybe go your route with Electric RC!
Mitch

[davidchoate]

I got the same kit in My inventory Bill. I will be watching. Is it possible to change the airfoil? I have thought about it,but lack experience and knowledge still. I will be happy to see retracts as well as what motor/electric stuff you will use. Please post alot of photos. Thanks

[Bill Gaylord]

Thanks for the comments Mitch and David. The motor I'm using is a 1400kv from Hobbypartz: http://www.hobbypartz.com/86ma01-2205-1400kv.html A good choice for this model with a bit of weight would also be a Park 370. The model will need some nose weight, and with the expected AUW a motor this size is a decent match. Something like the Comet Albatros DV I just built flies well with a 250 class motor, but for that model neither the nose weight nor added power was needed. For ESCs, I've become a big fan of the Dynam 12A, since it has a 2A switching BEC, and will drive the retract servo without worry. Most 10-12A ESCs have weak 1-2A liner BECs, which are questionable when driving 4 or 5 servos with retracts. I have an 18A Dynam on hand and may end up using it, albeit a bit larger than needed, since I'll need the nose weight anyway with a sheeted fuse, after building one of these in the past.

For the airfoil, I'll probably taper the bottom LE from roughly 1/2" back from the LE, removing roughly 1/16" from the forward most part of the bottom of the airfoil formers. It's easier to do that after construction, since the LE would become difficult to not break if I removed too much material during shaping, and the construction is much easier when the LE and formers can be aligned dead flat on the board.

I now have one wing panel finished, where the second will be much easier, since all the airfoil parts were cut to match the first panel, once everything was fitted. This is much easier to do with LC parts versus die-cut, since everything will be symmetrical with precision. It would be really nice if they provided aileron headers that were marked, and airfoil formers inked with cut lines for constructing ailerons. They would simply need to provide 4 headers and 4 small end framers for the inner aileron header and the adjacent header on the wing. There's actually 2 headers in the photo, where the aileron simply needs to be cut away, although it's a bit difficult to see.

[Mitch]

Thanks Bill, for now I'll stay with rubber bands... I will still enjoy watching your build. Mitch

[Bill Gaylord]

Thanks Bill, for now I'll stay with rubber bands... I will still enjoy watching your build. Mitch

That's always a good thing. I'd like to try some myself someday. I think both of us are good candidates to cross-over, since we appreciate the need for precision and building as light as possible, while still scale detailed. So many people start out concerned with all the technical details, without realizing that a dead straight airframe is the most essential thing to start with. On that note I'm pleased with a 100% dead straight wing with no warps, to start with. No matter how you construct these wings, it's difficult to do.

The retract mounts are now fitted, and I will definitely have a slightly different airfoil, as I will need to add to the wing bottom thickness to allow for the doors to shut flush with the wing bottom. This is even with using thin tires, and using very small Goldberg 1/16" wheel collars and hardened allen head Dubro 2/56" bolts for axle mounts and axles. The small collar allows for the tire to be as close the axle as possible without rubbing, minimizing the amount of airfoil thickening required for a flush gear door fit. To minimize added sheeting weight, only the front portion of the top wing will be sheeted with 1/32" to avoid the "starved horse" look, unlike my last 190 where the entire wing top is sheeted. The wing bottom will be sheeted around the retracts and gear door area. The resulting airfoil section will probably be something more like an E222 or other similar, slightly under cambered sections. http://airfoiltools.com/search/list?page=e&no=1

[Bill Gaylord]

This is all working about about as well as I could ask for. One main difference between my earlier builds with retracts and this one, is building light and efficient mounting structures instead of using 5 tons of ply and hardwood. I'm posting 2 update posts now, due to the photo limit.

[Bill Gaylord]

Gotta write something, so this is the second post of 2 submitted back to back.

[davidchoate]

Looks great. Thanks for the photos. I was wondering if you are using one servo for the aelerons, or a micro in each wing?

[Bill Gaylord]

Looks great. Thanks for the photos. I was wondering if you are using one servo for the aelerons, or a micro in each wing?

Thanks. I thought about using a single servo cable system, but I already have the wing marked out for 3.1gm servos for individual ailerons.

The near completed wing assembly will weigh a few grams under 3oz with aileron servo harness and partial top wing sheeting. That is well within reason, especially considering that all of the added gear weight is pretty much centered on and mostly forward of the CG. With this model, that will contribute to forward ballast, reducing the amount of needed noseweight, making some of it useful weight. My previous 400 series FW190 required noseweight, where this one will have the tail servos mounted further forward to reduce the need for ballast. The Zero is almost identical in that it requires some noseweight, with a 1/32" sheeted fuse.

[Bill Gaylord]

Retracts programmed and fully functional. With the wing held upright, the doors fully close. The resulting airfoil is slightly undercambered, with padding strips added to the wing former bottoms and sanded to taper, for a gradual blend from the sheeting edge, into the former bottoms. This eliminates an unsightly step.

[Bill Gaylord]

Finished the wing at 75gms. The resulting airfoil section looks better than the flat bottom stock airfoil IMO, but there is one drawback: Thickening the forward portion moves the CG forward, on an inherently tail heavy model. The stock 400 series section works well for the FW190 and Zero, in that the CG is relatively aft, reducing the need for nose ballast. I flew my previous build at 47mm from the LE which is rather aft but worked well, on the recommendation of another builder who successfully flew the model at that setting.

[davidchoate]

Looks nice Bill. I want to do retracts on mine too. Thanks for the link to that hobby supply place. I like their 3g servos because the Eflite (although very good quality, and a bit smaller require adapters to fit the Rx, or the Spektrum micro Rx which is nice, but pricey too. I do have my doubts about the 250 motor I got from them. when compared to the E-flite park250, the quality difference is obvious, but it was half the price, and I'm not going to fly My planes often. As a matter of fact; I'm not flying them at all til I get an instructor.I'm going to finish My PT-17 before the FW190. I got a 370 motor as its gona be heavy. I dont yet understand Motor power when given in Kv. Like you said 4100kv. I get the Park 250,and 370, and what that means. I put a 2300kv on My 300 Aeronca. It weighs 135g,and I believe its good. I think it may be equal to a 150 Park. I like E-flite cause they give you a sheet with specs. I put a park250 in My Edge,and according to the specs, It should go vertical. My Edge is around 120g. It can power a 400g scale model with a 8" slow flyer. I also picked up a park370 inrunner on EBay for very cheap. I think your supposed to run it with a gearbox,but I'd bet it would work without one.

[Bill Gaylord]

I hope the 4100kv was a typo David. That's ducted fan territory. This model will have a 1400kv motor which is maybe a bit high for the setup, but it's what I have. For the 24" high wing models, they should fly fine with a 10gm (180 class) outrunner, unless really heavy. The way to look at all this, is to build to spec. I size motors/batteries according to how much nose weight may be needed, as well as required power/flight time. A modern 350mah lipo will power a 300 class motor, where in the past you would need larger. I generally don't fly over 5 min, so if I don't need the ballast weight, then I try to keep the battery weight as low as possible as a personal preference. Another good thing now is that there are a number of successful builds with flight videos for reference, of most all of these Guillows planes. When I first started converting these kits in '04, we had people who would play "resident expert". These guys would Google search information on these kits and similar electric conversions, and then advise people based on what people "thought" would work or wouldn't, pretending that they actually knew something. You'd have be better off taking advice from a talking parrot versus those guys, although personally I'd prefer the parrot since parrots aren't arrogant. They were often very critical of Guillows kits to boot. We proved those guys so dead wrong that they should be embarrassed to post on any one of these forums.

I hear you on the micro JST connectors also. I bought a bag of 50, but try to avoid using them unless it's something like the little Robin build or smaller. As luck would have it, the BA2.5 servos I had on hand did not have JST, so I had to install them. Good thing I still have perfect close up vision since it's a real pain. Whenever I was using the standard S-connector, then as luck would have it, the BA2.5 servos I had on hand would be JST type.

I talked myself into adding a steerable/retracting tailwheel. After all the effort so far, why not. The strut and axle are bent from a single piece of .032" wire, with the scale correct "U" fork appearance. This was a bit tedious, since the second of 2 bends at the wheel had to be made after the wheel was installed. I pre-bent that location a bit, so it would bend easier after the wheel was installed. The strut wire then doubles up at the top of the upside down "U" fork, and can turn inside the aluminum tubing strut housing. It has to turn inside the strut housing, since the strut housing cannot turn, due to the clevis point mounted on it, which will be used for extending and retracting the unit. A telescoping aluminum tubing sleeve will be permanently glued inside the fuse, which the tail strut assembly can slide inside for retracting and extending. At the top of the unit, the inner strut wires bent 90 degrees and have a short piece of aluminum tubing which is crimped and glued on the wires. This piece has a small hole drilled in it, and is used for the steering arm. The arm has to be short due to the narrow fuse, which will require a reduction bellcrank to reduce the steering pushrod throw, since it will be driven from the rudder servo.

[Bill Gaylord]

Next to assemble the steering reduction linkage, which is the easy part. The tailwheel retract is now working, with a few thousands clearance from the end stops in either direction, allowing for a few percentage points of adjustment on the main gear if ever needed.

Short video of retracts in action:
https://www.youtube.com/watch?v=rzLSjoM ... e=youtu.be