Bellcrank and flaps for a .35 sized Sterling Yak-9

[RknRusty]

The Kit doesn't supply the bellcrank, so what's best, 3 or 4 inch nylon? I can look at the ply control horns in the kit to see what size they should be, and replace them with nylon. I assume the flap and elevator horn are the same.

After sanding and shaping the LE and TE to fit the curve of the wingtips, I placed the flaps against the TE. At the position that best blends into the tips, the other end of the flaps are 1/2" from the fuse side. Is that too much gap, or should I fix that?

Thanks,
Rusty

EDIT: After sanding the curves a little more, it' only about a 3/8" gap, so I'm not concerned about the flap fit any more. I can probably tighten it up some more too. Sorry, just that it's my first Sterling kit. The Goldbergs and Brodaks usually fell together if you shook it out of the box just right. I do still want to know which bellcrank size though.

[john e. holliday]

I believe you will only find room for a three inch bellcrank.   Remember to install a bolt long enough you can put a piece of plywood on the other end of the bolt. 

[RknRusty]

I believe you will only find room for a three inch bellcrank.   Remember to install a bolt long enough you can put a piece of plywood on the other end of the bolt. 

Thanks, John. I'll measure before I order a bellcrank.

[Balsa Butcher]

The Brodak 3" bellcrank is a good product. I prefer to use the inner most hole (closest to the pivot) to attach my pushrod to - either flap of elevator. It reduces the sensitivity of the controls and limits the travel a bit and actually gives one the feel of a 4" bellcrank. If a Sig 3" bellcrank is used a hole can be drilled through the dot of the "i" in "Sig" that is printed on the bellcrank. Use that. If you like more sensitive controls though, just go with the middle (Brodak) or closest to the pivot (no drilling) Sig. 

[RknRusty]

Thanks for the tip. If I need more sensitivity I'll widen the lines at the handle.

[Steve Helmick]

Are you going to make the flaps coupled to the elevator or fixed solid? The longer the flap horn, the less trouble you'll have with the pushrod/flap interference; also not a bad thing with a 3" bellcrank. Ignore the length of the stock plywood horns (they're too short!), and also avoid nylon control horns if you can. They flex, you lose. Sullivan makes some nice steel control horns, and they come in a set of LH/RH, which is good.    Steve
http://www.sullivanproducts.com/ProductIndexMainFrame.htm Look under "control horns", and use the 1.125".

[Terrence Durrill]

I used a good old PERFECT 3 inch belcrank and solid leadouts on my Sterling S-3 Yak-9.  The system has moving flaps and is still working good 26 years later.  The Yak-9 is a fun airplane.  I have flown mine with the Fox .35 stunt, the Fox .29 stunt and the Fox .25 stunt engines.....it's all good!.......TD.........    

[RknRusty]

I measured and it looks like the 3" crank is the best fit. I bid on this one on eBay and asked the seller what price he would accept to sell one before bidding ends in 6 days. No reply yet. It also comes with a nylon adjustable leadout bracket.
http://www.ebay.com/itm/321161643754?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
I'm trying to avoid Sig's $14.95 and Brodak's $9.00 shipping charges.

Mine will have a 1958 Fox Stunt .35 up front, and coupled flaps. This will be my first flapped plane. I have read a lot of posts about forward swept flap hinges binding. That took me to some threads on Lucky Boxes which allow some lateral play around the hinge wire to relieve the bind. I'm prepared to make a pair of these boxes, and am interested in any thoughts the Stunthangar crowd has on the binding flap hinge problem.
Rusty

[john e. holliday]

When I built my Yak 9 with the forward flaps, I never noticed any binding in the controls.  Of course back then with a Red Head McCoy .35 and 10-6 nylon prop who could tell if there was binding.   You will probably only have about 30 t0 35 degree movement while flying.   

[RknRusty]

Maybe I should just build it like it is, I could always change it later. I've had so many people tell me to build it with static flaps, because of the binding reason, that I'm just a little concerned about it. But I've never flown a flapped plane before, always wanted to, and am determined to make it work.
Rusty

[Steve Helmick]

Besides the swept hingeline, the tail moment is pretty short and the horizontal tail is pretty small. That makes the flaps less effective than desired, because of some technical stuff (pitch moment, I think is the techie term) that some will insist is critical.  But the wing is kinda small, so flaps seem like a good idea. If you were to lengthen the aft fuselage and increase the horizontal tail area, it would probably turn a harder corner, but I wouldn't suggest actually doing that. Still, as it is, you may not be impressed with the corner and probably will blame it on the flaps. At least you'll know why that is. IMO, for a small plane, (light) weight trumps complexity every time. A perfectly smooth and free control system is essential. 

Personally, I think you should build it however you wish, and as good as you can.    Steve

[RknRusty]

...Still, as it is, you may not be impressed with the corner and probably will blame it on the flaps. At least you'll know why that is. IMO, for a small plane, (light) weight trumps complexity every time. A perfectly smooth and free control system is essential. 

Personally, I think you should build it however you wish, and as good as you can.    Steve

Definitely will build it as I wish. I'm too hard headed to do otherwise. I'm getting better with every build, and work pretty slowly, else I cut things backwards and glue others upside down. My first larger than 1/2A plane is an old Goldberg Shoestring, given to me as a horrible wreck, that I rebuilt. But it turns a scary tight corner without flaps. I've been impressed so far. I've only begun to get past engine tuning, lap times, etc. and am only just beginning to concentrate on stunt flying.

Also, off topic; I did my first vertical 8 today with my Norvel powered Baby Streak. I don't think I went all the way to the top, but it turns so tight, I had plenty of air. I did two sets of double 8s. Just had to tell someone.
Rusty

[Paul Smith]

I've never liked a bent hinge line.  It's either a bind or a lot of slop. 

There are a couple of ways around it.

One is an X-crank with two outputs, one driving each flap with on horn on bottom and the other on top.

Another is to "back drive" the flaps off the elevators with no flap joiner. 

[Serge_Krauss]

You know, there have been many, many posts on the Yak, and it surprises me not at all that no one ever changes his mind on anything, despite what others say they've experienced. It is correct that short coupling and classically small tail should not allow for a great turn. Still, the plane does turn well for some. Leonard at SSWF swears by it, and mine turned OK with operating flaps, built from the kit parts just as in the plans. I may have been too ignorant or stupid to know the difference, but as a kid in 1960, I did vertical 8's that had the outside portion at the bottom and didn't go much above 60 degrees in elevation. Yes, it died doing those, but it actually could do them, and I didn't know that lazy-8's weren't figure eights. So it could turn.

Several of us have posted that you don't need the Lucky boxes to get flaps free enough to fall of their own weight - without a noticable slop. I've seen that. One key toward really free forward swept flaps with a single wire connector is to replace the kit part with one that has two bends rather than one.  Two other variants of this have been posted more than once on the two forums by folks who say they work. Why should I doubt them?  If one thinks that a lot of slop is necessary, consider that Bill Werwage's classic "Ares" models have completely free flaps with single-wire connections. Now I KNOW that this seems physically impossible, and I didnt believe it either, but I've checked these models out, two at our field, and they do somehow manage to be free, without noticable slop.

SO DO BUILD IT CLOSE TO AS SHOWN. Don't make it harder than necessary and destroy the simplicity of an iconic, even though imperfect, design that's lots of fun to fly. The double bend, weight box, and adjustable leadouts - plus better plywood and fittings - are all you need.

You can build something else, if you want a better plane, and lavishing huge amounts of new hardware will just dull the simple pleasure of a genuinely good OTS or Classic model. It's good enough for what it purports to be and can't be something "better" and still be your Yak-9. It simply "is what it is", and that's not at all bad. You can build something fancier later. This is a FUN model that looks nice. That's it.

[RknRusty]

Thanks, Serge. I clicked a "+" on you for that reply.
Rusty

[Ward Van Duzer]

Rusty,

Forget that Ebay deal! The leadout guide is way too big for the thin wing on the Yak.

Call Aero Products for your hardware and anything else you might need to finish up. And I really don't think Brodak would charge you $9.00 to ship a BC!

W.

[john e. holliday]

Take the easy way out and build it box stock with the exception of the glues and finishing materials.   It is a fun type plane that is supposed to represent a scale plane like the Sterling Mustang kit.   I believe both were made for combat back in the day.   I had a lot of fun with my Yak 9.  Even had it painted like the instructions color scheme.    .015 cable lines about 60 feet long and have a blast. 

Well some have won  Old Time Stunt flying the Yak 9.

[Garf]

Rusty,

Forget that Ebay deal! The leadout guide is way too big for the thin wing on the Yak.

Call Aero Products for your hardware and anything else you might need to finish up. And I really don't think Brodak would charge you $9.00 to ship a BC!

W.

They won't, IF you complain about it.

[RknRusty]

Alright. Thanks guys. I'll keep you posted on the build. I'm still working on the wing now. I did put a thicker #1 rib in it, but otherwise it's all stock. All sanded and shaped, looking nice.
Rusty

[john e. holliday]

Your care package should be there in a couple of days.   Forgot to ask if you need lead out material?   I use .027 cable for lead outs.

[RknRusty]

Got plenty, John. I have a whole spool of .018. If that's too light, I have a fishing outfitter in town that has 95# test (7 strand, I think) nylon coated stainless steel wire. When I use the coated wire, I flair the wingtip guides so it doesn't abrade the nylon. I have some brass or aluminum tube for those.
Rusty

[Jim Kraft]

Some of these old planes just defy reason. I built the Mustang a few years ago with movable flaps using cloth hinges from Tom Morris, and they are very free. I also have a sealed hinge line. It fly's very well and corners just fine. My flapped Magicians are also short coupled and built right off the Midwest plan, but fly very well and corner well. I know a lot of people say to move the stab back and build them with fixed flaps, but since I fly mine in Classic also, I build them just like the plans and they fly just fine. Since my Mustang has the swept forward hinge line, I did put a straight section in the connecting wire where it goes through the fuse. That may have helped instead of the "V" wire.

[RknRusty]

Some of these old planes just defy reason. I built the Mustang a few years ago with movable flaps using cloth hinges from Tom Morris, and they are very free. I also have a sealed hinge line. It fly's very well and corners just fine. My flapped Magicians are also short coupled and built right off the Midwest plan, but fly very well and corner well. I know a lot of people say to move the stab back and build them with fixed flaps, but since I fly mine in Classic also, I build them just like the plans and they fly just fine. Since my Mustang has the swept forward hinge line, I did put a straight section in the connecting wire where it goes through the fuse. That may have helped instead of the "V" wire.

Did you do as some of the guys have recommended to me, and use the inner hole in the bellcrank for the control wire? I've never done this on my 1/2As but the bigger planes are new to me. Some builders I respect on another forum agreed with that advice too. I certainly wouldn't have considered it otherwise.

[Jim Kraft]

I think the inner hole would be fine as you really don't need much throw on these smaller planes. I think on mine I drill one hole between the holes on a Sig bellcrank and use longer horns on the flap and elevator. I do use nylon horns and they seem to work fine and make things adjustable by changing holes with the push rods. If I remember right on my Mustang, I had to cut down a Sig bellcrank to about 2-3/4" to have room in the wing for it. And, as you say you can also adjust at the handle somewhat for fine adjustment. The main thing is to not have so much throw that you are stalling the plane a lot and make the plane jumpy and hard to keep level.

[Jim Thomerson]

The old Perfect(?) lead out packages had two pieces of the yellow plastic externally ridged tube, like in a nyrod, for the leadout guides. You should be able to get a piece from your RC friends. I have been using those for a long time and they do not wear.  I also use plastic coated leader wire for leadouts.  018 is not heavy enough, 95 pound is heavier than you need.  30 or 40 should be fine.

[Bill Little]

Hi Rusty,

I have never experienced a problem with the swept forward TE and only one control horn, and I have had several over the years.  Build it per the plans and it will be fine.

BIG Bear
RNMM/AMM

[RknRusty]

The old Perfect(?) lead out packages had two pieces of the yellow plastic externally ridged tube, like in a nyrod, for the leadout guides. You should be able to get a piece from your RC friends. I have been using those for a long time and they do not wear.  I also use plastic coated leader wire for leadouts.  018 is not heavy enough, 95 pound is heavier than you need.  30 or 40 should be fine.

I have a spool of 45# test that I used on the Shoestring leadouts. I was worried that it was too light. I figured .018 flying wire was stronger than that. Okay then, sounds like I've got what I need.

I wonder if that yellow plastic ridged tube is the same stuff used on Cox Killer Bee needle extensions. I have a bunch of those. I'll take a look at them. They are pretty stiff.

[RknRusty]

...If I remember right on my Mustang, I had to cut down a Sig bellcrank to about 2-3/4" to have room in the wing for it....

Yes, Jim, I'm having to lengthen the slot in the #1 rib to allow the bellcrank to swing fully in both directions. It took me some time of fooling around and test fitting before I finally realized the crank platform mounts on the outboard side of the #1 rib. There is no picture of the bellcrank actually mounted in the instructions. Boy, I'm learning one thing about Sterling... assume nothing!

The leadout holes in the ribs follow parallel straight lines from the crank connections all the way to the #9 rib with no sweep. They apparently are meant to exit at the same distance apart as the connections at the crank. That's pretty wide, and the front leadout will be pretty far forward. I suppose it's because of the amount of sweep back of the LE. I guess it's like this because it works, but before I cover the wing, I'll hang it from the leadouts and make sure it's slightly nose down. I'm trying not to get bogged in over complicating things, some of the stuff on this plane is just different from what I'm accustomed to.

If I can get this wing out of the way, I'll feel like I'm finally making some progress. And hopefully get this thing built before y'all decide I'm a hopeless doofus.
Rusty

[john e. holliday]

Hey Rusty, some will admit it and some wont, but we've all been there and done that at one time or another.  My last one was forgetting to mount the tail wheel assembly before planking the bottom of my P-47.   Need to get it in the air along with about half dozen other planes.

[Bill Little]

Over the 50 odd years I have been playing with these models, I have probably made every mistake possible............ some I don't even realize that I made a mistake!

BIG Bear
RNMM/AMM

[RknRusty]

My young new next door neighbor had never seen one fly until I took a Baby Streak to the churchyard across the street. He came out to see what all the racket was about and I was busting wingovers, loops and 8s with a screaming Norvel. By the time I landed he had the bug and ordered a Brodak 1/2A P-51 that night. He's building it on the opposite side of my table from the Yak. Very detail oriented, and worries about every part... a lot like me. I just tell him, "Don't worry, do the best you can. It'll fly." Kind of like y'all tell me.

Our Monokote, my white and his aluminum came today, along with my Sullivan control horns and red spinner.
Flying the Shoestring is my top priority this weekend, but our two kits are coming along.
Rusty

[Jim Kraft]

Hey Rusty, Ya caught one. It happens every so often. There are a certain number of people that are drawn to what we do. The rest are an exercise in futility to get interested. Sounds like you guys are well on your way to get those planes done.

Talking about mistakes when building, I somehow ended up the the weight box on the top side of the wing tip when I built my El Diablo. I thought "oh well, makes it easier since I don't have to turn the plane over to change weight." At least I didn't put the weight on the left tip.

[Dale Hymanyk]

Hey Rusty, Ya caught one. It happens every so often. There are a certain number of people that are drawn to what we do. The rest are an exercise in futility to get interested. Sounds like you guys are well on your way to get those planes done.

Talking about mistakes when building, I somehow ended up the the weight box on the top side of the wing tip when I built my El Diablo. I thought "oh well, makes it easier since I don't have to turn the plane over to change weight." At least I didn't put the weight on the left tip.

That's not mistake, it's a "feature". I did the very same thing on my recent Skyray project. I mean, after being away from c/l for 40 odd years, things have certainly changed a bit. Having a ball finding all the resources available on the 'net. Sure could have used that back in the '70s! Oh and I had a Yak back in the day, just loved that thing!

Dale

[RknRusty]

Dale, I've learned more in the past few years than I did since my first Cox Stuka when I was 12. Forums are a great thing, and this hobby in particular has the most generous helpful people I've ever been associated with in any other endeavor.

Rusty

[Bill Little]

Dale, I've learned more in the past few years than I did since my first Cox Stuka when I was 12. Forums are a great thing, and this hobby in particular has the most generous helpful people I've ever been associated with in any other endeavor.

Rusty

Hi Rusty,

I have been involved in a lot of different things, but this hobby/sport is the best as far as interactions with each other.  Regardless is a person is a beginner or a World Champion, all respect and help each other.

Bill

[Dale Hymanyk]

Hi Rusty,

I have been involved in a lot of different things, but this hobby/sport is the best as far as interactions with each other.  Regardless is a person is a beginner or a World Champion, all respect and help each other.

Bill

I agree. In the couple of months that I've been "back" I've had more help and been put straight (sometimes none too gently, lol) on quite a few points as I'd ever had before. The result is that I've made a successful comeback to at least where I was as a teenager when I went R/C. Instead of a box stock Banshee with an old Fox 35 (don't get me wrong, I loved that combination back then and will likely build another one) for my comeback I'd beed advised by Brett Buck to build a Skyray with his very reproducible setup. I'm glad I did because that is one sweet flying plane. At least if I have problems, I know it's me not the plane.

[RknRusty]

I finally got the bellcrank installed. It's actually a good strong design. I had to open the holes in the #1 rib because I had doubled it, and had to open some rib holes on up the line to keep the leadouts from touching the sides of the holes. I used 60# nylon coated 7 strand stainless fishing leader. I installed Nyrod tubes through the wingtips and they look perfect and shouldn't bind on my coated leadouts.

Now it's time to hinge the flaps. I've about decided on pin hinges, and this will be a first for me. I've always sewn or used fabric on my 1/2A hinges, so now I get to learn a new building trick, aligning and slotting for hinges. I've searched and read a few posts, but haven't found any magic way yet. I'll make or buy a tool to find the centerline. I think my edges are about 3/16", but I'm going on memory and will check next time I'm in the shop.
Rusty

[Steve Helmick]

A lot of people use this method for pinned  hinges, from Gordan Delaney and John Miller. Most use a single wire pin for each flap and each elevator, but probably no need on a SterlingYak 9. Sealing the hingelines would be a good idea. Click on the file attached below!  Steve

[David_Stack]

Good Afternoon Rusty;

  Mike Griffin has an article on how he installs recessed pinned hinges on stabilizers and elevators on the Tulsa Glue Dobbers Control Line site at: http://www.tulsacl.com/Building.html.

  Also, back in 2008 - 2009 Bob HUnt did a 'build along' series in Model Aviation where he walked readers through construction of the "Hole Shot".  The issue from July 2008 addresses construction of the stabilizer and elevator, complete with pinned hinge installation.  You can access the back issue on-line by logging into the AMA site, and then using the "Publications" link to access Model Aviation and the archived issues.

r/
Dave

[RknRusty]

Excellent. I can do that. I'll let y'all know how it comes out.
Thanks,
Rusty