Back to the Yak - Yak-9 Build, Part II

I think it will be OK, the two at the tip may cause issues if they are not perfectly in line with each other. I would only use one if it were mine though.

It's real good that you have Wayne with you. It helps to have someone better than you around. Not that you are bad or anything.......  it makes learning quicker

Looks like the Yak is coming along nicely!

Ron

Cribbs74 wrote:I think it will be OK, the two at the tip may cause issues if they are not perfectly in line with each other. I would only use one if it were mine though.

It's real good that you have Wayne with you. It helps to have someone better than you around.  Not that you are bad or anything.......  it makes learning quicker

Looks like the Yak is coming along nicely!

Ron

Wayne won first place in two events at the Brodak. He's a great coach too. And I am pretty bad. Flying wild random freestyle makes a pilot look more skilled than he is. I didn't know that until I started trying to fly stunts and make it look like it's on rails. The up-side is, you're a lot less likely to crash, just practicing the pattern. I think I wrote above that I'm re-visiting propellers and how I tune this engine. I think that's going to help me be more consistent.

It is coming along nicely, but more slowly than I'd hoped. I'm just being super careful, trying to be a perfectionist. Once I get this wing out of the way I should pick up the speed and get 'er done. I know I've joked about the wood and instructions as I've been working, so I hope you haven't taken any offense at my wise cracking. I'm enjoying the build and learning a whole lot. Though I rebuilt a good part of the Shoestring, it wasn't like building from the raw kit.

I fondle my Fox Stunt 35 every couple of days and make sure it's oiled up good. That thing has scary compression. I don't use gloves or a stick cranking the Thunder Tiger, but that fox is a bone breaker. I will show it more respect when I stick my hands near it. I've read more about assembling them and checking for binding as you torque the screws, so I'm going to re-check all that before I crank it again. Are you using castor-added Sig 10 in yours? That's what I used for bench running it.

Rusty

No, Originally I used some all castor home brew that was given to me. I just went through a gallon of Omega 15% with questionable repute with castor added. When I can get my hands on some Powermaster GMA 10/22 I will be a happy camper.

I think SIG sells some all castor 10% if you want to go that route.

Edit: I don't use a glove or a chicken stick either. I really should however, my Foxes are pretty broken in and very predictable I would use a glove until you get a feel for it. They do some funny stuff and run backward if too rich, then without warning it will pop and run forward. Sometimes they spit the prop during this moment of drama. Ken told me to use a glove as he has been bitten a couple times.

I've been out in the shop butche... I mean cutting hinge slots. 
The balsa I bought for the flaps is masquerading as oak. It's super hard, which is good for flaps, but ruined my forked slotting blade on the first hole. I'm using an exacto blade now and it takes some serious muscle to dig into this stuff. I've cut 5 slots so far, and I hope the TE wood is softer. I sure don't want to botch it up. I can cut a new flap if I ruin one, but not the TE. A word of advice, the Dubro slot cutting kit that comes with the 15 pack of hinges is worthless, all except for the hooked digging blade. I couldn't do it without that and so far it's holding up okay.

Okay, break's over. See y'all later.

Funny,

I have had my Dubro tools for years and never had a problem. That must be some wood!

Hey, I got 'er done! It is some tough stuff. But after I finished the flap with an exacto knife, I straightened the tool blade and went to town on the TE. It was easy to slot, and the increasing taper made it easier not to come through the side. I got 5 hinges installed, all line up nicely and move with no bind. I'll do the other side tomorrow if i can't go fly.

After I get them both fitted up, I'll finish sanding the taper of the flap tip into the curve of the wingtip. I might sew one stitch near the tip end to help prevent it from vibrating. That'll be after I Monokote it.

EDIT: I take back some of the asparagus I cast on the slotting tool. It just doesn't work well on super hard balsa. Sorry Dubro.

Excellent work!!!

Asparagus... that's a new one for me.

Cribbs74 wrote:Excellent work!!!

Asparagus... that's a new one for me.

 Never heard the term, "Casting Aspersions"? Kinky Friedman used to sing ... Ain't nobody castin' asparagus on me... in one of his songs. I'll have to put that on in my sig next time. I wonder if anybody ever listens to my songs of the week.

The Yak went on the back burner in August when I heard about Huntersville and the Stunt contest. I never expected to be involved in such a thing, but soon became obsessed with learning to do it. August, September, and the first week of October were consumed with making the plane work, not an easy task, I found out. The Second week of October I finally got down to flying patterns. Post contest, my shop was a wreck, having been neglected for so long, and finally I have a place on the table to work again.

I've put in a few hours since yesterday beginning to finish the Yak wing. I finished opening up the hinge slots on the inboard TE and fit the flaps in place so I could finish sanding the tapered ends to blend in with the wingtips. I also had to file out the hinge grooves for the control lever. This has been a point of some extra thought, due to the mechanics of hinging a flap that has a forward swept hinge line.

When a lever swings a flap or door or anything with an angled hinge line, if there is no lateral relief the hinge will bind and the flap, door or whatever will bind and twist. It took me a while to wrap my head around that problem, and many people advised me to do many different things. Some said, fix the flaps and don't use them. But I've been wanting a flapped plane, so I'm going to make it work. Some said, just glue them in place, it'll work fine. But at best, I think it would stiffen the controls. Others had exotic solutions, such as "Lucky Boxes," which allow lateral relief of the levers without introducing vertical slop. I opted for an in-between idea, which won't be as pretty, but will be functional. I will cut the grooves deep enough that the heavy lever wire is flush with the surface of the under side of the flap, and shape the groove like a narrow triangle wide enough approaching the ends, that when the flap deflects, the levers can have some play and not bind. I'll harden the wood in the cutout with epoxy so the levers hopefully won't wear through and come busting out, and cover them with some epoxy painted ply caps. I'll post pictures before I put it all together. It sounds goofy, but I think it'll work.

Today I finished installing and bracing the bellcrank, put new .028" leadout wires on it, and started covering it with the center sheeting. Just now, looking at the pictures, I hope my bend in the control wire isn't in the way of the exit hole in the sheeting. Luckily I can still remove the wire, because that screw and nut ain't ever coming apart again. It's all epoxied and locked in place.  So here are the pictures of where I left it for the day. The flaps are covered with primer and ready for sanding and painting prior to gluing and pinning the hinges in place.

Interesting Rusty,

I never perceived such a thing would be an issue. It makes sense though. I am not sure I fully understand your solution.

How was it done originally? What does the kit say to do? If you posted about this before I apologize I must have missed it.

Ron

The instructions say to just glue the wire lever rock solid to the flaps. It would work, just with some stiffness and possibly some twisting of the flap surface. The truth is, if you use a very small flap deflection, it really may not matter at all. It's more just me exploring things that are new and trying to be a perfectionist. I really don't have superior building skills, so I'm just trying to improve on that by doing things that are more meticulous than I've ever bothered with before. I know my explanation was unclear, but the pictures when I get it ready to assemble will clear it up. I made it sound harder than it is.

Rusty

With flaps less is more. I have only flown a couple flapped planes.

With the Clown when set up with full deflection it flares during maneuvers. It looks weird, but it's what it does. I have set the flaps to move less than the elevator and it does much better.

If you think you can make it better go for it. These older flapped designs weren't the best.

Here's what I was talking about for relieving the hinge binding on flaps with a angled hinge line.

I made the grooves triangular, wider at the top and deep enough to contain the hinge so that it's flush with the surface. Uglier than I meant for it to be, but I taped it up to the TE and tested it and it works.


Here's the hinge laying in the groove. It needs a slight re-shaping. I will secure the pivot point to the TE with a brass loop. When the flaps deflect the hinge arms can slide back and forth to allow free movement. I will harden the inside of the groove and cap it with a rectangle of plywood. This will be on the underside of the flap.


Rusty

You can build a box out of thin ply, and bolt it onto the wing. Really it is a half box, with a reinforcement in the balsa such as ply or epoxy.

Just a thought. I don't remember how my dad did flaps without a dead straight TE.

Another thought is to use independent controls so the flaps can move separately. You can run the wide through he fuse for one side, and connect it to a trailing link off the control horn on the other flap. You are far enough along I would expect you don't want to significantly change the approach.

Phil

Hey Rusty, If you've read this "Stuka Stunt" thread, accept my apology... It looks like you've made a good choice in cracking this "tough nut"!!!

Rog

http://www.clstunt.com/htdocs/dc/dcboard.php?az=set_linear_mode&forum=103&page=3&topic_id=209898&prev_page=show_topic

I read that some time ago. They're right, it's too thin for Lucky boxes, but I think my fix will work pretty well. I wish my work looked neater, but it won't show when I finish. If I catch a second wind, I'll try to finish sanding the last coat of primer and cap off the slots tonight.

I'm glad I'll be starting on the rest of the plane soon. The only real challenge is to mount the wing with no incidence, since the cutout doesn't match the airfoil shape. It fits a wider contour, so I'll tack it in place and wedge Balsa sheet in the gap to get it aligned.

Rusty

sending PM

Another option would be to cut smaller flaps out of the existing flap so they have a straight edge.

Flapped designs usually have more flap area than needed. I have picture of a flapped Ringmaster that shows what I am referring to.

Edit: Here is a picture, I hope Dee doesn't mind. As you can see the flap was cut on a straight edge out of the existing TE. In your case all you would have to do is glue the flaps on as fixed and then cut the smaller flaps out.





Ron

Cribbs74 wrote:Another option would be to cut smaller flaps out of the existing flap so they have a straight edge.

Flapped designs usually have more flap area than needed. I have picture of a flapped Ringmaster that shows what I am referring to.

Edit: Here is a picture, I hope Dee doesn't mind. As you can see the flap was cut on a straight edge out of the existing TE. In your case all you would have to do is glue the flaps on as fixed and then cut the smaller flaps out.





Ron

That's really a nice option... a "tapered" flap... the central wing-section gets the prop-wash anyway... and the rest of the wing's flow is undisturbed. More importantly, it's likely less of an offset for the elevator to cope with, on an "un-flapped" design... IMHO

Excellent idea. If I ever run into this again, I'll know another simple solution. It might be more stable without the flaps extending as far out towards the tips. But I'm outside of my range of knowledge with that statement.

Rusty

Range of knowledge.....sheesh

Your pretty darn smart in my books. I would have built it to bind  

I just got back in from the shop. I got all the slots and shaping done on the new fuse, ready to assemble. I'm glad I made a new one. Otherwise I may not have noticed the original would have had a lot of positive incidence. I doubt if it's supposed to be that way. Anyway it's going to be zero now. Other than lots of shimming to seat the top curve of the wing, it should go together pretty slick now. I wanted to get the doublers on the nose tonight but I was getting tired so I figured I better quit for now.

Tomorrow is going to be rainy and flying is postponed until Thursday. Watt Moore and Will Davis of the Huntersville gang are coming down to fly with Wayne and me. Watt is the one who built my Clownlikething with the .40 on it. I flew it last week. It's a real floaty plane, kinda wants to go where it wants to go. I didn't like it much. I liked it even less after I knocked the rudder off of it.  Turns out it has a Skyray wing, but it doesn't fly remotely like a Skyray... Ha! I said remotely.   
Anyway, due to sucky weather the Yak will continue to develop.

Sawdusty Rusty

I spent hours today sanding and shimming the wing seat in the fuse, trying to get it to fit with no gaps. I finally got it good enough. It sits straight with a couple of gaps where it's still not flush, but close enough that if I mix my 60 minute epoxy thick with sawdust and block it so it can't run back out before it hardens, the wing joint will be good and strong. I got the LG blocked in place and glued. All of the remaining parts, canopy and air scoop, stab and rudder cut out and ready for gluing on.

So after putting the canopy, and doublers on I'm going to sand and seal. I was going to ask about Minwax Polycryllic but saw in the racing thread where Jim used it and liked it. I had planned to buy some dope from Sig, but if the Minwax stuff is good, I'll go with it. I've had a can of it for a year and never used it.

I usually spackle and sand everything smooth, then primer and more sanding before the paint. But if I use the Minwax, should I spackle and sand first, or seal it with the Polycryllic and then spackle the dings?

Rusty