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Post  RknRusty Tue Apr 01, 2014 3:09 pm

It flies like it's on rails, very easy to control and the inputs are quick and solid. The Fox didn't behave as well as the airframe, so I was limited in what I could do as far as maneuvers. The first flight, the actual maiden was my best one of the day. There are only minor trim issues. The nose to tail balance is perfect. It was very light on its feet. It helps that I've finally found a handle that I really like a lot, and am going to have to copy it for my other planes. It's a home made job by Mark Boesen. The Yak's vertical C/G is way off. Wayne tells me it's because it's a low winger and we'll trim that with the flaps. Right now it flies with the outboard tip low.

Me in my new MCLS club shirt with the Yak-9 on it's first day in the Sun.
The Yak-9 grooves - Flight report Img_1211

So on the maiden I launched so rich it would hesitate before breaking into a two stroke. But after it was in the air, it leaned out and ran a solid 2 at 4.3 second laps. I did some climbs and dives and each time I pulled up, the engine cut out. So I just flew flat with the engine still cutting out. I kept thinking it had finally quit, but that went on for 5 more minutes. I'm used to floating in for a landing, but when the engine quit, it landed more like a refrigerator. Note to self... give it come UP to keep it from sinking so fast. Bounce bounce bounce, broke the prop and nosed over like a 1/2A. Glad I had clipped the NV. I didn't turn on the camera for that flight because I was trying to keep distractions to a minimum. I did video two more flights.

So after the first flight I turned on the camera, launched and got the lines hung in weeds, turning it into the circle only to nose over... and break the prop. Speaking of the prop, it was an APC 9x5. Ken Cook recommended I should step up the pitch a bit, but being the hardhead I am, I didn't take the advice and flew with it. Maybe I would have had a better run if I had done what I was told. Now I had the choice between an APC 9x6 and an MA 9x5, and I put the MA on it. When I hung the weeds, that one was busted.

So now I put an MA 9x5 wide blade on it, topped off the tank and cranked it up again.  It takes a LOT of prime to start this Fox. I don't know if that's normal or not, but I can only crank it by squirting fuel in the venturi. That engine knocked the chicken stick out of my hand 3 times! Scary beast. I took off and flew some circles, the engine sounding pretty good. I started nipping away at a wingover and it would cough, not as bad as before, but it wasn't really climbing with authority. By the time I confirmed it would do a 60 degree wingover, I flipped it inverted and flew about a lap and the engine quit. For some very stupid reason, and I know better, I tried to flip it again on the glide. Bad idea. I took off running to try and catch it and didn't stop until I heard it hit. Well, it didn't break the prop, but it did break the rudder in two, with no other damage at all, not even scraped paint. Wayne said I broke it because I was still dragging it after it was down. Can't stop on a dime any more. It's pretty easy fix, but I decided to park the Yak and fly the SS. I was tired and thought it best to fly one I was confident with. It did tear the edge of my rudder decal, but I can make a new one easy enough.

I am pleased with the Yak. Like I said, it really grooves and follows my input really nicely. I'll call it a success.

As I'm writing this, I got an e-mail with Wayne's pictures. I'll post what video I have later. I had zoomed all the way in order to locate my spot marker and forgot to zoom out, so all you can see is me holding the handle. That in itself is sort of interesting though.
Rusty

The Yak-9 grooves - Flight report Img_1213

I forgot to set the camera for outdoors, so the colors are off. The insignia on the tail is the Red Jacket Firearms Logo. I hope Will Hayden doesn't come shoot it down. lol! 
The Yak-9 grooves - Flight report Wp_20191

I cut the outside red field off. I think it's a cool logo and works nicely on the Yak.
The Yak-9 grooves - Flight report Rjf410

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Post  Cribbs74 Tue Apr 01, 2014 3:42 pm

Rusty,

I am very happy you liked the plane. I am not happy to hear about your engine runs. Ken had initially recommended a MA 9.5x6 for my Ringmaster. It's what I used for many months until I was given a APC 10x5 to try. For me the 10x5 puts my Fox 35's right in a sweet spot. I liked both props, but the 10x5 seems to fit better in my application.

The cutting out sounds possibly like a fuel delivery issue. I find this upsetting as I have had very good experiences with hard tanks even when I set them up all wrong. I have never experienced a cutout from a Fox ever.

For what it's worth this is my Fox setup(s) and it never ever fails me:

APC 10x5
3.5-4oz standard vent oval, center tank height roughly 1/4" above NV
Thunderbolt RC long plug
Powermaster GMA 10/22

Lose the Fox NV.... Or at the very least use fuel tubing on the needle.

Don't give up on the Fox. It will work very well if given the above items.

It also sounds like you were very rich. Would also explain the cutting out. At launch you should be at the ragged edge of 4 breaking into a 2 off and on. Upon release it will richen as the fuel slings out, but will give a flawless break when the nose goes up. Break in makes a huge difference as well....

I'll wait for the video.

Thanks for the flight report! Loving the Yak man great pictures.

Ron

Edit: my older 52' Fox likes a lot of prime as well. I usually dismiss the venturi and just give a healthy squirt through the exhaust port and then work the prop through with my thumb over the venturi until I feel the "bump" and then flip. Mine always fire off immediately after that procedure.
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Post  Cribbs74 Tue Apr 01, 2014 8:25 pm

Hey, re-read my post. After speaking with you it sounds more like a leaning thing. Possibly the NV like you mentioned.

I know you know this stuff already, I was kind of just going through possible problems.
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Post  RknRusty Tue Apr 01, 2014 9:18 pm

Here's the video. In this flight it would break into a 2 stroke but break back out before I finished my climb causing me to abort. Once I managed a 60 degree wingover I figured it was safe to invert. It wasn't.

https://youtu.be/uu_WegQO8ag

Rusty

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Post  Cribbs74 Tue Apr 01, 2014 9:52 pm

Now I see how you hold the handle, I have never seen it up close. Engine sounded higher pitched, probably due to the 9" prop. I heard a clean break, but couldn't see the plane to tell where it was breaking.

Don't know what to say, nice sprint though. You move pretty good for an old guy!
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Post  RknRusty Tue Apr 01, 2014 10:22 pm

Cribbs74 wrote:Now I see how you hold the handle, I have never seen it up close. Engine sounded higher pitched, probably due to the 9" prop. I heard a clean break, but couldn't see the plane to tell where it was breaking.

That's the thing, it broke into a 2 but while still climbing it would break back to a 4.

Cribbs74 wrote:Don't know what to say, nice sprint though. You move pretty good for an old guy!
 lol! Thanks... I think. Sounds like one of those back door compliments.

I'm going to fix the rudder tomorrow. Some bright white microballoons will make the repair invisible. I think I can mostly save the decal too. I'm itching to take it out again. I might go stooge it this weekend if the wind is calm enough.
Rusty

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Post  Cribbs74 Tue Apr 01, 2014 10:37 pm

It was a compliment... I couldn't discern a whole lot from the video so I commented on what I saw.

Once it breaks it should stay that way through the stunt. It should settle back into a 4 once level. Weird. I hope Ken comments.

If you have another tank I would give it a shot.
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Post  RknRusty Wed Apr 02, 2014 1:14 am

Cribbs74 wrote:It was a compliment... I couldn't discern a whole lot from the video so I commented on what I saw.

Once it breaks it should stay that way through the stunt. It should settle back into a 4 once level. Weird. I hope Ken comments.

If you have another tank I would give it a shot.
I have a brand new 4oz Dubro clunk I bought for the new Skyray. I'll plumb it and take it to the field. I like the utilitarian look of the oval profile but I'll use what works. Speaking of the Ray, I'll open the box after I paint the little reedy.
Rusty

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Post  Ken Cook Wed Apr 02, 2014 5:01 am

While it can be hard to assess problems from a video, I will say that your needle setting was sounding good. It sounded however as the engine climbed, it started to struggle for fuel. The initial pull up caused a nice break, but then it started to starve. This is certainly what caused the inverted cutoff. While I don't think this is a factor, but something I do just for the sake of doing it, I would check the spraybar. If this is the two hole spraybar, remove it and chamfer the holes with a #11 blade to deburr them. Align the holes so that when your looking down the stack you barely see them. You should just be able to see the tops of both holes. Absolutely check to make sure the back plate isn't leaking.This can certainly lead to unwanted shutoffs. Use gasket maker that's impervious to alcohol if need be.

When the plane is hanging by the leadouts, how's it's relationship to hanging level? The tank may need the rear canted out somewhat. Seeing that the rudder is broken off, I would place it back on with 0 incidence. Rudder offset isn't needed and it can and also will yaw the bird out causing fuel feel issues with the tank. Fix the plane's relationship of how it's flying. If tip low, temporarily bend your outboard flap downwards to lift the outboard panel back to level. This can affect your tank height.

I would also make the engine breath through one filler pipe. Capping the other and placing a piece of fuel tubing angled  into the slip stream. This won't hurt anything and will still be able to fly inverted. It will just promote fuel draw. This simple test is something that takes only a second and can really provide you with good info and is easily switched back.

Make sure all air leaks are fixed. Has the tank been pressure tested prior to flying? If there's even the slightest pinhole, problems will arise. Even if you checked it prior, check it again.

Wire tie your fuel line onto the stock Fox spraybar. If not, air leaks can be introduced into the feed line especially when a fuel filter is used in conjunction to your feed line due to the maneuvers throwing the fuel line up and down. Just another option to check.
Ken
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Post  RknRusty Wed Apr 02, 2014 5:48 am

The rudder will be a quick fix. It has no incidence, I've quit building offset into rudders. I never did a lead out hang test...me rushing again wrapping the eyelets on Monday night.

I have the tank shimmed out pretty significantly, but will check the spraybar and needle seal. And I'll redo the pressure test and make sure the line is secured to the nipple.
lt sounded like it was running pretty damn good to me in the flat laps too.
Thanks as always,
Rusty

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Post  RknRusty Thu Apr 03, 2014 12:27 pm

Well the Fox is fed by a whole new tank now. A Dubro 4oz. clunk, standard vent, padded and shimmed out at the rear. Made sure the spraybar is positioned correctly, and the needle sealed with silicon tube. The clunk tank looks like crap on the Yak, but it should run. Maybe this weekend I can get a good video of it flying like it's supposed to.
Rusty

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Post  crankbndr Thu Apr 03, 2014 12:40 pm

I don't understand the lack of greenies, great story with great photos. Have some anonymous greenies!
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Post  Cribbs74 Thu Apr 03, 2014 1:08 pm

Crank,

The rep points are a mystery... Sometimes I will do a whole writeup with video and pictures and all I get is crickets.

Sometimes I write something that I perceive as insignificant and I receive rep points for it.

I give many away as well. I assume it's that way with all of us. I also think that items outside of the Cox realm don't attract much attention from most. Rightfully so as we are a CEF after all.

In my opinion there are way more collectors than fliers. So that may have something to do with it.

I went ahead and gave Rusty a greenie as you are correct it deserved one and it just slipped my mind.

Ron

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Post  RknRusty Thu Apr 03, 2014 2:51 pm

Smoking 
Thanks dudes. I hadn't noticed I did not receive any before now. They don't usually occur to me unless I get one.  I'm always appreciative when I do. I give them, but probably omit giving them more than I should. The same with "Thanks" which are more weighted. But lately I've tried to be better about it.

On another note, Ron wanted to see my (now previous) fuel setup.

Here is exactly how it was outfitted during my maiden flights, except on the first flight I used uniflow. Did not video that one. After that I set it to standard vent.

Here it is in the shop after being degreased.
The Yak-9 grooves - Flight report Sam_2610

The Yak-9 grooves - Flight report Sam_2611

The Yak-9 grooves - Flight report Sam_2612

Now, guess what... after all the trouble to replace the whole fuel system, I picked up the filter to install it. It was hard to blow through! IT WAS HARD TO BLOW THROUGH!. Get it. I wonder if I wasted my time. Grrrr.
Rusty

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Post  Cribbs74 Thu Apr 03, 2014 3:01 pm

Well,

Your tank height looks spot on. The only difference I see is the pickup is on top of the tank whereas mine is on the bottom. Not that it makes a difference as my NV nipple is up top.

If you left that yellow cap on it would make a difference.  Wink 

I guess the clunk tank will let you know if it's the filter or not.

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Post  RknRusty Thu Apr 03, 2014 4:44 pm

Cribbs74 wrote:Well,

Your tank height looks spot on. The only difference I see is the pickup is on top of the tank whereas mine is on the bottom. Not that it makes a difference as my NV nipple is up top.

If you left that yellow cap on it would make a difference.  Wink 

I guess the clunk tank will let you know if it's the filter or not.

The yellow cap is on the uniflow vent. When I set it for standard venting. I cap that one and uncap the bottom overflow vent. The bottom is plugged in the picture because that's how I store it. For flying, I remove it and use the uni vent to fill the tank. Again, that's the standard vent procedure.

Will and Wayne are telling me it was just a symptom of too low pitch or length on the prop. Either way, I feel I can trust the fuel system now. If I get it all worked out, I'll try the wedge again. I'm big on aesthetics.

Now here's a quote from a Will Davis e-mail. It's funnier if you know the people, bet here it is:

"On a  more positive note , I guess you have learned a valuable lesson on landing inverted When the engine shuts off,

Only a few times out of a thousand can you pull the ole flip over routine, then only if the engine shuts off at the right place, high winds help you maintain speed on the downwind side , a heavy , big model  to help keep inertia  going , a gold horseshoe  and a picture of Watt  Moore in your pocket,

If all of these are going on at the time your engine stops , then you can pull it off  2 times out of a thousand , and if you ever do it ,  you will be flying by your self , with no one to back up your story

Next time , just float it in, stall it right before it hits the ground , , reset your needle  and have fun ,

Will"


I laughed my ass off at that.

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Post  Ken Cook Thu Apr 03, 2014 4:56 pm

Ok, seeing the tank up close and personal I can make a few suggestions. I dislike that plumbing due to similar problems your experiencing. The fact that the fuel line goes up and then down and back up is why there's some issues here. I stated this in a old post a long time ago. While this tank may work for some engines, it certainly sounds like why things are going haywire. That tank will work 100% better is the feed line is moved to the bottom of the tank. Not only will it feed better, it will make the fuel line 1" or better shorter which is always better.

The other thing to try here. If you choose to run uniflow which I wouldn't hesitate trying. My luck just hasn't been good using it with a Fox on a profile. Profiles prove problematic due to the turbulent air coming over the cylinder head. TO avoid this problem, install a piece of fuel tubing from your uniflow pipe and let it lay onto your cylinder head. This piece of fuel tubing will be approx 2" long. Any longer than that, your going to need to reroute a piece of solid tubing through your fuse and onto the opposite side of your plane on the inboard side.

Launch very rich and if your in doubt about your setting cap the uniflow pipe with your finger until it leans up and release. Check your setting once again. Keep the first launch very rich due to the second you release the plane it will go lean. If it doesn't go lean just fly it out and lean it a little bit at a time until you find the sweet spot.

If problems are still occurring using uniflow, don't give up all hope. Install a piece of 3/32" inch tubing inside of the fuel tubing that's hooked to your uniflow pipe. Let this piece of tubing stick out less than a 1/8" facing into the wind. This can really help stubborn uniflow runs. Ken
                                                                                             Ken
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Post  RknRusty Thu Apr 03, 2014 5:56 pm

Hi Ken. I haven't forgotten about your opinion on the top exit of the fuel tubes. After you wrote about it last Summer, I inverted the spraybar on the SS so I could run the line straight over the top to the nipple. It helped, but as you know, never cured it. My thinking is now that I have a system that should feed the Fox, I have the opportunity to rework a wedge tank and plumb it properly with a bottom exit to the engine, and eventually get the wedge tank back on it. I have eliminated the filter since I draw up the fuel through a filter and backwash it prior to filling. If all goes well, I'll probably put a new filter on it, but not for now. The line is very tight on the nipple now, and I've confirmed the spraybar is positioned properly, though I didn't remove it and chamfer the holes.
Rusty

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Post  Ken Cook Thu Apr 03, 2014 7:52 pm

I also have one more question. I recall you used threaded inserts on the fuse. Are you just tightening the engine and the aluminum shims tight to the threaded inserts? In other words although the bolts are tight, are they tightening the engine firmly enough to the fuse rather than just the inserts. I've seen the wood crush and now all the load is on the inserts. The engine now vibrates due to this.

Anytime you can use a filter your better off. This can eliminate bubbles by breaking them up and many times I've seen solder and plating that was loose in the tank find it's way into the filter. I do understand why it's removed, just making a suggestion.

Rusty, I have to tell you that you did a very nice job on this plane. I really mean it. I think things will work out just fine. Ken
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Post  RknRusty Thu Apr 03, 2014 9:37 pm

Ken Cook wrote:I also have one more question. I recall you used threaded inserts on the fuse. Are you just tightening the engine and the aluminum shims tight to the threaded inserts? In other words although the bolts are tight, are they tightening the engine firmly enough to the fuse rather than just the inserts. I've seen the wood crush and now all the load is on the inserts. The engine now vibrates due to this.

Anytime you can use a filter your better off. This can eliminate bubbles by breaking them up and many times I've seen solder and plating that was loose in the tank find it's way into the filter. I do understand why it's removed, just making a suggestion.

Rusty, I have to tell you that you did a very nice job on this plane. I really mean it. I think things will work out just fine. Ken
Ken, I used slightly larger oversized hard maple bearers from a Brodak Shoestring kit. Here's what I did:

I used brass inserts internally threaded for 4-40 threads. Before I bored the insert receptacles, I used the next larger bit to punch through the 1/16 ply doubler so as not to splinter it, but only cut through the ply. Then I measured the length of the insert, taped a marker on the 11/64" bit and bored into the maple to that depth. Epoxy on the inserts and screwed them in so they were flush with the face of the maple, not the ply. They were very difficult to bore into the maple and I took it very slowly. But when they were ll installed, there was no sign of distress, no cracks, no bulges, there is ample wood surrounding the inserts. Then I filled the small gap in the ply around the insert screw holes with epoxy. I hoped this restored integrity to the ply.

Then I made a pair of 3/32" Dural plates, drilled to fit the engine plus some Nylon 1 degree thrust shims.
Here's a picture of that:
The Yak-9 grooves - Flight report Yak-9_17
With the engine and washers in place I measured the depth of the screw holes and cut 4 steel(not black oxide) screws to the length that will use the whole insert and no more. I cross tightened, watching for shifting incidence and any bowing of the Dural plates, and after about 5 passes they were all tight. After double checking that the Dural wasn't bowing, after 24 hours, I re-cheched the torque, and in turn removed each screw, one at a time and put Loctite on it and screwed it back in to the same torque as before. Of course I did this in s cross pattern too.

Before and after flying I check for any sign og bowing of the plates and so far none has appeared. When the engine is running, It does vibrate some, but not like I expected from stories I've been told. Turning the needle is comfortable and easy. It appears to have a good fit in the threads and firm pressure to turn it, It feels good. I gripped the LE to feel for vibes, and it felt like any other plane in my limited but growing experience.

I will put a filter back on, but I'll have to cannibalize a Baby streak to get it, and flush it both ways with brake parts cleaner.

I hope this addresses your concerns. I'm really proud of this build, and couldn't have done it with all of you and the guys helping. It has a laser straight wing, and all control surfaces index perfectly to the thrust centerline and incidence marks I drew down the fuselage.It took a lot of work and I learned a lot. Now any plane I build will be better.
Thanks

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Post  RknRusty Tue Apr 08, 2014 11:48 am

Only have time to make one post, the car thread or this one.... okay, this one. lol! 

Just got back from the HS with a second APC 10x5, two APC 10x6, two MA 10x6, a pair of APC 9x7(already have two 9x6). A couple of hot plugs, 4 feet of fuel line and a fist full of epoxy brushes. I hope these props and plug will get this baby running right, because that's about it for this spending cycle.
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Post  Cribbs74 Tue Apr 08, 2014 1:30 pm

Thunderbolts?
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Post  RknRusty Tue Apr 08, 2014 3:13 pm

Cribbs74 wrote:Thunderbolts?
No I asked about them only to get a blank stare. So I bought OS6 hot, but found they're a millimeter shorter than the plug that was in it. That one has no markings except for a red insulator which I assume means hot. So I put the Sig RC long in it that Wayne gave me because it's new. But I don't see any temp rating on the package, no colored insulator and it has an idle bar, so I'm not feeling good about that. I think I'll switch back to the previous one. It glows brightly with the glow driver and it's obviously a hot long plug, but I don't recall where it came from. The one that was in the engine when I got it says "OK" on it but doesn't glow very brightly at all. I need to get on eBay about this.
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Post  Ken Cook Tue Apr 08, 2014 4:50 pm

You typically not going to find Thunderbolt plugs readily available. I order mine and they're only made certain times of the year. I purchase 100 at a time to get the price down and part them out. Hobby People carries them in stock usually. That being said, Thunderbolt makes a variety of plugs but the one that is used for stunt is the Thunderbolt r/c long. With your Fox, you want a idle bar. Your not idling, your guarding the plug against the tidal wave of fuel that loads up in the oversize bypass. Combine that with fuel that has a high oil content and the engine flames out. Don't worry about your idle bar. Back to the OS plugs. While they run good in the OS, it may just work fine for the Fox. I can only say this, the length of the plug also dictates the timing of the engine. While the Fox is primitive, it might not even be a issue. I know it is on other engines that I've tried.

The OK plug that was in your Fox is pretty archaic. I wouldn't count on using it at least not effectively. K&B 1L is another option, Mccoy MC-59 another good option, Enya #3 ( great plug, requires special igniter clip due to shape, expensive) Fireball H30 ( Good plug, can handle additional voltage), Fox long r/c ( These work but there my last resort, rpm's drop rapidly when battery removed, insulators blow out, very inconsistent runs) Ken
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Post  Mark Boesen Tue Apr 08, 2014 10:48 pm

I'll second Thunderbolts, I loved them.

Does Fox still make the "wonder plug" (4c plug) I remember reading that it was pretty hot and worked good.

That red colored base might be a Swanson Fireball? A lot of people bash them but I never had a problem with them, but I think the Thunderbolt worked better and never went back.
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