Bill Mixon

I just finished up my Yak 55 SP design and thought I should share it with y'all.
I originally designed this plane as a replacement for the 24x24" Pizza box (PBF). PBF was fun to play with for a while but there was only so much that you could do with it.

My idea was to make a cheap easy to build profile, that still sort of had good flying characteristics.
Construction is entirely 1/2" pink "Foamular" styrofoam insulation from the supplystore.
A 4" wide 1/16" thick balsa sheet is on each side of the fuse, along with some hardwood rails built in to bolt the engine and landing gear to.
Wing has a 2" x 1/16" balsa strip on top and bottom as spar if you could call it that.
Hinges are 3/8" tri stock glued to each foam part IE: Stab to elevator with robart hinges.
And that's it. Very simple.
I've got the balsa around the engine coated with epoxy, and will soon paint the wood with something to protect it.

This one spans 48" and is a bit over 50" long.
Weight is 4 lbs. this is with a TT Pro 46 and standard sized servos.

hroachen

Bill,

Looks VERY cool! Please let us know how it flies, I'm curious if the flat slab wing will be effective in a plane this size.

Thanks for the pics
D

Bill Mixon

I've only flown it once.
Seems to do pretty good considering the flat plate design. I also was concerned about the slab wing, and the thick square trailing edges on everything, but so far so good.

I took it up high to start with and did some stalls, spins, tumbles, etc to see how it was going to act. Next I tried an elevator, pulled full up and it flattened right out with a slight bit of aileron and rudder input to hold it steady. No wing rocking.
Next were some rolls and then rolling harriers. The roll rate is awesome, might be a little too much in fact.
And after that I just had to bring it in and torque roll the rest of the tank.

It doesn't fly as good as a real profile plane, such as the omp edge, a knife, etc..
It has that + to - transition problem like anything else with a flat plate airfoil. Not as bad as a BPF, but it's still there.

It was a little nose heavy when I flew it, so I need to move the cg back and see what happens.

Bill

Bill Mixon

I've been flying the Yak a good bit now, changing throws, cg, etc..
As mentioned in my last post, it doesn't fly as well as a good profile. But you have to keep in mind that the original idea was to use a smaller lighter engine and servos. Just didn't have the light weight equip to try in this project.
I found that it flies best to keep it a little nose heavy. If balanced tail heavy like a typical profile, it becomes very "pitchy".

It's fun to play with, and as soon as I get time I'll be building another one with a .32 and light radio gear. Should work great.

Bill

hroachen

I found some 1/2" Foamular insulation at Home Depot the other day while shopping for some SPAD material... I think I'm going to have to try something like this.

Thanks!

D

southern_touch9

My Feedback: (3)

I just got back from a fly in and got to see this plane in person. It looks super simple to build and Bill doesn't give enough credit to the way it flies. I thought the super fast torque rolls just a few feet off the ground looked great. Not to mention all of the other fancy rolling harrier stuff. It seemed to knife edge with very little rudder required. Of course this could just be Bills flying skills so I think I am going to find out. If you have the gear already then you basically have the plane b/c it wont take over a few bucks to build. I will let everyone know how mine turns out within a few weeks.

Bill,
If the .40 size goes well I have a Norvel .25 and some micro gear here that could be used on a smaller version. Maybe then the lack of airfoil wont cause any problems at all.

Bill Mixon

There were many people interested in the Yak at the fly in.
Lots of people saw me flying it from down the flight line, and when I finished the flight they walked down to see what I was flying. Some looked at it sitting on the ground and asked, Ok wheres the plane you were just flying.
They couldn't believe that a flat plate styrofoam plane could fly like that.
Others who walked by before seeing it fly didn't think much of it, some even laughed and one person asked if it would fly.
Their opinion changed once it was in the air.[sm=biggrin.gif]

Go for it Layne, the norvel on one the right size and weight should work great. I've got to get me a good 25-32 engine and mini servos and build another Yak this same size. Should come in about 1/2 to 3/4 lb lighter.

Bill

southern_touch9

My Feedback: (3)

Bill,

I sent some older semi long haired Engineer Guy down that way that is from Eastman to have a look at your plane. He builds a lot of basic park flier type of electrics (boring stuff) out of the Styrofoam. When I told him what you had built he said that it would never fly and the fuel will eat through all of the foam. I think he went down there and talked to you and probably had a look at it. If he said anything stupid then just keep in mind that he is a total loud mouth and thats just his way of saying hi. To be honest I would have never thought that it would have stayed together either but I always wait for the proof before I run my mouth. He told me that it would break after a few more flights. And it might we haven't found out yet but I say if you can get from 50 - 100 flights out of it then what does it matter if it breaks you only have a few bucks in it and not a whole lot of build time. Well worth it if it gets me torque rolling. All of my planes now hover great and I touch the tail a lot but they just don't torque around like they are supposed to.

P.S. I cut out the wing last night and plan to start on the fues today.

Bill Mixon

I remeber the guy you are talking about.
A few others also said that the fuel would eat the foam. Im going to pour some 15% straight out of the jug onto it and see if it will.

We will see how it holds up. I put several more flights on it at the fly in, doing blenders, landing from a hover, etc.. I fly it more than anything else right now, so I'll let you all know when and how it fails.

Bill

southern_touch9

My Feedback: (3)

Did you leave that plastic coating on the foam?

Bill Mixon

No, I pulled the plastic off after I got everything cut out.
I used an ink pen to draw the outline of all the parts on the plastic. It made a very good dark line to cut by, vs drawing lines directly on the foam.

Bill

southern_touch9

My Feedback: (3)

One final question

How many hardwood rails did you put in the front of the airplane? 2? 4? And did you bolt your engine on through the 1/16th sheeting or did you peel the sheeting back and bold onto the harwood rails?

You would think as close as I looked at this thing over there I wouldnt have any questions

Bill Mixon

I used 3 hardwood rails.
Two running from the front edge of the fuse spaced apart to fit the engine. I don't remember how long I made these, probably about 5" behind the leading edge of the wing on the top and bottom.

And the other rail went vertically between the two rails just behind the engine.

I drilled the gear so that the bolts went through the top and bottom rail. I left the balsa over the rails when I mounted the engine, it just crushed it down. Just as well notch out the balsa sheeting to fit the engine.

Bill

southern_touch9

My Feedback: (3)

Im getting closer to being finished

The wings are done, Tail feathers cut out and tristock installed. Fues is drying. I will cut the slot for the wings today (gotta take my time to ensure an accurate cut here). What about the horizontal?? I assume you do it the same as the wings (but leave un hinged??) That elevator is split, yet bonded together with some HD wire and epoxy to make it a 1 piece elevator. Do I put the elevator halves together, fish them through the horizontal hole and then slide the horizontal in afterwards, glue the horizontal and then hinge? Thats the only way I can think of doing it so far.

Bill Mixon

I glued my stab in first.
Then worked the elevator joiner wire in behind the stab, and did the hingeing and joiner wire glueing all at the same time.

Not easy, but I couldn't think of anything else to do except use two servos.

I run some hardwood dowels through each elevator half (2 inches) for the joiner wire to glue into.

Bill

hroachen

Bill,

Thanks again for sharing this, I'm about to get started on one here. I'm curious, did you round or taper the leading edges of the wing and stab, or did you just leave them squared? I can't really tell from the pics.

Thanks,

David

Bill Mixon

Your welcome,

All leading edges and tips are rounded.
Trailing edges have a square edge.

Don't know how tapering would work, probably be more trouble than it's worth.

I'll try to get some more detailed pictures.

Bill

southern_touch9

My Feedback: (3)

I was gonna cover mine and make it all pretty but I am itching to fly it so I think I will just slap some fuel proof paint on the wood like you did and go with that.

southern_touch9

My Feedback: (3)

Everything is dry fit on there. Its just a matter of making up my mind for sure if I will cover it or not.

Bill Mixon

Cool

Do you have any pictures of it.
I think covering it would be a PITA. IMHO

Bill

southern_touch9

My Feedback: (3)

I dont have any pics as of yet but I should have some this weekend with it almost ready to go. If only I wasnt going to the beach next week I could get a maiden out of this thing, oh well, looks like it will be a little over a week before it sees the sky.

southern_touch9

My Feedback: (3)

What kind of paint do you use to paint the canopy on the foam?

Bill Mixon

I used the Testors spray paint for plastic models. There are some that do not eat foam.
Used latex house paint to cover the wood.
Neither is very fuel proof, but I used epoxy on the wood around the engine under the wing etc.. before painting.

I poured some fuel on a section of the foam today to see if it would eat it up, and it doesn't just as I expected.

southern_touch9

My Feedback: (3)

I was ahead of you on that experiment. I meant to tell you that I tried that last week and left it on there over night. The foam is still as good as new.

Bill Mixon

Here are a couple of in flight or "in hover" pictures.
These were with the wind blowing, and of course it was blowing from behind. At least I got plenty of practice hovering while looking at the bottom of the plane.

Bill