OK, so I've been working on my Cobra. I figured I'd have to change out the elevator horn because the 2 to 3 hookup seemed to have problems. In flying, the thing was just too quick. I tend to set up my controls to be very, very slow and use a lot of line spacing to fine tune the feel. But with the Cobra, I ended up with very narrow line spacing (to the point of complete loss of control feel) in order to get it to be controlable ... sorta.

Anyway, after a lot of thought, I decided that the 2 to 3 hook up of the controls (per plan) wasn't really the problem, it was the pivot distance at the bellcrank. I decided that the pushrod pivot was just too far from the center and I was getting too much and too fast of movement. So I cut in and had to drill a new hole in the bellcrank and move the pushrod closer to the pivot. Nice thing about an I-Beam is no center sheeting. So just had to cut into the top and bottom block. Anyway, I moved the thing in about 3/16" of an inch and now, while I still get the 2 to 3 movement, I have a lot more throw the controls should be substantially slowed down. So that was easier than I thought it would be (did have to put a new ball link in - long story on the that).

I picked up some 30 minute stripper at the local hardware place. Turns out it works a bit too well. It went right through the paint, silkspan and all right down to the wood. Doesn't seem to have any effect on the balsa, but it takes EVERYTHING off. Sigh... So it will be starting from scratch. Not a bad thing since this was a quicky finish that was very heavy.

I figure to take as much as 6oz off the final weight with a new finish. Fun Stuff.

Mark,

I'll post some pictures when I get it stripped. I'm a little miffed that I didn't strip it first. Would have made patching the cuts to fix the bellcrank easier to do. Sigh... Oh well, I wanted to see if the change would fix things (as it has). The other advantage to stripping EVERYTHING off is, I can reshape the wheelpants and top and bottome blocks a bit to more closely match the original plane. I hadn't seen a picture of the original Cobra when I built this plane and was surprised to see how different it really was than the kit. Sigh again. But now I can make some changes to make it a bit closer.

Randy  I built four Cobra's over the years. I used very slow controls on all but the first one.Also I used a little less than one to one and the plane never needed more than 20 degrees of movement to fly very well. I built three Juno's also and found that the two planes flew very much the same. The first one was light and was powered with a .35 . The last three were powered but ST/40-46 motors and weighted from 47 to 53 and all flew very well. The heaver ones with the .46 in them were the best flying ones. Also I mounted the bellcrank behind the spar. The pushrod ran from the bellcrank to the elevator. The flap pushrod ran from the flap horn back to the center of the elevator pushrod. Very simple and bullet proof.
Ed Ruane

Randy I saw the remains of several of Steve's planes back in the 60's One used two pushrods from the bellcrank and one was done like I do them. Maybe that is were I first saw the method. I saw him fly the Argus and he was very smooth compared to most of the other flyers that day. Around 1961 at a contest in Buffalo NY. Also his Argus had a bubble canopy. I flew a All American Sr that day. On my first Cobra I used a three inch bellcrank but I used very tall horns in all of them. About 6 years ago I was ready to trash out my very old Cobra so I  removed the ST/46 from it and put in a ST/35. I added nose weight and a shaft extension. It flew fine.
Ed

One note. That stripper I picked up is NASTY. I accidentally spilled some on my arm tonight. I now sport a nice big, red welt. I washed it off with lots of water immediately as the directions say, but it didn't help all that much. I was wearing gloves, but I think I'll go with long sleeves for the next bit. Sheesh!

Randy, I told you to stay away from those nasty strippers.

Hi Randy,

Now I remember another reason I like to use full length nylon taffeta hinges.......... I never have to worry abut removing the flaps/elevators if I have to recover the plane!

Heck, Dude!  Just hit with some more of that "NASTY STRIPPER"!

Hi Randy,

Glad to hear that things are coming along with the Cobra. 

I have been starting to feel better, physically, and have been back at the table!  The Little/Hunt Mustang is finnally getting some more work done on it.  The wing is about ready to cover, just the final detail sanding and then the silkspan!   The tail pieces are covered, primed and ready for the blocking coat.  Front top block is read, and I am carving a foam buck for the rear turtle deck.  So far, so good.

I am VERY happy with the control system so far.  Just the weight of the flap horn makes the system slam from one xtreme to the other when you flip the wing over, but there is no slop in it!

Looking forward to seeing your Cobra back in paint!

PLEASE keep the artwork!  I liked the paint scheme a lot, but you might come up with something better. Something like "Tango Red" would be cool, and appropriate on a Classic, I think, maybe in different colors (not green!).  Steve

The Before Shots

Allen Brickhaus

Thanks for the pictures, Alan. I can remember it for what it was.   

Stevie,

Thank Bill Werwage's Juno. That's the general idea. Just hope the dark colors I'm planning will hold up in the Tucson sun.

OK guys,

Ya got me hooked!  I want a Cobra!  Which version is the one to build?  I think I would like the larger one--
55 inch span.  OK ot not???

Thanks,
Jim

This is the Walter Umland version with plans done by Pat Johnston. Only comment I'll make is when doing the controls, ignore the plans and uses a 1 to 1 hook up and put the pushrod closer to the bellcrank pivot.   

Jim,

I have the plans in .DWG format if you want them. I took them to a local print shop and had them printed. They are the Pat Johnston plans.

Mark,

I have a local print guy that does CAD plans, but the real deal is the local UPS store. They have one of those giant  36" photocopier/printer jobs. It's attached to a computer that has programs to print .pdf, .dxf and .dwg. At $5 a sheet, it's a deal.

I have the control surfaces, wheel pants, cowl and control hatch primed. I have a cold and just ran out of steam yesterday so I haven't primed the main airframe yet. I'll probably do that tomorrow. I spent this evening wasting time playing a computer game. I'll get back on the Cobra tomorrow. I'll take a couple of pictures when it's all primed and post them. If I can go easy on the paint this time, I should knock a few ounces off of it to boot.

I have, as I said, the colors picked out, but not the scheme (except vaguely in my head). I need to spend some time designing the paint scheme and redesigning the the fonts and stuff for the name and number, etc. Or I may stick with the same deal as before. Folks seemed to like Hot Rod Chick.

Pat's a pretty reliable guy. You should have them soon.

As I say, only comment is, be sure you don't set the controls up too fast. I used the outer hole in the bellcrank initially. Bad idea. I cut in and moved it to the inner hole. Should be much better now.

Guys,
Guess who just found the "last" Cobra short kit at Brodak's?

Hope I'm not disappointed.

Cheers,
Jim

Hi Jim,

Funny statement, why would there be a reason to be *disappointed*?  The Cobra is one of the great Classic planes.  The short kit is from Walter's kits, which are/were outstanding.

The only way to be disappointed is to build it 10 ounces overweight, or crooked, or put a poor choice of engine in it!

Use a 4" BC and Tom Morris horns (or equivalent), especially an adjustable elevator horn, put a good stunt engine in it, and build it straight and fairly light.  It will be awesome!  Steve designed the Cobra to overcome the shortcomings of the Argus, which he finished about 4th with at the WCs.  I am pretty sure he had a top 5 with the Cobra, too.  But it is like 99% of all the I-Beamers, it benefits from lighter construction.  And I would definitely suggest using enough power.

Good luck, it's an awesome airplane when done up right.

Yea, power isn't an issue with mine. It's PA 40 Ultralight. Weighs about 8oz. The plane, before refinishing, was a bit heavy at 48oz. I got carried away with the paint. Hopefully this time around, I can knock 4oz or so off that and it should be a killer. I shot the primer on the main airframe tonight. The sanding party starts tomorrow. Oh Joy.

(snip)
Please define "enough power". What would you use?
Thanks,
Jim

PS:  Looks like Randy's has a PA rear exhaust "something or other" (40?)

Aero Tiger 36, Magnum 36 XLS, St .46, or the PA 40UL if you can swing one.  At the mid to upper 40 oz range It will take something like that.  I would like to see it around 40-42 oz., max.

Scott Reise has been flying a Cobra from an Umland kit the last couple of years using a B40. Seems to work well for him.

Well, all the pieces parts are sanded. Took a lot more effort than I had at first thought. I really should have gotten a couple more coats of clear on before I put on the primer. I went through in several areas and had to reshoot primer ... a couple of times. But they are now complete and I can start on the main airframe. I didn't get to work on it as much as I had planned last weekend.

I really need to pay attention to my own advice more. I foolishly put silkspan over the fillets on the plane and have had nothing but problems with the fillets lifting. Something I haven't had to deal with in a long time. I finally gave up and went back and cut the silkspan off all of the fillets, ran a thin layer (very thin) of SuperFil over the fillets, sanded them down and reprimed the area and not things seem to be working well again.

So here is one of Randy's Rules: Silkspan the plane first THEN put the fillets on. If you a refinishing a plane, don't cover the fillets with silkspan.

Wasted many hours trying to get them to stay down and in the end just had to rip it up and do it again anyway. But al least it's all in primer now and looks pretty good. A lot of sanding ahead.

Gee Bill, thanks for the advice.   

It's OK now (after numerous hours of fixes). I'm about 2/3 done with sanding the primer. Man I layed it on thick. Lot of dust on the floor.

Bill,

I'm still debating on color. I had a scheme planned but it was going to be all dark colors and I decided that the Tucson sun wouldn't be kind to it. So now I'm considering using an off white as a base color and some interesting trim colors I have with basically the same scheme I used before. The sort of classic Bill Werwage Juno scheme. We'll see. Maybe I'll get a wild hair and do something else. I've got about 3 and a half wing sides of sanding to decide.

Gee, thanks Mark. I think that when I fix and repaint the Novi it's gonna be red.