I got some competition! Will John Wright be there again flying S70's ?
Can't wait to see ya!

You are correct that the solid wing was produced way after the hollow ones. But who in his right mind would ruin a collectors version by flying it? Not me, and I designed it! I have one original hanging in my office, and it will stay there in pristine condition until my great grand kids destroy it someday after I am gone.

All but the wing of the model being assembled is as it was produced in the 70s, and it isn’t likely to be all that competitive , so don’t be picky!

Besides, how many models at the meet use the original vintage engines? Seen many old Johnson’s or Green Head Torps in the pits lately? And as to new stuff, how about mufflers, muffler pressure to the tank, uniflo tanks, carbon fiber props, adjustable line guides and tip weight boxes. Seen anyone using a U-Reely in competition lately, or even an Easy-Just?

Actually, since I don’t have an original model to spare, I am only getting the model back to its original 10 ounce weight. Otherwise, the aerodynamics are as original, and only the tank capacity is changed. So there!

It’s a hobby, not life threatening, gimme a break.

John will indeed be there with his 30 year old Barnstormer from the first VSC for Old Time. He also plans to fly Super 70 and Ringmaster, as do I. My guess is that he will go for Classic too.

More progress photos.

The tank is replumbed with a new pickup tube and the old fuel pickup used as a uniflo vent.

The wing center section has a carbon strip reinforcement. the gaps above it are filled with lightweight spackle. There is strapping tape top and bottom for more rigidity.

The article was in the October 1974 Model Airplane news.  I have a pdf, but it is too big to post.  Send me an e-mail and I can mail it back to you.

Some new photos!

First the engine. It is a Killer Bee Crankshaft in a KB case. The cylinder and piston are old tapered bore Tee Dee (Couldn't find any of the newest ported ones    ). Flame barrier from the original engine. Killer Bee backplate/mount with bronze reed. Again, can't seem to find any of the steel reeds I prefer. Note that the exhaust ports are in the optimum fore-aft position. (That places the bypasses in optimum position for free flow, exaust is going out no matter where the ports are!) It ought to be a screamer. I have a high compression head with 4 gaskets, but that is an area that will require much experiment to get good performance with fuel economy.

Next up are the control system modifications.  in olden days, I used that second from inside bellcrank hole to limit the elevator travel while getting equal up and down travel.  This time, I lengthened the control horn with some squished 3/16" aluminum tube.  It now has slightly less elevator travel than bell crank travel using the outer hole, as it should be!  This will reduce the control force required and limit the necessary line tension for full control. I will tweak the pushrod length to get inside and outside performance equal.   

Also the bellcrank has metal bushings for the wire leadouts.  I plan to make an adjustable leadout guide after covering the wing.

Finally, the rudder snap retainer has been tapered to allow the elevator horn a bit more travel while still retaining all its strength.

Larry,
Are you going to clear-tape the open sections of the bottom of the fuse? For essentially zero weight, that cleans things up a bit.  I had my baby blue 'chip at the Valley Circle Burners 1/2A Day last year--but didn't get a chance to fly it. I don't remember trying to stunt with it back when I got it. I was pretty much at the wingover, inside loop skill level at that point....and not much has changed!

What is your intent/goal with the engine mods, beyond just having fun with it? Your comment on the cyl/piston and the KB parts implies you are going for all the horses you can find that will fit in your new tank. Are you going up in venturi diameter?  Regarding the reed, are you talking about the racetrack shaped stainless reed? What prop are you matching this up with? Cox 5x4 flexi? What lines?

Interesting project. Enquiring minds want to know....

McSlow McDivot

PS--Ron and I flew my new Cox-powered basic trainer two weeks ago at Whittier. It flies great!  Beautiful stable level flight.....

I covered the wing with Parklite film.  With the tipweight and covering the wing weighs 2.44 ounces.  I thought I had another wing for comparison, but I don't.  I weighed all the model components and the total weight is 9.88 ounces, which is just under the original folded wing flying weight! 

I need to find out the correct screws for final assembly, make the adjustable line guide, decorate it and it will be finished! 

I opened the box of the supposed new Chipmunk I have, and WOW it is an original folded wing model. The stickers are for a "Stunt Eagle"   version Cox must have done for a single customer like Sears (remember them?). Some stuff is missing, but I may just work this one over too. It is in way better shape than the one I am working on.  But that is for later, WAY later.

That is brilliant.   But I thought you would have test flights done already.

I never claimed it would do a "good" pattern, it won't. I just want to demonstrate that it will do every maneuver in a recognizable form. I am never going to win at VSC no matter what I fly, so I plan to have fun. 

Added power and long lines will ameliorate a lot of the wide maneuvering. I just want to demo one of my designs in the primo showplace for that era model. I have cut about an ounce out of the solid foam version bringing it in to the weight of the original folded foam wing version.

I plan to try 35' .008 lines, and hope to push it out to 40'. The hourglass is the killer in my experience, and I may not be able to do much more than a lumpy vertical 8. I also need to test to see if the wide venturi of the Killer Bee will pull fuel through maneuvers.  Lots of testing to be done, and not much time left!

I added an adjustable tip guide and did a test assembly. I discovered that the extended tank runs into the landing gear mount! 

So, I pulled the tank off the nose bottom, and modified the bottom mounting to allow the tank to move forward. This required removing the vent tube and some modifications there.

The tank is now attached to the upper fuselage and an aluminum tube replaces the plastic vent tube. The vent hole in the lower fuselage needed to be extended forward.

When the glue is all dry, I'll post photos of the setup when it is finalized.

If you are building the folded wing version, extend the spar several inches to keep the foam from collapsing. A 1/16" balsa extension will do just fine. The foam is the strength as long as it can't flex inward. Also, use a foam safe adhesive to glue the wings on in addition to the tape.

Looking at the folded foam wing version I have, the trailing edge bond is letting go. That needs to be repaired! Shucks that model was made 43 years ago. Gee, even Cox didn't make things that last. 

If you look carefully at the earlier photos, you will see that I have a carbon reinforcement at the center and strapping tape top and bottom out to the tips. It is probably more rigid than the un-cored wing. Besides, the aft part of the wing doesn't bear much of the load if you leave the high point intact.

The Killer Bee with 5x3 prop on 30% nitro should have nearly twice the thrust as the product engine with a 6x3 as originally provided on standard 15% fuel. That ought to give me some edge! 

When in doubt - Cheat! 

Next photos

It turns out there is a gap between the top and bottom fuselage halves because of a not quite accurate cut to mount the tank. However this is a good thing, because I can shave top or bottom depending on how the engine runs upright and inverted. Sometimes a screwup pays off! 

Final weight is 10.2 ounces.

  That's too bad Larry. What about the old double balloon type tank? Can those be made to hold enough fuel? All you need for structure is something slide it in. I'll be watching for further updates and hope to get to mine in the near future.
   Type at you later,
  Dan McEntee

Larry,
Any progress on your 'chip project? Very interested in what your fine-tuned config turns out to be.

On the fuel draw, are you thinking of going to a backplate with the smaller venturi?

As far as fuel draw for starts, wouldn't it be feasible to hold the plane with the outboard wingtip down and the tail up, maybe 30 degrees or so to aid via "siphoning?" With a full tank the pickup would be covered and the fuel head might be an inch or so? Once it is running, perhaps the draw would be sufficient for most maneuvers?

Do you think the aluminum u-tube is too restrictive? I've used these (actually a copper tube) inside Mouse 8cc tanks but there the overall fuel line is pretty much just the length of the u-tube. The silicone fuel line I use for a coupler is just that--the copper tube is actually touching the nipple of the backplate.

I have two projects in work that incorporate the plastic backplate/separate tank concept and hope to see how you dealt with similar issues.

Thank you for sharing your project with us!

McSlow

I need to get back to that project!

I have corrected a few things and put a smaller Venturi backplate on. Now it needs reassembly and testing.