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Chris & D.A.'s/Denny's Super Cub

Air wolf has exactly what I'm looking for. Thank you guys that also frequent FB for the answer.
 
When we bought Denny’s Cub we fully thought we’d have it flying by this summer if I had a chance to work on it. However, I just found a crack at a weld on one of the gear fittings, and knowing what the airplane has been through over the last 22 years, we thought this would be a good excuse to go ahead and strip it down to bare frame, clean it up, inspect it, repair anything we find and go back with a fresh restoration. We could easily do a localized repair and go but maybe this is a blessing in disguise. Who knows what we’ll find when we open it up, and if this crack was the only issue, that’s cool. It will give us an opportunity blast it, prime it, paint it, make it look like new and put it back together. Blessing in disguise.
 
I took the fabric off the fuselage tonight. The looks in great shape, it has the beef ups you normally see, its straight and rust free from what I can see. I found some pretty interesting things in the tail. Now we can do some other mods we wanted to do, more on that later.
 

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D.A. said:
I can't get him to come to the phone. I've got a huge list of parts that I need but the Javron connection isn't going to happen it looks like.
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I have had the same problem with Him. Called the other day about a part I needed yesterday. They promised to ship quickly. two days later, it was still in their shop. I bought elsewhere.
 
What comes in an almost 8' box, looks like it should be real heavy but you can carry with one hand - - - Our new Catto prop. With 180+ HP this thing should pull stumps out of the ground! Craig does such good work.
 

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"design rpm 2850 redline rpm max 3200" -- holy cats!

Per Ponk's website, sweet spot is .88-.92 mach-- higher tip speed (transonic or sonic) means lower efficiency

86" prop @ 2850 rpm = 728 mph tip speed ( .96 mach)
86" prop @ 2975 rpm = 760 mpg tip speed (1.0 mach)
86" prop @ 3200 rpm = 818 mph tip speed (1.07 mach)

I'm no prop-ologist, but it seems like a shorter prop might be more appropriate for those kind of rpms?
 
It is my feeling that the engine produces more thrust at the start of the takeoff run when the prop is turned back toward 2700 rpm. I've done nothing to document this, just that it seems to pull better. A shorter prop definitely doesn't pull as hard as the longer one at either 2850 or 2700 rpm.
 
Either slower-turning OR shorter diameter is what Ponk's info might suggest.
What RPM & prop length are the Valdez winner's turning?
I remember seeing someone's souped up Lycoming-powered PA-11 with a 90-incher at one of the NW SC fly-ins.
 
hotrod180 said:
Either slower-turning OR shorter diameter is what Ponk's info might suggest.
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I know what you're saying, the numbers say that once you've gone supersonic you've lost efficiency and I'm sure a lot of that is true, but from my experience, the really long prop pulls the hardest and the RPM brings the power. Remember, Denny did a documented 18' takeoff at Gulkana with a 90" 1A200 flattened to 26" of pitch and turned 3000RPM on Nitrous with the brakes locked. Another example is an old Stearman crop duster. You really needed the 108" -12 Blades. There were plenty of cheaper Twin Beech blades out there but they were shorter and didn't give near the pulling performance. Again, those -12 blades would split your ear drums going well past supersonic, but they pulled the best by far. I know the numbers don't make engineering sense and the best of both worlds would be a geared engine turning even faster with a slower turning prop that was even longer, but we're hoping the 86X35 will be a stump puller. Also, our 86" prop isn't as long as some, we're 4" shorter than our 1A200 that Denny ran and we probably won't be seeing 3000 static with our initial engine. We think the 86X35 will give us the most we can get out of our combination.
 
Theory is theory. We can (and need!) use it to explain and predict, but the information is only as good as the math model. We have a pretty good model for aero. Unfortunately, we don't have a great model for aero.

Damn elliptic equations are just too complex.

I was very interested to hear the real-world experiences from you guys in this and that other thread, it's all pretty neat stuff.
 
I'm sure you talked it over with Catto, he oughta have a good idea of what works best with what. IMHO prop design & selection is a black art as much as a science.
 
Bump. I thought about buying this plane. What's the status? How did you get it out of Yakutat?
 
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My buddy, David McRae bought the project and it was in my hangar.
After David's passing, another friend bought it and is gathering parts to get it flying again.
 
No. D.A. was fine last time I talked to him.
David McRae bought the project when D.A. decided to change directions a little.
 
Chris in Idaho said:
Does anybody know where I can find more Gulkana or other footage of this airplane? I found the link to the short video below on another thread here.

Click to expand...





I was there at Gulkana in 1990 ? when Denny hit that 150 horse Nitrous Oxide shot. It was intense ! He and Jerry Burr were also running a special mix of 100LL and Nitro Methane, and as I remember; 3% acetone to cool the valves. Old school, 1970s top fuel dragster Sneaky Pete technology. Those guys lived the leading edge of aerodynamics and engine tech. They invented most of the stuff we buy, and take for granted. Their Experimental was really experimental.

Hearing Jerry Burr talk about driving around for years with VGs and yarn tufts stuck to the hood of his truck, so he could analyze how to keep airflow attached around different shapes that where also stuck to the truck hood with double sided tape. The shapes and VGs where moved daily, so a true understanding of the airflow could be completly understood. Driving across a Seattle bridge in a high crosswind was a special treat that showed more data; instantly. Denny and Jerry were truely Experimental Pioneers with hundreds of hours of film movies shot of the airflow that their many mods created.

I spent 5 months in the basement of the NASA library doing research and came back to Alaska with 1500 hand Xeroxed and bound Tech Documents, only to find out Jerry not only possessed a large number of them, but also had a PRACTICAL understanding and was already applying the technology. Just meeting them was an amazing treat.

Jonny
 
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Excellent example of prop blast energizing the inboard wing then transitional lift help from the outboard portions. C-185 prop crack. Leaf blower tech..what's preferred prop volume or velocity?

Gary
 
Jonnyo said:
I was there at Gulkana in 1990 ? when Denny hit that 150 horse Nitrous Oxide shot. It was intense ! He and Jerry Burr were also running a special mix of 100LL and Nitro Methane, and as I remember; 3% acetone to cool the valves. Old school, 1970s top fuel dragster Sneaky Pete technology. Those guys lived the leading edge of aerodynamics and engine tech. They invented most of the stuff we buy, and take for granted. Their Experimental was really experimental.

Hearing Jerry Burr talk about driving around for years with VGs and yarn tufts stuck to the hood of his truck, so he could analyze how to keep airflow attached around different shapes that where also stuck to the truck hood with double sided tape. The shapes and VGs where moved daily, so a true understanding of the airflow could be completly understood. Driving across a Seattle bridge in a high crosswind was a special treat that showed more data; instantly. Denny and Jerry were truely Experimental Pioneers with hundreds of hours of film movies shot of the airflow that their many mods created.

I spent 5 months in the basement of the NASA library doing research and came back to Alaska with 1500 hand Xeroxed and bound Tech Documents, only to find out Jerry not only possessed a large number of them, but also had a PRACTICAL understanding and was already applying the technology. Just meeting them was an amazing treat.

Jonny
Click to expand...

Having spent lots of time under the wing of a Cub with Jerry I totally agree.
 
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