Bonding with my Cardinal

getback wrote:Looked and sounded good to me , if your happy that's what counts ! I hope your going to replace the wood screw in the engine mount that's just asking for trouble that you don't need after the work ya put into getting this far with a good practice model , Thanks for the write up and video / pics . getback

Eric, I'll eventually straighten the bend and tap and replace the screw(unrelated to the bend) with a 5-40. But it's extremely tightly threaded into metal and doing its job. But yes, I do not like that sort of thing. I'm not exactly sure how this mount is anchored.

There is a strange thing I haven't found the reason for yet, the pushrod is connected to the shortest hole in the elevator horn to get full throw. However it's not especially twitchy. It probably has a 4" bellcrank. Also, the hinge lines on the flaps are uneven too, curved, causing the flaps to bow across their length and requiring me to tweak them a bit and add a 25° x 3" trim tab.

Later on I'll write of my various prop trial results.
Rusty

Thanks Rusty. I think I see how it works. Wondering if the same might be accomplished by installing threaded inserts into the beams.. spaced far enough apart for the saddle-plate screws to provide for some fore/aft engine-adjustment? It looks like your base-plate has pulled up at the front from tightening? Maybe the base-plate could be designed to attach to the nose with it's screws "outside" of the holes for the saddle-plates? That would prevent the distortion when tightening.

Here's a crude sketch to show what I'm talking about.



Alternately; threaded-inserts installed in the beams to accept the saddle-screws.. instead of having to tap holes in two base-plates would save a lot of work and weight. Strips of thin rubber wrapped around the top/bottom of the case-lugs would help dampen vibration.. as well as keeping the engine from slipping. What do ya' think?

roddie wrote:

My Brodak P-40 came with that type of engine mount. Worked fine for what it was, but I did have some vibration and the top saddle would never tighten down enough. Always alittle bit of dark grey goop in that area .... (aluminum rubbing together ... sure sign that things aren't tight enough)

A few months ago I installed a 35FP and simply got rid of the top saddle. The base plates were marked with the engine lug hole pattern ... and drilled and tapped. Added some engine offset too ...

Its been rock solid ever since ....

larrys4227 wrote:



My Brodak P-40 came with that type of engine mount.  Worked fine for what it was, but I did have some vibration and the top saddle would never tighten down enough.  Always alittle bit of dark grey goop in that area .... (aluminum rubbing together ... sure sign that things aren't tight enough)

That's where I wonder whether adding rubber-strips (pieces of inner-tube) over/under the lugs might help. I've used bicycle tire inner-tube material for many model applications. It's thin, easily cut with scissors, heat and fuel resistant. It would eliminate metal-to-metal contact.. and where it "compresses"; it's also like having an extra lock-washer to help keep mounting-screws tight.

Roddie, I think isolating the engine with a rubber cushion, however thin, would let the engine vibrate more and cause performance problems. I am a firm believer that a solid nose with doublers and triplers coupling with the wing and good hard beams is the best way to attack vibration. My Twister even has a tripler on the outboard side.



If you want to prevent inferior aluminum from bending, maybe a piece of softer hardwood fore and aft of the lugs to act as squish blocks would help keep the clamping force distributed better. Harder metal for the whole assembly when it's first built is the real answer. I have it on good authority(learned it an hour ago) that Windy Urtnowski used 6061 aluminum.
Rusty

Hi Rusty,
I think the Cardinal is a great plane, one of my favorite (I also ran a .46LA) here's pics of the motor mount, same idea, but used countersunk (flathead) Allen head bolts up thru the bottom and attached with safety nuts. That way there's no way it can move and with cheep aluminum stock you can quickly make another set of mounts for a different engine or to reposition engine.

(Sorry for the fuzzy engine, its been hanging in the basement for tens years!)

Mark, AMA issued you another number for being a CD?

I understand you can drop all but the last 4 digits, at least that was Wayne's case. Unless it corresponds with an existing number, I guess. Then you'd have to change it.
I've been thinking of requesting dropping the zeros in my number. That would make it 16822 if t's not taken.

Mark, that's a nice Cardinal, what kind of silver paint did you use?
Congratulations on your 3rd place. That's not so easy to accomplish when you're not at Huntersville.
Rusty

Ken Cook wrote:            Mark, AMA issued you another number for being a CD?

I don't remember if it was automatic or an option, but back in the 90's, i think every CD had a 4 digit number.

The Cardinal is Sig dope with polyspan(?) a heavy duty type silkspan.

I may make a similar scheme for my Twister, though I'll be using Monokote.

yep, a lot of wet sanding and buffing...

More about flight trimming the Cardinal.

I managed to straighten the flaps out and replace the trim tab with a much smaller aluminum one bent down at 25° so not so much drag as the old giant brass tab.

The LA46 is a new power plant for me and I'm figuring out how I want it to run. At first I had an old Zinger 11x5 and ran the engine with a steady 2 stroke. It had extremely good authority, pulling tight even straight overhead. I was worried about the age of the prop, and the lack of availability, so I tried a new style Zinger 11x5 with a semi-scimitar shape, and even with a steady 2 stroke run, it was slow and gutless compared to the flat tipped older Zinger.

Wayne runs 12x5 or 12x6 APCs on his LA 46 engines and likes them. So I mounted a 12x5 Zinger scimitar to try. He insisted on needling it rich for a 4-2 break, launching at 9200 RPM and it was uncomfortably slow for me, and not at all confident in the wingover. But I flew a pattern until it burped in the first loop of the clover and ran out soon after I bailed out of the maneuver. I'm using a 4.5 ounce uniflow tank. I'm thinking the scimitar is wrong for this plane.

So next I tried an APC I had in my prop box, a 12.25 x 4.75. Launched at 9400 RPM, it flew much better and it really did a nice 4-2 break, but again burped in the first loop of the clover.

All this time I'm thinking how I loved that original hard pulling 5 second lap 2 stroke run I had with the old flat tipped Zinger, with 10 spare laps after the clover. Knowing I can't depend on replacements for the old style Zinger, I got online and ordered 3 each of 11x6 and 11x5 Master Airscrews. They are almost identical in shape to the old Zinger, slightly heavier, but I'm hopeful they'll get me back where I want to be. I don't care about a 4-2 break. It sounds cool, but the needle setting is more critical and subject to environmental mood changes. Besides, I have plenty of gas for a 2-stroke run, and I think the LA is probably happier doing that too, be it cool or not.

So I'm itching to get back out and put this plane to work with these new props and hope I get that authoritative engine run back. As I said, with the first old 11x5 Zinger, she was clipping along at 5 second laps. I want this bird to overpower the wind and that takes speed. So if I decide on one of these MA props, if it's too fast, I will add some length to the lines to slow the lap times. I think 5.2 seconds on the end of 62' lines would get it done. I hope these MAs are up to the challenge. Looks like Sunday and Tuesday might be good days to try it out..

Can't wait to file a flight report and have the results I'm hgoping for. I'm ready to start getting some consistent practice without having to screw with it every time.
Rusty

Old Zinger


New Zinger(what I call the scimitar)


Master airscrew

Rusty is that the prop I sent you some time back I know I have some of those but cant remember if it were 10-11" Towers has them, I didn't look any further .... http://www3.towerhobbies.com/cgi-bin/WTI0001P?I=LXLG02&P=8 getback