Panther 92

[woolleys]

Yuri. I've flown both the short and long wing with the balanced elevator. Have about 40 hours of long wing time in a non counterweighted spring type set up. I found no difference in the flying characteristics of the two types. The elevator feed back and feel mirrored the CW type.

The 40 hrs. of spring type elevator panther was in the prototype trike. As with all trikes, they tendency to have a slight rocking motion over terrain if it's not smooth. Since I live on a grass stripe, taxing the trike saw the elevator bounce up and down if the stick was not held; this is not the case in the balanced elevator. In flying the Panther, I have notice one thing; and no effect on the flying characteristics. Since the horizontal stab. is almost symentical, the feed back through the stick below 100 MPH is light a smooth. During perfectly trimmed flight conditions during turbulence, the stick will float just a very small amount with your hands off the stick. I notice under similar conditions, with the spring type Panther, that the stick had a slightly higher amplitude to the turbulence. This was only noticeable hands off below 100 MPH.

I believe that Dan put the CW elevator on the short wing due to the higher Vne; 210 MPH. Several of the builders around our airport are going long wing with CW elevators. But we all do heavy aerobatics with Lycoming 0320's and will regularly push the aircraft to the Vne of 200 MPH. I am currently building another Panther that will be a long wing. I will most likely put the spring type system on that aircraft just to save the 4 or so pounds of weight. The other thought is the CG with the CW elevator, that has turned out to be a no issue.

Bottom line; heavy aerobatics, your location of high altitude and potential higher true airspeed, I would most likely put the CW elevator on. Vne is a function of true airspeed and out there in the mountains you could get to Vne before you know it. Dan could tell you what the projected flutter speed is in the Panther and I'm sure he set the Vne at a limit that gives you a very safe margin for potential flutter issues.

[ykachuro]

Barry, thank you! With the experience behind you, you’ll be catching up to me soon!

Bob, thank you for sharing your experience and confirming what I’ve been thinking! At the moment, I plan to opt for a balanced elevator, however. Do you by any chance have a view on that?

[woolleys]

Yuri. The build looks great; very nice work. On your decision to stay with the long wing, I don't think you are going to be disappointed. Having over 200 hrs. of short wing time on my Panther and almost a hundred hours of long wing time, the main difference is in the overall roll rate. Unless you are going to do heavy aerobatics you will be pleased with the overall performance of the long wing. Since you are going to be operating in higher altitudes the long wing will give you that exact performance at the lower density altitudes. Short wing provides a little less climb and slightly higher stall speeds, faster roll rates and if you use more rudder at slow speeds you can achieve the better roll rates.

[Barry]

Looking great Yuri!! You are moving right along. I took a break from my Avid Magnum to work on the Panther. It is way fun!!!

[ykachuro]

Back in the groove...

[ykachuro]

A quick update. Received the rest of the kit before the holidays. It has been somewhat on a back burner because of family/friends visiting and because of my indecision about doing the short wings v. Long wings. The kit inadvertently came with the parts for the long wing, and I revisited this issue even though I thought I had decided on the short wings. After much heated but mostly friendly deliberation with myself, I’ve decided on the long wing.
And I’ve been prepping wing ribs in the meantime — will post some pics today/tomorrow. Will be setting up the wing jig per the BM.

[ykachuro]

Just to keep it in prospective, try asking Avdel about the use of their "cherry" pulled rivets for aircraft construction. I am sure your conversation will be just as short.
The amount and the layer thickness of epoxy used in the method I am describing is no more than the amount of primer you would use for priming the part. I can't see how it could possibly lower the structural integrity. You would still use the rivets as spec-ed.
Why do it? Why not?
I recently looked at pictures of an RV that experienced in flight tail and wing failure obviously due to exceeding the design loads. Other than spar failures (the airplane basically disintegrated in flight), you could see the failure of aluminum skins right along the rivet lines. The rivets stayed, but the skin failed at the rivet joint. So, on that RV the rivet/skin joint as a whole was a failure point. I doubt that strengthening the joint at the rivet line woul've made a difference in that case, but who knows.
Here is the accident report: https://app.ntsb.gov/pdfgenerator/Repor ... l&IType=FA
Here is the link to the appendices, including pictures: https://dms.ntsb.gov/pubdms/search/hitl ... 9E3BE61D8C

[Lowrider]

I would advocate use of composite materials in place of conventional construction methods...except I don't have the experience or expertise to know right from wrong. I talked to a lot of companies who produce these products and as soon as I mention private homebuilt airplane their response is uniformly..."thanks for your interest in our product, have a nice day". Doing the crossover from the defense industry to private use in home built planes is coming but no one that I talked to was willing to allow their products to be used for that purpose...that's why I'm bending alum and bucking rivets. The technology is out there but the lawyers have it tied up for now. I worked for General Dynamic for awhile after I retired and I remember a demo of a carbon fiber wrapped antenna that was attached to the F-16 with a "tube of stuff"...I wonder what it was.

[ykachuro]

5200 is amazing stuff. It would be quite messy and would add some weight though. The way I ended up experimenting with west epoxy is that I would dip very so slightly some maroon scotch brite in neat epoxy and would work it into aluminum surface until the thin film of epoxy turns slightly grey with aluminum powder (both surfaces to be riveted). I estimate it would take no more than an oz of epoxy to do all spar stiffeners (horizontal and vertical) on the tail. West testings show adhesion strength of 105/206 epoxy to aluminum of about 2,000 psi (2,500 psi with their g-flex epoxy). For comparison, the tensile strength of a 1/8 BSP rivet is 325 lbs. here is the link to West's testing http://epoxyworks.com/index.php/aluminum-adhesion/

Again, I am in no way advocating using epoxy or any other adhesive in addition to or, g-d forbid, instead of rivets!

[Lowrider]

Just for what it's worth I did a lot of experimenting with different bonding materials and the one that did not come apart during tests was 3M 5200 marine sealer/adhesive. 2024 alum up to 0.032 tore and the 5200 did not fail. I got the idea from an IA in Alaska...they use it routinely up there with great success on float bottoms. BTW, I had to use the bucket on my front end loader to tear the alum with a straight pull. The other one that was good was a 3M two sided adhesive tape used in construction of Semi trailers...can't find the stock number but it's used in place of rivets.

Take it for what you paid for it.