From: krnet-bounces@mylist.net To: John Bouyea Subject: KRnet Digest, Vol 346, Issue 115 Date: 6/23/2004 9:00:13 PM Send KRnet mailing list submissions to krnet@mylist.net To subscribe or unsubscribe via the World Wide Web, visit http://mylist.net/listinfo/krnet or, via email, send a message with subject or body 'help' to krnet-request@mylist.net You can reach the person managing the list at krnet-owner@mylist.net When replying, please edit your Subject line so it is more specific than "Re: Contents of KRnet digest..." Today's Topics: 1. Re: Ailerons (Charles Buddy & Cheryl Midkiff) 2. Re: KR structural analysis (Wesley Scott) 3. Re: Ailerons (StRaNgEdAyS) 4. Re: Ailerons (Mark Langford) 5. seat belts and spar strength (dead horse alert!) (Mark Langford) 6. Pine Bluff 2001 Pics (Dan Heath) 7. Re: steel frame (Wesley Scott) 8. Re: KR structural analysis (StRaNgEdAyS) 9. RE: High Alt (larry flesner) 10. Re: Ailerons (larry flesner) 11. RE: Speed Brake (larry flesner) 12. RE: Speed Brake (larry flesner) 13. seat belts and spar strength (dead horse alert!) (Ron Eason) 14. Re: seat belts and spar strength (larry flesner) ---------------------------------------------------------------------- Message: 1 Date: Wed, 23 Jun 2004 18:20:54 -0700 From: "Charles Buddy & Cheryl Midkiff" Subject: Re: KR> Ailerons To: "KRnet" Message-ID: <008801c45989$7f165c60$6401a8c0@charlesmidkiff> Content-Type: text/plain; charset="iso-8859-1" Mark, I have the Rand pre-molded wingskins and they have the ailerons already cut out for you. I measured them and all four pieces are 5 1/4" X 7 1/8" X 72 1/2". The extra fraction may be for trimming. Haven't got that far yet. Bud Midkiff KR2S Lynnwood, WA email: c.midkiff@verizon.net web: http://mysite.verizon.net/res18ums/index.html ----- Original Message ----- From: "Mark Jones" To: "KRnet" Sent: Wednesday, June 23, 2004 4:53 PM Subject: Re: KR> Ailerons > My plans show 7" at the root and 5" at the tip and 72" long. Sorry I > did not > make that any clearer. ------------------------------ Message: 2 Date: Wed, 23 Jun 2004 20:23:41 -0500 From: "Wesley Scott" Subject: Re: KR> KR structural analysis To: "KRnet" Message-ID: <003901c45989$e3c90450$c600a8c0@pbrain> Content-Type: text/plain; charset="iso-8859-1" Jeanette did say that she would be willing to provide a summary. I didn't ask what it would cost. She also said if you had a specific question about a small area, such as the firewall (her choice of part) she might be willing to extract that section of the analysis. It sounded a lot like she paid for it and doesn't think anyone else needs it. She did say that the KR planes have been analyzed several times and alway found to be overbuilt. I think a lot of it is a matter of not wanting to be helpful to design changes. Her opinion was that if you were going to be making changes then you should be willing to pay an engineer by the hour to analyze the changes. She also said that it was a lot easier to do now with computers than the way they had to do it in the old days. For those of us who don't have access to a finite element analysis program, the hand written data and calculations would be useful. This should be a case of, "it may take a structural engineer to perform the analysis, but any engineer should be able to understand the results." -- wesley scott kr2@spottedowl.biz ----- Original Message ----- From: "Brian Kraut" To: "KRnet" Sent: Wednesday, June 23, 2004 4:58 PM Subject: Re: KR> KR structural analysis > I would imagine that back in the 70s it was a bunch of hand written > data and calculations. I suspect that even if you had it you would need to be a structural engineer to understand it and in that case you could probably redo it on a computer in less time than reviewing what Ken did. > > I would also not be surprised to find that the spars and a few other > major items were calculated and a lot of the rest was eyeballed and fudge factored. I am not criticizing the design at all by saying this. I am sure that a lot of homebuilts are designed this way and we know that the KR is very structurarly sound. > > ---------- Original Message ---------------------------------- > From: "Dan Heath" > Reply-To: KRnet > Date: Wed, 23 Jun 2004 17:47:49 -0400 (Eastern Standard Time) > > >Did you ask her why you can't get the complete analysis? Can you get > >any part of the analysis? > > > > > > > >See N64KR at http://KR-Builder.org - Then click on the pics > > > >"There is a time for building and a time for flying, and the time for > >building has long since expired." > > > >Daniel R. Heath - Columbia, SC > > > >See you in Mt. Vernon - 2004 - KR Gathering > > > >See our EAA Chapter 242 at http://EAA242.org > > > > > > > >_______________________________________ > >to UNsubscribe from KRnet, send a message to KRnet-leave@mylist.net > >please see other KRnet info at http://www.krnet.org/info.html > > > > _______________________________________ > to UNsubscribe from KRnet, send a message to KRnet-leave@mylist.net > please see other KRnet info at http://www.krnet.org/info.html > > > ------------------------------ Message: 3 Date: Thu, 24 Jun 2004 11:27:27 +1000 From: "StRaNgEdAyS" Subject: Re: KR> Ailerons To: Message-ID: <40DA2DFF.000003.03976@motherfucker> Content-Type: Text/Plain; charset="iso-8859-1" Mark. It would be possible indeed to reduce the size of your ailerons, but the big limiter as I see it is going to be the aft spar. Unless you want to move it, I think you have to stick with the plane versions or you will suffer a reduced roll rate. If you did want to shift the aft spar, you could probably get away with reducing the length to 50% of the wing and increase the depth to 30% constant depth of the chord line. This should retain the existing roll rate and allow you to shorten the length of the aileron. Cheers. Peter Bancks. strangedays@dodo.com.au http://www.homebuiltairplanes.com http://canardaviationforum.dmt.net ------------------------------ Message: 4 Date: Wed, 23 Jun 2004 20:39:12 -0500 From: "Mark Langford" Subject: Re: KR> Ailerons To: "KRnet" Message-ID: <00c901c4598c$0db70c10$1202a8c0@basement> Content-Type: text/plain; charset="iso-8859-1" Peter Bancks wrote: > It would be possible indeed to reduce the size of your ailerons, but > the big > limiter as I see it is going to be the aft spar. Unless you want to > move it, > I think you have to stick with the plane versions or you will suffer a > reduced roll rate. If you did want to shift the aft spar, you could probably > get away with reducing the length to 50% of the wing and increase the depth > to 30% constant depth of the chord line. This should retain the > existing roll rate and allow you to shorten the length of the aileron. Oh, it'll work. See http://home.hiwaay.net/~langford/99101051.jpg . And now you've got the counterweight evenly distributed through the nose of the aileron. For more details see http://home.hiwaay.net/~langford/owings.html . I don't claim this is THE way to do it, but it's the way I did it. Shorter ailerons, deeper chord, less drag, roughly the same roll moment as the plans... Mark Langford, Huntsville, Alabama N56ML "at" hiwaay.net see KR2S project at http://home.hiwaay.net/~langford ------------------------------ Message: 5 Date: Wed, 23 Jun 2004 20:51:57 -0500 From: "Mark Langford" Subject: KR> seat belts and spar strength (dead horse alert!) To: "KRnet" Message-ID: <00cc01c4598d$d5891c50$1202a8c0@basement> Content-Type: text/plain; charset="iso-8859-1" NetHeads, There has been a lot of talk about seat belt brackets, bolt diameters, etc lately. I just ordered my seat belts today from Hooker Harness, and have been forced to think about attachment in order to come up with the proper belt lengths. The thing that concerns me most is the strength of the aft spar itself. If you think about laying the thing out flat between two sawhorses with a 32" space between them, I'll bet a lot of you would have second thoughts about merely STANDING on the middle of it, much less jumping up and down on it. I think the standard for seat belts is something like 20g's, so if you weigh 200 pounds, and have a 200 pound passenger with you (half of both would be 200 at the center), imagine 4000 pounds out there in the middle of that spar (laid flat). Do you think it would hold it? I'll bet you big money it won't. I stopped by my stress guy's office today, and talked him into working out the details for me (I'm more than just a little rusty). We assumed a 1" x 1" piece of spruce with 4000 pounds (pilot and passenger) of force out in the middle of that 32" span, neglecting the upper cap, and the vertical members and plywood connecting them to the "subject" lower cap (somewhat conservative). The number we calculated was 192,000 psi applied to that spar cap's spruce material in a 20g crash. The modulus of rupture in static bending is 9600 psi for aircraft grade spruce. So my apprehension of walking on that spar would be justified. Theoretically, 200 pounds would break that 1x1, and that passes my "common sense" test. Larry's idea of spanning the two caps with a bracket is a good one, since it calls both caps into play. Using that bracket to span the caps, and if you're the optimistic type and assume that the shoulder belt and lap belt will play equal parts bearing the load, and you have no passenger, then there's only 25 pounds (200/8) acting out in the middle of each cap, so the spar would handle something closer to an 8g crash. But I seriously doubt the shoulder belts do as much work as the lap belts do, so we're probably back to 6g's again, and that's with no passenger. My point is that although bolt diameter and bracket material are important factors, you also need to make sure the spar itself can handle it. Obviously the load of the seat belts needs to be shared with something other than the aft spar if you are preparing for a 20g crash. The two best ways I can think of are a compression member connecting the main spar to the aft spar (connected to both caps of each), or a cable connected to something like the tailwheel block. I know the cable thing will stir up the usual arguments, but I think that's exactly what I'm going to do...run cables from both center shoulder and center lap belt attachment points back to the something substantial in the tail (like the tailwheel block). I know we've all heard of KR's torn to pieces in a crash, and the guy walks away with the rear spar belted to his butt, but those are not the sort of full frontal crash that this 20g standard is based on. You say you're not going to worry about 20g frontal impacts because the chance of one is unlikely? I don't blame you. They are. But then why worry about bolt diameter or brace strength for a 20g crash if the spar's not going to take it anyway? And I'm not saying the cable strap is a 20g solution either, but that's what it'll take to make me comfortable, with minimal weight gain. Just thought I'd throw that out there. There are lots of ways to work this problem, and you're welcome to work it the way you want to. I need to get back to work if I'm going to fly to the Gathering. I just wanted to bring it up... Mark Langford, Huntsville, Alabama N56ML "at" hiwaay.net see KR2S project at http://home.hiwaay.net/~langford ------------------------------ Message: 6 Date: Wed, 23 Jun 2004 21:51:28 -0400 (Eastern Standard Time) From: "Dan Heath" Subject: KR> Pine Bluff 2001 Pics To: "krnet@mylist.net" Message-ID: <40DA33A0.000001.01800@COMPUTER> Content-Type: Text/Plain; charset="iso-8859-1" Jack, Thanks for pointing us to the old gathering pics. It was nice to look back. Richard still has one or maybe the most awesome KR that I have ever seen on the ramp or in the air. I really missed seeing that plane last year. "There is a time for building and a time for flying, and the time for building has long since expired." See N64KR at http://KR-Builder.org - Then click on the pics Daniel R. Heath - Columbia, SC See you in Mt. Vernon - 2004 - KR Gathering ------------------------------ Message: 7 Date: Wed, 23 Jun 2004 21:02:47 -0500 From: "Wesley Scott" Subject: Re: KR> steel frame To: "KRnet" Message-ID: <004701c4598f$5a3e6350$c600a8c0@pbrain> Content-Type: text/plain; charset="iso-8859-1" Steel doesn't require structural epoxy. I would much rather weld than glue. You don't have to worry about getting the mixture ratio correct, getting the components thoroughly mixed, more tolerance for gaps between parts, and you don't have to wait a week for the part to cure before you go on to the next operation. I also have this dream of having a low cost twin using a pair of VW engines (although the fact that the corvair engines can be run both ways may make them more desirable). I don't think hanging an engine on an existing KR wing spar is going to be practical. Because of the twisting moment generated by the engine hanging out in front of the wing, I expect the mounts are going to have to connect to both spars or the spars are going to need to be connected. Also, the spar loads will change significantly with the engine weight on the wing not the fuselage. I don't want to think about trying to do the design analysis with material that has directional strength properties (i.e. spruce). If you are going to use a steel (or aluminum) wing, you might as well convert the fuselage also. -- wesley scott kr2@spottedowl.biz ----- Original Message ----- From: "Colin & Bev Rainey" To: "KRnet" Sent: Wednesday, June 23, 2004 2:20 PM Subject: KR> steel frame > Wesley > Why would you want a steel frame? Pound for pound spruce is lighter > at the same strength unless you use one of the exotic metals, then you might as well pick a different plane. > > Colin & Bev Rainey > KR2(td) N96TA > Sanford, FL > crainey1@cfl.rr.com > http://kr-builder.org/Colin/index.html > _______________________________________ > to UNsubscribe from KRnet, send a message to KRnet-leave@mylist.net > please see other KRnet info at http://www.krnet.org/info.html > > > ------------------------------ Message: 8 Date: Thu, 24 Jun 2004 13:26:43 +1000 From: "StRaNgEdAyS" Subject: Re: KR> KR structural analysis To: , Message-ID: <40DA49F3.000005.03976@motherfucker> Content-Type: Text/Plain; charset="iso-8859-1" I have a comprehensive design analysis application, if anyone wants to get a copy contact me off the list for the details. Cheers. Pete. strangedays@dodo.com.au ------------------------------ Message: 9 Date: Wed, 23 Jun 2004 22:22:06 -0500 From: larry flesner Subject: RE: KR> High Alt To: KRnet Message-ID: <3.0.6.32.20040623222206.0079a100@pop.midwest.net> Content-Type: text/plain; charset="us-ascii" >Larry, >>Let's see if I understand... If I want better climb on a hot day or at >>high >altitudes, what is it that I need? OH, I know, longer wings. Darn, I >think I just flunked. OH OH, now I know, it's POWER. Daniel R. Heath - >Columbia, SC """""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" """"""""""""" Dan, I guess my question would be how much longer would the wing have to be to make up for a 20 to 30 percent loss of power and could the present design handle that or would you have to redesign the wing to handle the extra length. Jeanette Rand once told me that the extra wing length with the premolded skins cuts down the G rating of the wing by 1/2 G. I'm assuming she meant the wing attach fittings. As I stated in my earlier post: " Longer wings should help the climb rate and the penalty for the longer wings will be felt primarily in the cruise mode and is probably not more than a few miles per hour." If if's a hot day or high altitude and I had to chose between longer wings or more power I'll take more power every time. My "more power" fix is really just an engine that would produce the same hp at 6000 feet (or whatever) that a smaller engine would produce at sea level, i.e. a 100hp 0-200 or Corvair instead of an 80 hp VW. I'd bet anyone a steak dinner that you will find more "high hp" Cessnas then "long wing" Cessnas flying in the mountains. :-) :-) Larry Flesner ------------------------------ Message: 10 Date: Wed, 23 Jun 2004 22:22:28 -0500 From: larry flesner Subject: Re: KR> Ailerons To: KRnet Message-ID: <3.0.6.32.20040623222228.00799310@pop.midwest.net> Content-Type: text/plain; charset="us-ascii" Shorter >ailerons, deeper chord, less drag, roughly the same roll moment as the >plans... Mark Langford, +++++++++++++++++++++++++++++++++++++++++++++++++++++++ I don't have any answers on the aileron thing but I'll throw out some things to consider. My KR is basically plans built with the exception of the 24" stretch. My KR is not a rudder airplane. What I mean is I can't lift a wing using rudder at any speed. Willie Wilson from England says his nearly plans built KR handles the same way. When my stock wing stalls, with 3 degrees washout, I still have aileron control and ONLY aileron control to keep the wings level. I don't know how far out on the wing the stall developes before the nose drops. If I were to shorten my ailerons will I still have control through the stall or will the ailerons be in the stalled portion of the wing? What if I only have two degrees of washout? Like I said, I don't have the answers, just the questions. If I knew someone that weighed maybe 160 pounds, was brave as a Viking, and good with a camera, (read Mark L.) I might consider "tufting" my wings and checking it out. Larry Flesner - 60 hours since February and still grinning !! ------------------------------ Message: 11 Date: Wed, 23 Jun 2004 22:23:08 -0500 From: larry flesner Subject: RE: KR> Speed Brake To: KRnet Message-ID: <3.0.6.32.20040623222308.0079a8d0@pop.midwest.net> Content-Type: text/plain; charset="us-ascii" > Check Rich Siefert's KR on the link below. It looks to me like its >attached at the front spar. Jack Cooper +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ My non-engineered, gut feel, is that I want my speed brake behind the center of lift and/or the C.G. I guess for basically the same reason you put the feathers on the back end of an arrow. And Mark, if you could mount you brake just forward of the rear spar and could place the motor under the seat it will help keep you C.G. forward. My motor is behind my seat and heavier than yours and I wish it wasn't either of those. Larry Flesner ------------------------------ Message: 12 Date: Wed, 23 Jun 2004 22:35:09 -0500 From: larry flesner Subject: RE: KR> Speed Brake To: KRnet Message-ID: <3.0.6.32.20040623223509.0089fd10@pop.midwest.net> Content-Type: text/plain; charset="us-ascii" > Check Rich Siefert's KR on the link below. It looks to me like its >attached at the front spar. Jack Cooper >+++++++++++++++++++++++++++++++++++++++++++++++++++++++++ My non-engineered, gut feel, is that I want my speed brake behind the center of lift and/or the C.G. I guess for basically the same reason you put the feathers on the back end of an arrow. And Mark, if you could mount you brake just forward of the rear spar and could place the motor under the seat it will help keep you C.G. forward. My motor is behind my seat and heavier than yours and I wish it wasn't either of those. Larry Flesner ------------------------------ Message: 13 Date: Wed, 23 Jun 2004 22:51:38 -0500 From: "Ron Eason" Subject: KR> seat belts and spar strength (dead horse alert!) To: "KRnet" Message-ID: <003301c4599e$8dace680$6501a8c0@CADENGINEERING> Content-Type: text/plain; charset="iso-8859-1" Your dead in a 20 G crash any way so what dose it matter? I fabricated a bulkhead behind the main spar and anchored a cable from the middle of the bulkhead to the tailwheel reinforcement area. The bulkhead serves many purposes for my KR including a rear hinge reinforcement. I will be dead if that breaks away. KRron ----- Original Message ----- From: "Mark Langford" To: "KRnet" Sent: Wednesday, June 23, 2004 8:51 PM Subject: KR> seat belts and spar strength (dead horse alert!) > NetHeads, > > There has been a lot of talk about seat belt brackets, bolt diameters, > etc lately. I just ordered my seat belts today from Hooker Harness, > and have been forced to think about attachment in order to come up > with the proper belt lengths. The thing that concerns me most is the > strength of the aft spar itself. If you think about laying the thing > out flat between two sawhorses with a 32" space between them, I'll bet > a lot of you would have second thoughts about merely STANDING on the > middle of it, much less jumping > up and down on it. I think the standard for seat belts is something > like 20g's, so if you weigh 200 pounds, and have a 200 pound passenger > with you (half of both would be 200 at the center), imagine 4000 > pounds out there in > the middle of that spar (laid flat). Do you think it would hold it? > I'll bet you big money it won't. > > I stopped by my stress guy's office today, and talked him into working > out the details for me (I'm more than just a little rusty). We > assumed a 1" x 1" piece of spruce with 4000 pounds (pilot and > passenger) of force out in the middle of that 32" span, neglecting the > upper cap, and the vertical members and plywood connecting them to the > "subject" lower cap (somewhat conservative). The number we calculated > was 192,000 psi applied to that spar cap's spruce material in a 20g > crash. The modulus of rupture in static > bending is 9600 psi for aircraft grade spruce. So my apprehension of > walking on that spar would be justified. Theoretically, 200 pounds would > break that 1x1, and that passes my "common sense" test. > > Larry's idea of spanning the two caps with a bracket is a good one, > since it > calls both caps into play. Using that bracket to span the caps, and > if you're the optimistic type and assume that the shoulder belt and > lap belt will play equal parts bearing the load, and you have no > passenger, then there's only 25 pounds (200/8) acting out in the > middle of each cap, so the > spar would handle something closer to an 8g crash. But I seriously > doubt the shoulder belts do as much work as the lap belts do, so we're > probably back to 6g's again, and that's with no passenger. > > My point is that although bolt diameter and bracket material are > important factors, you also need to make sure the spar itself can > handle it. Obviously the load of the seat belts needs to be shared > with something other > than the aft spar if you are preparing for a 20g crash. The two best > ways I > can think of are a compression member connecting the main spar to the > aft spar (connected to both caps of each), or a cable connected to > something like the tailwheel block. I know the cable thing will stir > up the usual arguments, but I think that's exactly what I'm going to > do...run cables from both center shoulder and center lap belt > attachment points back to the > something substantial in the tail (like the tailwheel block). > > I know we've all heard of KR's torn to pieces in a crash, and the guy walks > away with the rear spar belted to his butt, but those are not the sort > of full frontal crash that this 20g standard is based on. You say > you're not going to worry about 20g frontal impacts because the chance > of one is unlikely? I don't blame you. They are. But then why worry > about bolt diameter or brace strength for a 20g crash if the spar's > not going to take it anyway? And I'm not saying the cable strap is a > 20g solution either, but > that's what it'll take to make me comfortable, with minimal weight > gain. > > Just thought I'd throw that out there. There are lots of ways to work this > problem, and you're welcome to work it the way you want to. I need to > get back to work if I'm going to fly to the Gathering. I just wanted > to bring it up... > > Mark Langford, Huntsville, Alabama > N56ML "at" hiwaay.net > see KR2S project at http://home.hiwaay.net/~langford > > > > > > _______________________________________ > to UNsubscribe from KRnet, send a message to KRnet-leave@mylist.net > please see other KRnet info at http://www.krnet.org/info.html > > ------------------------------ Message: 14 Date: Wed, 23 Jun 2004 22:55:02 -0500 From: larry flesner Subject: Re: KR> seat belts and spar strength To: KRnet Message-ID: <3.0.6.32.20040623225502.008a0640@pop.midwest.net> Content-Type: text/plain; charset="us-ascii" We assumed a 1" x >1" piece of spruce with 4000 pounds (pilot and passenger) of force out >in the middle of that 32" span, neglecting the upper cap, and the >vertical members and plywood connecting them to the "subject" lower cap (somewhat >conservative). >Mark Langford, ++++++++++++++++++++++++++++++++++++++++++++++++++++++ Mark, In my case, and most KR's, two brackets are attached near the vertical fuselage sides. That should cut the load in the center by one half. My brackets, as you stated, span both spar caps. Also I don't think the entire load is horizontal to the spar but some load would carry a vertical angle. The seat back where my sholder belts are attached has two pieces of 5/8" spruce with a piece of 3/32" ply on the top and a piece of 1/4" ply on the bottom and a spruce block between the two where the bolt goes through. My question: how big of a tree can I hit? :-) :-) Seriously, from what you stated and considering the KR design, I'd guess the simplest and lightest weight way to strengthen the spar for crash forces from the belts would be to run two steel tubes or wood structures from near center of the rear spar to the forward spar at the fuselage sides. Thoughts? Larry Flesner ------------------------------ _______________________________________________ See KRnet list details at http://www.krnet.org/instructions.html End of KRnet Digest, Vol 346, Issue 115 *************************************** ================================== ABC Amber Outlook Converter v4.20 Trial version ==================================