From: owner-krnet-l-digest@lists.teleport.com (krnet-l-digest) To: krnet-l-digest@lists.teleport.com Subject: krnet-l-digest V1 #20 Reply-To: krnet-l-digest Sender: owner-krnet-l-digest@lists.teleport.com Errors-To: owner-krnet-l-digest@lists.teleport.com Precedence: bulk krnet-l-digest Wednesday, May 21 1997 Volume 01 : Number 020 ---------------------------------------------------------------------- Date: Mon, 19 May 1997 19:23:46 -0400 From: "Curt Martin" Subject: KR: Re: HIGH RPM was (Shadbolt Cam Grinders/PC Dyno) > From: Micheal Mims > To: krnet-l@teleport.com > Subject: KR: HIGH RPM was (Shadbolt Cam Grinders/PC Dyno) > Date: Saturday, May 17, 1997 12:51 PM > > At 11:56 AM 5/17/97 -0400, you wrote: > I may be showing my ignorance here but if the dd soob guys are running > their engines at 3800-4000 rpm then why not run the VW at a little higher > rpm as well? I know that longevity could be a concern but how much would it > be affected? Curt Martin shows a 1918cc VW putting out 98hp @ 4000rpm in his > PC............. Please don't misunderstand me, 1.) I feel that the HP numbers spit out by the software are higher than they should be (and said as much in my original post.) Personally, I think the software has a built in bias towards liquid cooled V8's. All the predefined engine combinations provided by the software are for typical "muscle car" V8's. I know the software is pretty close on big displacement engines (Got within 2% if the actual HP peak on my 350 TPI) but may not be as accurate as the displacement goes down. However, since all the simulations are using the same software, the change in the torque and HP curves should be good, even if the actual HP and Torque numbers are over inflated. 2.) I don't advocate spinning a VW with a direct drive prop that fast. The purpose for running the simulation was to see the effects of different cam specs on the power and torque curves. My goal is to see what it would take to boost usable HP and torque below 3000 rpm. The purpose being to run a larger diameter and/or higher pitch propeller slower than the conventional KR prop. Curt Martin (cmartin@america.com) Ormond Beach, FL http://www.america.com/~cmartin ------------------------------ Date: Mon, 19 May 1997 19:31:07 -0400 From: "Curt Martin" Subject: Re: KR: VW Cam Specs/ PC-Dyno Runs: > I'm curious Curt, how's the engine life at these R's? I've always been told > that even VW's don't appreciate revs in the 4500+ range...but thanks for the > info! > > KitaruSapien No Idea how long it would last spinning that fast continuously. I included the high RPM numbers only because it showed the peak and backside of the curve. Curt ------------------------------ Date: Mon, 19 May 1997 18:48:58 -0500 From: Jim Faughn Subject: KR: VW Revs and Props It is my understanding, understanding that it is, that the speed of the engine is directly proportional to the speed of the prop. After all the most important item in the system is the prop. Depending on the length and RPM of the prop, the propeller tips will go supersonic at a certian speed. After this point the prop becomes inefficient. Therefore the speed of the VW is typically maximum at about 3600 RPM with a 52 inch prop. The other auto conversions will use a gear reduction unit to make the HP and still turn the prop at the correct RPM based on the length. It is also my understanding that a slower turning prop with a larger length is more efficient. That is why, again my understanding, that the Contential and other "aircraft engines" turn a slower RPM and have a larger length prop. The reason the VW has traditionally been chosen is that it can make the HP at the "slower" RPM of 3200 at cruise with a 52 inch prop and is much less expensive than a "aircraft engine. It is also more expensive to combine a reduction unit along with the fact that it adds more components to break. It is now time for all the people with alot more engineering than me to respond to the RPM vs prop length issue. See you at OSHKOSH.... I hope everyone is planning to go! - -- Jim Faughn N8931JF St. Louis, MO (314) 652-7659 or (573) 465-8039 ------------------------------ Date: Mon, 19 May 1997 19:17:39 -0600 From: "Larry Jacks" Subject: KR: Re: VW Revs and Props Jim Faughn wrote: > It is my understanding, understanding that it is, that the speed of the > engine is directly proportional to the speed of the prop. After all the > most important item in the system is the prop. Depending on the length > and RPM of the prop, the propeller tips will go supersonic at a certian > speed. After this point the prop becomes inefficient. Therefore the > speed of the VW is typically maximum at about 3600 RPM with a 52 inch > prop. The other auto conversions will use a gear reduction unit to make > the HP and still turn the prop at the correct RPM based on the length. > It is also my understanding that a slower turning prop with a larger > length is more efficient. That is why, again my understanding, that the > Contential and other "aircraft engines" turn a slower RPM and have a > larger length prop. The reason the VW has traditionally been chosen is > that it can make the HP at the "slower" RPM of 3200 at cruise with a 52 > inch prop and is much less expensive than a "aircraft engine. It is also > more expensive to combine a reduction unit along with the fact that it > adds more components to break. > > It is now time for all the people with alot more engineering than me to > respond to the RPM vs prop length issue. You're correct in your understanding. Larger diameter props are more efficient, especially in take off and climb performance. However, they are limited as to their maximum RPM. If you watch a plane with large propellors (like the C-130), you'll see that the props are turning quite slow compared to a light plane. The large propellors are also efficient at cruise speeds as well. The most extreme example that I know of is the Russian Tu-95 Bear bomber. At crusing speed, it's propellors are only turning about 700 RPM. It's also the fastest propellor powered airplane on earth. To illustrate the limitations of propellor diameter with increased rotational speeds, I calculated the maximum desired propellor diameter for RPMs ranging from 2000 to 4400. The assumptions are: Speed of sound at sea level, standard conditions is approximately 760 mph. The maximum desired tip speed is 0.8 Mach (based on the diameters of existing airplane propellors). Higher speeds will cause increased noise and, at some point, a sharp decrease in efficiency for most propellors. The Bear's propellors can handle supersonic speed, but the noise level is incredibly high (it's said to be one of the noisiest planes on earth -- intercepting fighter pilots sometimes report that the noise level from the Bear can be clearly heard in their cockpits!) The formula: tip speed = PI * Diameter * Revolutions Per Second, so 0.8 * 760 * 1.46667 * 12 (0.8 Mach in inches per second) Diameter = ---------------------------------- 3.14159 * Revs Per Second All diameters are in inches. I hope this prints properly. Propellor RPM Diameter 2000 102.2 2100 97.3 2200 92.9 2300 88.9 2400 85.2 2500 81.3 2600 78.6 2700 75.7 2800 73.0 2900 70.5 3000 68.1 3100 65.9 3200 63.9 3300 61.9 3400 60.1 3500 58.4 3600 56.8 3700 55.2 3800 53.8 3900 52.4 4000 51.1 4100 49.9 4200 48.7 4300 47.5 4400 46.5 These numbers may not be exactly correct, but they should get you in the ballpark. ------------------------------ Date: Mon, 19 May 1997 19:20:51 -0600 From: "Larry Jacks" Subject: Re: KR: fuel and CG If it's the same stuff I read about recently, the Navy is starting to put it in their fuel tanks. I've heard that the Air Force has been doing this for some time. Of course, the money isn't coming out of their pockets. > X-plo-Safe, though I'm not sure that is how they spell it. This stuff > really interested me until an engineer friend and former hobbyist-level > auto racer told me that it's fairly expensive and tends to pack down > over time, so that the fuel tank must be cut open and the packing > replaced > every few years. No doubt if I ever find myself with flaming gasoline > all over my lap, I'll think it would have been worth the effort. > However, > his report pretty well turned me off on it. > > Might be justified for the header tank, though, if you knew how long the > stuff is good for and had arranged for convenient access. Ditto the > under- > seat aux tank someone mentioned. (Or was that one of the other lists?) > > Owen Davies ------------------------------ Date: Mon, 19 May 1997 21:57:07 EDT From: jscott.pilot@juno.com (Jeffrey E. Scott) Subject: KR: Next progres report. Finally got my bird painted this morning. Looks great in bright white! Had a wonderful time painting between the raindrops while the weather turned sour and tried to rain on it, but it turned out well. Talked to the FAA today about arranging for an inspection only to find that our local FSDO doesn't do inspections any more. Instead they have inspections contracted out to retired FAA people. Cost is $150, but the guy is willing to come inspect the plane on a day or two's notice. When I asked if he wanted me to start my taxi testing before he inspected it, he said he didn't care if I flew it first as long as I stay over the runway and lift off and set it down in a straight line. Hope to move it to the airport in about a week and be flying in another week or two. - ---- Jeffrey Scott jscott.pilot@juno.com See construction of KR-2S N1213W at http://fly.hiwaay.net/~langford/kjeffs.html - ---- ------------------------------ Date: Mon, 19 May 1997 21:57:07 EDT From: jscott.pilot@juno.com (Jeffrey E. Scott) Subject: Re: KR: Diehl gear geometry On Mon, 19 May 1997 01:51:53 -0400 (EDT) MikeTnyc@aol.com writes: >>>> You guys that have installed the Diehl fixed gear: I wonder if >you would >>>> change the angle that the gear legs extend from the center main >spar, if >>>> you had it to do over again? >>>> Are you guys that used it, and have all of the weight sitting on >it, >happy >>>> with the camber? I'm about to install my spar/leg adapters, and >would >>>> rather avoid shimming the lower axle attach fittings if I can. >>>> You know what they say about changing things... >>>> > > >>>I wouldn't change a thing! I can wheel land the plane or 3 point it >>>without problems. In both cases I can do it with one or two on >board. >>>Once again I have a tail dragger and I think this is one of the best >>>things that Dan came up with! > >>Mine is a taildragger sitting on the Diehl gear although I have 30" >legs >>rather than the standard 24" legs. My empty CG is 4.4 inches in >front of >>the forward CG limit. It's certainly light in the tail when empty, >but >>won't tip over without some help even with the header tank full. The >>Diehl gear certainly puts the gear much farther forward than the >>retractable. I don't know about Rand's springbar gear. > > >The question in my mind is where do the wheels wind up in relation to the CG, >or does the Diehl gear automatically put them in the right place if >your CG is within specs? > >Mike Taglieri > > > The Diehl gear angles forward from the spar as it goes down. Makes it a bit easier to keep your CG behind the gear even without anyone in the cockpit. My CG is about 4 inches ahead of the forward CG limit when the plane is empty but is well within specs with pilot or pilot and passenger and any load configuration that is within the weight limits. Worse case loading puts me at midrange of the CG limits. That's why you want your landing gear to reach out well in front of your CG limit on a taildragger. Otherwise you might have to park with your nose on the ground over in the - -EZE parking area. ;o) FWIW, I dropped mine on it's nose when doing the W&B. Lifted under the front spar to set it on the scales and found that the eldest son was no longer holding the tail. The plane landed heavily on the air scoop on the cowl, but only caused some minor scratches and a few loud expletives on my part. - ---- Jeffrey Scott jscott.pilot@juno.com See construction of KR-2S N1213W at http://fly.hiwaay.net/~langford/kjeffs.html - ---- ------------------------------ Date: Mon, 19 May 1997 22:05:31 -0400 From: Vince Bozik Subject: Re: KR: Re: VW Revs and Props Larry Jacks wrote: > 4300 47.5 > 4400 46.5 > These numbers may not be exactly correct, but they should get you in > the ballpark. Well, I got bored and did the same thing as larry. I double checked, and my numbers area still high. I did mine in a spreadsheet and then charted it out. I'll post it if anyone's interested in seeing it. It's not that darn amazing anyway. Well, heres the formula, followed by what I came up with: Super=783360/(PI*d) Speed of sound in inches per minute @ sea level 32 degrees F = 783360 in/m "PI" = That irrational booger 3.141592654 "d" = Diameter of prop. in question "Super" = RPM @ which tips go supersonic Maximum RPM For Prop. Diameter Propeller Diameter (inches) RPM @ Sound Barrier 40 6234 41 6082 42 5937 43 5799 44 5667 45 5541 46 5421 47 5305 48 5195 49 5089 50 4987 51 4889 52 4795 53 4705 54 4618 55 4534 56 4453 57 4375 58 4299 59 4226 60 4156 61 4088 62 4022 63 3958 64 3896 65 3836 66 3778 67 3722 68 3667 69 3614 70 3562 71 3512 72 3463 73 3416 74 3370 75 3325 76 3281 77 3238 78 3197 79 3156 80 3117 I figured the diameter range was good enough for a KR. I can stick any in there if you like. Let me know what you think of these numbers. I appologize if there were two of these messages. I goofed, again... - -- Vince Bozik - Athens, Georgia Mailto:ICBM@ix.netcom.com ------------------------------ Date: Mon, 19 May 1997 19:58:30 -0700 From: Micheal Mims Subject: Re: KR: VW Revs and Props At 06:48 PM 5/19/97 -0500, you wrote: >It is my understanding, understanding that it is, that the speed of the >engine is directly proportional to the speed of the prop. After all the >most important item in the system is the prop. Depending on the length >and RPM of the prop, the propeller tips will go supersonic at a certian >speed. You can spin a 52 inch prop (in still air) 4800 rpm before the tips break over 750 mph. Not that Im gona do it, but I think this supersonic tip thing is over rated! _______________________ ~~~~~~~~~~~~~~~~~~~~~~ Micheal Mims Just Plane Nutts mailto:mimsmand@ix.netcom.com http://www.netcom.com/~mimsmand ------------------------------ Date: Mon, 19 May 1997 21:02:48 -0600 (MDT) From: Ron Lee Subject: Re: KR: Next progres report. (no archive) Jeff, Sounds great (except for the $150 inspection). I may have to come down again soon to see it taxi! Ron At 21:57 97/5/19 EDT, you wrote: >Finally got my bird painted this morning. Looks great in bright white! >Had a wonderful time painting between the raindrops while the weather >turned sour and tried to rain on it, but it turned out well. > >Talked to the FAA today about arranging for an inspection only to find >that our local FSDO doesn't do inspections any more. Instead they have >inspections contracted out to retired FAA people. Cost is $150, but the >guy is willing to come inspect the plane on a day or two's notice. When >I asked if he wanted me to start my taxi testing before he inspected it, >he said he didn't care if I flew it first as long as I stay over the >runway and lift off and set it down in a straight line. > >Hope to move it to the airport in about a week and be flying in another >week or two. > >---- >Jeffrey Scott jscott.pilot@juno.com >See construction of KR-2S N1213W at >http://fly.hiwaay.net/~langford/kjeffs.html >---- > > ------------------------------ Date: Mon, 19 May 1997 20:15:56 -0700 From: Micheal Mims Subject: Re: KR: Re: VW Revs and Props At 10:05 PM 5/19/97 -0400, you wrote: >Larry Jacks wrote: >> 4300 47.5 >> 4400 46.5 >> These numbers may not be exactly correct, but they should get you in >> the ballpark. > > Well, I got bored and did the same thing as larry. I double checked, >and my numbers area still high. I did mine in a spreadsheet and then >charted it out. I'll post it if anyone's interested in seeing it. It's >not that darn amazing anyway. Vince your numbers are right if you want 100% of mach. Larry was only spinning up to 80% of mach. (in still air) FYI a C-185 is in the 92% of mach at take-off! Don't limit yourself to 80% for take off Cessna doesn't! :-) _______________________ ~~~~~~~~~~~~~~~~~~~~~~ Micheal Mims Just Plane Nutts mailto:mimsmand@ix.netcom.com http://www.netcom.com/~mimsmand ------------------------------ Date: Mon, 19 May 1997 20:22:43 -0700 From: Micheal Mims Subject: KR: SOOB: dd vendors and RPM! Heres something I posted one night on the Soob list, anyway it got a lot of brain cells circulating and I couldn't remember if I posted it on the KR net. If I did I apologize and If you sell reduction drives I apologize! :-) >At 04:22 PM 5/16/97 -0400, you wrote: > >> Well, I said I wasn't trying to talk anyone into accepting >>what I'm doing regarding direct drive with the EA-81, but I just want to say >>I really think we're trying to complicate something that is dirt simple. Talk >>to the gyro guys. They were running these things direct drive years before us >>fixed wing guys even considered auto power. It works. Don't try to fix it. >>Why add the weight and complexity, not to mention the expense? >> >> Marty Hammersmith > > Not that it matters much but, I think Marty is absolutely correct! People have been there and done that so why reinvent? The Dragonfly guys are all running direct drive and I think as soon as a DD Soob powered KR2S hits the skies, eyes will really open wide in that arena! Spin that 60 inch prop up to 3600 or 3700 rpm! I think we are being way to conservative with propeller RPM! Just for kicks I did some number crunching last night on a few production built aircraft to try and find if there was anything that higher performance aircraft had in common regardless of propeller size. I know you have heard me argue that the KR seems to do better with a small propeller turning faster, and its a fact, they do but why? Well the one common factor I found was the tip speed (or propeller velocity in general) of the propeller at max rated HP! They were all in the 700mph+ range. That's getting pretty close to the speed of sound boys and girls and we in the homebuilt arena seem to think that's a big no no! Why? The big boys do it! A C-185 with the long float plane prop reaches velocities of 720mph at full power! Now I know someone out there is gona say "Well what about the Rare Bear, it has a 15 foot prop and turns only 1100rpm" well do the math my friend, guess what the propeller velocity ends up at that rpm? You guessed it! Pretty close to 700mph! Until we can get someone to actually design a "state of the art" propeller for us little guys, we have to work with what we have. I decided to call the prop velocity "percentage of mach" (for lack of an engineering term, I aint no engineer) for comparisons. It seems that most production planes (that have any performance to speak of)end up with a prop velocity in the 92%+ range for take off and 70 to 75% range for cruise. So what does this mean to us? I don't know, probably nothing! I could be totally wrong and just rambling! As I stated above, I aint no engineer but I love to do research and compile data, I guess this is the non-engineer way of figuring out what will work and what wont! Another interesting note, a Soob with a 1.85 to 1 reduction and a 65 inch propeller only has a prop velocity of 65% of mach at take-off power. that's assuming the engine RPM is 5500 (and it must be at least that to get the claimed HP) and prop rpm is 2900 or so. A 65 inch prop needs to spin at 3666rpm to fall into line with the F4U, C-185, A-36 etc.. Are we turning these props too slow? Another issue we face is not having the ability to control the pitch while inflight (unless you have the Ivo prop) so we have to come up with happy medium of cruise and take off pitch settings. I don't have the answers just the data! Floating in Cyberspace with my flame proof underwear on! _______________________ ~~~~~~~~~~~~~~~~~~~~~~ Micheal Mims Just Plane Nutts mailto:mimsmand@ix.netcom.com http://www.netcom.com/~mimsmand ------------------------------ Date: Tue, 20 May 1997 00:30:05 -0400 (EDT) From: EagleGator@aol.com Subject: KR: KR-2S Test Plan Proposal I'd like to ask everyone if it's ok to rename the test plan I'm working on from "Junkman's KR-2S Test Plan" to "KRNet KR-2S Test Plan". At the rate it's shaping up, it could be a good vehicle to promote the KRNet and KR's in general. If I can get folks to take some ownership in this thing, hopefully everyone will contribute something and we can get ourselves a very robust end product for everyone to use, or at least reference. I'll serve as the editor for the plan, so everyone could send their inputs to me for inclusion (with proper credit for the contribution, of course!). There could possibly be some liability questions if someone were to use our plan to conduct their test program, and then bust their butt for one reason or another, which is why I'm asking the membership and the administrator if it's ok to include the KRNet reference in the title. I'll add a disclaimer and whatever other legalese is required. By the way, I don't have any heartburn leaving my name on it, if that's more pallatable to everyone. To keep KRNet traffic down, please respond to me directly, unless there is an issue you'd like to make known to everyone. There's no reason to fill everyone's mail box with "It's ok with me" and "Don't you DARE put MY name on that thing!" messages. I'll keep everyone posted on what type of response I get. Thanks for your inputs. Cheers! Rick Junkin EagleGator@aol.com ------------------------------ Date: Tue, 20 May 1997 01:43:03 -0400 (EDT) From: MikeTnyc@aol.com Subject: KR: Re: VW Revs and Props > Well, heres the formula, followed by what I came up with. . . . >50 4987 >51 4889 >52 4795 >53 4705 >54 4618 * * * >71 3512 >72 3463 >73 3416 >74 3370 >75 3325 >76 3281 >77 3238 Wait a minute here: isn't the typical KR prop still 52"? According to this chart, a VW can swing as big as 73" without going supersonic at 3400 RPM, not much different from the 70-75" used on a Cessna 140 with 85hp Continental. So why aren't larger props being used? 52" may have been the limit for the retract gear, but I would think a larger one would be desirable on the fixed gear without coming dangerously close to the ground. Mike Taglieri ------------------------------ Date: Tue, 20 May 1997 00:54:16 -0700 From: Ross Youngblood Subject: Re: KR: Re: VW Revs and Props MikeTnyc@aol.com wrote: > So why aren't larger props being used? 52" may have been the limit for > the retract gear, but I would think a larger one would be desirable on the > fixed gear without coming dangerously close to the ground. > > Mike Taglieri My guess would be ground clearance. The retract gear is a bit short. I just lifted the tail up a bit in the driveway and scratched my new prop... . -- Ross - -- Ross Youngblood KRNET-L administrator mailto:rossy@teleport.com http://www.teleport.com/~rossy/N541RY.htm ------------------------------ Date: Tue, 20 May 1997 07:23:19 -0400 (EDT) From: Baleco@aol.com Subject: Re: KR: Re: HIGH RPM was (Shadbolt Cam Grinders/PC Dyno) In a message dated 97-05-19 22:20:42 EDT, you write: << Curt Martin shows a 1918cc VW putting out 98hp @ 4000rpm in his > PC............. >> Those were not necessarily accurate numbers. He was demonstrating a comparison between two different cam profiles. A stroked VW is simply not gonna be happy at 4000rpm. I've had two 2180's now and neither of them seemed comfortable at 3600. I don't want to be flying behind them at 4000. If you were to spin up an 1835 to 4000rpm which used to be done you'd get maybe 70-75hp but not a long engine life. Since you can get similar hp from the slower turning 2180, why turn up the 1835? Marty Hammersmith ------------------------------ Date: Tue, 20 May 1997 07:27:22 -0400 (EDT) From: Baleco@aol.com Subject: Re: KR: VW Revs and Props In a message dated 97-05-19 22:37:27 EDT, you write: << It is now time for all the people with alot more engineering than me to respond to the RPM vs prop length issue. >> I think when you boil it all down, you're looking for a compromise between engine power and durability. Select the prop diameter and pitch that allows you to run the engine in that rpm range to provide the best rate of climb or cruise-again a compromise. Marty ------------------------------ Date: Tue, 20 May 1997 11:56:53 -0400 From: smithr Subject: KR: Limbach I've been trying to find out about how Limbach has modified the VW to get it certified. Does anyone have any info. on this or a US or European contact address (email, phone or other) for Limbach. I assume Limbach is still in business. Bob Smith ------------------------------ Date: Tue, 20 May 1997 12:58:13 -0400 (EDT) From: Baleco@aol.com Subject: Re: KR: Limbach In a message dated 97-05-20 12:48:31 EDT, you write: << I've been trying to find out about how Limbach has modified the VW to get it certified. Does anyone have any info. on this or a US or European contact address (email, phone or other) for Limbach. I assume Limbach is still in business. >> Well, technically the Limbach is it's own engine. I don't think they're using brazilian VW cases, etc. It is a copy of the VW even if it's components are not of VW OEM manufacture. The last one I looked at was at Osh last '95 and it had aluminum finned cylinders. I'd love to get ahold of a set of those in 92mm! Marty ------------------------------ Date: Tue, 20 May 1997 17:00:45 -0600 From: "Larry Jacks" Subject: KR: Re: Re: VW Revs and Props Two things to consider when you're looking at tip speed: 1. Most production planes use metal props. They are more efficient (and thinner) than wood props. The composite props may be a different story. 2. Don't just consider the still air speed when you're looking at tip speed. Your aircraft is moving at considerable speed at max power (you have to consider the worst case) and that airspeed is a factor in tip speed as well. - ---------- > From: MikeTnyc@aol.com > To: krnet-l@teleport.com > Subject: KR: Re: VW Revs and Props > Date: Monday, May 19, 1997 11:43 PM > > > Well, heres the formula, followed by what I came up with. . . . > > >50 4987 > >51 4889 > >52 4795 > >53 4705 > >54 4618 > > * * * > >71 3512 > >72 3463 > >73 3416 > >74 3370 > >75 3325 > >76 3281 > >77 3238 > > Wait a minute here: isn't the typical KR prop still 52"? According to this > chart, a VW can swing as big as 73" without going supersonic at 3400 RPM, not > much different from the 70-75" used on a Cessna 140 with 85hp Continental. > So why aren't larger props being used? 52" may have been the limit for > the retract gear, but I would think a larger one would be desirable on the > fixed gear without coming dangerously close to the ground. > > Mike Taglieri ------------------------------ Date: Tue, 20 May 1997 20:07:26 -0400 From: Vince Bozik Subject: Re: KR: Re: Re: VW Revs and Props > 2. Don't just consider the still air speed when you're looking at tip > speed. Your aircraft is moving at considerable speed at max power (you have > to consider the worst case) and that airspeed is a factor in tip speed as > well. Anyone got a formula for that? I don't know anything about vectoring, or whatever kind the heck kind of equation it would take to figure this one out. Yea, at least I can apply sixth grade math! Considering most don't know what the airspeed is @ a given RPM, I guess that it would all be hypothetical, unless you took a notepad with you next time you were up. If anyones got an equation for the tip velocity with airspeed, I could probably make a chart or something. The information for each diameter would be very broad, because it would have to consider in airspeed. When I did the figures for RPM's, I'd considered doing them @ 80%, but thought it was fine left alone. After all, a calculator and two seconds can get you the desired answer. If anyone knows of an equation, send it over! I realize you guys probably really don't care, but I find it interesting just to look at the outcome. Cheers, Vince "getting a hat with a little prop on top" Bozik - -- Vince Bozik - Athens, Georgia Mailto:ICBM@ix.netcom.com ------------------------------ Date: Tue, 20 May 1997 22:39:41 -0400 From: Carlos Sa Subject: KR: VW Revs and Props <<<<<<<<<<<<<<<< > 2. Don't just consider the still air speed when you're looking at tip > speed. Your aircraft is moving at considerable speed at max power (you have > to consider the worst case) and that airspeed is a factor in tip speed as > well. Anyone got a formula for that? I don't know anything about vectoring, or whatever kind the heck kind of equation it would take to figure this one out. Yea, at least I can apply sixth grade math! >>>>>>>>>>>>>>> Hello, Vince I think you have to do a vector sum: Vt = SQRT (Vf + Vr) where Vt = velocity of tip (total) Vf = velocity forward (aircraft's) Vr = velocity of tip due to rotation and Vr = 2*3.14159*R*f, with R = prop radius and f = frequency (rotations per unit of time) thus, Vt = SQRT (Vf + 2 * 3.14159 * R * f) Me thinks. Now I leave it up to you to make sure the values belong to the same measuring system (piece of cake if you use metric :o))) i.e., if speed is given in metres/sec, then R = metres, f = rps. Have fun... Carlos ------------------------------ Date: Wed, 21 May 1997 00:59:50 -0400 (EDT) From: Wcktpckt@aol.com Subject: Re: KR: VW Revs and Props My undersanding of props relates to axcial flow fans. The determination of the optimum fan or prop effeciency is based on the manufacturer's curves for the prop (or the fan). Should'nt the most efficient speed, horsepower and rpm be based upon the curves which should have details on air density, corrections for altitude etc, so that the user is able to determine the optimum operating range of the prop? Also in axial flow fans there is 1st, 2nd and 3rd degree of harmonic frequencies that the prop will go through? And the prop should not be operated in? The fans I am used to dealing with have a maximum tip speed of 12000 FPM and although props may have something signifigantly different, I think there are some "Fan Laws" or if you will "Prop Laws" that are known and would allow the user or selector of a prop to determine the optimum prop for the engine configuration?? Aren't there curves available for the user to review to make the proper selection? Let me know your thoughts. Regards, Steve Pickett - Hopefull KR2S future owner builder ------------------------------ Date: Wed, 21 May 1997 04:30:51 -0400 From: "Jim Fields" Subject: KR: 1/2 Mazda Package Available KRNetters, Interested in the 100 HP 1/2 Mazda that weighs 102 lbs? All that's needed is to send me a self-addressed, stamped envelope to the address listed below. Inturn, I'll send you a copy of the free information package that I so graceously received from Alturair. For those "Doubting Thomas' " out there, it may be worth wasting a stamp just to see the data. It really is impressive and includes some very helpful information. And the address is... SKYTECH Innovations, Inc. Chief Cook & Bottle Washing Dept. 3167 Woodsboro NE Grand Rapids, MI 49505 - ---------------------------------------------------------------------------- - --------------------------------------------------------------------------- NOTE: This free offer in no way implies an endorsement of any kind for the aforemented product by SKYTECH Innovations, Inc. nor is there any, written, verbal or subliminal message intended. - ---------------------------------------------------------------------------- - --------------------------------------------------------------------------- Take care, Jim SKYTECH Innovations, Inc. Mail To: skytech@iserv.net ------------------------------ Date: Tue, 20 May 1997 14:32:55 -0700 From: Donald Reid Subject: Re: KR: VW Revs and Props Following up on the thread with some more geek engineering: The ideal diameter for a prop can be found using the following equation: DIA = 360 * [H.P. / (N^2 * V)] ^ 0.25 (the ^2 means N * N, ^0.25 means the quantity raised to the 1/4 power) With N in RPM, V in feet/sec, and H.P. in horsepower, then the result is feet. This equation is found in many aero reference books. Assuming 75 hp, 3600 RPM, and 180 mph = 264 ft/sec, then the diameter would be 4.38 feet, or 52.5 inches The rotational velocity of the tip is then approximately 523 mph, plus the vector addition of the forward velocity. With the ideal diameter calculated, and using a set of graphs published in the March 1997 issue of Sport Aviation, you come up with a theoretical prop efficiency of 87%. This is just about as good as you can get from a two bladed, conventional prop. That is why a relatively fast VW powered A/C will use a prop in the neighborhood of 52 inches long. This is all theory stuff, and it appears that prop design is as much a black art as science. - -- Don Reid donreid@erols.com ------------------------------ Date: Wed, 21 May 1997 10:57:51 -0700 From: Ross Youngblood Subject: KR: KRNET ARCHIVES & NEWSLETTERS I was running out of space at teleport >10Mb, and getting nasty messages that my account would be disabled if I didn't do ..somthing.. So for the moment, I have pulled the KRNET archives from my webpage and will be temporarily pulling the krnet digests from the majordomo area, cleaning them up, then replacing them. I also may be removing the KRONLINE back issues as these compressed word files take up LOTS of space. I think the .html version or the acrobad version might be better. I will try and wait to do this until I have time to get the .html versions installed. We shall see. My #1 priority is to keep the account and therefore KRNET alive. Since Carlos is doing a great job of archiving, I don't think I will do too much other than some minor compressing. You can keep tabs on the digest archives by sending an email to mailto:majordomo@teleport.com with the body text: index krnet-l or index krnet-l-digest You will get an email of all the KRNET digests saved that you can have mailed to you. These are files limited to 40K in size. To get one of the files send another email to mailto:majordomo@teleport.com with the body text: get krnet-l-digest v01.nxx get krnet-l-digest v01.nyy And majordomo will mail you the digests... its pretty simple. (I just deleted all the digests and will be compressing them, so wait a while before trying the index command... there is nothing there right now!) -- Regards Ross - -- Ross Youngblood KRNET-L administrator mailto:rossy@teleport.com http://www.teleport.com/~rossy/N541RY.htm ------------------------------ Date: Wed, 21 May 1997 18:05:33 -0400 (EDT) From: JEHayward@aol.com Subject: Re: KR: Fuel Tank CofG In a message dated 97-05-18 20:53:08 EDT, you write: << The ideal may be tanks in the leading edge of the outboard wing where at least the fuel would be "out there" in a crash and on the CofG anyway (the RV's have this arrangement). I wonder if anyone has put their fuel in the leading edge? I am trying to design a suitable LE wing tank at the moment, any suggestions will be welcome. >> Seems like there was a fellow at the '93 KR fly-in that had a length of 5" PVC pipe installed along the outer wing spars (I think). He claimed 4 gallons per pipe length. I don't know who it was or how it worked out. Jim Hayward ------------------------------ Date: Wed, 21 May 1997 18:18:43 +0000 From: Steve Bennett Subject: Re: KR: Limbach dollars or in this case, marks. sb ------------------------------ Date: Wed, 21 May 1997 18:27:11 +0000 From: Steve Bennett Subject: Re: KR: Fuel Tank CofG I have a pair of leading edge aluminum fuel tanks for sale. each one holds about 6 gallons. steve ------------------------------ Date: Wed, 21 May 1997 17:05:57 -0700 From: Micheal Mims Subject: KR: Rutan Web Site http://www.scaled.com/index.html ________________________________ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Micheal Mims Just Plane Nutts mailto:mimsmand@ix.netcom.com http://www.netcom.com/~mimsmand ------------------------------ Date: Wed, 21 May 1997 20:36:56 -0500 From: Paul Eberhardt Subject: Re: KR: VW Revs and Props Carlos Sa wrote: > > <<<<<<<<<<<<<<<< > > 2. Don't just consider the still air speed when you're looking at tip > > speed. Your aircraft is moving at considerable speed at max power (you have > > to consider the worst case) and that airspeed is a factor in tip speed as > > well. > > Anyone got a formula for that? I don't know anything about vectoring, > or whatever kind the heck kind of equation it would take to figure this > one out. Yea, at least I can apply sixth grade math! > >>>>>>>>>>>>>>> > > Hello, Vince > > I think you have to do a vector sum: > > Vt = SQRT (Vf + Vr) CARLOS! - You're close. Vt = SQRT (Vf^2 + Vr^2) I did the same thing and got: Vt = SQRT[(DIA*pi/(12*5280)*RPM*60)^2 + Vf^2] Where: Vt = mph (tip) DIA = in (prop dia) pi = 3.14159 Vf = mph (plane) > where Vt = velocity of tip (total) > Vf = velocity forward (aircraft's) > Vr = velocity of tip due to rotation > and Vr = 2*3.14159*R*f, > with R = prop radius > and f = frequency (rotations per unit of time) > > thus, Vt = SQRT (Vf + 2 * 3.14159 * R * f) > > Me thinks. Now I leave it up to you to make sure the values belong > to the same measuring system (piece of cake if you use metric :o))) > i.e., if speed is given in metres/sec, then R = metres, f = rps. > > Have fun... > Carlos ------------------------------ Date: Wed, 21 May 1997 20:42:25 -0500 From: Paul Eberhardt Subject: Re: KR: 1/2 Mazda Package Available Saw 'em @ Osh. If I had 8 grand to put into my bird, I'd make it my first chioce. Paul Eberhardt Jim Fields wrote: > > KRNetters, > > Interested in the 100 HP 1/2 Mazda that weighs 102 lbs? All that's needed > is to send me a self-addressed, stamped envelope to the address listed > below. Inturn, I'll send you a copy of the free information package that I > so graceously received from Alturair. For those "Doubting Thomas' " out > there, it may be worth wasting a stamp just to see the data. It really is > impressive and includes some very helpful information. > > And the address is... > > SKYTECH Innovations, Inc. > Chief Cook & Bottle Washing Dept. > 3167 Woodsboro NE > Grand Rapids, MI 49505 > > ---------------------------------------------------------------------------- > --------------------------------------------------------------------------- > NOTE: > This free offer in no way implies an endorsement of any kind for the > aforemented product by SKYTECH Innovations, Inc. nor is there any, written, > verbal or subliminal message intended. > ---------------------------------------------------------------------------- > --------------------------------------------------------------------------- > Take care, > > Jim > SKYTECH Innovations, Inc. > Mail To: skytech@iserv.net ------------------------------ End of krnet-l-digest V1 #20 ****************************