From: KR-net users group digest[SMTP:kr-net@telelists.com] Sent: Wednesday, June 16, 1999 12:20 AM To: kr-net digest recipients Subject: kr-net digest: June 15, 1999 KR-net users group Digest for Tuesday, June 15, 1999. 1. Test pilot 2. Cutting foam 3. prop RPM 4. Re: Cutting foam 5. Re: prop RPM 6. Re: Cutting foam 7. Re: Cutting foam 8. Cutting foam 9. instruments 10. Re: wich belt 11. Re: redrives and prop RPM 12. Re: prop RPM 13. Re: redrives and prop RPM 14. Re: redrives and prop RPM 15. Re: redrives and prop RPM 16. Re: redrives and prop RPM 17. Re: redrives and prop RPM 18. Vortex Generators ---------------------------------------------------------------------- Subject: Test pilot From: Oscar Zuniga Date: Tue, 15 Jun 1999 04:47:49 PDT X-Message-Number: 1 Jeff wrote: >Fly the pattern for landing at 80 mph, over the fence at >70,If he flies a hot approach, the plane will happily >fly right past the runway without ever touching down. Let's see: the runway at Montague is 7500' long. At 70, he will be happily flying over the runway for about 1 min. 15 sec.- which can be a long time if you're wondering how to get the thing down ;o) Oscar Zuniga Medford, OR website at http://www.geocities.com/Pipeline/Dropzone/5610/ _______________________________________________________________ Get Free Email and Do More On The Web. Visit http://www.msn.com ---------------------------------------------------------------------- Subject: Cutting foam From: Oscar Zuniga Date: Tue, 15 Jun 1999 05:02:31 PDT X-Message-Number: 2 Dana wrote: >if you are going to be cutting lengths of foam....... >forget using a blade and straight edge, go for the table saw. >I know it seems like overkill but you end up with perfect cuts. If you have the EAA "Wood" book, one of the articles in there is about how to use a table saw to cut your foam ribs. Basically you make a template out of metal or something else thin and hard, along with a raised guide or fence for the template to follow. For designs with lots of foam ribs (e.g., the M-19) this can speed things up and the saw can follow curves pretty well. The same article and technique describes how to make taper cuts on spars. Again, you have a straight edge for the raised guide or fence to follow. FWIW- I had my first visit from an EAA Tech Counselor over the weekend. Ernie Moreno flew down from Independence (near Salem) with a buddy in Ernie's Tri-Pacer and spent a few hours critiquing my project and helping with tips. I actually got a "good workmanship" comment on the mail-in card. I also finally did a decent-sized layup without a single air bubble or resin-starved area. I'm using the plastic sheeting method to wet out the piece of glass and then transfer the half-sandwich to the already-microed area on the airplane. It works pretty good! No snagging the cloth weave with your squeegee; the plastic lets things slide smoothly into place. I'm learning. Oscar Zuniga Medford, Oregon website at http://www.geocities.com/Pipeline/Dropzone/5610/ _______________________________________________________________ Get Free Email and Do More On The Web. Visit http://www.msn.com ---------------------------------------------------------------------- Subject: prop RPM From: Richard Parker Date: Tue, 15 Jun 1999 05:36:29 PDT X-Message-Number: 3 >velocity. A common thing I have found is that on a good performing >aircraft (certified and eXperimental) the prop tip speed is very close >to supersonic at max power. Usually in the 80% to 90% mach range. What actually happens to the prop once it goes supersonic? Will it self destruct due or just lose efficiency? RP _______________________________________________________________ Get Free Email and Do More On The Web. Visit http://www.msn.com ---------------------------------------------------------------------- Subject: Re: Cutting foam From: Steven Eberhart Date: Tue, 15 Jun 1999 08:49:09 -0500 (CDT) X-Message-Number: 4 On Tue, 15 Jun 1999, Oscar Zuniga wrote: > Dana wrote: > >if you are going to be cutting lengths of foam....... > >forget using a blade and straight edge, go for the table saw. > >I know it seems like overkill but you end up with perfect cuts. > > If you have the EAA "Wood" book, one of the articles in there is about how > to use a table saw to cut your foam ribs. Basically you make a template out > of metal or something else thin and hard, along with a raised guide or fence > for the template to follow. For designs with lots of foam ribs (e.g., the > M-19) this can speed things up and the saw can follow curves pretty well. > > The same article and technique describes how to make taper cuts on spars. > Again, you have a straight edge for the raised guide or fence to follow. > My next project is to make up a foam hotwire band saw. It will have a plywood table with a hotwire extending vertically, strung between a C frame, that will let you, using a cutting fence, slide a raw Dow styrofoam flotation billet log through it to cut it down to usable size slabs. If you have access to an insulation supplier that carries the foam logs, this will give you a cheaper source of foam planks. Steve Eberhart ------------------------------------- http://www.newtech.com/nlf One test is worth a thousand expert opinions but a thousand opinions are easier to get. --plagiarized from an unknown author All information, in any of my aircraft related correspondence, is strictly food for thought and is in no way intended to imply that it is anything more than ideas requiring additional, qualified, engineering analysis. ---------------------------------------------------------------------- Subject: Re: prop RPM From: Tobin Dunham Date: Tue, 15 Jun 1999 07:01:40 PDT X-Message-Number: 5 >What actually happens to the prop once it goes supersonic? Will it self >destruct due or just lose efficiency? >RP It will become VERY noisy due to constant sonic "booms". Has anyone ever seen that old WWII fighter that was designed to run with a supersonic prop? I saw it at an airshow once and it was about the loudest thing I've ever heard. It was kewl though... Anyway, depending on what kind of prop you have, it may or may not self-destruct. Going supersonic puts a lot of stress on the prop. And your efficiency will drop dramatically, because you essentially create little vacuums at your prop tips, meaning the air you are trying to push is actually moving to fill the vacuums instead. Toby Dunham Houston, TX _______________________________________________________________ Get Free Email and Do More On The Web. Visit http://www.msn.com ---------------------------------------------------------------------- Subject: Re: Cutting foam From: "Rick Hubka" Date: Tue, 15 Jun 1999 8:14:8 X-Message-Number: 6 That hot wire band saw is such a great idea Steve. Thanks. I think I may take it one step further though. I built my big table 16' X 4' in 2 sections so that when I'm done the boat stag I could dis-assemble half, but now I'll make the second half into a hot wire table saw complete with a side mount tilting(45 degree) hot wire bow. I'll have time to think about this though. I just finished my 3rd(scraped the first one) boat side and will start skinning/scarfing them with 3/32 av plywood this weekend. Rick Hubka rick@hubka.com Calgary, Alberta, Canada www.hubka.com ---------------------------------------------------------------------- Subject: Re: Cutting foam From: Steven Eberhart Date: Tue, 15 Jun 1999 10:35:36 -0500 (CDT) X-Message-Number: 7 On Tue, 15 Jun 1999, Rick Hubka wrote: > That hot wire band saw is such a great idea Steve. Thanks. > I think I may take it one step further though. > > I built my big table 16' X 4' in 2 sections so that when I'm done the boat > stag I could dis-assemble half, but now I'll make the second half into a > hot wire table saw complete with a side mount tilting(45 degree) hot wire > bow. > > I'll have time to think about this though. I just finished my 3rd(scraped > the first one) boat side and will start skinning/scarfing them with 3/32 av > plywood this weekend. > I am using a powersupply from TEKOA, about $50, that is marketed to model airplane builders. It is rather simple and uses a commercial light dimmer in the primary circuit of a step down transformer with a suitable series power resistor in the secondary. I have been using standard stainless steel safety wire for the cutting wire. Plans are to have a hot wiring demonstration at the Gathering showing how you can hot wire stabilizer/elevator cores. Steve Eberhart ------------------------------------- http://www.newtech.com/nlf One test is worth a thousand expert opinions but a thousand opinions are easier to get. --plagiarized from an unknown author All information, in any of my aircraft related correspondence, is strictly food for thought and is in no way intended to imply that it is anything more than ideas requiring additional, qualified, engineering analysis. ---------------------------------------------------------------------- Subject: Cutting foam From: Richard Parker Date: Tue, 15 Jun 1999 08:52:49 PDT X-Message-Number: 8 >My next project is to make up a foam hotwire band saw. It will have a >plywood table with a hotwire extending vertically, strung between a C >frame, that will let you, using a cutting fence, slide a raw Dow styrofoam >flotation billet log through it to cut it down to usable size slabs. I made a horizontal one similar to a planer as I was doing more cutting in that direction. RP _______________________________________________________________ Get Free Email and Do More On The Web. Visit http://www.msn.com ---------------------------------------------------------------------- Subject: instruments From: donald.norris@natinst.com Date: Tue, 15 Jun 1999 12:40:06 -0500 X-Message-Number: 9 Does anyone know where I can find a 2.25" art. horizon? A web link would be great or email me offline donald.norris@natinst.com Thanks. Donald 38TF ---------------------------------------------------------------------- Subject: Re: wich belt From: "Eduardo Iglesias" Date: Sun, 13 Jun 1999 02:02:43 -0300 X-Message-Number: 10 -----Mensaje original----- De: w.g. kirkland Para: KR-net users group Fecha: Viernes, 11 de Junio de 1999 12:34 a.m. Asunto: [kr-net] Re: wich belt >Eduardo: I think "reductions" uses the trapezoidal teeth because they allow >the air to escape more gradually from the tooth pully interface. With the >round teeth the air is expelled from the pocket very rapidly (supersonic >speeds) thus creating a very noisy belt. It also better approximates the >ideal hypoid gear tooth which is designed to ensure constant speed of the >gears. Check a book on gear design I haven't read one in 40 years. >W.G. KIRKLAND >kirkland@vianet.on.ca > >---------- Dear The weight of the motor is of 105 Kg (some 230 pounds) in flight order (it includes accessories, water, oil, etc.)But I am in treatments with Don Clarke to buy the Subaru EA81 that has smaller weight. What I worry still is the type of teeth that better they work for this use: round or trapezoidal. I donīt know if somebody can have some information, but if the round tooth produces bigger level of noise because it expels the air to supersonic speed, as long as the trapezoidal one is more silent, wich is the one I must use? This last one also transmits bigger power with wide equal. I am again in communication with people of Gates and I wait that this time it can make an order with the security that what they send me is what I need. I donīt know still if I need a type or the other of teeth! Is the circular tooth the one I seen in the reducers and the trapezoidal one transmit more power with smaller noise (why the guys don't use it?) I will thank any information. Cordially Eduardo ---------------------------------------------------------------------- Subject: Re: redrives and prop RPM From: "Tom Andersen" Date: Tue, 15 Jun 1999 21:17:08 -0400 X-Message-Number: 11 Mike, You are so right about this. The other thing people are way to concerned with is getting the max efficiency out of the prop. What good is getting max efficiency if you're not getting decent speed? Did you derive that from the prop tip speed formula? Could you tell me what rpm would result in 95% mach at 200mph on a 52" wood prop at 10,000 msl? Wasn't there a spreadsheet for this calculation available somewhere? -Tom A common thing I have found is that on a good performing >aircraft (certified and eXperimental) the prop tip speed is very close >to supersonic at max power. Usually in the 80% to 90% mach range. With >that in mind a 54 inch prop can turn 3700rpm which is about 80% mach. >Micheal Mims ---------------------------------------------------------------------- Subject: Re: prop RPM From: "Bruce S. Campbell" Date: Tue, 15 Jun 1999 21:32:09 -0400 X-Message-Number: 12 Ok Toby, I'll take a run at this one. Tobin Dunham wrote: > >What actually happens to the prop once it goes supersonic? Will it self > >destruct due or just lose efficiency? > >RP > > It will become VERY noisy due to constant sonic "booms". Has anyone ever > seen that old WWII fighter that was designed to run with a supersonic prop? > I saw it at an airshow once and it was about the loudest thing I've ever > heard. It was kewl though... Or...ever payed attention to a turbo prop? When they are turning within theirrange of efficiency they get louder as they spin faster. They also look like paddle fans :o) > Anyway, depending on what kind of prop you have, it may or may not > self-destruct. Going supersonic puts a lot of stress on the prop. And your > efficiency will drop dramatically, because you essentially create little > vacuums at your prop tips, meaning the air you are trying to push is > actually moving to fill the vacuums instead. Not exactly--because sonic speed is relative to density at standard atmosphere, ie, density at sea level in January over central Alaska vs standard atmosphere density vs density at 30,000' over Texas in July will each result in different sonic speeds, sonic is an estimate. A propellor creates a vortex and subsequent low pressure area near the axis of rotation. The air in the low pressure area is less dense than the surrounding air beyond the prop tips. As the prop spins faster the vortex widens, as well as the low pressure area, and the "bite" is taken closer to the tip of the prop. That's why the paddle fan shape of turboprop tips. They are designed to spin at near sonic (what ever that is) speeds. The noise is caused by the surrounding air moving to lower pressure and colliding with the prop. The prop becomes less efficient as the low pressure area of the vortex spreads beyond the prop tips. It's not really a vacuum. It' a pressure differential. What sonic is, where the prop is spinning, doesn't matter. It's the pressure differential between the center of the vortex and the surrounding air that sets off all the racket. It's the prop tips taking a "bite" in less dense air that decreases efficiency. Bruce S. Campbell Tampa de Florida ---------------------------------------------------------------------- Subject: Re: redrives and prop RPM From: Mike Mims Date: Tue, 15 Jun 1999 20:09:09 -0700 X-Message-Number: 13 Tom Andersen wrote: > > Could you tell me what rpm would result in 95% mach at 200mph on a 52" wood prop at 10,000 msl? Wasn't there a spreadsheet for this calculation available somewhere? > My little formula is only good in still air at sea level. Someone on the KRNet did some calcs and forward airspeed seem to have very little affect. 95% of 720 mph on a 52 inch prop is something like 4500 rpm. Gee this is close to the RPM that the formula one guys (Nemesis, Pushy Galore, etc.) run as well as the coffee brewing turbo charged direct drive Dragonfly from north of the border! :o) I really don't think you want to spin a wood prop that hard. The guys who are doing more than 4000 rpm are using composite props for the most part. Keeping all this in mind don't get caught up thinking that swinging that 65 inch warp drive @ 2500 rpm is "efficient", it not. This is where I could never figure out what good a re-drive is on a plane like the KR. You can only fit a 65 inch prop max and to get the tip speed up where they need to be it needs to turn 3200 to 3400 rpm. With a 1.8 to 1 re-drive that means you engine would have to turn between 5800 and 6100 rpm. With a 2 to 1 re-drive your talking 6800 rpm!! Can you say "pop goes the weasel" ? :o) Also if you decided to cruise your engine at 4500 rpm that means your prop will be loafing at 2500, can you say 110 mph KR? :o) FWIW a C185 with 86 inch float plane prop is at 99% @ max RPM, with the standard 80 inch prop its at 92%. -- zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz Micheal Mims Filling and Sanding again! http://www.geocities.com/CapeCanaveral/Hangar/4136/ http://members.home.com/mikemims/ Aliso Viejo CA ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ---------------------------------------------------------------------- Subject: Re: redrives and prop RPM From: John Bryhan Date: Tue, 15 Jun 1999 21:37:01 -0600 X-Message-Number: 14 --------------EFBC7964D07A297D1B724D93 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit > Also if you decided to cruise your engine at > 4500 rpm that means your prop will be loafing at 2500, can you say 110 > mph KR? :o) > > FWIW a C185 with 86 inch float plane prop is at 99% @ max RPM, with the > standard 80 inch prop its at 92%. On the other hand, a C-85 up here at 7000' maybe making 65 hp turning 2550 rpm with a 60" prop is indicating 140mph --------------EFBC7964D07A297D1B724D93 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit
 Also if you decided to cruise your engine at
4500 rpm that means your prop will be loafing at 2500, can you say 110
mph KR?  :o)

FWIW a C185 with 86 inch float plane prop is at 99% @ max RPM, with the
standard 80 inch prop its at 92%.

On the other hand, a C-85 up here at 7000' maybe making  65 hp turning 2550 rpm
with a 60" prop is indicating 140mph
  --------------EFBC7964D07A297D1B724D93-- ---------------------------------------------------------------------- Subject: Re: redrives and prop RPM From: Mike Mims Date: Tue, 15 Jun 1999 20:43:41 -0700 X-Message-Number: 15 John Bryhan wrote: > > On the other hand, a C-85 up here at 7000' maybe making 65 hp turning > 2550 rpm with a 60" prop is indicating 140mph > Oh come on now John that's because its really making 85 hp where as a EA-81...........:o) -- zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz Micheal Mims Filling and Sanding again! http://www.geocities.com/CapeCanaveral/Hangar/4136/ http://members.home.com/mikemims/ Aliso Viejo CA ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ---------------------------------------------------------------------- Subject: Re: redrives and prop RPM From: jscott.pilot@juno.com Date: Tue, 15 Jun 1999 21:53:20 -0700 X-Message-Number: 16 > >You can only fit a 65 inch prop max and to get the tip speed up where >they need to be it needs to turn 3200 to 3400 rpm. With a 1.8 to 1 >re-drive that means you engine would have to turn between 5800 and 6100 >rpm. With a 2 to 1 re-drive your talking 6800 rpm!! Can you say "pop >goes the weasel" ? :o) Also if you decided to cruise your engine at >4500 rpm that means your prop will be loafing at 2500, can you say 110 >mph KR? :o) > >FWIW a C185 with 86 inch float plane prop is at 99% @ max RPM, with the >standard 80 inch prop its at 92%. > >-- >zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz >Micheal Mims >Filling and Sanding again! >http://www.geocities.com/CapeCanaveral/Hangar/4136/ >http://members.home.com/mikemims/ >Aliso Viejo CA >^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Mike, I've got to disagree with you on this. My C-85 turns my 60 inch prop at 2500 RPM and my KR is definately not a "110 mph KR". Before I had some pitch taken out of the prop for high altitude climb performance, I was getting 160 mph at 2500 rpm and 2500 feet. Now that I have had the pitch trimmed back, it takes 2700 rpm for the same performance at that altitude. At 1100 lbs gross weight, I don't think that is too doggy. Normal cruise at 9500 feet trues up to just over 140 mph. That is flying at 1150 lbs gross and down to 1065 gross at landing due to fuel burn. A shorter prop may not reach the peak efficiency we would all desire, but I think the statement that "a 60 inch prop at 2500 rpm will make at 110 mph KR" is simply untrue. Regards, Jeff Scott - Los Alamos, NM mailto:jscott.pilot@juno.com See N1213w construction and first flight at http://www.thuntek.net/~jeb/krjeff.htm ___________________________________________________________________ Get the Internet just the way you want it. Free software, free e-mail, and free Internet access for a month! Try Juno Web: http://dl.www.juno.com/dynoget/tagj. ---------------------------------------------------------------------- Subject: Re: redrives and prop RPM From: John Bryhan Date: Tue, 15 Jun 1999 22:24:48 -0600 X-Message-Number: 17 > > > Oh come on now John that's because its really making 85 hp where as a > EA-81...........:o) > at sea level 85hp up here? in your dreams. My turbo on the other hand!!! can't wait. :^) ---------------------------------------------------------------------- Subject: Vortex Generators From: "Terry Adair" Date: Tue, 15 Jun 1999 23:25:15 X-Message-Number: 18 Iam interested to know if anyone has used Vortex Generators on a KR2.Art Matson made a cherokee140 go real fast using them,and now sells them for 140s. Any comments? Terry Adair Melbourne--Australia. --- END OF DIGEST --- You are currently subscribed to kr-net as: johnbou@timberline.com To unsubscribe send a blank email to leave-kr-net-17800J@telelists.com