---------------------------------------------------------- Kitfox-List Digest Archive --- Total Messages Posted Thu 12/02/10: 18 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:31 AM - Re: Losing rpm on takeoff (Noel Loveys) 2. 06:22 AM - Re: drilling/tapping fiberglass tank (carlisle) 3. 09:26 AM - Re: Re: drilling/tapping fiberglass tank (Guy Buchanan) 4. 11:43 AM - Re: Losing rpm on takeoff (mikeperkins) 5. 12:10 PM - Re: Re: Losing rpm on takeoff (Lowell Fitt) 6. 01:55 PM - Re: Re: Losing rpm on takeoff (b d) 7. 02:54 PM - Re: Re: Losing rpm on takeoff (Dave G) 8. 02:57 PM - Re: Re: Losing rpm on takeoff (Dave G) 9. 03:01 PM - Re: Losing rpm on takeoff (mikeperkins) 10. 03:43 PM - Re: Re: Losing rpm on takeoff (b d) 11. 03:50 PM - Re: Re: Losing rpm on takeoff (b d) 12. 04:05 PM - drilling/tapping fiberglass tank (rez) 13. 05:34 PM - Re: Re: Losing rpm on takeoff (b d) 14. 10:47 PM - Re: Re: Losing rpm on takeoff (Guy Buchanan) 15. 10:54 PM - Re: drilling/tapping fiberglass tank (Guy Buchanan) 16. 11:19 PM - Re: Re: Losing rpm on takeoff (b d) 17. 11:51 PM - Re: drilling/tapping fiberglass tank (Michael Gibbs) 18. 11:51 PM - Re: Re: Losing rpm on takeoff (Michael Gibbs) ________________________________ Message 1 _____________________________________ Time: 05:31:12 AM PST US From: "Noel Loveys" Subject: RE: Kitfox-List: Losing rpm on takeoff Lynn: The only reason I can see to use the westach is it comes with the kit. (?) I found the tinytach worked really well on the 582. When I get the 9122 going it's anyone's guess. Noel -----Original Message----- From: owner-kitfox-list-server@matronics.com [mailto:owner-kitfox-list-server@matronics.com] On Behalf Of Lynn Matteson Sent: November 30, 2010 11:58 PM Subject: Re: Kitfox-List: Losing rpm on takeoff Noel- I often wonder why anybody would use a Westach....I haven't heard of much in the way of reliability from any of their products. Lynn Matteson Kitfox IV Speedster, taildragger Jabiru 2200, #2062 Sensenich 62"x46" Wood (summer) Electroair direct-fire ignition system Rotec TBI-40 injection Status: flying...1070 hrs (since 3-27-2006) On Nov 30, 2010, at 9:31 PM, Noel Loveys wrote: > I'd doubt the tach too. My plane was doing almost the same thing > as yours and one day I had an ivo set for a go around and after an > hour on the ground firewalled the throttle for a takeoff. Imagine > my surprise when the plane leapt into the air and the tach > spiralled up to the wrong side of seven grand, make that the low > side of 8 grand! I got a Tiny Tach and quickly found my Westach > read a consistent 20% too high. > > > I often wonder how I was ever able to get the plane into the air > with a true take off rpm of around 5400 rpm. > > > Noel ________________________________ Message 2 _____________________________________ Time: 06:22:57 AM PST US Subject: Kitfox-List: Re: drilling/tapping fiberglass tank From: "carlisle" Thanks Lynn...Sounds like my fiberglass boat repair, which contains a sheet of fiberglass cloth and some epoxy resin might do the trick. Chris Read this topic online here: http://forums.matronics.com/viewtopic.php?p=322048#322048 ________________________________ Message 3 _____________________________________ Time: 09:26:26 AM PST US From: Guy Buchanan Subject: Re: Kitfox-List: Re: drilling/tapping fiberglass tank On 12/1/2010 8:46 PM, Lynn Matteson wrote: > I roughed up the surface with coarse sandpaper, then added about > 1/4"-3/8" thickness of fiberglass, using fiberglass mat and > resin/hardener. I did the same thing with 1/4" G-10, which is pre-made fiberglass plate available from most plastics houses, locally or on-line. Make sure you rough everything well and epoxy it in place. Use at least 1 1/4" diameter pad. Guy Buchanan Kitfox IV-1200 / 582-C / Warp 3cs / 500 hours ________________________________ Message 4 _____________________________________ Time: 11:43:42 AM PST US Subject: Kitfox-List: Re: Losing rpm on takeoff From: "mikeperkins" I have never heard a discussion involving aircraft props that mentions cavitation, stirring air, humidity, or higher RPM during a static run-up. If you have some references, please let me know. A prop during a static run-up experiences a higher angle-of-attack than a prop moving forward through air. The higher AOA produces more drag, thus more load on the engine, and thus a lower RPM for a given power setting, not higher RPM. Some very high-performance aircraft with fixed-pitch props (long time ago) produced so little prop thrust (blade lift) during a static run-up that they had to be pushed to get them rolling - the prop was stalled. Once rolling, the AOA would gradually decrease and thrust (lift) would increase because the prop was un-stalling. A properly set-up Rotax 2-stroke will produce 5800 to 6200 on a static run-up (temp dependent), and max RPM of 6600 while climbing at Vx. I would not be looking at the prop pitch for this particular problem. Mike Read this topic online here: http://forums.matronics.com/viewtopic.php?p=322085#322085 ________________________________ Message 5 _____________________________________ Time: 12:10:44 PM PST US From: "Lowell Fitt" Subject: Re: Kitfox-List: Re: Losing rpm on takeoff Mike, I think you answered your own question. Just substitute stalled prop for cavitating prop. I think the concept is the same In each case the prop is pitched too high for conditions. Lowell -------------------------------------------------- From: "mikeperkins" Sent: Thursday, December 02, 2010 11:41 AM Subject: Kitfox-List: Re: Losing rpm on takeoff > > > I have never heard a discussion involving aircraft props that mentions > cavitation, stirring air, humidity, or higher RPM during a static run-up. > If you have some references, please let me know. > > A prop during a static run-up experiences a higher angle-of-attack than a > prop moving forward through air. The higher AOA produces more drag, thus > more load on the engine, and thus a lower RPM for a given power setting, > not higher RPM. > > Some very high-performance aircraft with fixed-pitch props (long time ago) > produced so little prop thrust (blade lift) during a static run-up that > they had to be pushed to get them rolling - the prop was stalled. Once > rolling, the AOA would gradually decrease and thrust (lift) would increase > because the prop was un-stalling. > > A properly set-up Rotax 2-stroke will produce 5800 to 6200 on a static > run-up (temp dependent), and max RPM of 6600 while climbing at Vx. > > I would not be looking at the prop pitch for this particular problem. > > Mike > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=322085#322085 > > > ________________________________ Message 6 _____________________________________ Time: 01:55:28 PM PST US Subject: Re: Kitfox-List: Re: Losing rpm on takeoff From: b d Yes, it's semantics, with a prop in a liquid (a hydrofoil) it's called cavitation and with an prop in air (an airfoil), it's called a stall but essentially the same-o same-o. We all know what is meant, we just have to be tolerent of each others linguistics. To be technical I really don't believe there is such a word as "un-stalling". It's either stalled or not stalled but correct me if I'm wrong. But I do not what you mean and what your getting at, it's like coming out of a stall condition. Bruce On Thu, Dec 2, 2010 at 12:08 PM, Lowell Fitt wrote: > > Mike, > > I think you answered your own question. Just substitute stalled prop for > cavitating prop. I think the concept is the same In each case the prop is > pitched too high for conditions. > > Lowell > > -------------------------------------------------- > From: "mikeperkins" > Sent: Thursday, December 02, 2010 11:41 AM > To: > Subject: Kitfox-List: Re: Losing rpm on takeoff > > >> michael.perkins@rauland.com> >> >> I have never heard a discussion involving aircraft props that mentions >> cavitation, stirring air, humidity, or higher RPM during a static run-up. If >> you have some references, please let me know. >> >> A prop during a static run-up experiences a higher angle-of-attack than a >> prop moving forward through air. The higher AOA produces more drag, thus >> more load on the engine, and thus a lower RPM for a given power setting, not >> higher RPM. >> >> Some very high-performance aircraft with fixed-pitch props (long time ago) >> produced so little prop thrust (blade lift) during a static run-up that they >> had to be pushed to get them rolling - the prop was stalled. Once rolling, >> the AOA would gradually decrease and thrust (lift) would increase because >> the prop was un-stalling. >> >> A properly set-up Rotax 2-stroke will produce 5800 to 6200 on a static >> run-up (temp dependent), and max RPM of 6600 while climbing at Vx. >> >> I would not be looking at the prop pitch for this particular problem. >> >> Mike >> >> >> >> >> Read this topic online here: >> >> http://forums.matronics.com/viewtopic.php?p=322085#322085 >> >> >> >> >> >> >> >> >> >> >> > > ________________________________ Message 7 _____________________________________ Time: 02:54:06 PM PST US From: "Dave G" Subject: Re: Kitfox-List: Re: Losing rpm on takeoff I have received enough email to establish a plan of action here. Despite the fact that reducing pitch WILL result in an overspend situation with my particular experimental installation, I will reduce the pitch and see what happens during high speed taxi and then climb. Many people actually using Warp props tell me that I achieve the results I am looking for. I understand it is counter-intuitive, but apparently it is at least somewhat common. I have a couple of theories, but for now I'll accept positive results and remain in doubt about the actual reason. Over a long work life I've had to do that on many occasions, because results are what really matters. Thanks to Guy, Lucien and those who contributed positive and helpful advice off list. To those who offered unhelpful advice and lectures, thanks for the efforts. It all reminds me of a saying a friend repeats from time to time. "In theory, theory and practice are the same; in practice they are quite different!" This may be one of those cases. Dave Goddard KF IV 1050 / 582 / Warp ----- Original Message ----- From: b d To: kitfox-list@matronics.com Sent: Thursday, December 02, 2010 5:52 PM Subject: Re: Kitfox-List: Re: Losing rpm on takeoff Yes, it's semantics, with a prop in a liquid (a hydrofoil) it's called cavitation and with an prop in air (an airfoil), it's called a stall but essentially the same-o same-o. We all know what is meant, we just have to be tolerent of each others linguistics. To be technical I really don't believe there is such a word as "un-stalling". It's either stalled or not stalled but correct me if I'm wrong. But I do not what you mean and what your getting at, it's like coming out of a stall condition. Bruce On Thu, Dec 2, 2010 at 12:08 PM, Lowell Fitt wrote: Mike, I think you answered your own question. Just substitute stalled prop for cavitating prop. I think the concept is the same In each case the prop is pitched too high for conditions. Lowell -------------------------------------------------- From: "mikeperkins" Sent: Thursday, December 02, 2010 11:41 AM To: Subject: Kitfox-List: Re: Losing rpm on takeoff I have never heard a discussion involving aircraft props that mentions cavitation, stirring air, humidity, or higher RPM during a static run-up. If you have some references, please let me know. A prop during a static run-up experiences a higher angle-of-attack than a prop moving forward through air. The higher AOA produces more drag, thus more load on the engine, and thus a lower RPM for a given power setting, not higher RPM. Some very high-performance aircraft with fixed-pitch props (long time ago) produced so little prop thrust (blade lift) during a static run-up that they had to be pushed to get them rolling - the prop was stalled. Once rolling, the AOA would gradually decrease and thrust (lift) would increase because the prop was un-stalling. A properly set-up Rotax 2-stroke will produce 5800 to 6200 on a static run-up (temp dependent), and max RPM of 6600 while climbing at Vx. I would not be looking at the prop pitch for this particular problem. Mike Read this topic online here: http://forums.matronics.com/viewtopic.php?p=322085#322085 m/" target="_blank">www.aeroelectric.com omebuiltHELP www.homebuilthelp.com http:/r generous support! ronics List Features Navigator to browse s.com/Navigator?Kitfox-List" target="_blank">http://www.matronics.com/Navigator?Kitfox-List ronics.com/" target="_blank">http://forums.matronics.com ============= ________________________________ Message 8 _____________________________________ Time: 02:57:00 PM PST US From: "Dave G" Subject: Re: Kitfox-List: Re: Losing rpm on takeoff Yes that should be overspeed or over-rev, although either one could lead to overspend so I guess it works. ----- Original Message ----- From: Dave G To: rotaxengines-list@matronics.com ; kitfox-list@matronics.com Sent: Thursday, December 02, 2010 6:51 PM Subject: Re: Kitfox-List: Re: Losing rpm on takeoff I have received enough email to establish a plan of action here. Despite the fact that reducing pitch WILL result in an overspend situation with my particular experimental installation, I will reduce the pitch and see what happens during high speed taxi and then climb. Many people actually using Warp props tell me that I achieve the results I am looking for. I understand it is counter-intuitive, but apparently it is at least somewhat common. I have a couple of theories, but for now I'll accept positive results and remain in doubt about the actual reason. Over a long work life I've had to do that on many occasions, because results are what really matters. Thanks to Guy, Lucien and those who contributed positive and helpful advice off list. To those who offered unhelpful advice and lectures, thanks for the efforts. It all reminds me of a saying a friend repeats from time to time. "In theory, theory and practice are the same; in practice they are quite different!" This may be one of those cases. Dave Goddard KF IV 1050 / 582 / Warp ----- Original Message ----- From: b d To: kitfox-list@matronics.com Sent: Thursday, December 02, 2010 5:52 PM Subject: Re: Kitfox-List: Re: Losing rpm on takeoff Yes, it's semantics, with a prop in a liquid (a hydrofoil) it's called cavitation and with an prop in air (an airfoil), it's called a stall but essentially the same-o same-o. We all know what is meant, we just have to be tolerent of each others linguistics. To be technical I really don't believe there is such a word as "un-stalling". It's either stalled or not stalled but correct me if I'm wrong. But I do not what you mean and what your getting at, it's like coming out of a stall condition. Bruce On Thu, Dec 2, 2010 at 12:08 PM, Lowell Fitt wrote: Mike, I think you answered your own question. Just substitute stalled prop for cavitating prop. I think the concept is the same In each case the prop is pitched too high for conditions. Lowell -------------------------------------------------- From: "mikeperkins" Sent: Thursday, December 02, 2010 11:41 AM To: Subject: Kitfox-List: Re: Losing rpm on takeoff I have never heard a discussion involving aircraft props that mentions cavitation, stirring air, humidity, or higher RPM during a static run-up. If you have some references, please let me know. A prop during a static run-up experiences a higher angle-of-attack than a prop moving forward through air. The higher AOA produces more drag, thus more load on the engine, and thus a lower RPM for a given power setting, not higher RPM. Some very high-performance aircraft with fixed-pitch props (long time ago) produced so little prop thrust (blade lift) during a static run-up that they had to be pushed to get them rolling - the prop was stalled. Once rolling, the AOA would gradually decrease and thrust (lift) would increase because the prop was un-stalling. A properly set-up Rotax 2-stroke will produce 5800 to 6200 on a static run-up (temp dependent), and max RPM of 6600 while climbing at Vx. I would not be looking at the prop pitch for this particular problem. Mike Read this topic online here: http://forums.matronics.com/viewtopic.php?p=322085#322085 m/" target="_blank">www.aeroelectric.com omebuiltHELP www.homebuilthelp.com http:/r generous support! ronics List Features Navigator to browse s.com/Navigator?Kitfox-List" target="_blank">http://www.matronics.com/Navigator?Kitfox-List ronics.com/" target="_blank">http://forums.matronics.com ============= ________________________________ Message 9 _____________________________________ Time: 03:01:53 PM PST US Subject: Kitfox-List: Re: Losing rpm on takeoff From: "mikeperkins" I'm not sure, but I think the drag on the prop airfoil would decrease as airspeed went from 0 to climb. Then RPM should go up somewhat, not down, as airspeed increased. Would that be right? Read this topic online here: http://forums.matronics.com/viewtopic.php?p=322107#322107 ________________________________ Message 10 ____________________________________ Time: 03:43:10 PM PST US Subject: Re: Kitfox-List: Re: Losing rpm on takeoff From: b d I don't know if you're asking me or anyone, but as speed increases, engine RPM increases just like a car. If your climbing, your speed decreases and so does your rpm. This is because your prop is essentially one and the same with the air. When you are descending or diving your speed increases as well as your rpm. Regarding sitting still on the ground (static or stationary), the prop does lose efficiency because of stalling at higher rpms and typically doesn't move as much air. (the prop is not one with the air as when it's in motion) At that time the prop may stall or cavitate just as a boat prop does in the water. We can see a hydrofoil cavitate but we can't see an airfoil stall) This means that the air rather than be driven through the prop as does a fan, the air begins to rotate with the prop (stalled blades due to high angle of attack) thereby allowing the engine to run faster but exerting less power. Once the plane begins moving, the prop then becomes more efficient, the angle of attack from the prop to the relative air/wind becomes less, the efficiency increases thus making the prop more efficient thereby changing from a stalled blade to a non-stalled blade. Does any of that make any sense? I'm trying to explain it in comparable terms between a hydrofoil and an airfoil terminology. The thing is to understand that when the difference between the prop and the forward airspeed becomes less, the lesser angle of attack and the more efficient the airfoil. Of course we have not discussed the variable angle of attack found on a prop where the angle is great towards the prop shaft than it is towards the tip. That's another topic for another discussion and it does play a part in the big picture. For the discussion we are only talking about a mean section of the prop. I hope I didn't just confuse it even more. Sorry if I did. :-) Bruce On Thu, Dec 2, 2010 at 2:59 PM, mikeperkins wrote: > michael.perkins@rauland.com> > > I'm not sure, but I think the drag on the prop airfoil would decrease as > airspeed went from 0 to climb. Then RPM should go up somewhat, not down, as > airspeed increased. Would that be right? > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=322107#322107 > > ________________________________ Message 11 ____________________________________ Time: 03:50:44 PM PST US Subject: Re: Kitfox-List: Re: Losing rpm on takeoff From: b d Dave Results is truly the main issue, no matter how you get them. If you want to try to understand it later, take a ride in a certified plane with a constant speed prop AKA variable pitch prop preferably hydraulic or electric actuated as opposed to fly-weighted. Then you can adjust it on the ground to see the effect or pitch. Then do it again in flight in acsending and descending conditions. Now this prop is not like one found on the ultralites. Some ultralite props can warp by design to achieve different effects that a constant speed solid metal prop won't do so there is some difference. Bruce On Thu, Dec 2, 2010 at 2:51 PM, Dave G wrote: > I have received enough email to establish a plan of action here. Despite > the fact that reducing pitch WILL result in an overspend situation with my > particular experimental installation, I will reduce the pitch and see what > happens during high speed taxi and then climb. Many people actually using > Warp props tell me that I achieve the results I am looking for. > > I understand it is counter-intuitive, but apparently it is at least > somewhat common. I have a couple of theories, but for now I'll accept > positive results and remain in doubt about the actual reason. Over a long > work life I've had to do that on many occasions, because results are what > really matters. > > Thanks to Guy, Lucien and those who contributed positive and helpful advice > off list. To those who offered unhelpful advice and lectures, thanks for the > efforts. It all reminds me of a saying a friend repeats from time to time. > > "In theory, theory and practice are the same; in practice they are quite > different!" This may be one of those cases. > > Dave Goddard > KF IV 1050 / 582 / Warp > > ----- Original Message ----- > *From:* b d > *To:* kitfox-list@matronics.com > *Sent:* Thursday, December 02, 2010 5:52 PM > *Subject:* Re: Kitfox-List: Re: Losing rpm on takeoff > > Yes, it's semantics, with a prop in a liquid (a hydrofoil) it's called > cavitation and with an prop in air (an airfoil), it's called a stall but > essentially the same-o same-o. We all know what is meant, we just have to > be tolerent of each others linguistics. To be technical I really don't > believe there is such a word as "un-stalling". It's either stalled or not > stalled but correct me if I'm wrong. But I do not what you mean and what > your getting at, it's like coming out of a stall condition. > > Bruce > > > On Thu, Dec 2, 2010 at 12:08 PM, Lowell Fitt wrote: > >> >> Mike, >> >> I think you answered your own question. Just substitute stalled prop for >> cavitating prop. I think the concept is the same In each case the prop is >> pitched too high for conditions. >> >> Lowell >> >> -------------------------------------------------- >> From: "mikeperkins" >> Sent: Thursday, December 02, 2010 11:41 AM >> To: >> Subject: Kitfox-List: Re: Losing rpm on takeoff >> >> >>> michael.perkins@rauland.com> >>> >>> I have never heard a discussion involving aircraft props that mentions >>> cavitation, stirring air, humidity, or higher RPM during a static run-up. If >>> you have some references, please let me know. >>> >>> A prop during a static run-up experiences a higher angle-of-attack than a >>> prop moving forward through air. The higher AOA produces more drag, thus >>> more load on the engine, and thus a lower RPM for a given power setting, not >>> higher RPM. >>> >>> Some very high-performance aircraft with fixed-pitch props (long time >>> ago) produced so little prop thrust (blade lift) during a static run-up that >>> they had to be pushed to get them rolling - the prop was stalled. Once >>> rolling, the AOA would gradually decrease and thrust (lift) would increase >>> because the prop was un-stalling. >>> >>> A properly set-up Rotax 2-stroke will produce 5800 to 6200 on a static >>> run-up (temp dependent), and max RPM of 6600 while climbing at Vx. >>> >>> I would not be looking at the prop pitch for this particular problem. >>> >>> Mike >>> >>> >>> >>> >>> Read this topic online here: >>> >>> http://forums.matronics.com/viewtopic.php?p=322085#322085 >>> >>> >>> m/" target="_blank">www.aeroelectric.com >>> omebuiltHELP www.homebuilthelp.com >>> http:/r generous support! >>> >>> ronics List Features Navigator to browse >>> s.com/Navigator?Kitfox-List" >>> target="_blank">http://www.matronics.com/Navigator?Kitfox-List >>> ronics.com/" target="_blank">http://forums.matronics.com >>> ============= >>> >>> >>> >>> > * > > href="http://www.aeroelectric.com">www.aeroelectric.com > href="http://www.buildersbooks.com">www.buildersbooks.com > href="http://www.homebuilthelp.com">www.homebuilthelp.com > href="http://www.matronics.com/contribution">http://www.matronics.com/chref="http://www.matronics.com/Navigator?Kitfox-List">http://www.matronhref="http://forums.matronics.com">http://forums.matronics.com* > > * > > ________________________________ Message 12 ____________________________________ Time: 04:05:40 PM PST US From: rez Subject: Kitfox-List: drilling/tapping fiberglass tank Fiberglass tanks seem to be one of the really major sources of posts here. My KF2, which I did not build, came to me with aluminum tanks which have never given me any trouble at all. So two questions. 1. In light of all the problems, why does the whole world, it seems like, use fiberglass tanks? 2. Are there any potential problems with aluminum tanks that I should know about? How about steel tanks? I wonder how much weight they would really add over fiberglass. Jim KF2/582/Pahrump ________________________________ Message 13 ____________________________________ Time: 05:34:41 PM PST US Subject: Re: Kitfox-List: Re: Losing rpm on takeoff From: b d Guess what I just ran across . . . a discussion about "prop cavitation on takeoff". An interesting play on terminology again. Thought I would throw this in to confuse the doubting Thomas's even more :-) Bruce http://www.oshkosh365.org/ok365_DiscussionBoardTopic.aspx?id=1235&boardid=147&forumid=520&topicid=5819 *Oshkosh365 Forums* *Ultralight Strip* *Search* *Log In or Register to Create New Topic* *Back To Ultralight Strip* ** ** *Propeller cavitation?* *Posted By:* *[image: David Lacy]* ** *David Lacy* * * *Posted: 11/30/2010 15:15:08 * *Hello every one! I am new to this forum but have read several threads with some great info. I hope someone can help with my issue.* *I purchased a mid 90s Rans S 12 XL with a Rotax 582 and a four blade Warp Drive propeller about a year ago. Between me and my instructor, the plane has about 45 hrs flying time since purchase. The plane and the engine have performed flawlessly.* *The issue occurs during acceleration for take off and occasionally early in climb out. For a very brief moment (about 1 second or less) the engine will over speed (my normal rpm during climb out is~6,300; it jumps to~6,700). * *Or assumption is that the prop is cavitating due to disrupted air flow around the engine and muffler. If anyone has knowledge of this or solutions, I would be grateful. TIA * On Thu, Dec 2, 2010 at 3:48 PM, b d wrote: > Dave > > Results is truly the main issue, no matter how you get them. If you want to > try to understand it later, take a ride in a certified plane with a constant > speed prop AKA variable pitch prop preferably hydraulic or electric actuated > as opposed to fly-weighted. Then you can adjust it on the ground to see the > effect or pitch. Then do it again in flight in acsending and descending > conditions. Now this prop is not like one found on the ultralites. Some > ultralite props can warp by design to achieve different effects that a > constant speed solid metal prop won't do so there is some difference. > > Bruce > > > On Thu, Dec 2, 2010 at 2:51 PM, Dave G wrote: > > >> I have received enough email to establish a plan of action here. Despite >> the fact that reducing pitch WILL result in an overspend situation with my >> particular experimental installation, I will reduce the pitch and see what >> happens during high speed taxi and then climb. Many people actually using >> Warp props tell me that I achieve the results I am looking for. >> >> I understand it is counter-intuitive, but apparently it is at least >> somewhat common. I have a couple of theories, but for now I'll accept >> positive results and remain in doubt about the actual reason. Over a long >> work life I've had to do that on many occasions, because results are what >> really matters. >> >> Thanks to Guy, Lucien and those who contributed positive and helpful >> advice off list. To those who offered unhelpful advice and lectures, thanks >> for the efforts. It all reminds me of a saying a friend repeats from time to >> time. >> >> "In theory, theory and practice are the same; in practice they are quite >> different!" This may be one of those cases. >> >> Dave Goddard >> KF IV 1050 / 582 / Warp >> >> ----- Original Message ----- >> *From:* b d >> *To:* kitfox-list@matronics.com >> *Sent:* Thursday, December 02, 2010 5:52 PM >> *Subject:* Re: Kitfox-List: Re: Losing rpm on takeoff >> >> Yes, it's semantics, with a prop in a liquid (a hydrofoil) it's called >> cavitation and with an prop in air (an airfoil), it's called a stall but >> essentially the same-o same-o. We all know what is meant, we just have to >> be tolerent of each others linguistics. To be technical I really don't >> believe there is such a word as "un-stalling". It's either stalled or not >> stalled but correct me if I'm wrong. But I do not what you mean and what >> your getting at, it's like coming out of a stall condition. >> >> Bruce >> >> >> >> >> >> >> On Thu, Dec 2, 2010 at 12:08 PM, Lowell Fitt wrote: >> >> >>> >>> >>> Mike, >>> >>> I think you answered your own question. Just substitute stalled prop for >>> cavitating prop. I think the concept is the same In each case the prop is >>> pitched too high for conditions. >>> >>> Lowell >>> >>> -------------------------------------------------- >>> From: "mikeperkins" >>> Sent: Thursday, December 02, 2010 11:41 AM >>> To: >>> Subject: Kitfox-List: Re: Losing rpm on takeoff >>> >>> >>> >>>> michael.perkins@rauland.com> >>>> >>>> I have never heard a discussion involving aircraft props that mentions >>>> cavitation, stirring air, humidity, or higher RPM during a static run-up. If >>>> you have some references, please let me know. >>>> >>>> A prop during a static run-up experiences a higher angle-of-attack than >>>> a prop moving forward through air. The higher AOA produces more drag, thus >>>> more load on the engine, and thus a lower RPM for a given power setting, not >>>> higher RPM. >>>> >>>> Some very high-performance aircraft with fixed-pitch props (long time >>>> ago) produced so little prop thrust (blade lift) during a static run-up that >>>> they had to be pushed to get them rolling - the prop was stalled. Once >>>> rolling, the AOA would gradually decrease and thrust (lift) would increase >>>> because the prop was un-stalling. >>>> >>>> A properly set-up Rotax 2-stroke will produce 5800 to 6200 on a static >>>> run-up (temp dependent), and max RPM of 6600 while climbing at Vx. >>>> >>>> I would not be looking at the prop pitch for this particular problem. >>>> >>>> Mike >>>> >>>> >>>> >>>> >>>> Read this topic online here: >>>> >>>> http://forums.matronics.com/viewtopic.php?p=322085#322085 >>>> >>>> >>>> >>>> m/" target="_blank">www.aeroelectric.com >>>> omebuiltHELP www.homebuilthelp.com >>>> http:/r generous support! >>>> ronics List Features Navigator to browse >>>> >>>> s.com/Navigator?Kitfox-List" >>>> target="_blank">http://www.matronics.com/Navigator?Kitfox-List >>>> ronics.com/" target="_blank">http://forums.matronics.com >>>> ============= >>>> >>>> >>>> >>>> >>>> >>> >> >> * >> >> href="http://www.aeroelectric.com">www.aeroelectric.com >> href="http://www.buildersbooks.com">www.buildersbooks.com >> href="http://www.homebuilthelp.com">www.homebuilthelp.com >> href="http://www.matronics.com/contribution">http://www.matronics.com/chref="http://www.matronics.com/Navigator?Kitfox-List">http://www.matronhref="http://forums.matronics.com">http://forums.matronics.com* >> >> * >> >> >> > ________________________________ Message 14 ____________________________________ Time: 10:47:22 PM PST US From: Guy Buchanan Subject: Re: Kitfox-List: Re: Losing rpm on takeoff On 12/2/2010 1:52 PM, b d wrote: > Yes, it's semantics, with a prop in a liquid (a hydrofoil) it's called > cavitation and with an prop in air (an airfoil), it's called a stall > but essentially the same-o same-o. OOO I LOVE semantics. Actually, cavitation is quite different from stall. Cavitation involves a phase change from liquid to gas due to pressure drop over the airfoil. Since the gas is compressible it vacates the low pressure region of the airfoil destroying lift. Stall is where the streamlines in the low pressure region depart catastrophically from the airfoil surface. It can happen in liquids and well as gasses. Stalling the liquid does not result in gas formation, or cavitation, but results merely in turbulent flow. I used to do it in the sailboat all the time. Guy Buchanan Kitfox IV-1200 / 592-C / Warp 3cs / 500 hrs. ________________________________ Message 15 ____________________________________ Time: 10:54:54 PM PST US From: Guy Buchanan Subject: Re: Kitfox-List: drilling/tapping fiberglass tank On 12/2/2010 4:03 PM, rez wrote: > 1. In light of all the problems, why does the whole world, it seems like, use fiberglass tanks? > Purely subjective answers: * Easy to manufacture, particularly in compound shapes. * Relatively light. * Corrosion proof, fuel corrosion notwithstanding. * Very high fatigue resistance. > 2. Are there any potential problems with aluminum tanks that I should know about? > * Potential for fatigue failure, particularly at any attachments or baffles. * Corrosion due to water in the fuel. * Corrosion due to water sitting below the fuel. > How about steel tanks? I wonder how much weight they would really add over fiberglass. > Just a guess, but I'd say - lots. Quite a lot of aircraft, certificated and otherwise, do just fine with aluminum tanks. I'd say stick with 'em. Guy Buchanan Kitfox IV-1200 / 592-C / Warp 3cs / 500 hrs. ________________________________ Message 16 ____________________________________ Time: 11:19:51 PM PST US Subject: Re: Kitfox-List: Re: Losing rpm on takeoff From: b d Cavitation and stall are quite the same but with different mediums, it's still only semantics. And yes a sail luffs too yet another analogy to describe the same thing. Nothing new has been added. You only said the same thing the first feller said a long time ago but yet another way. We all get it. The horse is absolutely dead and has now been drug down the road several miles . . . :-) On Thu, Dec 2, 2010 at 10:44 PM, Guy Buchanan wrote: > > > On 12/2/2010 1:52 PM, b d wrote: > >> Yes, it's semantics, with a prop in a liquid (a hydrofoil) it's called >> cavitation and with an prop in air (an airfoil), it's called a stall but >> essentially the same-o same-o. >> > > OOO I LOVE semantics. Actually, cavitation is quite different from stall. > Cavitation involves a phase change from liquid to gas due to pressure drop > over the airfoil. Since the gas is compressible it vacates the low pressure > region of the airfoil destroying lift. Stall is where the streamlines in the > low pressure region depart catastrophically from the airfoil surface. It can > happen in liquids and well as gasses. Stalling the liquid does not result in > gas formation, or cavitation, but results merely in turbulent flow. I used > to do it in the sailboat all the time. > > Guy Buchanan > Kitfox IV-1200 / 592-C / Warp 3cs / 500 hrs. > > ________________________________ Message 17 ____________________________________ Time: 11:51:25 PM PST US From: Michael Gibbs Subject: Re: Kitfox-List: drilling/tapping fiberglass tank >1. In light of all the problems, why does the whole world, it seems >like, use fiberglass tanks? The explanation I heard from John McBean is that Kitfox and Avid wings flex far too much for a rigid tank to withstand. >2. Are there any potential problems with aluminum tanks that I >should know about? Yes, they come apart at the seams. Literally. Aircraft that use aluminum tanks successfully have wing structures that are much stiffer than the root area of the Kitfox/Avid wings. Mike G. N728KF, Kitfox IV-1200 Speedster Phoenix, AZ -- "My airplane is quiet, and for a moment still an alien, still a stranger to the ground, I am home." --Richard Bach ________________________________ Message 18 ____________________________________ Time: 11:51:45 PM PST US From: Michael Gibbs Subject: Re: Kitfox-List: Re: Losing rpm on takeoff Bruce sez: >Cavitation and stall are quite the same but with different mediums, >it's still only semantics. Guy's explanation shows clearly that this is NOT the case. From Wikipedia : "Cavitation is the formation of vapor bubbles of a flowing liquid in a region where the pressure of the liquid falls below its vapor pressure." No mention of angle of attack or separation from a surface. And air doesn't changing phases in a stall! >You only said the same thing the first feller said a long time ago >but yet another way. We all get it. Apparently not... :-| Mike G. N728KF, Kitfox IV-1200 Speedster Phoenix, AZ >On Thu, Dec 2, 2010 at 10:44 PM, Guy Buchanan ><gebuchanan@cox.net> wrote: > ><gebuchanan@cox.net> > > >On 12/2/2010 1:52 PM, b d wrote: > >Yes, it's semantics, with a prop in a liquid (a hydrofoil) it's >called cavitation and with an prop in air (an airfoil), it's called >a stall but essentially the same-o same-o. > > >OOO I LOVE semantics. Actually, cavitation is quite different from >stall. Cavitation involves a phase change from liquid to gas due to >pressure drop over the airfoil. Since the gas is compressible it >vacates the low pressure region of the airfoil destroying lift. >Stall is where the streamlines in the low pressure region depart >catastrophically from the airfoil surface. It can happen in liquids >and well as gasses. Stalling the liquid does not result in gas >formation, or cavitation, but results merely in turbulent flow. I >used to do it in the sailboat all the time. > >Guy Buchanan >Kitfox IV-1200 / 592-C / Warp 3cs / 500 hrs. ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message kitfox-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Kitfox-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/kitfox-list Browse Digests http://www.matronics.com/digest/kitfox-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.