---------------------------------------------------------- Zenith701801-List Digest Archive --- Total Messages Posted Sun 05/08/11: 5 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:30 PM - 701 Buffet at slow speeds (Philip Smith) 2. 12:59 PM - Re: 701 Buffet at slow speeds (Tommy Walker) 3. 01:35 PM - Re: 701 Buffet at slow speeds (Gordon) 4. 02:01 PM - Re: 701 Buffet at slow speeds (Mark Sherman) 5. 07:50 PM - Re: 701 Buffet at slow speeds (ronlee) ________________________________ Message 1 _____________________________________ Time: 12:30:22 PM PST US Subject: Zenith701801-List: 701 Buffet at slow speeds From: Philip Smith OK Listers, I have about twelve hours on my 701 - Rotax 912 ULS with Warp Drive three blade (68 inches) set at 13.5 degrees. So far it's the most fun I've had with my clothes on - at least since flying T-38s in the mid sixties...sigh!! So what's bothering me?? In climb at very low speeds such as 40 - 60 I have a very stable platform with no buffet or oil canning - however when I pull the power back to a lower RPM (2000 - 4000) IN THE PATTERN such as turning base at 65 and slowing to fifty or so on final - and below - I begin to pick up a "rumbling buffet" that seems to increase as the plane slows. I think the key here is POWER OFF OR LOW POWER SETTINGS - The buffet can be felt as a light buffet in the stick and just sounds like a whole lot of oil canning. I have also slowed the plane at altitude in level flight and get the same results - buffeting and oil canning sounds. I'm perty much convinced that it is caused by a separation of the air flow over the cockpit and the front part of the top of the fuselage. When I built the plane I put false ribs in the wings and also added diagonal "L" braces between all fuselage stations in the rear - top, bottom and sides. This seemed to take a lot of the "flex" out of the skin. I also added sound dampener material - stuff used on HVAC ducts - to the back of the baggage compartment wall and under the baggage compartment floor. This also seemed to deaden the panels. Been noodling with strengthening the top and sides of the fuselage from just behind the top window back to the rear of the baggage compartment - in each bay - with two diagonal "L's". Additionally, putting a single diagonal "L" on the side walls behind the door and then in the next bay in the baggage compartment. Also would add the sound insulating material to the inside top and side. I added the material in the cowl boot area and behind the fire wall and like the looks and it seems to quiet things down. So what's the problem??? As usual I am trying not to reinvent the wheel and asking what the rest of you 701 - 750'ers have done to control the buffet / clatter. Contact me off net if you like or leave your response for all to see on the site. Still grinnin Phil Buhl, ID 710, Rotax 912 ULS ________________________________ Message 2 _____________________________________ Time: 12:59:52 PM PST US Subject: Re: Zenith701801-List: 701 Buffet at slow speeds From: Tommy Walker Hi, One 701 driver said the sound you hear is the built in 701 Stall warning horn... lol.... rattles like a wagon filled with loose tin.... On Sat, May 7, 2011 at 9:56 PM, Philip Smith wrote: > OK Listers, > > I have about twelve hours on my 701 - Rotax 912 ULS with Warp Drive three > blade (68 inches) set at 13.5 degrees. So far it's the most fun I've had > with my clothes on - at least since flying T-38s in the mid sixties...sigh!! > > So what's bothering me?? > > In climb at very low speeds such as 40 - 60 I have a very stable platform > with no buffet or oil canning - however when I pull the power back to a > lower RPM (2000 - 4000) IN THE PATTERN such as turning base at 65 and > slowing to fifty or so on final - and below - I begin to pick up a "rumbling > buffet" that seems to increase as the plane slows. I think the key here is > POWER OFF OR LOW POWER SETTINGS - The buffet can be felt as a light buffet > in the stick and just sounds like a whole lot of oil canning. > > I have also slowed the plane at altitude in level flight and get the same > results - buffeting and oil canning sounds. > > I'm perty much convinced that it is caused by a separation of the air flow > over the cockpit and the front part of the top of the fuselage. > > When I built the plane I put false ribs in the wings and also added > diagonal "L" braces between all fuselage stations in the rear - top, bottom > and sides. This seemed to take a lot of the "flex" out of the skin. I also > added sound dampener material - stuff used on HVAC ducts - to the back of > the baggage compartment wall and under the baggage compartment floor. This > also seemed to deaden the panels. > > Been noodling with strengthening the top and sides of the fuselage from > just behind the top window back to the rear of the baggage compartment - in > each bay - with two diagonal "L's". Additionally, putting a single diagonal > "L" on the side walls behind the door and then in the next bay in the > baggage compartment. Also would add the sound insulating material to the > inside top and side. I added the material in the cowl boot area and behind > the fire wall and like the looks and it seems to quiet things down. > > So what's the problem??? As usual I am trying not to reinvent the wheel and > asking what the rest of you 701 - 750'ers have done to control the buffet / > clatter. > > Contact me off net if you like or leave your response for all to see on the > site. > > Still grinnin > > Phil > Buhl, ID > > 710, Rotax 912 ULS > > > * > > * > > ________________________________ Message 3 _____________________________________ Time: 01:35:56 PM PST US From: "Gordon" Subject: Re: Zenith701801-List: 701 Buffet at slow speeds Phil, Mine does exactly the same thing ---no false ribs or x braces. Gordon ----- Original Message ----- From: Philip Smith To: zenith701801-list@matronics.com Sent: Saturday, May 07, 2011 10:56 PM Subject: Zenith701801-List: 701 Buffet at slow speeds OK Listers, I have about twelve hours on my 701 - Rotax 912 ULS with Warp Drive three blade (68 inches) set at 13.5 degrees. So far it's the most fun I've had with my clothes on - at least since flying T-38s in the mid sixties...sigh!! So what's bothering me?? In climb at very low speeds such as 40 - 60 I have a very stable platform with no buffet or oil canning - however when I pull the power back to a lower RPM (2000 - 4000) IN THE PATTERN such as turning base at 65 and slowing to fifty or so on final - and below - I begin to pick up a "rumbling buffet" that seems to increase as the plane slows. I think the key here is POWER OFF OR LOW POWER SETTINGS - The buffet can be felt as a light buffet in the stick and just sounds like a whole lot of oil canning. I have also slowed the plane at altitude in level flight and get the same results - buffeting and oil canning sounds. I'm perty much convinced that it is caused by a separation of the air flow over the cockpit and the front part of the top of the fuselage. When I built the plane I put false ribs in the wings and also added diagonal "L" braces between all fuselage stations in the rear - top, bottom and sides. This seemed to take a lot of the "flex" out of the skin. I also added sound dampener material - stuff used on HVAC ducts - to the back of the baggage compartment wall and under the baggage compartment floor. This also seemed to deaden the panels. Been noodling with strengthening the top and sides of the fuselage from just behind the top window back to the rear of the baggage compartment - in each bay - with two diagonal "L's". Additionally, putting a single diagonal "L" on the side walls behind the door and then in the next bay in the baggage compartment. Also would add the sound insulating material to the inside top and side. I added the material in the cowl boot area and behind the fire wall and like the looks and it seems to quiet things down. So what's the problem??? As usual I am trying not to reinvent the wheel and asking what the rest of you 701 - 750'ers have done to control the buffet / clatter. Contact me off net if you like or leave your response for all to see on the site. Still grinnin Phil Buhl, ID 710, Rotax 912 ULS ________________________________ Message 4 _____________________________________ Time: 02:01:04 PM PST US Subject: Re: Zenith701801-List: 701 Buffet at slow speeds From: Mark Sherman Philip I have no extra braces on my fuselage. The only time I have oil canning is w hen the ball is off center, at any speed. I have done my best to get this thing to stall but all it will do is mush in at about 900fpm. Quiet all the time, unless the ball is off. I put L braces on the back of the baggage compartment, it would oil can on r ough fields when landing. Instead of adding all that weight you might just get a better head set. 701/912ULS 150hrs Sent from Mark's iPhone On May 7, 2011, at 7:56 PM, Philip Smith wrote: > OK Listers, > > I have about twelve hours on my 701 - Rotax 912 ULS with Warp Drive three b lade (68 inches) set at 13.5 degrees. So far it's the most fun I've had wit h my clothes on - at least since flying T-38s in the mid sixties...sigh!! > > So what's bothering me?? > > In climb at very low speeds such as 40 - 60 I have a very stable platform w ith no buffet or oil canning - however when I pull the power back to a lower RPM (2000 - 4000) IN THE PATTERN such as turning base at 65 and slowing to f ifty or so on final - and below - I begin to pick up a "rumbling buffet" tha t seems to increase as the plane slows. I think the key here is POWER OFF OR LOW POWER SETTINGS - The buffet can be felt as a light buffet in the stick a nd just sounds like a whole lot of oil canning. > > I have also slowed the plane at altitude in level flight and get the same r esults - buffeting and oil canning sounds. > > I'm perty much convinced that it is caused by a separation of the air flow over the cockpit and the front part of the top of the fuselage. > > When I built the plane I put false ribs in the wings and also added diagon al "L" braces between all fuselage stations in the rear - top, bottom and si des. This seemed to take a lot of the "flex" out of the skin. I also added sound dampener material - stuff used on HVAC ducts - to the back of the bag gage compartment wall and under the baggage compartment floor. This also se emed to deaden the panels. > > Been noodling with strengthening the top and sides of the fuselage from ju st behind the top window back to the rear of the baggage compartment - in ea ch bay - with two diagonal "L's". Additionally, putting a single diagonal " L" on the side walls behind the door and then in the next bay in the baggag e compartment. Also would add the sound insulating material to the inside t op and side. I added the material in the cowl boot area and behind the fire wall and like the looks and it seems to quiet things down. > > So what's the problem??? As usual I am trying not to reinvent the wheel an d asking what the rest of you 701 - 750'ers have done to control the buffet / clatter. > > Contact me off net if you like or leave your response for all to see on th e site. > > Still grinnin > > Phil > Buhl, ID > > 710, Rotax 912 ULS > > > ========================== ========= ========================== ========= ========================== ========= ========================== ========= > ________________________________ Message 5 _____________________________________ Time: 07:50:03 PM PST US Subject: Zenith701801-List: Re: 701 Buffet at slow speeds From: "ronlee" My 701 does the same thing. What makes it do that I have no idea, but I do make use it to control my speed on landings. It's like a built in stall indicator except no conventional stall occurs, just the big controllable mush. Do I wish the wing profile continued over the cabin, you bet. I truly believe it would be a better plane if it did, as I suspect the buffeting MAY start there. For one thing I could peer into the wing at a sight glass and know exactly how much gas I have. I could run a vent line between the gas tanks to equalize the pressure of the tanks so they would feed evenly, Cessna does it that way. Does the stall (buffeting) start over the cabin long before the rest of the wing, I have no doubt. All in all I love to fly the 701 very much but believe there is room for improvements in several areas. To be fair you could say that about any airplane though. -------- Ron Lee Tucson, Arizona Read this topic online here: http://forums.matronics.com/viewtopic.php?p=339277#339277 ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message zenith701801-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Zenith701801-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/zenith701801-list Browse Digests http://www.matronics.com/digest/zenith701801-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.