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"Lippsing" a Q-tip propeller
Thought I'd ask for comments before doing something stupid and irreparable
to our propeller. We have a Hartzell Q-tip prop on our Glasair. That's the fancy bent over tip that gets all the jokes about the FAA Inspector who grounded a Cheyenne when the propellor first came out. (Looks like the prop had a ground strike.) When we got it, the Q-tip was a hot thing, and we were coming off a Prince P-tip, which also had a turned under "winglet." Then Paul Lipps came along and wrote that putting a big hunk of metal out there on the prop tip is about the stupidest thing one could do, since the prop tip is where velocity - and therefore, drag - is highest. He wrote about cutting the tips off a Prince wood prop and getting a phenomenal improvement in propeller efficiency. I'm not going to cut off the Q-tip entirely. But I thought I would try a compromise solution, and cut part of it off. I should link a photo to show you my markups on the tip, but the plan is to cut the front of the winglet to put a 60 degree shear on the front, like you see on the Katana wingtips and on Paul Lipps' Lancair. I will be careful, will sand out the stress risers, etc. I have a good gram scale to weigh the cutoffs to match, and a dynamic prop balancer to rebalance after the operation. It's a homebuilt, so I'm deep into "experimental" mode on this one. Anyone want to warn me about how I might kill myself doing this? Has anyone done this before? Thanks, Mike Palmer |
#2
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"Lippsing" a Q-tip propeller
"MP" wrote in message
... Thought I'd ask for comments before doing something stupid and irreparable to our propeller. ... It's a homebuilt, so I'm deep into "experimental" mode on this one. Anyone want to warn me about how I might kill myself doing this? Has anyone done this before? Sure, I'd be happy to warn you. Has anyone killed themselves after cutting down a prop? Yup. Cut down props were popular on the early T-18's - at least until the first few fatal accidents. When the blade broke due to resonance / fatigue the engine would part company with the aircraft and the result was typically a dead pilot / passenger. Changing the length of the prop changes the resonant frequencies with unpredictable results. http://www.t18.net/technical_info.htm#Cutdown -- Geoff The Sea Hawk at Wow Way d0t Com remove spaces and make the obvious substitutions to reply by mail When immigration is outlawed, only outlaws will immigrate. |
#3
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"Lippsing" a Q-tip propeller
Joe Brophy wrote:
On Thu, 16 Apr 2009 21:14:38 -0400, "Capt. Geoffrey Thorpe" The Sea Hawk @See My Sig.com wrote: "MP" wrote in message ... Thought I'd ask for comments before doing something stupid and irreparable to our propeller. ... It's a homebuilt, so I'm deep into "experimental" mode on this one. Anyone want to warn me about how I might kill myself doing this? Has anyone done this before? Sure, I'd be happy to warn you. Has anyone killed themselves after cutting down a prop? Yup. Cut down props were popular on the early T-18's - at least until the first few fatal accidents. When the blade broke due to resonance / fatigue the engine would part company with the aircraft and the result was typically a dead pilot / passenger. Changing the length of the prop changes the resonant frequencies with unpredictable results. http://www.t18.net/technical_info.htm#Cutdown That is why, after you finish with the sawzall, then smooth it off with a harbor freight angle grinder, make sure the prop gets a heavy coat of 3m rubberized undercoating. It dampens out those nasty vibs before they have a chance to rattle their way through the prop and cause a catastrophic failure. Good luck, make sure you wear eye protection using those power tools....regards, Joe. Are we making a test club with no thrust requirements, or are you just trolling? |
#4
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"Lippsing" a Q-tip propeller
On Thursday, April 16, 2009 at 6:38:17 AM UTC, MP wrote:
Thought I'd ask for comments before doing something stupid and irreparable to our propeller. We have a Hartzell Q-tip prop on our Glasair. That's the fancy bent over tip that gets all the jokes about the FAA Inspector who grounded a Cheyenne when the propellor first came out. (Looks like the prop had a ground strike.) When we got it, the Q-tip was a hot thing, and we were coming off a Prince P-tip, which also had a turned under "winglet." Then Paul Lipps came along and wrote that putting a big hunk of metal out there on the prop tip is about the stupidest thing one could do, since the prop tip is where velocity - and therefore, drag - is highest. He wrote about cutting the tips off a Prince wood prop and getting a phenomenal improvement in propeller efficiency. I'm not going to cut off the Q-tip entirely. But I thought I would try a compromise solution, and cut part of it off. I should link a photo to show you my markups on the tip, but the plan is to cut the front of the winglet to put a 60 degree shear on the front, like you see on the Katana wingtips and on Paul Lipps' Lancair. I will be careful, will sand out the stress risers, etc. I have a good gram scale to weigh the cutoffs to match, and a dynamic prop balancer to rebalance after the operation. It's a homebuilt, so I'm deep into "experimental" mode on this one. Anyone want to warn me about how I might kill myself doing this? Has anyone done this before? Thanks, Mike Palmer so how did it work? |
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