X-CGP-ClamAV-Result: CLEAN X-VirusScanner: Niversoft's CGPClamav Helper v1.23.0 (ClamAV engine v0.103.0) X-Junk-Score: 0 [] X-KAS-Score: 0 [] From: "Charlie England ceengland7@gmail.com" Received: from mail-ot1-f49.google.com ([209.85.210.49] verified) by logan.com (CommuniGate Pro SMTP 6.3.5) with ESMTPS id 377483 for flyrotary@lancaironline.net; Wed, 20 Oct 2021 20:11:38 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.210.49; envelope-from=ceengland7@gmail.com Received: by mail-ot1-f49.google.com with SMTP id b4-20020a9d7544000000b00552ab826e3aso8353102otl.4 for ; Wed, 20 Oct 2021 17:11:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=message-id:date:mime-version:user-agent:subject:content-language:to :references:from:in-reply-to; bh=HZLpdLT4PyhNp4KWO8NzPHOwwbYYiCYqRWMt500OPw0=; b=l/Juwq8KWtyKpYmitbwrqv5fJk/wnX4xNAfLocol7dGlg2jh9SSk0OwNF9lZUTTB1m oLGycfrCKPezJcFJpWzf1o3MELWwwb0ss72KrMyoniqomPyqUk7VawfnAwC/WufdowlS sPJup7POGAT5NzHJVyx8TDQ82boD5PzG1OSrglvjxzZ5PCMFfS5+NZNIZptJsArjkHds DBjN5mNF8aqcgCFShi5AedPvHgvMMXFfPCuiryobzWQUR18R3SysDUWibS+v5bO0Hs/B q150dD/75537oAM9yAZcGbhlV3n74bLK0RRtSpGm2oQjPPpZpBmXBidfiZZAczlnwIPV XFZQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:references:from:in-reply-to; bh=HZLpdLT4PyhNp4KWO8NzPHOwwbYYiCYqRWMt500OPw0=; b=TJBIUWCoUzvKpKDStVuKh68rIwbTj2lutR5ezrtnGfc42ssDagnMkbLNmlU/39jtB6 1W2lYFS37SBMn7TucR+RJe9yQK6jTVD/udnGRJJOvA289UzD3QsEHTzdLnvS/JB5CuSQ 0qDZL9KaWj3ecM1k6bwB7pvb0Ywz0dayiPfRiAcH+Ht7ncmINYxUeMOSFhX4cf1Cjuju a+PHbLatXKfzeNZwA4pg376IFoC1GEWCZuV0lR1wA6qGrhX5BThVsTpLJek6FKT80p7b J+/AseKPOVhtkLDtfesFHEDvKtq12hlNNMxtkSENqPW8BgpooH8/g1+mIDndNU7g/QWd X34g== X-Gm-Message-State: AOAM531No6WAnrdpBwWGLVzQLVPvNISIjhEYtEs0DqYeNGIbGQ/2etdy EWheJZZPUbp1KXv4bJLFULwUNpMfx5Q= X-Google-Smtp-Source: ABdhPJx1BryBP/1CKRzxmR8xVQrN7RSmmUI2VNh1s24Slpb3m7Tbd7zGW+OZUeYexTmQFLz3z5D6wA== X-Received: by 2002:a05:6830:90b:: with SMTP id v11mr1985045ott.254.1634775082044; Wed, 20 Oct 2021 17:11:22 -0700 (PDT) Return-Path: Received: from [192.168.1.17] ([172.58.145.67]) by smtp.googlemail.com with ESMTPSA id f13sm769382oto.53.2021.10.20.17.11.20 for (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Wed, 20 Oct 2021 17:11:21 -0700 (PDT) Content-Type: multipart/alternative; boundary="------------CBgjAZUVAWRb22d2JBeRg9HN" Message-ID: <8ac9bbea-701e-182d-c74f-15cab216d132@gmail.com> Date: Wed, 20 Oct 2021 19:16:09 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Subject: Re: [FlyRotary] Re: Props and gear boxes Content-Language: en-US To: Rotary motors in aircraft References: In-Reply-To: X-Antivirus: Avast (VPS 211020-4, 10/20/2021), Outbound message X-Antivirus-Status: Clean This is a multi-part message in MIME format. --------------CBgjAZUVAWRb22d2JBeRg9HN Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Ed will have to let you know about the A models. The 72" on the short leg RV4 got broken when the partner slammed the throttle closed in the pattern on a still-cold engine, the engine quit with the prop vertical, and he then did a very high speed wheel landing on a wet/muddy strip. He hit a puddle and the nose tipped down just enough to get a tip in the dirt. When I flew the 76" on the same short leg RV4, I was very careful to make tail low takeoffs and 3 point landings. It's been a long time, but IIRC I probably had less than 8" clearance with the tailwheel on the ground. I only made a couple of test flights using that (borrowed)  prop; I never intended to put it into normal use. 6"-7" on a trike *sounds* like you could get away with it with decent technique, but the safest thing to do might be to ask your type group who has the least clearance, and what surfaces they fly from. Charlie On 10/20/2021 5:50 PM, Stephen Izett stephen.izett@gmail.com wrote: > Thanks for the real prop knowledge and feedback Charlie and Ed. > > Ground clearance is another area I’m left wondering about after > hearing what Charlie has played with. > I think I’ll have just over 6.7 inches when the 72” MT goes on. I > wasn’t game to go for 74”. > What clearance does an RV-xA have with a 72” prop? > > Steve Izett > > > > > > >> On 21 Oct 2021, at 2:23 am, eanderson@carolina.rr.com >> wrote: >> >> When I had Tracy's 2.17 PSRU, I swung a 67 dia x 72 pitch prop.  >> Climb and cruise were fine but takeoff (especially from a short >> runway on a hot day left something to be desired). >> >> When I got Tracy's 2.85 PSRU, I had a 76 x80 wood prop build by >> Performance propellers.  I flew a few times with it as such and while >> performance was much better rpm was only around 5800.  Plus the prop >> was only a couple inches from the ground on my RV-6A Nose gear >> aircraft - was concerned about landing of grass strips with possible >> mole holes. So I had the diameter reduced to 74 Inches.  That was >> what the doctor ordered. >> >> There was a considerable difference in aircraft performance >> particularly during take off.  With the new combination, I had to tap >> the left brake to keep runway alignment (if I cobbed full power from >> a standing start) until airspeed reached approx 40 mph at which time >> the rudder authority became adequate to hold the nose down the >> runway.  Starting acceleration was considerably better with the new >> combination, it literally push me back in the seat.  Climbout >> improved up to around 1700 fpm previous had been around 1000 fpm. >> >> I had thought I would probably have to give up a few knots on the top >> end, but it turned out I actually increased airspeed by approx 4 >> mph.  So it was really a win win for me.  I could get up to around >> 6200-6250 WOT at cruise, so apparently at high airspeed the >> prop/gearbox unloaded the engine to pick up a few more HP. >> >> It appears that for takeoff there is nothing better than the volume >> (mass) of air your prop is able to push behind it.  So even though >> the prop turned slower with the 2.85, the much larger prop and the >> engine increase from a take off rpm of around 56-5700 rpm to 6000 and >> the increased torque pushed a much larger volume (mass) of air. >> >> I really like the change the 2.85 gear box made possible - oh, yeah, >> now the prop also turned in the conventional direction.😄 >> >> Ed >> >> ------ Original Message ------ >> From: "Charlie Englandceengland7@gmail.com" >> To: "Rotary motors in aircraft" >> Sent: 10/20/2021 9:01:32 AM >> Subject: [FlyRotary] Re: Ag Ops >> >>> Hi Steve, >>> >>> I can't claim any expertise, but I do have some experience with >>> various prop diameters on RVs. Van started out recommending 68" dia >>> props on the 2 seat RVs. My 1st RV4 had a Warnke 72x72. With 160 HP, >>> it had 1200-1500fpm climb and would cruise at 170 kts @ ~9.3 gph >>> rich of peak, ~75% power for a Lyc 160. The cruise matched Van's >>> numbers, and climb was at least as good, if not better than Van's >>> numbers. After my partner in the RV damaged the Warnke, I replaced >>> it with a 68" from another mfgr and the plane never performed as >>> well in either cruise or climb. At one point, I tried a 76" dia IVO. >>> Climb was incredible, but the plane would hit a wall at about >>> 145-150 kts (known problem with IVO's blades; they don't have >>> enough twist for high speed operation). Another data point: Van's >>> current catalog lists a Hartzel 74" dia c/s prop for the 2 seat a/c >>> and the f/p props are in the 72" dia range. >>> >>> My calculations on optimum dia & ratio for the Renesis are similar >>> to yours. If you start with the Lyc-standard 2700 prop rpm, with the >>> realization that 74" is not too large a diameter (for tip speed >>> issues) at 2700, then the optimum ratio would be determined by your >>> desired max engine rpm. With a controllable prop, you can give up a >>> little bit in diameter & get back low speed thrust by going to >>> flatter pitch & more HP. But if fixed pitch, I try for the largest >>> dia I can safely fit on the plane. With a typical fast 2 seat >>> homebuilt, gear leg length, not tip speed, will almost always be the >>> limiting factor even at 2700+ rpm. The bigger the diameter, the >>> better the low speed mass flow (thrust), and there will be little to >>> no penalty at any cruise speed under the 180-190 kt range (well >>> above 200 mph). >>> >>> The above assumes a properly designed prop, of course. One reason to >>> desire that 2.4-2.5:1 ratio is that it gets prop rpm where the prop >>> carver is used to working, and we're much more likely to get a >>> usable prop on 1st try if he's in familiar territory. If you tell >>> him, say, 200 HP @ 2700 prop rpm & cruise at 75% will be 170 kts, >>> he'll likely be able to get it right, 1st try. If, on the other >>> hand, you're telling him the same HP & speed, but you want, for >>> instance, 76" dia & 2300 prop rpm, he's going to be guessing on how >>> to carve the prop. >>> >>> Bottom line: I fit the largest dia I can safely swing, regardless of >>> f/p or c/s (because low speed thrust will always improve with >>> diameter increases), knowing that ground clearance will be a problem >>> long before tip speed becomes an issue. If you haven't already >>> bought the 72", I'd be asking them for a 76" if they'll sell you one >>> and you can safely swing it on your plane. And be sure to tell them >>> the actual rpm range where it will operate. Their 'stock' 72" for a >>> Lyc will be sub-optimal turning in the ~2000 rpm range with a 2.85 >>> drive, unless you intend to really flog the engine hard all the time >>> & pour a lot of fuel through it. >>> >>> FWIW, >>> >>> Charlie >>> >>> On Tue, Oct 19, 2021 at 7:38 PM Stephen >>> Izettstephen.izett@gmail.com wrote: >>> >>> Hi Andrew >>> >>> Continuing to fine tune the Renesis cooling system and aircraft. >>> Completing a new exhaust system after a leaking gasket warped a >>> flange. >>> Last flight temps max’d at 91C (196F) on takeoff with 20C >>> (68F)OAT and we got her up to 189knots but only 2600 feet due to >>> cloud. >>> Learning that increasing the IAS by ~10knots in climb has a >>> significant effect on cooling. >>> >>> Also in the process of changing the current 66.5” Airmasterto >>> for a 72” MT prop. >>> I only read after going with our gearbox/prop combination that >>> Tracy recommended only using the 2.85:1 with props of >=74” >>> For those with expertise in this area, is it true that we should >>> choose: >>> 1. Largest prop dimeter with acceptable clearance >>> 2. Target cruise tip speed of ~0.8-0.85 speed of sound for best >>> efficiency >>> If this is correct then with a 72” prop and a chosen engine >>> redline of 7500 RPM (4 port Renesis) a better gearbox ratio >>> would be ~2.5:1 >>> The 2.85:1 would be better suited to a 74-76” prop at that redline. >>> >>> Hope you have a great harvest and get back in the air soon Andrew. >>> >>> Steve >>> >>> >>>> On 20 Oct 2021, at 7:52 am, Andrew >>>> Martinandrew@martinag.com.au wrote: >>>> >>>> Hi Steve, hows the Glasair going? I been away from flying for >>>> awhile, hopefully back into it in new year. Did start mine >>>> recently after it been sitting idle since feb 2020, So happy I >>>> persevered with the mazda, it started & ran so sweet I >>>> contemplated doing a couple of circuits but for the legalities. >>>> No MR and I need AFR first. >>>> >>>> Neil, not sure I agree with your rotor setup proposal, ( not >>>> that mine is better) can get some weird aerodynamics with >>>> intermeshing rotors. >>>> Whole thing of nurse cart & drone need to be a package, rotors >>>> will never be stopped during refill so drone needs to land on >>>> roof of truck or trailer for refill from underneath to keep >>>> blades clear of dumbasses like me. >>>> Truth be told, I dont think we can get anywhere near the >>>> efficiency of a ground rig or Ag plane, we easily average 80 >>>> ha/hr each machine + nurse cart, going to need a swarm of >>>> drones to get near this. But could be a fun project. >>>> Andrew >>>> >>>> On Tue, 19 Oct. 2021, 9:07 am Stephen >>>> Izettstephen.izett@gmail.com, wrote: >>>> >>>> Good to hear your voice Andrew. >>>> My son-in-law in Kojonup would be very interested in what >>>> you guys are talking about. >>>> >>>> Cheers >>>> >>>> Steve Izett >>>> >>>>> >>>> >>>> -- >>>> Regards Andrew Martin Martin Ag >>> > -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus --------------CBgjAZUVAWRb22d2JBeRg9HN Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: 8bit
Ed will have to let you know about the A models. The 72" on the short leg RV4 got broken when the partner slammed the throttle closed in the pattern on a still-cold engine, the engine quit with the prop vertical, and he then did a very high speed wheel landing on a wet/muddy strip. He hit a puddle and the nose tipped down just enough to get a tip in the dirt.

When I flew the 76" on the same short leg RV4, I was very careful to make tail low takeoffs and 3 point landings. It's been a long time, but IIRC I probably had less than 8" clearance with the tailwheel on the ground. I only made a couple of test flights using that (borrowed)  prop; I never intended to put it into normal use.

6"-7" on a trike *sounds* like you could get away with it with decent technique, but the safest thing to do might be to ask your type group who has the least clearance, and what surfaces they fly from.

Charlie


On 10/20/2021 5:50 PM, Stephen Izett stephen.izett@gmail.com wrote:
Thanks for the real prop knowledge and feedback Charlie and Ed.

Ground clearance is another area I’m left wondering about after hearing what Charlie has played with.
I think I’ll have just over 6.7 inches when the 72” MT goes on. I wasn’t game to go for 74”.
What clearance does an RV-xA have with a 72” prop?

Steve Izett






On 21 Oct 2021, at 2:23 am, eanderson@carolina.rr.com <flyrotary@lancaironline.net> wrote:

When I had Tracy's 2.17 PSRU, I swung a 67 dia x 72 pitch prop.  Climb and cruise were fine but takeoff (especially from a short runway on a hot day left something to be desired).  

When I got Tracy's 2.85 PSRU, I had a 76 x80 wood prop build by Performance propellers.  I flew a few times with it as such and while performance was much better rpm was only around 5800.  Plus the prop was only a couple inches from the ground on my RV-6A Nose gear aircraft - was concerned about landing of grass strips with possible mole holes.  So I had the diameter reduced to 74 Inches.  That was what the doctor ordered.

There was a considerable difference in aircraft performance particularly during take off.  With the new combination, I had to tap the left brake to keep runway alignment (if I cobbed full power from a standing start) until airspeed reached approx 40 mph at which time the rudder authority became adequate to hold the nose down the runway.  Starting acceleration was considerably better with the new combination, it literally push me back in the seat.  Climbout improved up to around 1700 fpm previous had been around 1000 fpm.

I had thought I would probably have to give up a few knots on the top end, but it turned out I actually increased airspeed by approx 4 mph.  So it was really a win win for me.  I could get up to around 6200-6250 WOT at cruise, so apparently at high airspeed the prop/gearbox unloaded the engine to pick up a few more HP.

It appears that for takeoff there is nothing better than the volume (mass) of air your prop is able to push behind it.  So even though the prop turned slower with the 2.85, the much larger prop and the engine increase from a take off rpm of around 56-5700 rpm to 6000 and the increased torque pushed a much larger volume (mass) of air.

I really like the change the 2.85 gear box made possible - oh, yeah, now the prop also turned in the conventional direction.😄

Ed

------ Original Message ------
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: 10/20/2021 9:01:32 AM
Subject: [FlyRotary] Re: Ag Ops

Hi Steve,

I can't claim any expertise, but I do have some experience with various prop diameters on RVs. Van started out recommending 68" dia props on the 2 seat RVs. My 1st RV4 had a Warnke 72x72. With 160 HP, it had 1200-1500fpm climb and would cruise at 170 kts @ ~9.3 gph rich of peak, ~75% power for a Lyc 160. The cruise matched Van's numbers, and climb was at least as good, if not better than Van's numbers. After my partner in the RV damaged the Warnke, I replaced it with a 68" from another mfgr and the plane never performed as well in either cruise or climb. At one point, I tried a 76" dia IVO. Climb was incredible, but the plane would hit a wall at about 145-150 kts (known problem with IVO's blades; they don't have enough twist for high speed operation). Another data point: Van's current catalog lists a Hartzel 74" dia c/s prop for the 2 seat a/c and the f/p props are in the 72" dia range.

My calculations on optimum dia & ratio for the Renesis are similar to yours. If you start with the Lyc-standard 2700 prop rpm, with the realization that 74" is not too large a diameter (for tip speed issues) at 2700, then the optimum ratio would be determined by your desired max engine rpm. With a controllable prop, you can give up a little bit in diameter & get back low speed thrust by going to flatter pitch & more HP. But if fixed pitch, I try for the largest dia I can safely fit on the plane. With a typical fast 2 seat homebuilt, gear leg length, not tip speed, will almost always be the limiting factor even at 2700+ rpm. The bigger the diameter, the better the low speed mass flow (thrust), and there will be little to no penalty at any cruise speed under the 180-190 kt range (well above 200 mph). 

The above assumes a properly designed prop, of course. One reason to desire that 2.4-2.5:1 ratio is that it gets prop rpm where the prop carver is used to working, and we're much more likely to get a usable prop on 1st try if he's in familiar territory. If you tell him, say, 200 HP @ 2700 prop rpm & cruise at 75% will be 170 kts, he'll likely be able to get it right, 1st try. If, on the other hand, you're telling him the same HP & speed, but you want, for instance, 76" dia & 2300 prop rpm, he's going to be guessing on how to carve the prop.

Bottom line: I fit the largest dia I can safely swing, regardless of f/p or c/s (because low speed thrust will always improve with diameter increases), knowing that ground clearance will be a problem long before tip speed becomes an issue. If you haven't already bought the 72", I'd be asking them for a 76" if they'll sell you one and you can safely swing it on your plane. And be sure to tell them the actual rpm range where it will operate. Their 'stock' 72" for a Lyc will be sub-optimal turning in the ~2000 rpm range with a 2.85 drive, unless you intend to really flog the engine hard all the time & pour a lot of fuel through it.

FWIW,

Charlie

On Tue, Oct 19, 2021 at 7:38 PM Stephen Izett stephen.izett@gmail.com <flyrotary@lancaironline.net> wrote:
Hi Andrew

Continuing to fine tune the Renesis cooling system and aircraft.
Completing a new exhaust system after a leaking gasket warped a flange.
Last flight temps max’d at 91C (196F) on takeoff with 20C (68F)OAT and we got her up to 189knots but only 2600 feet due to cloud.
Learning that increasing the IAS by ~10knots in climb has a significant effect on cooling.

Also in the process of changing the current 66.5” Airmasterto for a 72” MT prop.
I only read after going with our gearbox/prop combination that Tracy recommended only using the 2.85:1 with props of >=74”
For those with expertise in this area, is it true that we should choose:
1. Largest prop dimeter with acceptable clearance
2. Target cruise tip speed of ~0.8-0.85 speed of sound for best efficiency
If this is correct then with a 72” prop and a chosen engine redline of 7500 RPM (4 port Renesis) a better gearbox ratio would be ~2.5:1
The 2.85:1 would be better suited to a 74-76” prop at that redline.

Hope you have a great harvest and get back in the air soon Andrew.

Steve


On 20 Oct 2021, at 7:52 am, Andrew Martin andrew@martinag.com.au <flyrotary@lancaironline.net> wrote:

Hi Steve, hows the Glasair going? I been away from flying for awhile, hopefully back into it in new year. Did start mine recently after it been sitting idle since feb 2020, So happy I persevered with the mazda, it started & ran so sweet I contemplated doing a couple of circuits but for the legalities. No MR and I need AFR first.

Neil, not sure I agree with your rotor setup proposal, ( not that mine is better) can get some weird aerodynamics with intermeshing rotors.
Whole thing of nurse cart & drone need to be a package, rotors will never be stopped during refill so drone needs to land on roof of truck or trailer for refill from underneath to keep blades clear of dumbasses like me.
Truth be told, I dont think we can get anywhere near the efficiency of a ground rig or Ag plane, we easily average 80 ha/hr each machine + nurse cart, going to need a swarm of drones to get near this. But could be a fun project.
Andrew

On Tue, 19 Oct. 2021, 9:07 am Stephen Izett stephen.izett@gmail.com, <flyrotary@lancaironline.net> wrote:
Good to hear your voice Andrew.
My son-in-law in Kojonup would be very interested in what you guys are talking about.

Cheers

Steve Izett

 



-- 
Regards Andrew Martin Martin Ag



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