The old Raf, stabs, and CLT thing!!!

Aussie_Paul

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I thought that I would start a new topic, as I hope that there will be some great discussion re this post.<br><br><br>Quote from a previous post.<br><br>"A pitch stable aircraft is one that tends to return to its previous trim condition after being upset (push your plane's stick and let go; it will oscillate a little and then return to trimmed flight)".   <br> <br>Larry you said, "That was a perfect description of what a RAF does with the Ultimate stab.  Except it doesn't "tend to return", it returns."<br><br><br>Larry, I don't want to start a flame war, but for the many people out there who are new to the gyro world I have to make a comment.<br><br>That is not possible at all the allowable Raf speeds. I know from my testing that at the minimum power required speed, and perfectly smooth conditions, the Raf fitted with the average size stabs, like yours and others, will return to the original flight regime. How often does one get to fly in perfect conditions?<br><br>Aerodynamics says it is not possible with a Raf thrust line/VCoG offset.<br><br>Yes a stab is wonderful improvement for a Raf, and when I had gained that improvement I was quite happy. I actually argued that it was good enough. Didn't I Chuck B, and Ellsworth?<br><br>Being me, mostly bad, I just had to see if this CLT thing, which made sense to me, did in reality work.<br><br>That was the beginning of Firebird, and did CLT work? It sure did. To think that I was happy with the stabbed Raf!!!!!!! I was missing out on what is really possible.<br><br>Hybrid, that we know as the test bench for Firebird fly’s more pitch stable in average conditions without a stab than the Rafs do with stabs. Hybrid is CLT, and when we add the stab, wow!!!!! Is it possible to get any better than this? I don't know yet. Maybe.<br><br>We have opted for CLT so that we can keep the entry and exit user friendly. A lot of gyro designs have gone well past CLT, having the thrust line well below the VCoG. This has made a lot of the newer designs more difficult to enter/exit than Firebird. Does it matter? It certainly does for me as a would be supplier of Firebird kits, and fully built aircraft, to the general populace, who by the way, are the people who will grow the Gyro sport/industry etc.<br>The machines with the lower thrust line than CLT do have a slightly negative side. The stab has to be holding the nose down in s/level flight. That is just wasted energy. Also a sudden engine stoppage will cause the nose to lower more quickly than CLT, and the drag of the lower gyro parts increase this tendency. The machine will have "more towards negative G" than CLT with a sudden engine stoppage, and as the lower induced drag of the rotor allows the nose to start5 dropping, the lower parts of the gyro's parasitic drag makes the condition a little self-feeding. <br><br>The machines with the lower thrust line than CLT do have a slightly negative side. The stab has to be holding the nose down in s/level flight. That is just wasted energy. Also a sudden engine stoppage will cause the nose to lower more quickly than CLT, and the drag of the lower gyro parts increase this tendency. The machine will have "more towards negative G" than CLT with a sudden engine stoppage, and as the induced drag of the rotor slightly lowers the nose a little, the lower parts of the gyro's parasitic drag makes the condition a little self-feeding.<br><br>Now don’t get me wrong, I would rather have a Dominator or Sparrow Hawk over a Raf, even with a stab, any day. But at this point in time I would prefer to have CLT and not have to climb up into the cabin. Now I know a lot of you gyro people don’t mind doing this and will argue that it is not that difficult. That is your decision and you are entitled to choose the way you want. If it were just myself to consider, I would as a passionate gyro person put up with climbing into the cabin if it were the only way. Many people will not. From my perspective now, I have to, after safety, consider this side of things. <br><br>One thing that you have to give the people at Raf credit for is that they had the “sizzle” correct and marketed it well. The “sizzle” being a fully enclosed 2 place 4 stroke cross country gyroplane.<br><br>My point is that I do not believe that there are any benefits in going go past CLT, and if there is, I don't believe that they would out weigh the ease of entry and exit, and the more aesthetic appeal to the general populace, than the CLT machine. Once again, remember it is a % of the general populace who will grow the Gyro sport/industry etc, not us gyroplane diehards.<br><br>Aussie Paul.<br><br>
 

Aussie_Paul

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Re: The old Raf, stabs, and CLT thing!!!

I have had to alter a section of my CLT post. I posted it in a bit of hurry and had not proofed it.<br><br>Aussie Paul.
 

CLS447

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Re: The old Raf, stabs, and CLT thing!!!

Paul, are you saying that Groen Bros. upgrade goes past CLT to a below CLT? How about my new Air Command?
 

Mayfield

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Re: The old Raf, stabs, and CLT thing!!!

Chris,<br><br>I admire Paul's efforts vis-a-vis the Firebird.  Notwithstanding my admiration, he apparently thinks we have gone too far with lowering the engine thrustline, we, of course, do not think he has gone quite far enough.<br><br>There may be a few issues at work.<br><br>1.  There is no such thing as a CLT gyroplane if the variable load is not all concentrated at a point.  We know that this is not posible.  We can therefore say that the Firebird or the Dominator, the SparrowHawk, or your aircraft can be CLT at some load.<br><br>2.  Paul publishes that the uncorrected thrustline offset of the RAF is 10 inches.  I do not know at what load distribution he made his measurements.  We compute that the thrustline offset is about 13 to 14 inches too high with full fuel, and about 400 pounds of people.  I'm sure that the build on different aircraft will make this a variable as well.<br><br>3.  The Stability Augmented RAF 2000 and the SparrowHawk, has a thrustline offset from about 1 inch high to about 1.7 inches low, depending on loading.<br><br>Jim
 

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Re: The old Raf, stabs, and CLT thing!!!

Jim, Besides the cabin change & the stability upgrade kit, are there any other changes in parts ,materials or workmanship over the standard RAF?  I am trying to decide if I should start looking for an unfinished RAF or just buy a complete Sparrowhawk!!!!
 

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Re: The old Raf, stabs, and CLT thing!!!

Chris,<br><br>First, what are you and I doing at this hour sitting in front of computers?<br><br>Chris, there are some changes.  They are mostly in materials.  I want to be careful, because I believe that for the most part the RAF 2000 is structurally robust.  But to get certain things past my engineers I had to make some concessions:<br><br>1.  The landing gear blocks are 7075-T6<br><br>2.  The axles are 4440 instead of 4130<br><br>3.  The fuel filler is a fluid proof fitting with a check valve for breathing.  I can not guarntee that there will never be a fuel spill, but wanted to do as much as possible to prevent one.<br><br>4.  The seats are individual buckets with longitudinal adjustment.<br><br>5.  We are using a SkyDat flight instrument and engine monitoring system instead of analog instruments<br><br>6.  There is a host of other little things, that are hardly worth mentioning: McCreary Flight Trac tires, aircraft grade wiring, Potter and Brumfield circuit breakers and switches, No anodizing on anything other than the PSRU sprockets because, frankly, we could not make it work re: fatique.  All bearings are Timken, Aurora, SKF, Heim, etc.  I just did not want to cut corners here.<br><br>Thanks Chris.  I want to say again that for the most part, we think the basic RAF 2000 airframe is very robust.<br><br>Jim<br><br>"Stability is not an opinion"
 

CLS447

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Re: The old Raf, stabs, and CLT thing!!!

Jim, this is what I do first, every morning, except this morning I'm having pumpkin pie with my coffee!!<br><br>  How about rudder pedals, trim system, mast, rotor head, & that kind of stuff? Pretty much Identical?<br><br> I still have not had a ride in one of your machines, & am very anxious to do so!
 

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Re: The old Raf, stabs, and CLT thing!!!

Chris,<br><br>The rudder pedals and trim system are similar.  We have a separate trim attachment at the back of the rotor head vice the front, but still a spring trim system.<br><br>Our rotorhead is a typical offset gimbal.  We make it out of 2024-T3 because we are comfortable with that material.  We do not think there is anything wrong with the 6061-T6 heads out there.<br><br>Jim<br><br>"Stability is not an opinion"
 

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Re: The old Raf, stabs, and CLT thing!!!

Jim,<br><br>I seem to recall from our discussions that the rotor blades also represent a significant difference, not in construction quality perhaps, but in, I dunno, do rotor blades have a philosophy? Maybe even more so now, with RAF moving to a new blade. <br><br>Also, I don't want to put words in your mouth but I believe that your fasteners are all aircraft grade, and theirs historically have not been (I really hope that they are changing this, as it has caused otherwise preventable mishaps). <br><br>I also note that post-crash fire is common in RAF crashes. Since most of these accidents are nonsurvivable, that may be a matter of no consequence (I don't believe the fire has killed anyone, yet), but what about a fuel cell (in the motor racing, not hydrogen-electric sense) as a piece of safety gear?<br><br>I was looking at James Bodie's story of his crash in a Marchetti, and realised that if that accident had started a fire it could have killed him and pilot Si Smith. They were seriously hurt and not up to athletics at the time. <br><br>cheers<br><br>-=K=-
 

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Re: The old Raf, stabs, and CLT thing!!!

Kevin,<br><br>I have not, as of yet, found a suitable cell.  I have found many, but not yet one that will work.<br><br>I suspect, when funds allow, that I will have to go with a bladder.<br><br>Jim Mayfield<br><br>"Stability is not an opinion"
 

Aussie_Paul

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Re: The old Raf, stabs, and CLT thing!!!

Chris, I don't know without doing the calculations. I am extremely familiar with the Raf, and variations of.<br><br>Jim, the 10" offset has come from Dr. Stewart Houston at the Glasgow university. I believe that his people weight was over 400 lbs and 1/2 fuel.<br><br>Our gyroplane association conducted the VCoG of 6 dual seat and 6 single seat gyros 18 months ago at our National flyin. My Raf with a little over 400 lbs of people and I think it was 1/3 fuel came out at a little over 10".<br><br>Of course I have done the figures also.<br><br>That is a number of different calculations, so I believe I can reasonably assume that the 10" figure would be close. Below are the results from the Flyin 18 months ago.<br> ***************************************<br>Organised by mceagle who was part of the team who conducted the measurements.<br><br><br>Table of measured offset between engine thrustline and the vertical centre of gravity (c.g).<br><br>Positive values indicate that the thrustline is above the vertical c.g. while negative values indicate that it is below the vertical c.g. <br><br>Larger negative numbers reduce the pitch down moment that can result from reduced rotor loading, but increase the pitch down moment with loss of thrust. .<br>Larger positive numbers increase the pitch down moment resulting from reduced rotor loading, but reduce the pitch down moment with loss of thrust.<br>Research is ongoing to determine a safe range but most experts seem to agree that close to zero would be a stable gyroplane in most conditions.<br><br>The following figures are not corrected for standard pilot weight and are provided for general information.<br><br>http://www.firebirdgyros.com/VCoG OZ and US.jpg  <br><br>(The American figures are for comparison only and were taken from an article by Ralph E. Taggart, Kitplanes –May 2000. They were calculated using the same website “C of G program”)<br><br><br>Aussie Paul.
 

Aussie_Paul

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Re: The old Raf, stabs, and CLT thing!!!

I wouldn't think so Phil. <br><br>As the post said, those figures came from  a Ralph Tagget gyro article in Kitplanes a few years back.<br><br>Aussie Paul.
 

dae

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Re: The old Raf, stabs, and CLT thing!!!

Jim, your statement above about not getting the annodizing to work bothers me. Could you elaborate<br>on what you did to come to the conclusion that it was not a good choice for your application? How did you test the annodize? I have annodized all my parts myself and have had no problems........yet. I powder coated all my parts that I did not paint or annodize but I prefer the annodize finish and was going to annodize more on the next machine. Now you have concerned me. Thanks,  David Eiland
 

GyroRon

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Re: The old Raf, stabs, and CLT thing!!!

David do you still have any gyro stabs for sale? If so please email me privately. Thanks Ron
 

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Re: The old Raf, stabs, and CLT thing!!!

David,<br><br>I'm sorry that I worried you.  We would have liked to anodize several of the parts on the SparrowHawk.<br><br>I am not indicating that anodizing is bad.  We simply are of the opinion that we (AAI) do not understand enough about anodizing process control to safely anodize anything other than the PSRU sprockets at this time.<br><br>Everything about this seemingly simple process appears to us to give us too many unknowns until we better understand it.  Specifically:  The acidity of the bath, the time and amperage of the current flow, the post anodizing process, etc.<br><br>We know that anodizing hardens the surface of the aluminum.  How much with what process?  Can we do something wrong that results in cracks forming or spreading?  Are the cracks we are observing in many of the machines we are modifying the result of the anodizing process?<br><br>Again David, we are not indicating that anodizing is a bad process.  We simply have not yet had the time to develop the process control documents that will give us enough confidence to anodize our parts.<br><br>Jim<br><br>"Stability is not an opinion." <br><br>
 

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Re: The old Raf, stabs, and CLT thing!!!

Oh just tape it off and hit it with a touch of Rustoleum in the rattle can! Works for me ;D
 
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