Posted: Sun Oct 14, 2007 7:04 pm Post subject:
--------------------------------------------------------------------------------
A clueless bag of wind!
Mark
How you doing buddy?
1. - 3 point, no flaps ..... 250'
2. - Tail high, no flaps ..... 280'
3. - 3 point, flaps 2 ..... 280' carb heat on
4. - same, carb heat off ..... 200'
5. - 3 point, full flap at L/O ..... 280'
1. – 3 point, no flaps 230’
2. – 3 point two notches 230’
3. – 3 point no flaps 230’
1. - 3 point, no flaps 270 Temp 82, wind reported 180/8
2. – 3 point, two notches 280
3. – 3 point, no flaps around 400’
4. – 3 point, no flaps 310’ Temp 72, wind reported 240/6
1. – 3 point, no flaps 250’
2 – 3 point, flaps 2 190
3 – 3 point, no flaps 265
September 11, 2007 – 88RF – Joe and me at just above ½ tank – 82 deg F, avg wind 320/10
1. – 3 point, no flaps 270’
2. – 3 point, flaps 2 210
3. – lift tail, flaps 2 240
4. – 3 point, no flaps 300
bob turner said:,
Here's the deal - you can call me every name in the book, but if you have no numbers of your own, you really cannot argue with my numbers. Mark Drath can; he has actually taken the time to get data.
.
S2D said:Before the installation I was consistently getting off in one stripe and one space (just at the start of the next stripe)
This was stepped off at 65 steps or approximately 195 ft
After installation I was getting off in one stripe and half of a space.
this was 53 steps or approximately 159 feet.
This was a gain of 36 feet or 18% improvement
bob turner said:We have wash-in that is supposed to be 2.6 degrees less than that.
AkPA/18 said:Bob
If you look at my replies I have not called you any names--said you were lousy pilot or any of that. My contention frankly is that your data is meaningless due to multiple factors. When I posted your data I thought I was posting something that clearly showed that the TL does not enhance TO on 88RF. After reading your data---I can't clearly see that. You say your data clearly shows takeoff roll differences. I can't see anything clear in your data.
A: I assume you were testing for TO performance. Does this mean the shortest TO roll?
B: Why the lack of performance TO's IFyou were testing for shortest TO roll?
C: Do you feel that testing in winds 10kts gusting 20kts are valid conditions for testing?
No name calling here---just looking for some real simple answers to the above simple questions.
Mark
Absolutely UNBELIEVABLE!. YOU WERE NOT EVEN TESTING FOR THRUSTLINE DATA????????? But yet you write that " Alas. my data seems to indicate a decrease in takeoff performance"My original tests were not for Thrustline. They were to determine if raising the tail on takeoff was of any significant benefit. I was also checking to see if delaying flap extension was of significance. My answer to both, to my satisfaction, was no
Posted: Sat Sep 01, 2007 7:37 pm
We just got another Cub with the thrustline mod. Owner says that now it needs less trim.
One of the neat things about this particular Cub is that it never needed much in the way of trim - zero flap takeoff to full flap landing, and never think about the trim handle.
Another thing about it is that I have a reasonably full set of data from before the mod. We will get another set - with the usual caveat that there are so many uncontrollable variables in aircraft performance that the best one can hope for is to notice a trend. One variable is that the owner reports 2650 RPM static with a cruise prop - it used to be 2400 at 50 mph in the climb. And even then it was a screamer!
Posted: Thu Sep 06, 2007 4:26 pm
Got any ground roll numbers on that prize winning takeoff? We are just about to put a thrustline on a borer/160 Cub, and have a whole set of baseline data. They say 30% ground roll reduction - so we have numbers in mind for next week's tests.
posted: Fri Sep 07, 2007 12:28 pm
Thanks for the numbers. Here at sea level and 70 degrees, we have no Cubs that can come anywhere even close. I will take the time to do a sort of scatter chart, but right off the bat, we are getting 200 foot plus takeoff rolls in most variants of the 160 Cub.
Let me rephrase that: We have no Cubs with this pilot that can come anywhere close. Lots of room for improvement; we have averages of about 230' with a heavy borer 160 and two pilots (one to record the data). We are expecting an average of 160' after thrustline . . . 30%.
Takes time.Posted: Sun Sep 09, 2007 11:24 pm
My friends (we have four Thrustline kits installed here, all on my students' Cubs) all report significant improvements in all areas.
I will only have data on two aircraft, as the other two were converted without baseline data. If for some reason I do not get at least a 10% improvement, I will defer to data posted by someone who has gained such an advantage. I think a 10% improvement in takeoff distance would be way more than enough to justify the purchase of a Thrustline kit.
I won't post more until next week. We need about twelve data points on each aircraft, on varying days, to match the baseline data.
Posted: Tue Oct 02, 2007 1:51 pm I have collected data on about six different variations of Super Cubs, and have found that power and prop have more effect than any fancy techniques. I have data on 3-point, tail high, yank flaps, set flaps first, thrustline, no thrustline, stock wing, VGs, Charlie Center wing, and so forth. My data says best takeoff is lightweight Cub with 160 and Borer, and carb heat off. All the other stuff is lost in the noise, except for one thing that simply baffles me.
Posted: Thu Oct 04, 2007 12:49 am
None of these neat mods weigh much. A pound here, a pound there - what's the big deal. Best performers are still absolute stock with lots of power. Opinion, backed with numbers.
Posted: Fri Oct 05, 2007 12:58 pm
By the way, my tests emphatically show that the only mods that really enhance takeoff performance are those that increase power (160HP), thrust at low speeds (Borer) and aircraft weight (the lighter the better). I suspect extended gear will give you an un-measurable increase in takeoff performance. It will be probably under ten feet out of a total ground roll of 150-250 feet, and we get that kind of variation by the way we grit our teeth on liftoff. In comparison, forget the carb heat and add eighty feet!
Posted: Fri Oct 05, 2007 12:53 pm
On the other hand, if you take a single aircraft, test it, then modify it (as I assume Jerry has done) then if you take enough data (to smooth out external variables including pilot technique and atmospheric differences) you will get useful data.
I don't have a clue on wingtips, VGs, extended gear, etc. That's because all my tests are on different aircraft. I do have a clue on ThrustLine. That's because two of our aircraft have fairly good data before and after. I would never pretend to be good enough at reading airspeed indicators to tell any difference, but with two pilots - one flying and the other watching for liftoff - we get reasonably good takeoff data. I have shared most of it with you, and anxiously await somebody else to share before and after data on ThrustLine.
Posted: Fri Oct 05, 2007 6:59 pm
I got the data. I have not posted it. I have not said what my results are. I have said that I can see no difference in flight, but I qualified that by saying that I am not the best judge of flying characteristics. Martha has said that she can see an incredible improvement in handling. Joe has not said anything about flight handling. They, of course, both have far more experience in their Cubs than I do.
Joe took the data, while I flew. He will surely share it with you and you can post it. He can tell you anything you want to know about how it was taken. He has data taken in Martha's aircraft as well.
Martha reported that her static RPM went from 2400 to 2600 as a result of the throttle cable adjustment done when TL was installed. We have found that a decrease of 100 rpm will add about eighty feet to a Super Cub takeoff roll. When you look at Martha's data, look for the performance increase you would expect from a 200 rpm increase in static runup.
Re-post your data. I think your kit is extremely well done and has the best paperwork of any STC I have yet messed with. You do have raw data?
Posted: Sun Oct 07, 2007 7:27 pm
Mark is right - we ought to start a new thread for data only. Nobody, except three local pilots and Mark, know what my results are, except that before I did the tests, I said I would not post if I got less than ten percent improvement. I kept my word.
Posted: Mon Oct 08, 2007 1:01 am
You know Dave, there are sixteen pages of good stuff on the Thrustline - one guy asks a reasonable question, and qualifies it by saying he may not be a good judge of handling, and you want to throw darts at him? Here's my challenge: tell me how many feet it takes in ground roll to get off the ground before and after Thrustline., in the same aircraft at the same weight, etc. So far, I am the only guy who has stated he has actual numbers. Christina and Mark must have numbers, since otherwise they would have no basis for their 30% and 50' statements. I will only give my numbers to Mark; my students have copies and can give them to anyone they want.
Posted: Tue Oct 09, 2007 5:12 pm
You can tell from photos? Anyway, thanks for posting Mark Drath's numbers. I will forward my data to you, and maybe we could start a new thread with Mark's data? I might be able to extract the two or three cruise data sets, but I have no idea what the conditions were on those. At least Mark stated that conditions were similar.
You cannot make one trial before, and one trial after, and get meaningful data. However, you can do a hundred in all kinds of winds and loads, and get fairly precise data.
bob turner said:S2D - that was a reasoned reply. Let me see your actual numbers - trials, weights, techniques, weather, and then we can compare.
aktango58 said:First, if you do not fly the plane by feel, you won't know the difference in the TL, or VG's for that matter. Most of the gains in these have to do with how the plane feels in the edge, (square corner area???) YOU may not notice a difference, but I do, and it is not just hocus pocus belief, it is rock clearing, willow jumping, not stalling on the edge fact.
bob turner said:You guys make me feel like I should be defending myself. Remember, I said I cannot feel anything in an airplane - I was indeed an airline driver who didn't know anything except the book speeds. I did say it will be a cold day in hell when I land on one of those short rock-filled sandbars. And I gave you all the parameters of my tests, so you could see exactly what I did. I made no claim of using ninth grade science project accuracies; indeed I stated that I had no confidence in less than +/- ten feet.
I am not sure why it is necessary to beat me up. All the things you are beating me up about I have admitted beforehand. The right way to beat me up is by presenting data that refutes mine. Just stating that you are always airborne in less than a hundred feet is not particularly convincing - and telling me that detailed data is posted elsewhere is not helpful unless you tell me where. I went through this thread, and so far I haven't seen any specific trials posted, except for the ones I posted.
Sure, my data is suspect. I expected a couple percent improvement - I too thought that pointing the thrust up slightly ought to yield a slight improvement in takeoff roll. I have drawn only one conclusion from all of this - that is, if somebody says something you do not like, hold him or her in some gentle form of contempt. No real point in countering with any factual data.
You may find my skills as a Cub pilot not up to your standards - you are all welcome to come down here and fly with me in my aircraft. That way you can determiine my skill level by my flying, as opposed to my sub-ninth grade grasp of engineering terms. And as a bonus, I get to see you fly. Maybe I can learn how to consistently cut my takeoff rolls in half, just by changing my technique!
bob turner said:You guys make me feel like I should be defending myself. Remember, I said I cannot feel anything in an airplane - I was indeed an airline driver who didn't know anything except the book speeds. I did say it will be a cold day in hell when I land on one of those short rock-filled sandbars.
I am not sure why it is necessary to beat me up.
!