Has anyone used the Eagletree data logger in their racer?
I am considering purchasing one but would appreciate any info particularly from pylon racers to help with my decision.
www.eagletreesystems.com

I have never used a data logger. I have seen a few people try them out. The device provided information but how to use it seemed to be the issue. The few people that I know did not follow up and really put the information to good use. It seemed more like idle curiosity. You may be able to us it for your application but racing is pretty basic stuff. We can tell if we are fast enough for free.

I could see a monitoring device where in flight adjustments could be made. But just an information collector I am not so sure. There are not too many racers that bother with them.

Ed S

My racing partner and I split the cost of one earlier this year. We are both going faster now. If nothing else, it's great for choosing among different propellers. Some make the engine sound terrific, but don't improve the airspeed. Others go well in the straights, but bog down in the turns. All this is useful information.

I like it better than the radar gun because you don't have to stand under the flight path, and the readings are not affected by wind.

Duane

I have to agree to the last poster "dhg". Being in the UAV field it has proved to be a valuable tool. You must be aware of the aiborne measurements it can gather. Using this information will fine tune your airframe for all environmental conditions.

Yes, Duane and I have been using the eagletree system to test planes, props and engines, clearly an advantage to finding out what props work well, which props slow down too much in the turns and which props work well in the straights and in the turns, I could not see a 5mph to a 7mph difference in speed, but the data recorder can!!! It clearly helped up to develope props, we run the black prop and see if we can beat that with wood, what was interesting is like Duane said, some that ran 24,500 or 25k on the ground sounded awesome in the air, we thought we had the mother load... Wrong, it sounded great, but was not faster, but slower by 8-10mph than the prop peaking at 23,200 or so... We thought by sound and looking at it the higher rpm prop was smoking, but in reality it was slower!!! WE had one prop that would unload and go like stink across the field, but when put down on the course it bogged down to much and ended up being 10-12mph slower than the black apc prop... let it go across the field and it was 4mph faster than the black prop, this was usefull info!!! They can also measure by a dual axis g force meter acceleration out of the turns and off the line to # 1.
Rpm in the air is helpull too... You can make sure you are reaching that majic 27k number in the air and when you reach it!!! Is it right after the turn, or is it half way down the straights or is it right at the end of the straight right before you pull again???
These are great quesions that can be answered by the data recorder... The clock will give you total lap times, but to study what the props and plane and engine are really doing in the turns and in the straights, the recorder can not be beat!!!
If nothing else it let me know the apc black prop is hard to beat and out of 15 props, I made one that was slightly better!!!
That let me know which one to run!!! Then we ran Duane's plane and it was on fire, it let me know how the extra weight on my plane affected speed in the straights and turns!!! He had 8mph on me!!! Boo Hoo, if first you do not succede, try try again... I would have never know this because our lap times were almost identical!!! This shows you can take a plane that is 8mph slower and still turn the same lap times as another pilot with a faster plane, now if I could get my plane going that extra 8mph, I would be set eh???!!!
Of course Duane was running his monster BSE Jett Motor...

I will take back some of what I said. Obviously there are at least two exceptions. Interesting to note they kept it secret!!!!

Ed S

Yea, that makes me wonder how benificial to my racing cause it is to spread all my secrets and knowlege to the entire pylon community??? I have already been yelled at for talking too much... Ed thats right "the data recorder is useless, there is nothing you can find out from it than you can find out from using the trusty stop watch!!! Big waste of money!!! Do not try this at home...
Save you're money for a new engine instead...

Judging from the instant popularity of Ed's backwards fuel tank idea, I'd say the safest place to keep your speed secrets is right here on the Web. After all, if a guy's willing to spread the info around, how good can it be?

Ok, Ok it is war is it?


So with all the money spent on the Data Logger how come it took yuo guys so long on the NMPRA site to figure out head shims??????????


Data logger, sounds like something they use to chop down trees!

Ed S

"Data logger, sounds like something they use to chop down trees! "


Yeah, let the "chips" fly!

Ok, I have to reply to this one, aaaaa it did not take me any time to figure out my shims, what I wanted to do was switch from my delponte method of measuring timing and try Darrols low timing of 189 and 10, but he would not give me a simple straight answer and asked me to post it on the nmpra web site, and bye the way I got many emails from fai guys and speed guys telling me they do take into account between 2000 and 3000 in qm motors and fai motors and the speed guys informed me they not only take into account the 3000 for rod slop the also must put in another 2000 for rod stretch in a motor that turns 40k, they assume the piston will go up 5000 higher than you would measure from bdc minus stroke!!! So its not that I did not know how to measure a motor both ways, as I have tried all the timings many times for over 5 years now, its just I wanted his way of measurement, not the actual numbers, but he wanted me to post that on the nmpra so everyone could see the question and he could answer it.... NOt My Choice!!!
So with all that said, I did switch from my normal way of measuring to the bdc minus stroke method and the motor is going pretty good now, so I will leave it... On my qm motors, I have been running them right were Dave sends em out, they are new and run very well, thank you....
and thats all I have to say about that.....

How did you guys position the pitot tube?

I had been considering getting the Eagle Tree System unit, but I couldn't figure out how to place the pitot tube out of the prop stream without causing drag or changing the flight characteristics. I've even considered building wings with the pitot tube built into the wing.

Are you using the [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXHBZ0&P=7]Eagle Tree Systems Flight Data Recorder V2 [/link] or the original V1??? Since the original doesn't mention the G-Force module, I'm guessing that you have the V2 version.

For those interested, the manuals for the FDR V2 and accessories can be found at [link]http://www.eagletreesystems.com/Plane/plane.html[/link]

We are using the v-2 version, has 16 datum points... I drilled a small hole 3/32 in or close to leading edge of wing about 15" out from fuse and ran the tubing inside of hollow composite wing and had it drop out inside fuse... Duane made a foam wing core and made a trench to lay the tubing in, all of our planes now have the set-up built right in the wing so we can plug in the recorder at any time in any plane!!! It only weighs about 3/4oz and is the same size as a small receiver...

So after all the allowances for "Rod slop" all the allowances for "Rod stretch" the beating with the mallet AND the data logger, they run best as supplied by somebody who really knows what he is doing.

For even better performance try the backwards tank!

Ed S

Ok, you have pulled me in again, I must reply to you're elitist attitude, I guess you would have to re-read all my post to know what I am talking about and how motors are measured, but as I stated before, Dave Shadel and Mike Del ponte and John Williams all measure them the same way!!! So the motors sent to me by Dave are set up by the mallet method!!! They do take into account that 3000 mentioned!!! So I would get the same readings as Dave or Mike and when I measure them as they arrive from Dave they are 190 to 191 and 13..... If you measured it you would say its 193 to 194.... So whatever, since I usually run them in this area anyway, I do not change them.... What this has told me is not many people know about the issues of piston speed and inertia.... YOu included, I should have kept my mouth shut and will not fall into Darrol's trap again, Darrol and I have been arguing this point for over a couple of years now... He does not belive it should be part of the equation and Dave just sends them out thinking they are all 185 with no shims, I feel Dave knows exactly what he is doing and he adds this 5000 under to get the 190-191 with mallet method or at least he subtracts out the 3000 I have mentioned, I do not whack them anymore, but just assume the forces of inertia at 27k are enough to overcome the compression forces and the piston is going up farther than you measure with the bdc minus stroke... I do not want to argue about this anymore, some do it some do not, I have tried both methods and what I have learned is they run better when you take this into account for qm motors, but not so much for quickee motors, another thing I learned is when you take this into account for quickee motors they run good on the small props, say 20,300 on a good quickee on the 8.8x8.75, but not so good on big props and what this taught me is there is two ways to set up you're motor, either for small props turning high rpm's Mallet method, or set up for big props with no account for rod slop... What this really means is you can have a low liner and low head, but not a high liner and low head...
I now have the knowledge to make my motors run good for either set-up... I was never sure why some motors would go like stink on the small props, but not on the big ones, now I know, I was setting them up for high rpm and small props and then trying to get the big props to run good at that high rpm setting, so I did learn something from all this discussion of piston speed and inertia forces and where they begin to take over the compression forces.... I learned I must choose what type of prop I want to run and maximize my motor for that prop!!! That is working very well and I went faster than I ever have at our last race a couple of days ago...
So what ever works for you is great, I will use what works for me, and as far as the data recorder is concerned, there is no question it has helped me to better understand what I need to do to get my planes to go faster!!!!
See Ya,

John,

I'm really glad you shared the info about the Eagle Tree Flight Data Recorder. I had been tempted, but wasn't sure if it would be worth the money and effort (and risk). Now I'm convinced that it is worthwhile, and I want to get one soon. I'll have to figure out some way of mounting the rpm sensor on Quickies as well, unless you guys have already done that too and will share your method.

I'm already trying to figure out how to build the pitot tube right into composite wings. I can probably do what is done with tail skids and just notch the top and bottom wing molds on the LE. For wings without a pitot, I can put in a short section of fiberglass rod and sand it off after popping the wing out.

BTW, what is the fastest airspeed you guys have gotten from a QM-40?

John,

I don't know what is going on - I must have some sort of filter installed. Not sure what your previous message said????

Kurt

(just kidding)

Its the JayZBaby filter

You guys are funny, that made me laugh... I guess I do have a tendency to whine a little....
I have heard from Travis and Fred they got a qm in a dive and it peaked at 224mph, must be over-running the prop at that point...
What was interesting is what we saw at sea level and up at 5330' in Boulder, we saw about 175 to 184mph on the course at the nats and 159-168 on the course at the Boulder field, about a 10% loss in speed, just about 20mph slower up here at altitude, it seems about right, I always think, these things are sure doggy up here, I heard one of our local racers state the same thing, " Do you find yourself taking a nap on the way to one???"
I always wondered what the loss was, now I have a pretty good idea, what nice is that also fits the engine loss ratio's of about 10-15%...
Oh Yea, Kurt and I now have Jay Z Baby filters on sale!!! 15.99 obo...

200 + mph's, too cool. I don't know why anybody would waste time on those delta wing things for speed when you can do Q40's

I went to a fly-in in cheese land this weekend and the wowed the crowd with my old Q40. Nothing like stopping the crowd with one of those hot rods.

Maybe you guys should run the short course. That would liven things up a bit.

Thanks for the airspeed info. Now I can feel comfortable stating 180 mph for Q-40.

Yea, that is a good point, the delta wing guys and other speed demons, like the jets seem to make big circles and then fly by the pits in a low high speed pass... Now that sounds cool and looks pretty cool, but nothing like the qm's... I like to do a simular high speed pass and then right when the plane is in from of the crowd, I pull it hard and rocket out the other direction... People are blown away at how hard these planes can turn... That is what is impressive in my book, the turning capability is so awesome, its always fun to hear all the pilots commenting on the g- forces, speed and turning capability of these racers, much more fun in my opinion, Just think of one of those deltas or jetts trying a 180 degree turn at 190mph!!! Can you say wing fold and or high speed snap??? I knew you could...
Go Quarter 40....

I'll second that. The ability to swap ends quickly is what sets the QM-40s apart from the straight-line speed airplanes. (Of course we never do it coming toward the pits.)

Don, regarding the installation of the pitot tube: The Eagletree unit comes with a short section of plastic tubing that looks sort of like inner Nyrod but has a different inner diameter. If you want to set up several airplanes and get meaningful comparisons, you'll need to use the same size tubing on all of them (and probably a very similar installation, although we haven't yet figured out what all the important variables are). That would mean settling on some kind of tubing that you can get plenty of at a reasonable price, and that will be around for a while. Inner Nyrod would be one possibility.

Because the data logger measures airspeed using static pressure, and the size of the opening on the sensor is fixed, if you change the size of the pitot intake you'll either have to recalibrate the sensor or live with the fact that your airspeed readings will only be "IAS" (indicated airspeed), not "TAS" (true airspeed). As long as you're making your own test runs and comparing your own in-house IAS readings, that won't matter. For example, you'll still be able to tell whether one propeller is giving better speeds than another. But if you want to know whether your setup is going faster than somebody else's in another part of the country, you'll want to use TAS readings. That means either buy more pitot tubes from Eagletree at $5.00 a pop, or recalibrate the sensor for whatever tubing you're using instead.

Oh, and another thing about comparing one airplane to another: If one of the airplanes has a hole in the nose or tank compartment somewhere that's boosting the pressure inside the fuselage, and the other airplane doesn't, it will make the first airplane look slower than the second airplane even if they're equally fast. John (JayZBaby) and I suspect that's what we have going on with our Pole Cats, since mine reads several mph faster but they "look" the same speed and our heat times are very similar. We thought maybe the routing of the pitot tube through the wing was affecting it, but now we suspect it's the fact that he opened up one of the holes in the fuselage where the fuel lines come out, and it's ramming air in there. More pressure inside the fuse, less difference between that and the pressure at the front of the pitot tube, adds up to a lower airspeed reading.

Bottom line, I'd say the data logger is better for improving one airplane than for comparing two airplanes. But then, as Ed has already pointed out, we get those comparisons for free at every contest!

Science Guy

__________

Duane Gall
RCPRO

FYI - IAS is measured from the difference in dynamic and static pressure, if done properly. Dynamic pressure is what is being "rammed" into the front of a pitot probe. Static is a reference, based on your absolute pressure. If you are saying that the size (diameter) of your pitot probe inlet makes a difference, then that is an incorrect statement. Pressure is pressure as far as the dynamic pressure goes, as long as the system has no leaks. Doesn't matter if you have a 1" or .10" hole there. Odds are that you'll see huge errors by not having the static port outside of the fuselage. The best way to measure is via combined pitot-static probe setup.

Michael

Good point, we were not sure about that one... We now think the large holes in the front of my fuse was the cause for different airspeeds, they were grommet size holes that ended up being without the grommet, so I have a ram air affect going on inside the airplane where the recorder is and this recorder has a static port and also measures altitude, with pressure changes due to the ram air affect of 180mph air coming inside one plane and not on another, the one with ram air reads significantly lower...
Duane actually had it right the first time, he explained why the size should not matter and I listened and was not so sure, we had somthing going on, but we were not sure what it was. The tech at Eagletree said there is a 9% error for our altitude about 5330'
but I was originally seeing 153mph and Duane's was at 168mph and they looked close. The tech suggested pitot tube size can make a difference??? You seem to know this is not true, the only other explination he could think of was a change in static pressure by either a kinked line or air coming inside the fuse and changing the static pressure and giving a false reading, if its not the pitot tube size, its either a kink in the tubing or the fact I have two 7/16 size holes in the front of the fuse that are allowing air to rush in at high speed and change my static reading, which changes the dynamic difference, which gives a false low reading....
GEEZE, I would have prefered a high reading, you know 205mph, man my Polecat is Hawling Butt!!!
Thanks for the input, I will seal holes and re-test...