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Author Topic: Just for fun - Dynomite Launch pics  (Read 1255 times)
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ptlove
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« on: January 29, 2011, 08:06:09 PM »

I liked this sequence for some reason, so since there is lots of IKE fever going around, figured I'd post some pics of my Dynomite doing the launch wiggle during a recent practice session. I've been trying different techniques to see how high I can get on the launch with a good transition, and this sequence is from one of my highest, as reported by my How High altimeter under the wing.

Enjoy!

Paul
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ptlove
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« Reply #1 on: January 29, 2011, 08:36:02 PM »

Another to the same altitude, viewed more from the front. Anyone else have any sequence photos of your best launches?
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Rewinged
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« Reply #2 on: January 29, 2011, 09:37:19 PM »

Cool, Paul! Looks a lot like my launches...

I have some sequences. Not really my best launches--from early last year--but not bad, either, and pretty typical of my "form."

There's a sequence of me in this thread, and several good pics of others:
http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=4550.0

Here's another launch from another angle.
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Olbill
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« Reply #3 on: January 29, 2011, 10:49:36 PM »

Maybe I'm just opening my eyes but I see something in these pics and in others by Rewinged that I haven't noticed before - the tailboom twisting counter clockwise (viewed from the rear) right after release. I'm not sure what the effect of this is on the flight path but for sure it wouldn't happen with a cross tail with equal rudder area above and below the boom. Also the smaller rudder area of the TLG compared to the R/C gliders probably contributes to the TLG maintaining the left turn after launch longer than the typical R/C glider.

But I guess everyone else already knows all this.
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Tmat
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« Reply #4 on: January 29, 2011, 11:01:33 PM »

Photo #2 from Paul's first sequence shows a wild amount of boom bend! Wow! I can see why the R/C boys are obsessed with stiff tailbooms.

Bill, I've seen similar shots from cross tail launches and they bend and twist in a similar manner.

Tony
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Olbill
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« Reply #5 on: January 30, 2011, 11:42:49 AM »

Tony
I'm familiar with the bend and understand why that happens but I'll have to go back and do some more research on the twist. I think the point I was getting at is that the Y-tail seems to have some unique effects during the launch that probably have a lot to do with why they work differently from the typical R/C type tail. Possibly if everything was a lot stiffer and more rigid the gliders might not behave in the way they do now.

Here's a pic that I may have posted before of my Apogee at release. It's hard to see the boom but you can get an idea of the bend by comparing the stab angle (normal flat stab) to the wing angle. There doesn't seem to be much twist here even though this is a very light indoor glider tube.

Another thing I noticed is that in Paul's picture there seems to be a lot of tailboom bend right behind the wing while the Apogee boom (no DT joint) has a more gradual bend that increases toward the tail.
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dephela
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« Reply #6 on: January 30, 2011, 12:29:54 PM »

Yes, the cross tail will also bend the boom and it's not an artifact from a digital camera. It happens the other direction for leftie tosses.

Interestingly, the first r/c dlg's were V tails!
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Dennis
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« Reply #7 on: January 30, 2011, 05:31:56 PM »

Ptlove, really incredible pictures there. Your practice field looks perfect, but you can't tell us that you are using the how high altimeter with out telling us how high!???
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sweepettelee
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« Reply #8 on: January 30, 2011, 08:00:38 PM »

Just picked up this channel and must join Big Jon S in asking How High? Undecided If I don't, someone else will be singing the "Curious minds need to know" psalm... Grin

So Paul, please bring that fine camera to The IKE, so you can compare some other flex/twists of larger TLGs with the bigger, stiffer booms than DynoMite-sized ones use.
I for one wonder if going to 25deg stab d'dral gives less tail waggle than 30deg? FYI, all my more recent ones are 25deg, as are Bruce K's, I see on Hoosier Daddy plan. A very good TLG, BTW.

A side note re the waggle of our fixed surfaces TLGs: I heard Stan thinks it may even be an aid to climb and transition. Reason is that stiffer booms tend to launch too straight, not making the left carve pattern seemingly needed to settle into proper ascent.

Leeper
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ptlove
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« Reply #9 on: January 30, 2011, 09:46:03 PM »

Jon, I knew I wasn't going to get away with that Shocked Shocked Shocked

Actually I didn't want to put it in there because I really don't know how accurate it is and don't want to start any altitude wars Grin. As has been discussed before on the forums there is skepticism as to how accurate this device (and other altimeters) are. In this case the sample rate is once per second, and as we all know a second is actually a long time when you're talking about the transition of a glider. I'd like to believe what it tells me is true, but I use it more for comparison. While it may not get the altitude just right for several reasons, if I measure enough flights and compare results for different techniques, I think it can be quite useful. This time around, i finally got organized with it's use. I let the video run for about 15 minutes, and never let the glider circle more than a quarter circle just in case there was some lift. I would launch, retrieve, and then walk up to the camera and state the altitude. Over the course of the test, I tried a few different variations on throwing style in hopes I could see a measurable difference between them...the main difference being an attempt to vary the steepness of the release. Also tried a bunch with lots of concentration vs. a bunch where I just grab the plane and wail it without thinking at all. I did about 5 launches of each kind so I could average the times.

So what did I learn? Not really sure. It takes a lot of time to analyze it all and there is definitely some fluctuation on the altitudes of each group of flights. I noticed that regardless of what I thought I was doing, the release angle was almost always very constant, and not as steep as I had wanted for the steeper trials. I need to do it all again with even more care, but it was clear that the launches done without concentration were better than those when I tried hard to focus on technique. When I did not concentrate, I found my arm hooking around to the left after release, and often my body would be kind of flying forward and to the left as well where I'd almost stumble. This is in contrast to how I was taught which is to end the launch with the arm pointing up and not hook it around to the left. I had been thinking this style (arm straight up at end of launch) does not seem to allow my body to follow through with that much energy, which I started wondering about. Then I went online to study slow motion videos of baseball pitchers since i was a pitcher as a kid and I remember that I'd stumble forward on the follow through. I found this:  http://www.youtube.com/watch?v=nTXNg2C1TaM&NR=1 Which i think is interesting because you can see that the body is moving forward after the release and the arm swings down under the chest and back around the other side of the rib cage. Food for thought I guess, but I know launch techniques have been discussed a lot on these forums. On the one hand i want to emulate the guys that throw the highest, but on the other hand I like to think there are several ways to skin the cat Smiley

I was throwing as hard as I ever have. When I started the video I had been throwing for about 45 minutes, and I felt pretty strong, although by the end of it I was getting a bit tired which definitely hurt the times near the end. So that also made this experiment less useful than hoped. Next time I'll start the video earlier.

So, you've been reading patiently. Here are the numbers:
My best two flights of the day were 112 feet. I had about 7 or 8 others between 105 and 110 feet. There was never more than I'd say 2 mph of wind to throw into, and often dead calm. I've had the altimeter on there before but there was always a bit of wind to throw into and I never got higher than 105 even with a bit of wind, so I believe my practice is paying off. The best two flights of the day were during the non thinking part of the trials. The other variations all had good and bad flights, so I'm just not that consistent I guess. The one thing I found was that keeping a wider stance definitely helped for me.It's a bit hard to describe what I mean by that since we're talking about a spinning motion, but I've been trying to focus on unwinding my upper body at the last minute and I think I manage to do that better when I try to keep my feet spread apart during the "dance." I start this by taking a very large step like a baseball pitcher. Another thing I was able to see in the frame by frame video is that I think the reason I kept launching at a lower angle than intended when trying to launch steeper was because I was letting my wrist open up too early so that during the last 180 degrees of spin before the launch the boom was no longer parallel to my arm, but rather was perpendicular so the plane is flying, which keeps the outside wing from dropping as low as I wanted it to in order to release at a steeper angle. I will try to remedy this next time out.

The worst flights of the session were between 85 and 90 feet according to the altimeter.

I will have my camera and altimeter at IKE, so would be happy and interested to take lots of videos of other flyers and with or without the altimeter on board. It would be especially fun to do comparisons with anyone that is flying the same plane. While I love my Dynomite, I'm starting to think about building something with less drag on the way up. Clearly addicted!!!

Regarding the boom bend, yah, that's cool to see in the photos. I have yet to ponder the science of the various choices one could make on that front, and for now am very happy flying a proven design.

Paul
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jim_buxton
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« Reply #10 on: January 31, 2011, 01:54:20 PM »

Altimeters are fun. Even if the absolute is not 100% accurate (and I think the better ones can be pretty darn close), they certainly give one an idea of trending towards better or worse technique.

High speed cameras are fun also. Here are a few that Stan took of me flying one of his NOS gliders, the Windenbox at the NATS last year.
~Jim
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Olbill
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« Reply #11 on: January 31, 2011, 04:12:54 PM »

Wow! Look at the rotation in the stab in the last pic.

Also before the launch there is a bunch of outward bend in the boom. It took me a long time to realize that this was NOT the part of the throw that stressed the boom the most but it's really interesting to see a picture of what should happen.

Lee
My comment earlier about boom bending was headed in the direction of what you say Stan thinks - that a stiffer boom might make undesirable changes in the launch profile. Since I have little experience with F/F TLG I didn't want to sound like I knew what I was talking about.
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ptlove
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« Reply #12 on: January 31, 2011, 08:11:15 PM »

Nice Pics Jim! I'm going to try the tongue thing next time out Tongue

What altimeter do you think is most accurate if you've tried a few?
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jim_buxton
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« Reply #13 on: January 31, 2011, 08:28:01 PM »

Ha, the tongue thing is incurable, but perhaps worth a third of a foot.

I have tried the How-Hi and te RAM3. I also did research on many others. I think any of the logging altimeters such as the RAM3 are pretty good. The how-hi seemed flakey at times.
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« Reply #14 on: January 03, 2012, 05:06:15 PM »

I liked this sequence for some reason, so since there is lots of IKE fever going around, figured I'd post some pics of my Dynomite doing the launch wiggle during a recent practice session. I've been trying different techniques to see how high I can get on the launch with a good transition, and this sequence is from one of my highest, as reported by my How High altimeter under the wing.

Enjoy!

Paul
great pics Paul. Note how all movies and stills of tip glider launches show large twist and inward bend of the tail boom. This is somewhat of a surprise as one would expect centrifugal force would bend the tail boom outward. Apparently there is enough tail aero force to twist and bend the boom inward overcoming the centrifugal force component.
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