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Author Topic: Launch grip finger position and crash report  (Read 1303 times)
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Rewinged
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« on: August 16, 2009, 02:19:55 AM »

I finally got some flying in on my Mumbo Jumbo...

I crashed the first flight (I flew without fear, badly), but no breakage.

 After coaching from my flying partner for the day, Ed Berray, I had some good flights, and one very good one. My problem was a rollover to the left, along the lines of an earlier thread by Randy Reynolds. Most of my OK flights had a little of that, but recovered. My very good flight had no rollover, but a perfect climb and transition.

Then I threw it into the ground again. The result is shown below. Fortunately the fuse and tail weren't damaged, and I was able to repair the glider. (Or so I believe--test glider yet to come. The repaired glider "flying" in the flower garden while the wing is clamped is in the 2nd pic.

My problem was releasing too late, and too high, so that the glider was already rolling to the left as it left my hand.

One issue that came up was how I was holding the glider. I am using the thumb-on-bottom approach, but I didn't have good control. I was using a glove which gave me a great grip, but either the glove gave me a lack of feel or my fingers were in a bad position on the top of the wing. I was mostly holding with the side of my index finger, and Ed said I should have my fingers spread out on top, holding more with my fingertips.


I watched some of the videos from USIC, but I couldn't tell how people grip the tip. Does anybody have any pictures showing the proper (thumb-under) grip?


Another thing, watching the videos, is that I was starting with the glider too low, which forced my acceleration to be up, perhaps causing my late release with the glider already rolling left. Does that make sense? Watching video of Stan B--it was especially clear with the 1-step, no-spin launch--it looked like he started with the glider high, and first went down then back up.

Thanks,
Bill
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Launch grip finger position and crash report
Launch grip finger position and crash report
« Last Edit: August 16, 2009, 02:35:43 AM by Rewinged » Logged

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geneulm
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« Reply #1 on: August 16, 2009, 11:45:57 AM »

You experts chime in here...

I'm sure there are folks with MUCH more launching talent than I, who are able to consistently launch at an upward angle. I am not one. I try to launch as level with the horizon as possible -- shoulder height, getting full rearward extension and releasing at the same level at a point on the near horizon. Like pitching, if you are right handed, the model will go the exact direction that your left foot is pointing. Pick a spot on the horizon you want it to point and end up there w your left foot.

Let the model's wing do the climbing -- don't pitch it up.

So... are you launching level (good) or at some angle from the horizon toward vertical? (bad)

If I am understanding right, it also sounds like it is 1) slipping from your hand; and/or (depending on the launch) 2) holding on to it too long. Need to do whatever it takes (grippier sand paper, post, whatever it takes?) to allow the model to stay in your hand while keeping a lighter grip -- thumb on the bottom, first three fingers on the top works best for me.

Make sense?

Gene
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Rewinged
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« Reply #2 on: August 17, 2009, 11:26:33 PM »

Thanks, Gene.

I think the tip about throwing at a target will be very helpful. It seems obvious now that you said it, but I wasn't doing that. As you mentioned, some people are able to launch at an upward angle. However, I think that is something to work toward, not something I should try now, because it makes the release timing more critical. I was holding on to it too long. I will try and launch more level for now, and the release timing shouldn't be as big a deal. Aiming at a target should help the timing, so with those two things, plus some other advice I received via e-mail, my launches should at least be a little safer.

Thanks again,
Bill
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JonSayre
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« Reply #3 on: August 19, 2009, 12:25:03 AM »

Bill,

I also throw very flat, just as Geneulm said let the glider do the climbing, if I throw even slightly upward the glider wont roll out perfect. Release timing is just as critical as launch angle, with practice it will be easy! It took me four flying sessions to get it down and only now am I getting consistent. I hope the repair went well make sure that wing will stay on! I use the thumb on bottom with usually two or three fingers on top. I have a strip of sandpaper on top and bottom of the tip where it feels best. Can you explain the climb path a little?
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« Reply #4 on: August 19, 2009, 10:54:13 PM »

Thanks for the comment, Jon.

Re the climb path: On my best flight, I did launch fairly level, and it climbed at about a 45 degree angle, perhaps peak angle a bit more and average a bit less, and it turned 180 to the left and leveled out. When it leveled out, it was probably at an azimuth about 70 degrees from the original launch direction, and about 60 degrees up from the horizon.

Maybe. That's from my bad memory.

I'm going to try the 2 or 3 fingertips on top method. I was holding it with the edge of my index finger on top.

FYI, Stan B tells me that there is no issue with launching horizontal or more vertical, depending on the incidence. For now, I am definitely going to keep it relatively flat, and try to grow into more of an upward trajectory. Right now I just want to keep my only TLG in one piece!

Speaking of which, I am quite confident in my repair of the wing/fuse joint. I took my time, used Ambroid with pre-gluing, and clamped it very well for a couple of hours. I prefer CA, but even the slow stuff would not have given me enough time to make sure the wing was set properly.

And I hope to build another glider for a backup--but not before this weekend.
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Randy Reynolds
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« Reply #5 on: August 20, 2009, 12:18:00 AM »

There are at least four grip methods and I'm not so sure there is a "proper" version. Most of us in the MMM club grip with thumb on top and the index finger crooked on the bottom surface. Notice that it seems to use an entirely different set of arm and wrist muscles. I felt much more control this way when releasing the airplane.

One thing we have learned is that the launch can certainly produce several anomalies as can structural joinery. Some gliders behave right away and others take dis-assembly before they're right. Can you try having someone shoot some videos of you launching for self-analysis?

I know it's frustrating trying to sort out a problem becuase the worst results can be broken airplanes with the subsequent repairs which often add their own set of issues as I have previously documented. Lately we had two new airplanes develop the dreaded wing-overs only to find out that the finish and paint used began to warp flying surfaces under the hot sun. Sanding out the flying surfaces to get rid of the offending paint solved the problem. Stick with Design Master is our motto these days.
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« Reply #6 on: August 20, 2009, 12:56:09 AM »

I'm glad Stan mentioned that angle depends on incidence. As you saw in the USIC video Stan seems to launch at an angle that mimicks a javelin launch climb angle. I assume he uses a bit less incidence. One thing I always wonder is if launching more vertical is better. Considering that getting from point A to point B would be easiest in a straight line. My Maxine goes out in front of me then spirals right while progressively increasing climb angle. It seems to travel twice the distance to get from A to B than if it were to go in a straighter line. I notice Bruce's models climb remarkably straight then magically plop out at the top requiring less launch speed to achieve the same height!

Bill I will be coming down friday and will make sure to hang out with you through the weekend as I have a new glider that I need to try and trim so maybe we could bounce ideas off each other.
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« Reply #7 on: August 20, 2009, 02:44:22 AM »

Thanks, guys.

Randy, I am totally new to TLG (and relatively new to semi-serious modeling) so I am pretty sure that my issues stem totally from my launch. The outing was my first ever, and I did have some success, including one very good launch and transition, with decent altitude. So I don't think it is the plane. Also, I am also using Design Master, and not much of it. The finish is the same as I have been using on my CLGs, which should be even more sensitive, and I have been pretty successful there. My most recent flew perfectly the first time off the catapult, and subsequent flights remained perfect

So, for now I am focused on launch technique. I've got some things to think about, and I think I'll be OK. I think the video is a great idea, and I'll see if I can get some this weekend. Jon seems like a potential cinematographer, based on his post!

Jon, you're obviously way ahead of me in this, both in launch experience and building. It will be a pleasure to spend time with you this weekend. What are you flying besides TLG? Unless I suddenly turn my One Night 28 into a One Day 28 and build it on Friday for P30, I'll just be flying TLG and CLG. This will be a good weekend for learning, regardless, and I expect my CLGs will fly well. Picking air will be my problem there.

--Bill
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« Reply #8 on: August 22, 2009, 09:38:26 PM »

Just a few observations with respect to grip finger position (I'm no expert on this so please take this with a grain of salt!).
If you look at the classic grip used in R/C TLG with the throwing peg, you'll find the index finger on top, the 2nd finger on the bottom of the wing (with the peg held in the finger tip pads only) and the thumb resting lightly on the wing leading edge. Note that this grip rotates the wrist nearly 90 degrees and the elbow joint is now closer to vertical than it is to horizontal.

The thumb on bottom grip (with either one, two, three or four fingers on top) rotates the wrist so that it is near horizontal. The elbow joint is also rotated closer to horizontal also.

The thumb on top grip (such as what Randy uses) more closely mimics the wrist and elbow position used with the throwing peg. Thus the wrist is rotated to a more vertical position, and the elbow joint is also partially rotated towards vertical.

I spent about 15 minutes at work with a flat ruler (while no one was watching! Shocked) trying various finger grip positions and I have a few observations:
- with the thumb on top grip it is much easier to lock the elbow. Try it in the air and you'll see what I mean.
- it is also easier to cock the wrist backwards. This is a wrist position that allows a greater lateral movement than when rotated towards horizontal as when using the thumb on bottom grip.
- the thumb on bottom grip is more prone to allow a bend in the elbow. It's harder to keep your forearm straight.
- it's harder to cock the wrist backwards with the thumb on bottom grip
- as Randy says, the thumb on top grip appears to use different muscles, or at least keep some more immobile. There's a different feeling in the shoulder and wrist.

I've always used the thumb on bottom grip with several (2 or 3) fingers on top. I tend to suffer from both the bent arm syndrome (from time to time) and the hook launch (because of holding on too long).

Tonight, while flying some small catapult gliders with my 7 year old nephew Jack, I decided to try tip launching the 8" clg with different finger grip locations.
I was very pleased with the results I got with Randy's thumb on top grip. I was able to keep my arm straight (it's hard not to with this grip) and seemed to have more control with release timing. I got some very nice 40 to 50 foot high launches with nice recoveries (hey, it's an 8" glider that weighs 4 grams, I think that's pretty good eh? Grin).

I think I'll try switching to the thumb on top grip with my big gliders the next session out.

Tmat
-by the way, I had no idea if such a small glider could be tip launched successfully. And no Y tail in sight! Shocked
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Randy Reynolds
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« Reply #9 on: August 23, 2009, 04:12:40 AM »

Tony, to tiplaunch an 8" standard set up glider successfully is remarkable I'd say.

The thumb on top grip allows a pretty good snap at the end of the launch release which increases launch velocity in my view, similar to a golf swing. This however also permits one to "overcook it" so some practice is useful. Mark Covington in our club who is a pretty powerful thrower had to re-time his release a bit earlier to avoid this.

I've also found that a sharp grit sandpaper increases the security of the launch at some cost of skin on the side of the index finger if you throw too long. What's a sharp grit? This requires some shopping around but for me the 3m wet or dry 220 grit abrasive paper is the right stuff for non-slip but I have to dull the grit somewhat or I'll remove skin after 6-8 launches.
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« Reply #10 on: August 23, 2009, 03:17:05 PM »

Randy, I did re-trim the 8" glider to have a left/right trim. But I did have some successful launches with the left right trim. But it required a very straight launch.

I agree that the thumb on top launch can allow for a healthy dose of "wrist snap" at launch. If timed correctly (and that's the rub isn't it?) it should add some extra velocity. Timed incorrectly (ie: too late) it either does nothing for the launch or can cause a bit of a hook if you hold on too long.

Thanks for the sandpaper grit tip.

Tony
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« Reply #11 on: August 23, 2009, 05:13:36 PM »

Excuse me if I'm spouting from the wrong orifice but it seems to me there is a big difference between TLG with and without a throwing peg.

Without a peg, you are pinching the wing between thumb & fingers and almost certainly forcing an attitude of sorts.

The plane swivels from a peg and may take a more natural attitude on launch. This may be part of the "forgiving" launch that Leeper and other gurus talk about. They also say TLG should have a lot more difference in AoA between wing & stab to retain this nice feature.
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Tmat
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« Reply #12 on: August 23, 2009, 05:53:56 PM »

Ricardo,
Most modelers that use the throwing peg just let the peg rest on their finger tip pads and don't "pinch" it with the thumb very much. It's held lightly so no attitude is "forced" on the model. The model is allowed to "fly" in the hand. So not that much difference imo (peg or no peg).

Leeper and most of the other TLG experts are not using the peg. The forgiving nature on the launch is due in part to the extra declage most use (about 1.5 to 2 degrees versus 0.5 degrees for a clg).

Tmat

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ricardo
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« Reply #13 on: August 24, 2009, 06:04:08 AM »

Quote from: Tmat
Most modelers that use the throwing peg just let the peg rest on their finger tip pads and don't "pinch" it with the thumb very much. It's held lightly so no attitude is "forced" on the model. The model is allowed to "fly" in the hand. So not that much difference imo (peg or no peg).

What I meant was, without a peg, you have to pinch. So unless you are a guru, you many not be allowing the model to "fly" in the hand.

But I may be spouting from the wrong orifice as usual Huh
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« Reply #14 on: August 24, 2009, 08:23:03 AM »

Ricardo,
I see what you mean now.
Yes, a light grip is required in both cases. Hence the requirement for either a good sandpaper grip or a grippy rubber glove. More friction allows for a lighter grip.

Tmat
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Randy Reynolds
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« Reply #15 on: August 24, 2009, 10:22:45 AM »

I'm not buying the light grip idea. In golf that is certainly the notion but one holds a round grip with both hands and several fingers.....not the same thing.

Also in golf the experts want you to putt without using the small motor muscle movement in the hands and wrist. I'm not buying that either, at least to some degree.

I believe that the human mind is conditioned to controlling small movements during athletic activities and thus the throwing motion involved with the tip launch is built in naturally. I suppose that some people are more gifted or skilled in their athleticism and this will have a bearing on what grip is best. Not that I'm against the peg at all and there are times I'm sure I would do better if I had one. However the pegless concept is one of what's best for the glider during thermal flying and that's probably most important.
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geneulm
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« Reply #16 on: August 24, 2009, 11:56:14 AM »

More spouting? The following is the answer (via Larry Pelatowski) to your "light grip" needs: rubber "Finger Tips" available through Office Max. Stock number OM97430. Sort of a nubbly natural rubber finger and thumb condom sold to allow people to easily count stacks of money and other paper (no joke!). One over your thumb and another over your index finger will cure any slipping issues, while requiring almost no grip.

The large seems to work for me.

Thermals
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« Reply #17 on: August 24, 2009, 06:25:01 PM »

I tried throwing with a peg this weekend on a new glider and found that I did not like it at all. Personally I don't feel connected to the model as much. I had less control over the model in heavy wind and it was alot harder to control the exact amount of nose elevation at launch. I will be grinding it off and putting 100 grit 3m on the tip like always! I think that if skin is not being removed from my fingertips after every flight I am not throwing hard enough! After time the pads of your fingers will get thicker.
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« Reply #18 on: August 24, 2009, 11:24:54 PM »

To update my comments in this thread...

With the help of numerous people--I'll post thanks elsewhere--my launches are now at least pretty safe, if not particularly powerful. The biggest single thing for me was to reach out toward the target on my follow-through, with the target pretty much straight out, not up. I don't think the grip itself is a big issue, although I am now using 3 fingers spread on top, rather than with pressure on the side of the index finger with the hand in a partial fist.

--Bill
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« Reply #19 on: August 28, 2009, 08:16:29 AM »

I fly mine (limited at the moment due to health - but I have an entire airfield to myself as and when i need it - courtesy of the gliding club I belong to) by using both methods. I have two tlg - one with a peg and one without. I find that in strong wind where thermals are hard to get into due to the speed that they are being blown along and all you seem to feel is the constant infill, then the throwing peg is ideal. Here though I have the thumb on the leading edge as it gives more stability to the wing before release.

The other method is the lighter model - used on days when its thermic as hell and I cant get into my Diamant glider as someone else is having a go. Here I do have wet and dry patches on both the top and bottom - these are cut into strips about 3/4 inch long x 2-3mm wide and with them going accross the wing but in line with the airflow over this. I have a thin bit on the leading edge for my thumb as well.

One thing I can and do advocate is the use of the surgical rubber gloves. These allow you to have a vice like grip on the model and I have used these successfully over the years to hold hundreds of hlgs when throwing. These tend to have talc on the inside, so your hand doesn't sweat that much and it can be used again and again or until they split and are cheap enough.

That's my ten cents - however, the model looks great from the pics I saw and typical of Stan's quality. Hes a good man. Keep at it. It will come.
Best wishes
Kev
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