Tow line recovery

[gunny11]

Which tx and Rx did you wind up getting?

[kjkavaney]

https://www.mikesfalconry.com/FMV-LEG-MOUNT-TRANSMITTER-216Mhz-p/2000.htm

we use the radio tracking receiver rather than GPS as it is less expensive but also much simplier and not needing lap tops etc...
these transmitters are quite small and Larry is threading their antennae into the Parachute cord, heat shrinking and then putting the body of the transmitter inside orange golf whiffle balls..
hopefully this will all work. We have different frequencies for each tow line (4) so if one is lost for good, we can switch frequencies and not keep "seeing" that frequency while we are looking for a new one...We are adopting a policy that we will NOT leave a tow line behind this year and plan to make good on that promise to the farmer who had extensive damage to his machinery last fall after our aero tow event last year.

[gunny11]

Well thought out nice!

[ljsoarinson]

Just to be clear, the farmer did NOT have any damage to his equipment from our lines. He did, however, have to stop and collect one before the combine ingested it.

A hassle for him but no damage.

[ARUP]

Those transmitters/receivers are nice! They would be perfect for Dawn Patrol and other events where the models drop ordinance.

[edfmaniac]

Am I reading the price right on the receivers? I wonder how the freeflight trackers compare with these systems on performance.

[lenb]

I don't know?

[edfmaniac]

I can't find what receiver they use but I'm guessing it's a scanner for general purpose. http://www.leobodnar.com/shop/index....roducts_id=217

[kjkavaney]

We don't know either, most of the time we are surrounded by a sea of corn over our heads and we are hoping for the best possible signal to find the lines that otherwise are impossible to locate.
Heck, even a model airplane in that much corn can be hard to locate as I experienced last year with a fly away towplane and then a dead stick landing 3/4th of a mile away from the field...
I am putting one of these in my tow plane this week for our event...and future events.

[BryanB]

kjkavaney, How did the system work? Did you get a chance to test it out?

[kjkavaney]

Indeed. Bad news and some good news...We lost two tow planes during our event, a bidule 111 lost control and totally destroyed for unknown reasons and this morning our beloved 1/3rd scale Super Cub DA-150 that I co built with Larry Sorenson...both struts on one side appear to have let go...heart breaking....Larry had hundreds and hundreds of flight on her over the last 8 years...

The good news, is that the tracking system allowed the guys to pretty much walk straight to their planes with tow lines still attached to the tow planes in 8 foot corn...blazing hot in there..

We discovered that we had one antennae break making the signal weaker.... we threaded the Antennae up into the Parachute line at the sailplane end and placed the transmitter itself inside orange golf Whiffle balls....we used small F3j parachutes to slow the descent and we had one accidental release by me and the line was spread out a lot more than if the parachute had not done it's job...

We will continue to experiment more but feel that all the money we spent IMMEDIATELY paid for itself in being able to quickly find planes in super dense high corn. The first day of the event I didn't make it back to the field and put my HKM-28 down in the corn and it took 4 of us over an hour to find that 7 meter plane in the same corn...almost died in that corn with the heat...wish I had placed a transmitter inside the sailplane...I plan to look more into that as well for future flying...

[edfmaniac]

I'm wondering how the RF meter on the transmitter would work for getting close to a downed aircraft. I ran across a video on youtube on the topic but never found any other references. Seems pretty sensitive during range check procedures. Congrats on the other equipment working for you.

[kjkavaney]

We saw someone using RF meter on their transmitter trying to find their sailplane at HH aero tow this year in 6 feet of corn and it DID NOT WORK according to that pilot...
Might well work if in a bean field etc...
Yes, we spent a lot of money, but when it was 90 plus degrees in horrid humidity and the guys were able to walk right to their downed towplanes with tow lines still attached, we all felt it was worth the money.....We never lost a tow line this event...at HH aero in June, I believe there were 6 tow lines lost in the farmers' fields...I actually bought an additional Transmitter and put it in my tow plane...fortunately I did not need it although I came close at one point of losing my Tow Plane the last day of the event...
from now on, we ALWAYs use this system....even at fun flies on private property...

[kjkavaney]

I forgot to include a link to the person who makes great parachutes of all kinds and made up our 10 inch ones to experiment with:
Mr. Kite: MrKite@integra.net
Web Site: 4mrkite.com
check Crag Christianson out on rcgroups for positive feedback from all the TD guys using winches...he makes the BEST chutes and these will really help slow the decent of a lost tow line, even
if you are not using the Falconry tracking system, the chutes give you a prayer of seeing where the line went...

[BryanB]

I got to thinking what is causing all these tow release failures. If we solve that problem we won't have to worry about loosing or finding tow lines. Is it the release itself that is failing or the tow release servo? In my mind it has something to do with the strain on the glider end since after the tow plane releases the line the glider is able to drop it. Is this a correct assumption?

[68mustang]

Hi Bryan, in my experience towing full size, the glider always releases when the glider pilot wants to. The only time the tow pilot releases is on landing or in an emergency. Usually a tow line was lost due to a break in the line and the glider pilot released his end off field. Usually the releases on both full size and models are made in such a way that the harder the pull the tighter they stay closed.

[kjkavaney]

Up till this event, almost every tow line lost for us, has been when a glider pilot said they could NOT get off in spite of hitting their switch...tow pilot shows down...glider tried switch again...still not released...
tow plane dumps the tow line and 99% of the time the tow line falls out of the glider's nose...straight to the ground with OUT a clue where it landed. This year by using Winch Chutes in reverse and of course our tracking devices, but also at the Pilot's Meeting each AM, Larry Sorenson would remind everyone that if they were the glider pilot and couldn't release after multiple attempts to close their tow release BEFORE the tow plane dumped the line...perhaps this verbal request might have had more to do with our success at NOT losing a single tow line this 4 day event..

[BryanB]

Kjkavaney, I think it’s great you didn’t loose a single towline at your event. But, the question still stands. What is causing the inability of the glider to release in the first place? If that can be solved we wouldn’t have to worry about the towplane having to disconnect 99% of the time and having to spend extra money on high tech retrieval systems. Is it a faulty release and/or an inadequate servo? With these high dollar models it should be a no brainer to spend the little extra money on a powerful tow hook release servo. No excuse for putting a cheap servo in such an important function. So, Is there a fault in current tow hook design?
i might have to make some towhook simulators and hang crazy weights on them to test some things like design and adequate servo torque for the application. But how do we measure what kind of force is actually being applied to a towhook of a given glider weight/drag under tow? Anybody have a strain gage or recording digital scale laying around we can do some towing with?

is there a formula or rule of thumb for servo torque selection for the glider tow release or do we just go with around 200oz.in.?

[ARUP]

FWIW: I have been making my own releases. They are the 'retracting pin from the hoop' design. The servo arm is positioned so that it points directly to the nose of the model. By doing this the servo has time to 'ramp up' speed/torque and the pin's linear travel/loop resistance is minimal in this phase of servo arm rotation. I have not used weight but the release function has been tested while another person pulls extremely hard on the loop captured in the release. While on tow ask the tow pilot to pull power then release. This will reduce the force needed by the servo to operate the release.