Pawnee with Tost internal tow rope system

On Saturday, February 7, 2015 at 9:07:03 PM UTC+13, bumper wrote:
Jim Indrebo (Crazy Creek Soaring) and Rex Mayes (Williams Soaring) have both built tow reels for the Pawnee. I copied some features of their design, and added some features of my own in building three tow reels for SoaringNV.

My reel mounts to the Pawnee tubing just ahead of the pilot. The tow reel uses a #35 chain drive for low maintenance. There are 3 magnets embedded in the reel flange that trigger a hall sensor. This allows a single push of the retract button to retract the full length of rope (pilot does not have to hold button). When the rope fully retracts the reel slows and the hall sensor shuts down the motor (there's a anti-bounce feature that prevents cycling if a magnet should line back up with the sensor).

On reel payout, the line person manually pulls out the rope, connect to glider, and Pawnee taxis forward. The reel motor, is wired to through a resistor to provide a small amount of dynamic braking to the spool so that on taxi forward the reel does not have a tendency to "over spool" (IIRC, resistor is 2 to 4 ohms and is connected across motor leads only when motor is not powered.

Motor is 1/15 hp (from surplus source and designed for robotics I think, cost $20 each) and is sized to allow retraction at any speed up to Pawnee VNE, no need to slow down to retract rope, which on the ground retracts at a rate of about 10 feet per second.

Reel is built "modular" in that electronic box and motor unplugs from reel frame to facilitate swapping out parts.

Note, I have no interest in making more reels!

bumper

So is there no facility to release the rope at the tow plane end?

So is there no facility to release the rope at the tow plane end?

Bruce - as far as I can remember, the original Tost set-up had a guillotine built in, which allowed the tow pilot to 'release' the line from his end, if needed.

Uli

At 16:49 07 February 2015, GM wrote:
So is there no facility to release the rope at the tow plane end?

Bruce - as far as I can remember, the original Tost set-up had a
guillotine
built in, which allowed the tow pilot to 'release' the line from his end,
if needed.

Uli

Uli is correct. there is a guillotine at the end of the towplane. Doug

I've towed with the TOST reel on the Skyline Soaring Club's Pawnee, the Rex Mayes reel on a tow plane I bought when SoaringNV opened, and Bumper's proprietary reel on another SoaringNV tow plane. All had guillotines: I never used that feature. I liked having the spool between my feet so I could see it spooling out and would be reminded to reel it in after glider release.

The best reel was Bumper's, but as he says, he has zero interest in building more. I don't blame him: he spent a whole lot of time on the installations he made for SoaringNV as he trouble-shooted (?) little features of the design.

One thing to remember about reel systems with guillotines is that if you use the guillotine you lose the rope and the weak link. At least with a hook on the tow plane tail you can drop the line and hope the glider pilot is sharp enough to remember to bring it back to the field so you can re-use it.

I liked using a reel mainly so I didn't have to approach high over fences, power lines, trees, etc. This is particularly important if you have a short towplane runway.

One thing to keep in mind with a reel is that if you break a rope, have it jump off the reel as it is reeling in, or have to guillotine it, you are probably out of service for about 30 minutes, maybe more. With a tail hook you just clip another rope on and start up again.

Thanks for the input, Fred.

There is some built in redundancy with a tow reel, one can always leave the rope trailing behind if the retract mechanism fails. In the event of some sort of other failure that would have a the rope partially retracted or hopelessly tangled, planning ahead with a new rope at the ready and with a length of heavy weed whacker line taped to the tug end as a "fish tape", a temporary fix should take just a few minutes.

1) If the partial rope or broken rope is hanging out the back of the tug, pull it clear of the guillotine and conduit (the fairlead tube running from the guillotine to the tail fitting.

2) Push the nylon "fish tape" from the back to the front. Then, if the reel is inop and half full of rope (a condition I have not experienced), tie the new rope around the reel using a bowline (easy to undo later) and use as a normal drag behind tow rope. Or, if the reel is operable, replace as normal.

As Fred says, all the reel installations I've seen have a guillotine. I did not make the guillotines used with my tow reels on the SoaringNV ships. Those were sourced from Rex, as he had some extras made - - a good design too..

Tost makes some tow reels that use a frangible mount for the reel behind the pilot seat. There is a slug clamped on the line and that stops the rope payout when is should and places the towing loads on the tail post cluster (unlike the forward mount reels, we are talking about, that put the load on the landing gear and fuselage main cluster where the spray tank would go. I don't like the Tost design as much, though have never flown with it. Seems in the event of some sort of tangle or other problem that locked up the reel before the towing slug reached the tail, the frangible mount could break loose and see the reel go bouncing down the fuselage towards the tail - with attendant collateral damage.

I recall reading about just that issue here on ras, but it's been a few years back.

Bumper reminds me of one thing I did come up with at SoaringNV when we had a rope break and had trouble fishing the new rope through the tube. I started carrying in the towplane a 15 or 20' length (long enough to pass through the tube) length of the white plastic tubing used to plumb in refrigerator ice makers. It is rigid enough to push through the tube from either end and flexible enough to go around any bends and pass any joints you might have. Put some kind of hook in the end to pull the tow rope with and you're back in business pretty quickly. F

Originally Posted by

I've towed with the TOST reel on the Skyline Soaring Club's Pawnee, the Rex Mayes reel on a tow plane I bought when SoaringNV opened, and Bumper's proprietary reel on another SoaringNV tow plane. All had guillotines: I never used that feature. I liked having the spool between my feet so I could see it spooling out and would be reminded to reel it in after glider release.

The best reel was Bumper's, but as he says, he has zero interest in building more. I don't blame him: he spent a whole lot of time on the installations he made for SoaringNV as he trouble-shooted (?) little features of the design.

One thing to remember about reel systems with guillotines is that if you use the guillotine you lose the rope and the weak link. At least with a hook on the tow plane tail you can drop the line and hope the glider pilot is sharp enough to remember to bring it back to the field so you can re-use it.

I liked using a reel mainly so I didn't have to approach high over fences, power lines, trees, etc. This is particularly important if you have a short towplane runway.

One thing to keep in mind with a reel is that if you break a rope, have it jump off the reel as it is reeling in, or have to guillotine it, you are probably out of service for about 30 minutes, maybe more. With a tail hook you just clip another rope on and start up again.

Correct me if I'm wrong but wouldn't the rope still be attached to the glider along with the weak link after the rope is guillotined at the tug end unless of course you are towing off a belly hook with a back realease

:-) Colin

On Monday, February 9, 2015 at 7:43:05 PM UTC-6, Ventus_a wrote:
;896658 Wrote:
I've towed with the TOST reel on the Skyline Soaring Club's Pawnee, the
Rex Mayes reel on a tow plane I bought when SoaringNV opened, and
Bumper's proprietary reel on another SoaringNV tow plane. All had
guillotines: I never used that feature. I liked having the spool
between my feet so I could see it spooling out and would be reminded to
reel it in after glider release.

The best reel was Bumper's, but as he says, he has zero interest in
building more. I don't blame him: he spent a whole lot of time on the
installations he made for SoaringNV as he trouble-shooted (?) little
features of the design.

One thing to remember about reel systems with guillotines is that if you
use the guillotine you lose the rope and the weak link. At least with a
hook on the tow plane tail you can drop the line and hope the glider
pilot is sharp enough to remember to bring it back to the field so you
can re-use it.

I liked using a reel mainly so I didn't have to approach high over
fences, power lines, trees, etc. This is particularly important if you
have a short towplane runway.

One thing to keep in mind with a reel is that if you break a rope, have
it jump off the reel as it is reeling in, or have to guillotine it, you
are probably out of service for about 30 minutes, maybe more. With a
tail hook you just clip another rope on and start up again.


Correct me if I'm wrong but wouldn't the rope still be attached to the
glider along with the weak link after the rope is guillotined at the tug
end unless of course you are towing off a belly hook with a back
realease

:-) Colin




--
Ventus_a

Yes Colin, and that's why you have a radio to hear the tow pilot tell you that he/she cut the cord. You can then drop the towline over the glider field so the valuable Tost rings can be retrieved (at least that's what I would do).

On Tuesday, February 10, 2015 at 9:56:17 AM UTC-5, wrote:


Correct me if I'm wrong but wouldn't the rope still be attached to the
glider along with the weak link after the rope is guillotined at the tug
end unless of course you are towing off a belly hook with a back
realease

:-) Colin




--
Ventus_a

Yes Colin, and that's why you have a radio to hear the tow pilot tell you that he/she cut the cord. You can then drop the towline over the glider field so the valuable Tost rings can be retrieved (at least that's what I would do).

I doubt most pilots will need to be told that the rope just got cut.
Depending upon how it falls back, it is fairly likely to back release.
We should assume it didn't and do as Herb says by operating the release where it would fall safely and possibly be retieved.
UH

On Saturday, February 7, 2015 at 4:02:36 AM UTC-8, Bruce Hoult wrote:
So is there no facility to release the rope at the tow plane end?

The Crazy Creek and Williams Soaring setups have guillotines aft of the drums.