Tender Descender and Cable Cutter

[kswing]

Does anyone out there still use a Tender Descender or a Cable Cutter? How well do they work? I'm looking at building something new that would use electronic ejection, so, I'm considering one of these to handle releasing the main since I'll already have an altimeter on board. I have a JLCR, but, I typically use that in another rocket (a 4" upscale Alpha) and I thought it might be nice to have other options without the cost of a JLCR.

 

[Nathan]

I tried a cable cutter several times. I stopped using it when the little piston became permanently stuck in the end of the tube.

 

[mpitfield]

I have several cable cutters with both the stainless and aluminum piston. The stainless piston is better, however I stopped using my cable cutters as I always felt a bit uneasy. To my comfort there is just too much flopping around in the air-stream to get tangled or come lose. Having said that I never had a failure but I used them a limited number of times.

Personally I think you have the right tool in your arsenal now, the JLCR.

Good luck.

 

[dhbarr]

I would only recommend cable cutter at 38mm and below; and only in pairs. If you've got about 2in or better, JLCR is easy peasy.

I know some folks do JLCR in 38, but I can't get a reliable fit even with the thinnest chutes. YMMV.

 

[ksaves2]

I would only recommend cable cutter at 38mm and below; and only in pairs. If you've got about 2in or better, JLCR is easy peasy.

I know some folks do JLCR in 38, but I can't get a reliable fit even with the thinnest chutes. YMMV.

I agree with that. Only time I use the cutter is in a 38mm screamer. It works fine but I have the parachute pack setup with a pilot/drogue that
pulls the chute free.

Been able to fit a JLCR in a long necked 38mm rocket and the chute didn't fill. Rocket survived 'cause it was fiberglass landing on soft dirt. Kurt

 

[plugger]

I use cable cutters regularly in my single break dual deploy md flights. I've only had one issue with a cable cutter flight (a blackhawk38 flight years ago) but that was due to an issue with electronics, not the cable cutter. I use them in a non redundant configuration from 54mm and below and for 75mm I use them in a redundant configuration. So I have two cutters per one zip tie so even if one fails the zip tie still gets cut in bigger rockets. I always use 0.3 grams (grains, whatever, I use the measured vial) instead of the 0.1 recommended to ensure the zip tie cuts. Sometimes I've had issues with getting the pistons out because of how energetic the charge is in such a small enclosure. I've found tapping the non threaded end of the cylinder with a slightly larger diameter drill bit (but still much smaller than the piston) I can knock out stuck pistons more easily. Personally I reckon the chamfered pistons are unnecessary but I've yet to cut over to solid slug cylinders which I reckon would work better. I've got it under good authority that the original cable cutter Archtype's model was based on had this style design.

Two caveats. First, always seal the threaded screw end where the ematch is seated with hot glue. That pretty much eliminates bp leakage which could cause a sub-optimal recovery. Two, always incorporate a swivel on your recovery harness about 1/3 of the way down from the NC (in terms of total harness length). I suspect that if you don't use a swivel the chances of a tangle and therefore unsuccessful main deployments go up quite substantially.

 

[rfjustin]

Tender Descender, Cable Cutter, and other mechanical devices to hold/tie a parachute burrito shut are typically (not always) used for shorter rockets that didn't have room for "normal" dual deploy. With many pure filament wound nose cone offerings and head end dual deploy being more common, needing to pin the chute shut is really not needed anymore. Save yourself time and just build the rocket with head end dual deploy and be done with it. I'd rather have a smaller chute in the nose cone rather than a burrito flopping in the wind.

My .02... YMMV

 

[prfesser]

I've used a Tether (older dual-deploy device) on my L3 and on a number of other flights. It always worked just fine. The Tether is a bit different; it doesn't cut a cable, it releases a couple of links by separating two nesting aluminum "cups". Amount of BP needed for that is about the size of a match head.

Best,
Terry

 

[dhbarr]

Tender Descender, Cable Cutter, and other mechanical devices to hold/tie a parachute burrito shut are typically (not always) used for shorter rockets that didn't have room for "normal" dual deploy. With many pure filament wound nose cone offerings and head end dual deploy being more common, needing to pin the chute shut is really not needed anymore. Save yourself time and just build the rocket with head end dual deploy and be done with it. I'd rather have a smaller chute in the nose cone rather than a burrito flopping in the wind.

My .02... YMMV

...unless you're trying to trim out every possible gram for Max Speed

 

[kswing]

Thanks for all of the insight and advice. I considered doing a dual deploy from the nose cone, but, I'm also planning to put a GPS tracker in the nose cone, so, I thought it was best to keep the other electronics a little further away.

 

[Igotnothing]

What plugger said above.

I have done cutters in 54 and 75mm MD. I think they work regardless of size. I did have to scale up the zip tie when I went to 75mm rocket. The size that worked at 54mm broke at apogee in 75. More forces being applied to everything. Main deployed at apogee for a long decent. (Rocket still landed 20 yards from the road, so no prob.)

Made my own cutters with a small threaded hole in the opposite end. If a piston gets stuck, just twist in a screw and drive the piston back out. The pistons seem to smash the little bit of cut ziptie into a blob of melted plastic that sticks. But the screw drives it back out.

Sometimes the tangle factor gets pretty extreme on a long drogueless decent. However, main has always deployed.

I put wire protection sleeve and tapes around my cutter wires and their lanyards.

 

[emckee]

I have used the Archetype cable cutters many times, and only had one failure - which happened to be in a redundant configuration on my initial L3 cert flight. I think the advice given here is valuable, particularly about putting a bit more than the recommended 0.1g (I now do ~0.2 or so) and sealing the hole around the igniter in some fashion (hot glue is a good idea, petroleum jelly might work too).

I haven't had an issue with the tangle factor, but I have always secured the parachute directly to the nose cone or to the rocket body. I would be concerned about electrical connectivity being broken if the wires were experiencing significant motion. In the same line of thought, it's a good idea to secure your wires (perhaps to the shock cord) if you're going to have any measurable length.

Good luck!
-e

 

[FMarvinS]

If you are interested in acquiring a Tender Descender, I have one with the protective pouch that works well and has only been ground tested. If you PM me maybe we can arrange a deal.

Fred, L2
member of ICBM
Camden, SC
KG4YGP