Chute protector size vs chute size vs body tube diameter

[Sooner Boomer]

Kind of a silly question, but are there any rules of thumb regarding how big of a chute protector (kevlar sheet) to use with what size parachute? I guess you could always "go big". What about in relation to body tube diameter? It's all got to fit inside somehow, then come out again when needed.

I've been sitting on the couch at night when I can't sleep, working on improving my chute packing techniques. Folding the chute and getting the shroud lines tucked, then getting the JLCR around everything takes a bit of thought and practice. Getting it all wrapped up comfy for flight adds another layer of complexity. Right now, I *think* I have a good way to pack a 45" chute w/JLCR and 9" sq. kevlar protector in a 54mm body tube.

I'd really like to stop scorching chutes. Some of them look like they were attacked by hungry moths. Probably the result of just jamming everything in and hoping for the best.

Another thing I'm considering is the addition of dog barf. This adds complexity, but security as well.

Finally - this is more important now, because I've started using altimeter eject (e match/bp charge). Although the idea is the same as motor eject, in practice it takes more care. because these are (typically) bigger and higher flying rockets.

 

[MidOH]

Some rockets get dog barf, then the blanket, then the laundry on top.

Some get dog barf, and the chute gets burrito'd.

Baffled rockets get no barf, just a blanket.

It's good to have a few options. Sometimes, I use a larger blanket, sometimes not. Often use lettuce instead of barf for zero litter.

 

[Banzai88]

Ever since I bought a bale of dog barf, I use it in EVERYTHING. When I did that, the occasional scorching of parachutes went away completely. My burrito wrap technique was already providing 100% coverage, but I guess burning particles have a way of getting where they should not. Now my routine is a few handfuls of barf on the powder charge side before the recovery burrito goes in and still perfect deployment without any fears of damage. There is no added complexity, and the layer of barf is worth it's weight in gold.

 

[waltr]

I do not know of any 'rule of thumb' for blanket size.

I try using a blanket that that is big enough to totally enclose the chute , burrito style.

On some rockets I add a blanket on the shock cord to protect the nylon cord (Kevlar from attachment to a few inch above the BT then Nylon) and gives another layer of protection to the burrito wrapped chute.

 

[sriegel]

FWIW, here is my pack of a 36" ellipsoid in a 10"x14" nomex blanket. I like the rectangle as it gives me more length to enclose each end of the burrito. I also use dog barf with the nomex.

 

[mtnmanak]

The various makers of the chute protectors have some guidelines on their sites:

Apogee:

3" (7.6 cm) square size = Great for small rockets up to a diameter of 1.5 inches (38.1 mm). For example, this size will fit fine in a BT-50 to a BT-55 size tube.

6" (15.2 cm) square size = Rockets with a diameter greater than 1.5 inches (38.1 mm), but less than 2 inches (50 mm) in diameter. For example, this size will fit fine in a BT-60 size tube.

9" (22.8 cm) square size = Rockets with a diameter greater than 2 inches (50 mm), but less than 3 inches (76 mm) in diameter. For example, this size will fit fine in a BT-70 and BT-80 size tube.

12" (30.5 cm) square size = Rockets with a diameter greater than 3 inches (76 mm), but less than 4 inches (101 mm) in diameter.

18" (45.7 cm) square size = Rockets with a diameter greater than 4 inches (101 mm), but less than 6.5 inches (159 mm) in diameter.

24" (45.7 cm) square size = Rockets with a diameter greater than 6.5 inches (101 mm), but less than 8.0 inches (203 mm) in diameter


Fruity Chutes:
https://shop.fruitychutes.com/collections/nomex-blankets
Onebadhawk:
http://onebadhawk.com/nomex-blankets.html
Rocketman:
https://the-rocketman.com/flame-shields/
TopFlight:
https://topflightrecoveryllc.homestead.com/page3.html
If you look at all the charts on those sites, they don't quite match up. I would imagine that is because they are all using different fabric weights, geometries, etc. I would use their charts as a starting point and then adjust from there. I often go about a size up from the recommendations in order to protect my chutes better.

Having said all of that, I think nomex blankets have a range of uses and are not the only thing you should have in your inventory.

For LPRs and MPRs, as Tom noted above, dog barf is preferable, in my opinion. It falls into the "it just works" category.

For HPRs, in smaller diameters (around 3" and below), dog barf is great, especially for drogue deployment. For mains on 3" diameter rockets, I prefer to use the nomex pouches from Fruity Chutes.

For all drogue deployments in 4" and above rockets, I use a nomex blanket that is sized up from the manufacturer recommendations. On big rockets, I use kevlar shock cords from Onebadhawk that have the blanket sewn onto the cord.

For main deployments in 4" and 5" rockets, I generally use the Fruity Chutes pouches.

For main deployments in any rocket 6" and larger, I use a deployment bag (I do have a couple 5" rockets that are big enough for a deployment bag as well). I would highly, highly recommend deployment bags for any chute bigger than about 6 feet across.

 

[mh9162013]

I think there are several additional factors that could affect the parachute protector size requirements. For example:

- Use of a baffle (I still use a parachute protector with a baffle, but that's b/c I'm paranoid and want to keep soot off my parachute)
- Ejection charge characteristics
- Ease in which the nose cone pops off
- Distance between the ejection charge and the parachute
- Etc.

 

[user 30299]

I use the Banzai88 and Waltr methods for my chutes. Dog Barf is a "must have" if you want to suppress the little embers from a BP charge.
I'll use a Chute Protector just large enough to do a modest burrito wrap of a chute. And I'll use a Shock Cord Protector (sleeves) on the ends
of the Kevlar and nylon cords closest to the charge.

The sleeves are usually 30" in length - but I experimented with 15" and found it was adequate, thanks to the dog barf. I'll order a 30" sleeve
from Top Flight or Mac Performance and have them make it into two 15" sleeves.

I stopped using the body tube size as the selection method. The "thin mill" chutes, from any of the chute makers, seem to easily get
those little pin-hole burns. They always get a solid burrito wrap.

 

[JSW]

Great question! Can I add on?

I'm building a 7.5" dia LOC Warlock with a 60" chute and JLCR. I'm wondering how best to protect it in this larger dia tube than I'm used to?

Looks like I'd need a 24" nomex blanket. Assume that would be bulky enough that it wouldn't come unrolled in the 7.5" tube?

Or if I use an XXL SkyAngle deployment bag,... the instructions say that it is for "recovery of the rocket body,... the nose cone needs to have a separate chute,... or else risk entanglement". I guess folks still connect the nose cone without problems?

Would I still put in dog barf with the nomex blanket or deployment bag? How much? Fill the space in the motor tube itself? Or fill the body tube,... say 2" above the motor tube?

Thanks!

 

[MidOH]

I'd go with a little in the body tube, if it tumbles into the motor tube, so be it.

It's such a personal choice, for each rocket.

 

[Sooner Boomer]

Looks like I've figured out how to pack a 45" chute into a 54mm body. I'm worried that the JLCR might be too loose, but we'll see (and, yes, I know how to shake test). I'll either use dog barf (if I can borrow some at the launch), or sheets (not ribbons) of crepe paper. I'm also thinking of trying out upscaled paper chute protectors.

 

[Sooner Boomer]

Great question! Can I add on?

I'm building a 7.5" dia LOC Warlock with a 60" chute and JLCR. I'm wondering how best to protect it in this larger dia tube than I'm used to?

Looks like I'd need a 24" nomex blanket. Assume that would be bulky enough that it wouldn't come unrolled in the 7.5" tube?

Or if I use an XXL SkyAngle deployment bag,... the instructions say that it is for "recovery of the rocket body,... the nose cone needs to have a separate chute,... or else risk entanglement". I guess folks still connect the nose cone without problems?

Would I still put in dog barf with the nomex blanket or deployment bag? How much? Fill the space in the motor tube itself? Or fill the body tube,... say 2" above the motor tube?

Thanks!

I'm interested in this, too. I hope to have a Warlock one day. I can see two solutions. 1) put the JLCR on the *outside* of the nomex chute "burrito". There is a kevlar/nomex protector made for the JLCR. 2) use a tube mounted inside the body (on top of the upper centering ring) that would hold the parachute. Pack the shock cord/parachute so the the nosecone gets blown off, then the chute is pulled out of its tube.