Wadding

I've built shuttle flight system with a BT 80 main tube. What's the easiest way to protect the chutes, without using a whole bag of wadding?

A nomex blanket is a permanent solution. Little more expensive, but then that particular rocket never needs anything else.

Same for an ejection baffle - another popular permanent solution. Just don't use one with AP single use motors - they have rather energetic ejection charges, and can blow a baffle right out of the BT.

Many people use "dog barf" - our quaint name for cellulose insulation. It's available in bales at your local big-box building supply store for about $10. One bale is a lifetime supply for most rocketeers. You just grab a handful, and crumble it into the BT to an appropriate depth - say a few inches. Biodegradable and inexpensive - what's not to like. I carry mine in either a big plastic pretzel jug or a 1 gallon ziplock bag.

Note that "dog barf" is inexpensive, and one package of it lasts a lifetime. Or you can sell some to a friend and it will still last a lifetime. But you can't go wrong with a Nomex or Kevlar cloth. Wrap the chute and shroud lines inside and fold it up like a burrito. However, you should also use a Kevlar recovery harness, as unprotected elastic cord will burn through.

Dog barf is probably your cheapest, best bet. Throw in a handful and go launch!

I would like to warn you about Nomex blankets. They are NOT ejection charge PROOF. A direct hit of ejection charge can burn through it in 1-2 times use (I have burned up 2 blankets from different makers). But when used in conjunction with dog barf, which is not always perfect by itself either, it is very effective. The dog barf takes the brunt of the ejection charge and the blanket protects against anything that gets by the dog barf. This allows you to reuse your reusable blanket, and not throw it away like I have had to do in the past.

Baffles, on the other hand, are my personal favorite. With wadding or blankets, you have to do it right on each and every flight. With a good baffle design, you just have to build it right once. It's the best in "set it and forget it".

Sean, any good sites out there for effective baffle designs?

Here are some. BTW, I was just in Delaware about 2 weeks ago visiting in-laws in Lewes. I was hoping MDRA or Wallops Island were launching while there, but unfortunately they were not.

https://www.apogeerockets.com/Building_Supplies/Parachutes_Recovery_Equipment/Ejection_Baffles

https://www.rocketarium.com/Build/Ejection-Baffles

https://www.sunward1.com/tags/baffle-kits

https://www.jonrocket.com/index.php?main_page=index&cPath=36

Fliskits has them, but only to BT-70 https://www.fliskits.com/products/01prod_fs.htm

CZ Brat said:

I would like to warn you about Nomex blankets. They are NOT ejection charge PROOF. A direct hit of ejection charge can burn through it in 1-2 times use (I have burned up 2 blankets from different makers). But when used in conjunction with dog barf, which is not always perfect by itself either, it is very effective. The dog barf takes the brunt of the ejection charge and the blanket protects against anything that gets by the dog barf. This allows you to reuse your reusable blanket, and not throw it away like I have had to do in the past.

Baffles, on the other hand, are my personal favorite. With wadding or blankets, you have to do it right on each and every flight. With a good baffle design, you just have to build it right once. It's the best in "set it and forget it".

Click to expand...

+++ on this one. I have several blankets with burn holes in them. I always use dog barf with blankets now. I also like baffles, but I like pistons too. Either are OK, but I use the dog barf on the DD rockets.

If you're using dog barf, it works best in larger tubes (and some smaller ones, too) to wrap some in a piece of sheet wadding and make a 'piston' plug first, then heap more on top of it once you seat the plug down around the top of the motor. Most people use 1-2 calibers worth of barf. Just be careful that it doesn't shift position on launch and mess with your CG/CP relationship. THAT situation gets sporting, to say the least!

For baffles, I use the JonRocket style a lot. I've learned that they work best when you use the side with the holes on the OUTSIDE of the coupler toward the motor, and the side with the holes in the CENTER toward the nose. Doing it this way makes it a pain to attach the Kevlar line I use for a shock harness, but once you install it, it makes two expansion chambers. 1 above the motor, and 1 inside the coupler, and I've never singed a chute doing it this way. With the center holes toward the motor, the only expansion chamber you have is the coupler.

The zig zag style with half moon inserts like the Apogee ones I've always had some sort of burn through issues and I don't like them.

I install all my baffles one caliber above the top of the motor.

Two things that I've learned about baffles in LPR. Use epoxy to put them together, and epoxy coat the blast face of the baffle before final installation! Ask me how I know!

Any of you guys DIY your own baffles? And (keep in mind I'm doing LPR Estes kits) any advice for adding them to assembled kits? I'd love to reduce my consumables and not have to really deal with recovery wadding if I can avoid it.

SirNomad said:

Any of you guys DIY your own baffles? And (keep in mind I'm doing LPR Estes kits) any advice for adding them to assembled kits? I'd love to reduce my consumables and not have to really deal with recovery wadding if I can avoid it.

Click to expand...

Baffles aren't hard to make, just takes a little time. You just need scrap tube, heavy mat board and a leather punch:
https://modelrocketbuilding.blogspot.com/2010/08/do-it-yourself-baffle-part-1.html
https://modelrocketbuilding.blogspot.com/2010/08/make-baffle-part-2.html
https://modelrocketbuilding.blogspot.com/2010/08/do-it-yourself-baffle-part-3.html

These type of baffles work well in BT-55 and BT-60 size tubes.

Here's how a baffle held up after 15 flights with just a white glue coat on the exposed plates:
https://modelrocketbuilding.blogspot.com/2013/01/centurion-autopsy.html