card stock v. wood for baffle ends

[nosecone]

Hi,

I was wondering if anyone has anything to say about using heavy card stock rather than wood for their baffle ends. I'm wondering if the card stock will not last many flights, or if there isn't really any noticable difference. I appreciate any input.
Thanks, N.C.

 

[gdiscenza]

If I make a baffle using card stock, I will coat the motor side with JB Weld. If I use balsa, it gets a coating of 15 minute BSI epoxy. If I'm using plywood, I coat the motor side with Titebond II.

Otherwise, my preference is that the larger the airframe, the thicker the aft baffle plate needs to be, but whatever it is needs to withstand the worst ejection charge overpressure I can imagine - think 2x D12 shotgun ejections...

G.D.

 

[Micromeister]

Baffles do not last forever:
But I learned a trick that has greatly extended the service life of baffles I've installed in several models regardless of which material was used for the end pieces.

Normally I use brich light ply or 14ply sho-card for end pieces, All sides are precoated to 30minute epoxy and the ejection facing sides also get a layer of adhesive backed Stainless Steel tape. To date these baffles show very little burn damage as compared to simply epoxy clad baffle ends, or the burned though ends of uncoated plywood or CA soaked cardstock ends.
It's a McMaster-Carr purchase, I don't have the Cat No. right now if you need it let me know I'll try to look it up
Hope this helps a little.

Ps: Changed the Photo adding the McMaster-Carr Cat numbers. Hope it's a help.

 

[El Cheapo]

Nice tip, John. Why didn't I think of that? One should be able to find aluminum duct tape at any decent hardware store.

 

[Micromeister]

Nice tip, John. Why didn't I think of that? One should be able to find aluminum duct tape at any decent hardware store.

That is true El Cheapo but please note we're talking about Stainless Steel Foil tape not Aluminum

I've Tried all three thicknesses of Aluminum tape with very limited success. it just doesn't stand up to the intense flame & heat like the Stainless does.

I think the stats on the Stainless tape say something about -30 to 350°f but i'm almost positive that pertains to the adhesive. I tried two and three layers of Aluminum which slows the damage but not as well as a single layer of Stainless. It's been noticed that I've burned thuough the aluminum tape with a single 4 D12 cluster flight, and one of the reasons I went searching for Stanless Steel foils.
Your choice of coarse as the Stainless Steel tape is on the expensive side, but I'm very happy with it's results. Also used in most of my Cluster Booster tube bulkhead ends with the same excellant ware results.

 

[El Cheapo]

There's the Ah Ha. I'll have to run what I have through some heat tests. It's aluminum but on the thicker side. We used to use it to seal up the duct work on our race cars.

 

[Stymye]

I've used the aluminum tape in some of my tlp builds to protect the tube beyond the recessed motors..I found the adhesive will give out easily to heat
I would recommend epoxying the aluminum tape down.

can't speak for the stainless tape ..but I think it's a great idea for that !

 

[troj]

I have to wonder if there isn't a ballistic factor at play, in regards to the aluminum versus stainless, as well.

The aluminum, being softer, may well be getting damaged by the ejected particles, as well as the heat.

-Kevin

 

[ClayD]

I have to wonder if there isn't a ballistic factor at play, in regards to the aluminum versus stainless, as well.

The aluminum, being softer, may well be getting damaged by the ejected particles, as well as the heat.

-Kevin

well, my guess is that the aluminum tape is probably not very aluminum at all. Probably a Very cheap alloy... that is more like a beer can than aluminum.

Although my aluminum av bays i have built HATE black powder, they corrode fast and bad... so maybe some chemistry is at play too.

I ahve done baffles in a few mpwr rockets, and stopped in highpower. I found balsa wood to be best, and just a good coating of epoxy.. .

The few estes rockets i put baffles in, i made two 2/3 circles separated by 1/2" x 1/2" piece of balsa, with an eyelet screw through them to attach my shock coord. I have bever been ablet to burn/blast through my epoxy. Usually, i see a residue buildup.. and i think that actually has added protection for me. i coppied the method in the apogee newsletter with some small shortcuts...


I personally woulnt use stainless steel or metal period, the epoxy should handle the charge anyway. But i would use wood over cardstock.(it absorbs the epoxy)

 

[Micromeister]

Thanks Stymye!
Since using the Stainless tape haven't seen any sign of damage other then discoloring from the after burn flame. I do use .005" aluminum tape inside some Cluster mix chambers to help dispurse some of the heat but I really like they way this Stainless tape holds up without melting as i've noticed when replacing a motor mount in one of my earlier clusters.

I coated two 3/32" x BT-20 bulkheads epoxied directly to the shoulders of the Plastic intake nosecones on a 3 motor clustered SR-71 that woreout the main BT-50 (about 20+ flights with no real damage to these bulkheads for ncs. I'm actually planning on reusing them in the next SR-71 I convert.