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Internal paper tube prep techniques?

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Cabernut

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For paper tubes, what method do you use to treat or prep them, if any?

Are the interiors of paper tubes often neglected? What methods do you use to strengthen or provide longevity?

I'm asking because up until now, I haven't done anything except the occasional CA to the tube end. I can see soot buildup on the interior of a few and have read that this will absorb moisture and eventually ruin the tube.
 

neil_w

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Coating the inside with CA has come up quite a bit recently. Top Ramen has discussed it and Gary Byrum CA'ed the small tube on his Magic Dart to stiffen it up (see here). I haven't tried it personally.

I don't know that I'd want to coat the entire interior surface of all tubes, but applying the technique selectively seems sensible.
 

Cabernut

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That was one of the triggers for my inquiry. But then I look at my expensive little half-full bottle of super thin CA and then look at 26" of BT-80, and 36" of 3" tubing and think - there has to be another option... A good heavy spray of rattle can lacquer perhaps?
 

neil_w

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Wood hardener has also been talked about for this purpose recently. If you search you can find the thread(s); I don't have links handy right now.

I agree that a CA bath is not gonna be practical for 3" airframes. :)
 

Micromeister

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I've been building and flying model rockets over 50years now. in all that time I can't recall more than one or two models that I did anything to in interior motor and/or stuffer tubes. I have quite a few models still flying from the 1980-1990's with more then 30-50 flights without any interior "strengthing" at all.

As I think about this the only time I really do any kind of interior stuffer tube coating or strengthening is on D12 clustered Up-Scale models where I'm using a coupler as a mixing chamber for the ejection charges (they never ignite at the same time) and to handle the .5 to 1.3 second afterburn that all BP motors subject our motor/stuffer tubes to.

in most of these clustered model cases the interior of the coupler and about 1-1/2" of the BT-50 to BT-70 stuffer tube is lined with adhesive backed Stainless Steel tape. edges and flat forward plates also recieve a coating of 30minute epoxy. All this wouldn't work to well on most smaller LPR BT20 and below models but that's how I handle the ejection and afterburn in all my larger clustered models.
 
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Sabrina

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YES- YES- YES- I like this topic. ;)

I fly at Bong, a location well known for it's "Water Hazards".

I would love to learn about some techniques to make "paper" rockets more water resistant. Something like spray painting the inside of the tube.

The keys would be to make it
-easy to do
-not add too much weight
-inexpensive

I would love to hear some ideas!!!

IMGP1435.jpg
 

BABAR

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Not sure any paper based product is going to hold up to prolonged immersion no matter how much coating you have.
CA glues are pretty cheap at Hobby Lobby, much cheaper than the itty bitty bottles you get elsewhere. Quality is adequate for most purposes.
Where I have seen it used is to harden body tube ends where cuts are made. I doubt this adds much to the bending or crush strength and of the tube.

What is the goal of your "strengthening?" If it is a tougher tube overall, consider blue tube. You can also make a full length coupler by cutting lengthwise a similar size tube and sliding it down inside, effectively doubling your tube thickness (you can cut out a small section if you want it to lay perfectly flat.). Use white glue and work fast so you don't get premature lock up. Avoid wood glue as it shrinks and sets up too fast.

A typical weak spot is just above the engine mount, where repeated ejection charges and the short residual flame after ejections will broil the inside of the motor mount or tube just above the engine. This is especially true if you use a narrower diameter "chimney" or duct. A rolled up piece of aluminum can tucked inside the tube just above the engine will self expand nicely, just about any glue will work to hold it in place.
 
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BDB

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Igotnothing

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Waterglass or sodium silicate - $7 for a pint at the auto parts store. Same stuff they put between the layers can be brushed on the inside. Also makes it more fire-resistant.
 

neil_w

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Gary Byrum recently recommended DEFT Sanding Sealer to me instead of the Minwax, at least for fin hardening. Maybe something else to consider, with less odor. Haven't tried it yet myself.
 
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Amsterdam

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I used thin CA to coat the inside of a small rear MMT eject rocket, I probably did way more that was needed but after sanding all the up to 1000 grit the inside is like glass.

but on normal designs I don't do anything
 
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GregGleason

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If you fiberglass the outside, you don't have to worry very much about the inside.

Greg
 

The_Lone_Beagle

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Gary Byrum recently recommended DEFT Sanding Sealer to me instead of the Minwax, at least for fin hardening. Maybe something else to consider, with less odor. Haven't tried it yet myself.
I tried the Minwax sanding sealer, as per Mike Binder's recommendation, and it seems just as good as the Deft laquer based sanding sealer, without the weeks/months long off-gassing that I got from the Deft. I'm telling you, my garage absolutely stank with those fumes. It was nice to use the Minwax and not feeling like I was going to pass out...

I was just about to try the Minwax wood hardener on some of my larger diameter body tubes...
 
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Jozef

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I have used Minwax Polycrylic applied to body tube interior using a length of dowel inserted into a one inch section of a 3/8 nap touch up paint roller. It is water based and has no odor. I also use it on the exterior of paper body tubes after filling spirals with bondo spot and glaze putty. Three coats sanded between coats before primer. It also firms up the airframe a bit and is a neutral to any primer or topcoat system. I have also used epoxy laminating resin thinned with denatured alcohol and applied to the interior of body tubes using the dowel with the small paint roller section technique.
 

watermelonman

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YES- YES- YES- I like this topic. ;)

I fly at Bong, a location well known for it's "Water Hazards".

I would love to learn about some techniques to make "paper" rockets more water resistant. Something like spray painting the inside of the tube.

The keys would be to make it
-easy to do
-not add too much weight
-inexpensive

I would love to hear some ideas!!!
I am guessing this is not what you want to hear, but for surviving water my only suggestion is to move to fiberglass.

For general strength, outside of water, I cannot imagine CA drizzle or lacquer competing with a body length coupler or fiberglassing the outside.
 
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