# Building to last

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#### Back_at_it

##### Well-Known Member
Nothing really bonds to glassine. I run into this all the time when doing my restorations. 9 times out of 10 the fins will simply pop right off the tube with all of the glue attached to the fin itself. Any remaining glue on the tube can typical he be pulled off with the fingernail living a pristine body tube.

I typically cut or sand an 1/8 to 1/4 inch outside the fin for the fillets.

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#### BABAR

##### Builds Rockets for NASA
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Should the glassine be lightly sanded before priming, for better paint adhesion?

#### Back_at_it

##### Well-Known Member
Should the glassine be lightly sanded before priming, for better paint adhesion?
It wouldn't hurt anything. I've only had a couple of instances where paint has peeled up and that was only when peeling tape for multi colored paint jobs. This was back before I learned to use Tamiya and blue painters tape.

If you sand the tube you will need to do at least two coats of primer as there will be little fuzzy strands that popup with the first coat. These will needed to be sanded and a second coat applied.

#### neil_w

##### Good at some things
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Should the glassine be lightly sanded before priming, for better paint adhesion?
I have certainly never done this. Theoretically, isn't this the actual job of the primer? Primer peeling off a body tube is not something I've ever experienced.

#### Nytrunner

##### Pop lugs, not drugs
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What the heck is “% wood failure”?
It means the wood itself failed around the joint instead of the glue (notice the heated glue is 0% wood failure)

Looking at the plyywood mid-power rockets, a purely quick-n-thick fillet may fail in teh glue itself and leave more restorable parts whereas TBII may lead to more tube/fin breakage on a bad day.

But for balsa (papered or no) either one is fine. I just like a thin seam/fillet of TBII first because it locks things in place for the Q&T fillets

#### BABAR

##### Builds Rockets for NASA
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I have certainly never done this. Theoretically, isn't this the actual job of the primer? Primer peeling off a body tube is not something I've ever experienced.
Helpful. Thanks!

#### TALON

##### Well-Known Member
I have been a "BAR" for over 8 years. I have incorporated just about everything mentioned here plus some. I have used cardboard gussets and chute buckets & anti zipper harness! I will over design for G forces more than longevity. The shock cord is the failure that bites me the most often. So I have switched to kevlar and stainless steel cable to solve that problem. I had my 1st BAR rocket land in a rock pile and get dragged across it by the wind in the chute! Did wonders for the balsa fins! I haven't had a air frame last more than 9 flights. I do notice that the paint bubbles from the heat and the spirals that I labored to fill start showing up from G force stress. Which leads to another topic, "The Finish"! I paper fins for the finish just as much for strength. I still try to fill the spirals as best as possible with different techniques (depending on the rocket), and try to get the best finish. But now I don't sweat it and spend as much time as I use to. And I don't agonize over paint bubbling and other dings and wearing from flights like I use to. When an air frame is showing its age and air worthiness is near its end, I will make it a hanger queen.

#### rklapp

##### NAR# 109557
TRF Supporter
What the heck is “% wood failure”?

who puts their rockets in the bun warmer overnite?

does PSI strength account for the much thicker fillet?

as opposed to maple, something tells me that 3000psi exceeds the strength of balsa and cardboard, so anything over that seems like overkill.

back to original question, @neil_w (or any others with experience), does the addition of a small TB2 (or other classic wood glue) demonstably (meaning “in flight or recovery or storage”) improve fin retention?
Sorry, just trying to give some information I found.

#### BABAR

##### Builds Rockets for NASA
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#### jeffgeraci

##### Well-Known Member
Lots of good stuff already posted.

The following applies to low power rockets, maybe to mid power. Being L-0, I know nada about high power construction.

Some of this depends on your goals for your rockets.

If you want beautiful showpiece Rockets, fly them once on a calm day with a large chute in a big field and then relegate them to display/“Hanger Queen” status. Beware even one flight can result in catastrophe. Classic and tragic example is here

Absolutely unique and beautiful design and finish, with an unfortunate maiden (and only) flight

@jeffgeraci

(Note: if you want it to stay pretty, don’t tempt fate by giving it a name like “Suicide King.”)

Even with the best of circumstances, few if any rockets maintain their “show room” looks for more than a few, say five, flights. So “building to last” and “building for looks” are not often complimentary goals.

With great and certainly due respect to @rklapp , who makes and flies beautiful rockets, for low power balsa to cardboard or paper joints, epoxy is overkill. MAKE SURE YOU SAND OFF THE GLASSINE OUTER LAYER OF THE BODY TUBE. Once you do that, wood glue for balsa to cardboard or paper is structurally just as strong, lighter, and smells better. Epoxy is needed if you are attaching plastic or fiberglass, but not wood and paper and cardboard.

If your design allows for forward swept fins (which IMHO look cool regardless), your rocket’s first interaction with terra all too firms (and sometime cementa or asphalta or playa) will be the motor casing or motor hook, either of which generally handle the impact better than the fin tips of the typical Rear swept fins of the quintessential Alpha. If stability allows and you can place your fins a bit forward of the rear edge of the tube (certainly do-able for long skinny rockets) so much the better.

Papering fins, especially with white glue instead of adhesive paper, adds a lot of strength, although many will say even adhesive paper helps.

Nobody has mentioned reliable recovery yet. Lawn darts tend to lose their showroom looks quickly and are frowned upon by most RSOs. Make sure your wadding and chute and streamer are packed loosely enough that you could literally blow them out with a puff of your breath, and the nose cone isn’t too tight. Estes Cosmic Cobra is a Great example of trying to fit too much into too little a space (interestingly the HeliCat is almost the identical rocket, just made a few inches longer, and is a dream to pack and fly.)

Avoid flying on windy days, rockets tend to either weathercock and disappear upwind or drift away and disappear DOWN wind. Putting your name and phone number somewhere on the rocket may help you in getting it back, but may get you in trouble if it drops into, let’s call it “unfriendly “ territory.

Even Kevlar shock cords can eventually burn through and break. Here’s @hcmbanjo ‘s article on a set up that allows you to check and if needed place them.

Best of luck!
I haven’t logged in for several years now, and I came to find your post from last month, how cool! I’m not forgotten, I love it! Thank you BAR

#### icyclops

##### Well-Known Member
Fins are the weakest link.....paper your fins with card stock to increase their strength. This simple lamination technique using thick card stock and 3M Spraymount 77 on your balsa is easier than wood seal and sanding....Also, make nice and even fillets and paint primer, then paint using a good enamel.....besides the top body tube, fins take the most punishment in LP landings and lift-off.....

#### Lee

##### Member
I just came upon this thread – your recommendation on papering fins with card stock is timely for me. I just completed an Este Door Knob Rocket. When I purchased this kit, I was mildly concerned that the balsa fins might be too weak for this mid power rocket. During the build, I followed instructions. Actually, even exceeded them by filling the grain with CWF and applying a filet of Fix It epoxy clay along the root edge. In order to maintain fin strength at the point of ground contact, you’ll notice from the pictures that I did not bevel the trailing edge corners.

Used a D12-3 for first launch (as recommended) which went as expected. Went up about 500 feet, chute deployed, rocket landed within 100 feet on the grass soccer field I was at – perfect. Then when I retrieved the rocket, found one of the fins cracked upon landing. My concerns re the balsa fins were confirmed. I immediately thought – should have been basswood or even plywood.

How to best repair?

My thoughts are to first get TB wood glue into the crack(s), apply wax paper, wood blocks and clamp until dry.

Then, upgrade. Sand off the combo primer/paint and add card stock. Apply more Fix It epoxy clay to the root edge. Will have to bevel the fins again “in place”. I suppose I should weigh the additional fin material and then then add that much weight to the nose cone to maintain the CG. I am not concerned about performance as I am purely a recreational guy.

I am looking for any thoughts or recommendations anybody might have.

Thanks.

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#### Lee

##### Member
I'd suggest that any rocket that uses some form of paper or cardboard for the airframe be lined with fireproof paper prior to each flight. This helps a bunch with longetivity, and the material is very inexpensive. I bought a huge roll of it online (I can't remember the vendor, but not a rocket-centric company as I remember). I simply roll a length into a tube form and push it into each model that uses paper/cardboard before each flight, then toss the "liner" and replace with new before the next flight. I haven't done it yet, but I'll also use it for 3D printed as well as phenolic-airframed models too.
Has anyone ever tried spraying fire retardant paint inside the body tube?

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#### Back_at_it

##### Well-Known Member
Has anyone ever tried spraying fire retardant paint inside the body tube?
I have coated the inside of large body tubes with the same minwax sanding sealer that I use on the fins. Not sure how much it helps with fire proofing but it makes the inside real nice and smooth so it's very easy to wipe clean.

#### neil_w

##### Good at some things
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Then, upgrade. Sand off the combo primer/paint and add card stock. Apply more Fix It epoxy clay to the root edge. Will have to bevel the fins again “in place”. I suppose I should weigh the additional fin material and then then add that much weight to the nose cone to maintain the CG. I am not concerned about performance as I am purely a recreational guy.
Gluing cardstock to the fins *will* strengthen the fins. Doing it to an already-painted rocket could be a bit of a challenge. If the fins are beveled to the "scale-shaped fin" profile, it'll be between difficult and impossible to clamp the entire span of the fin. Clamping just the rear part of the fins might well be enough to keep the fins from warping, which is the primary goal.

I'm completely unsold on the use of Fix It epoxy clay for fillets, although fillet strength doesn't seem to have been your problem here, and also it might indeed be the easiest thing to apply to a previously finished rocket.
Has anyone ever tried spraying fire retardant paint inside the body tube?
I cannot quite imagine trying to spray paint onto the inside of a body tube. Better to use materials that can be wiped on with a mop-like contraption or equivalent (e.g. a chunk of foam attached to the end of a dowel).

#### ZEDL1

##### Active Member
Lee, thank for for bringing this thread back to life.
My long-ago post that you'd quoted mentioned the fire retardant paper that I now use, but I couldn't recall from where I'd bought it. A subsequent post by one of our members noted that he or she hoped that I could eventually remember my source. I have now found that information:

I purchased a 36" wide X 300 foot long roll from "ULINE", website uline.com, phone number 1-800-295-5510. Their Item Number is S-22458. When I bought it last October, the purchase price was $95.00 plus shipping, total$123.41.
There is a LOT of material on the roll, more than one will need for quite some time, but I hope that this additional information will help others.

Jim

#### teepot

##### Well-Known Member
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I have sprayed high temp paint inside of tubes. And one booster I painted the inside and outside with it.

#### neil_w

##### Good at some things
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I have sprayed high temp paint inside of tubes. And one booster I painted the inside and outside with it.
How big a tube?

#### Lee

##### Member
I have sprayed high temp paint inside of tubes. And one booster I painted the inside and outside with it.
Were the results satisfactory?

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#### teepot

##### Well-Known Member
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Were the results satisfactory?
Yes. no evidence of scorching. It's the same paint I use on my propane grill.

#### rklapp

##### NAR# 109557
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I’ve been spraying this on my nylon chutes. No scorches yet. Wonder if it would work inside tubes? Usually the insides of my rockets are sooty but not scorched.

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#### BEC

##### Well-Known Member
who puts their rockets in the bun warmer overnite?
In some parts of the country (like where I grew up in the Southwest) a closed car on a warm day can reach 150 degrees pretty quickly. That will certainly soften some water-based glue joints.

But the reason I popped back into this thread was because I wanted to post about a shock cord that is nearly 53 years old and still good. The attached horrible quality scan shows a junior high school friend (David Ridgley, on the left) and I setting up a rocket launch under the auspices of the Shiprock Jr. High Science Club. The picture appeared in the October 29th, 1968 issue of the Farmington (NM) Daily Times. While the scan is lousy, this version was clear enough for me to recognize both the model and the launch pad. And as it turns out, I still have this model....a BT-20-based streamer-recovery model that was probably my first original design. I found it in one of my model boxes and pulled it out after I was able to recognize it in this picture. It has a length of 1/8 inch Sig contest rubber (for rubber powered model airplanes) installed in it as the shock cord, using the two-slits-and-a-knot shock cord attachment method that predates the tri-fold.

After getting it out and giving it a tug, and after recognizing that the pad in the picture is my original Tilt-a-Pad (which I also still have) instead of the Electro-Launch I thought I'd been using (from an even worse scan of that article), I decided to set the model and the pad up at Sixty Acres and fly it again. So after more than 52 years Nameless One I took flight again on March 30th of this year on an A8-5 and turned in a very nice flight. And that half-century old piece of rubber shock cord did not break. [John Boren isn't the only one who thinks naming a rocket is one of the hardest parts....and my 7th grade self was just as bad at it as I am now, if not worse.]

#### shockie

##### High Plains Drifter
I hope you can remember, I'd like to get some of that. I think I just read around here somewhere that some are actually foiling inside their tubes. It'd be tough on some of our little tubes, though.
You could use nomex paper as a body tube liner. Just glue some aluminum foil to the nomex paper first then roll it and insert.

#### shockie

##### High Plains Drifter
Replace balsa fins with plywood. Replace paper centering rings/motor mounts with plywood .
Use kevlar for the shock cord. Use a removable/replaceable shock cord by using a lariat loop.

#### aviserated

##### Well-Known Member
Would epoxy finishing resin be good for fins, I know zep makes a two part version, but it is a little brittle. There are other thinner stronger epoxies you could use to finish balsa fins. Could you use epoxy to paper fins?

#### rklapp

##### NAR# 109557
TRF Supporter
Would epoxy finishing resin be good for fins, I know zep makes a two part version, but it is a little brittle. There are other thinner stronger epoxies you could use to finish balsa fins. Could you use epoxy to paper fins?
I think thin CA is better, not as heavy as epoxy.

#### GlueckAuf

##### Well-Known Member
Despite everything one might painstakingly do to make rocket-flying a low-turnover proposition, the rocket gods always seem to have the last word...

Good skies,

GlueckAuf

#### BEC

##### Well-Known Member
One other counter example for the "Estes rubber shock cords are crap" folks: I'm building an Alpha using parts from a black/red livery kit (circa late 1980s). The white shock cord that came in this partial kit is both long enough and in very usable condition. I did use the tri-fold/Kevlar leader mount that I mentioned in one of my posts above, but I will use this rubber shock cord when I start flying this model (within the next week or two) despite it being ~30 years old. It will be fine.

Hopefully I'll keep it out of rocket eating trees like the one in the post just above this one! It is being built with the aim to fly it at least 100 times.