The reason why many rockets instructions have some sort of fin filling recommendation is because if you don't fill the fins with a light weight wood sealer of some kind, the fins will absorb most of the topcoat paint. As balsa can absorb 5 times its weight in water, that can be a lot of extra paint and added weight. Sandable primers do a basic job of sealing the balsa wood but aren't as good a sealant as sanding sealer or balsa fillercoat. You need at least two coats or more of something to prevent the balsa from soaking up all that topcoat paint, or your rocket will weigh more than the recommended weight on the package, and then I would only fly that rocket with shorter than recommended delay charge.

But that's entirely up to you. If you think it's too much work, then don't worry about. Your rocket can still fly as well without filling as with filling the fins, as long as you don't use too much paint. Stability should be about the same. As for looks, well... you get what you put into it.

This is one of those subjects where everyone has a favorite method of finishing the balsa, and every one of these methods has its pros and its cons. I've tried many different grain-filling ideas, from talcum powder mixed in clear dope, to Fill-N-Finish, to Kilz, to water-based polyureathane, to just painting them with enamels. Currently, my method-of-choice for fins involves none of these...

...well, not directly, anyhow...

I'm becoming quite fond of a very simple technique which takes a piece of self-adhesive mailing-label stock, cutting it to the outline of the fin, applied and pressed in place on both sides, then sealed around the outer edges with thin CA. To date, I've had none peel up (delaminate) from the balsa, and when you hit it with primer, it's sealed. The paper is lightweight, and completely hides the balsa grain in one step.

This method has the one cardinal advantage of not contaminating the room with foul solvent odors (other than what you get from CA and accelerator). You can get sheets of the label stock from any office supply store (Office Max, Office Depot, Staples), and it doesn't require the most expensive brand. I'm using the "house brands" with equal success. You can even run a sheet through the printer first and lay out your cutting patterns to get an absolutely accurate outline. Just run your #11 along the lines with a steel ruler for guidance.

I try to think of this as "modern classic" construction. It's a composite lay-up, like applying glass cloth and resin, just cleaner and less noxious (less ob-noxious ) to your housemates. The results are more than acceptable to this old fart...

I don't know who came up with this idea first, but it was Jay "Tau Zero" Goemmer who (I think) got me started.

__________________
Craig McGraw

BARCLONE Rocketry -- http://barclone.rocketshoppe.com
BARCLONE Blogsite -- http://barclone.wordpress.com
BARCLONE Forum -- BARCLONE Forum

BARs helping BARs

SAM 0044
AMA 352635

I'm very happy to admit that it was David J. "Sirius Rocketry" Miller of Neenah, Wisconsin fame:

http://www.rocketreviews.com/review...terrogator.html

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Jay Goemmer
"Centuri Guy"/"Tau Zero"
YORF Member 28
Semroc SAM #0029
NAR 86131


"I think about organizing things all the time. Never seems to happen. I find something that piques my interest and I'm off on a quest. Or a Centuri. "

--Bill Eichelberger, 02/22/2022


“Centuri fret buzz in an updated form.”
Bill “Wallyum” Eichelberger re: Estes Flutter-By
03 Sept 2014

No contaminating the room with foul solvent odors ?
C'mon now.....
I prefer to refer to the scent of Aero Gloss Dope (or Sig, Brodak, etc.) Sanding Sealer or Balsa Fillercoat as a PLEASANT AROMA, NOT a "foul odor".
This step in the build contributes to the "nostalgia" of being a BAR.
Thankfully, my wife finds the scent of drying butyrate dope pleasant as well !
Most of the time I actually apply my Sanding Sealer and Balsa Fillercoat to fins/nose cones/transitions where I usually build/work on my rockets, the KITCHEN COUNTER, which my wife does not even bat an eye at....probably because she has an entire room of the house dedicated to her scrapbooking activity.

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When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, and HAVOC !

Tim,

To make a long answer short, fillin' and sealin' are not required if you're just out to fly 'em and don't care how high they go or how good they look.

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Don
NAR 53455
"Carpe Diem"

Tim,

I seem to recall reading an Estes publication (admittedly, long ago, probably an issue on Model Rocket News) that dealt with the subject of finishing model rockets. In the article it stated that the performance plus of a smooth finish (i.e. lower air friction/resistance) outweighed the performance minus of any additional weight as a result of the finishing technique. So a really pretty rocket will probably outperform its scruffy cousin. Why heck, in the old days Estes even sold little containers of rocket wax to polish up your rocket and get the finish even smoother! Yep, believe it or not!

Joe

Heh, I can see it now. Hey Bill, what are you doing over there with that magazine? Oh, just polishing my rocket.

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Scott D. Hansen
Ye Olde Rocket Shoppe - Your One Stop BAR Shoppe!
Ye Olde Rocket Plans - OOP Rocket Plans From 38 Companies!
Ye Olde Rocket Forum
WOOSH NAR Section #558

I prefer "Big Bertha" style flights -- low, slow, I can see the rocket all the way up, I do not have to walk a mile to get it. I preferred this type of flying when I did high power. Fly to 20K feet? Are you insane? I want that rocket to return. And for all the money I spent on that reload, I wanted to enjoy SEEING every Newton-second of burn!

Hence, any potential performance losses due to a heavy finish, are, in my opinion, a blessing!

I want the rocket to look great, and for me that drives me to fuss over the littlest imperfection.

Call me crazy! I'll agree with you.

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Lee Reep
NAR 55948

Projects: Semroc Saturn 1B, Ken Foss Designs Mini Satellite Interceptor
In the Paint Shop: Nothing! Too cold!
Launch-Ready: Farside-X, Maxi Honest John, Super Scamp

LMAO!

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Don
NAR 53455
"Carpe Diem"

I agree with you. When I did my bigger HPR projects, I kept the altitudes down between 2700 ft and 5800 ft. My biggest, a 12 ft rocket, was still easy to see even at a mile. The first flight of that Aerobee was only about 2700-2800 ft. and was the best flight of the week at LDRS (IMHO, of course)