Tonight's work was interrupted by family illness, but I got the transition, payload and nose cone sanded and sealed. This is what the whole shebang looks like at the moment. (Note the newly clean floor of my build room. I don't remember it having carpet before. )

__________________
Bill Eichelberger
NAR 79563

http://wallyum.blogspot.com/

I miss being SAM 0058

Build floor: Centuri Mini Dactyl Estes - Low Boom SST Semroc - Marauder, Shrike, SST Shuttle

In paint: Canaroc Starfighter Scorpion Estes F-22 Air Superiority Fighter, Multi-Roc, Solar Sailer II, Xarconian Cruiser Semroc Cyber III

Ready to fly: Estes - Solar Sailer II Semroc - Earmark, Groonie Der V 1/2

For ease of use, I have been using the label paper method. I don't trust glue alone on a two piece joint like that anymore. I cracked a fin clean at one of the two piece joints on my Hustler model with the stock chute in a cotton field end of last year. Didn't have the label paper lamination on the Hustler and I'm not sure how much it would have helped given the Hustler is a large model with lots of fin area. The glue may not have penetrated the tighter end grain of the basswood as well as it would have balsa, not sure. Ground was a little hard but one fin broke clean on the glue joint ..... bummed me out because I was only able to fly it once that day.

Easy repair though .....

Your Centaur model is coming along great! I really loved those old two stagers. The Centaur sustainer reminds me of a smaller version of the Lil' Hustler.

.

__________________
Steve Naquin
TRA# 677 L2
NAR# 85518 L2
SAM# 0052

🚀 In Construction: Der Blue Maxx/Minie-Magg 5.5” & Vander-Burn MDRM Clone w/Stickershock23 Custom Decals
🚀 In Paint & Detail: USR Banshee
🚀 In Build Queue: Estes Doorknob w/Vander-Burn Rocketry Upgrade Kit [Sport Decor], Semroc Centurion-F, Semroc Egg Crate
🚀 In Repair: SLS Lil’ Hustler, SLS Aero-Dart 1969 Trim
🚀 Stay Tuned For Fall 2021 Launch Dates

Another easy method to toughen fins and fill grain is to fiberglass the fins. If you use 3/4 oz, it is superthin, and pretty easy to work with once you've practiced a little. You might want to glass a body tube or two for practice.

I've done glassing with regular 30 minute epoxy, thinned with maybe 15-20% lacquer thinner so it spreads easily.

The beauty of 3/4 oz. cloth is that you can cut it the same shape as the fin, and it easily feathers when sanded so you do not see an edge. I've even used it over launch lugs, and you cannot see the "patch" of cloth once it is sanded, primed, and painted.

Here is a 5X Mosquito completely glassed over the fins (and onto body tube between fins) with 3/4 oz. cloth. I wanted to toughen the balsa fins, which are scaled up to 1/4" thickness, and needed to glass over the heavily rounded edges.

__________________
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

You can get Silkspan covering by ordering it online from any number of model aeronautics suppliers, such as, e. g., Sig Manufacturing:

http://www.sigmfg.com/cgi-bin/dpsma...uFV4.html?E+Sig

It comes in three weights; from lightest to heaviest, they are "00," "GM" ("gas model"), and "SGM." The 00 weight is probably the most commonly used variety and would probably be the best choice for reinforcing balsa fins.

Here is a handy write-up about silkspan, along with tips for applying it over open framework (if you happen to be building an R/C glider, for instance) or to cover balsa, which is more to the point for most of us here in the rocketry community.

http://members.cox.net/sandiegodron...ts/silkspan.pdf

Silkspan is normally attached using dope (not yellow glue), and the author of the above pdf recommends using only nitrate dope at that. Nitrate dope supposedly shrinks less than butyrate during curing, and is also fuel- (i.e., gasoline-) proof. Since the shrinkage issue is mainly a concern when applying coverings over open framework (when it can cause wings, etc. to warp) and since we don't use gasoline in our models (at least I would hope not, anyway ), we can get away with using the more common butyrate dope, such as (thinned down) clear Aerogloss. (Sig does sell nitrate dope, in case anyone is interested: http://www.sigmfg.com/cgi-bin/dpsmart.exe/MainMenuFV4.html?E+Sig).

Hope this helps.

Mark

__________________
SAM # 0011

I was going to suggest light fibreglass/epoxy lamination as well.
That's what I used on one of my Hustler clones, which has fins almost the exact shape as the Centaur booster, but much larger.

__________________
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, TURMOIL, FIASCOS, and HAVOC !

Well, that didn't work out like I'd hoped. Things looked like they were going well with the label paper, but after I CA'd the edges, I noticed that it started peeling up. I kinda gave a little tug to see if I could salvage things and the whole piece of label peeled right off.
So now I'm back to my regular finishing techniques. I f&f'd it tonight and I'm going to give some thought to covering the fins with tissue paper after I sand it. (Just to get a little more strength in the area of that joint.) I want to fly it next weekend, so nothing too complicated.

__________________
Bill Eichelberger
NAR 79563

http://wallyum.blogspot.com/

I miss being SAM 0058

Build floor: Centuri Mini Dactyl Estes - Low Boom SST Semroc - Marauder, Shrike, SST Shuttle

In paint: Canaroc Starfighter Scorpion Estes F-22 Air Superiority Fighter, Multi-Roc, Solar Sailer II, Xarconian Cruiser Semroc Cyber III

Ready to fly: Estes - Solar Sailer II Semroc - Earmark, Groonie Der V 1/2

Not that this helps you *now* (since my inevitably after-the-fact timing is impeccable, as usual ), but remember when I had problems with some label-papered fins "bubbling" after I painted them?

http://www.oldrocketforum.com/showthread.php?t=1042

It turns out I'd forgotten to rub the paper down onto the fin with a Sharpie cap , but after I did that, it solved the problem.

Sorry. Maybe next time.


Cheers,

__________________
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

Lots of folks here swear by label paper. I just swear at it.

I tried three different kinds of labels. No matter how I burnished the stuff down, I had troubles. The edges would lift when I painted it. The edges would lift more when I tried to CA them back down. But worst of all I got bubbles under the labels over time.

I gave up and now use plain printer paper and 3M 77 spray adhesive. Bingo! Very solid bond.

I forgot about that one. I haven't painted it yet. I'll have to look while I'm out today.

__________________
Bill Eichelberger
NAR 79563

http://wallyum.blogspot.com/

I miss being SAM 0058

Build floor: Centuri Mini Dactyl Estes - Low Boom SST Semroc - Marauder, Shrike, SST Shuttle

In paint: Canaroc Starfighter Scorpion Estes F-22 Air Superiority Fighter, Multi-Roc, Solar Sailer II, Xarconian Cruiser Semroc Cyber III

Ready to fly: Estes - Solar Sailer II Semroc - Earmark, Groonie Der V 1/2

That's exactly how I do mine.....works everytime.

__________________
Don
NAR 53455
"Carpe Diem"