Fin attachment

[sveinbjorn]

Hello all,
I seem to have a lot of trouble attaching fins in proper alignment, ie: either 90 or 120 degrees apart, and standing straight out from the Body tube. Other than constructing some sort of fin jig, are there any tips for doing this? Failing that, any ideas for simple fin jigs?
Thanks,
Ed

 

[Justin Horne]

A tool (which ive totally forgot the name of) which is just a right angle metal piece is really useful.

 

[DynaSoar]

Originally posted by sveinbjorn
Hello all,
I seem to have a lot of trouble attaching fins in proper alignment, ie: either 90 or 120 degrees apart, and standing straight out from the Body tube. Other than constructing some sort of fin jig, are there any tips for doing this? Failing that, any ideas for simple fin jigs?
Thanks,
Ed

Make a mark longer than the fin root, marking inside the tube if the fin goes all the way to the after end of the tube. Center the fin on the line. If you've drawn the lines 120 or 90 degrees apart, the fins will be in the right place. If they're tilted afterwards, hold the fin joint over a bare light bulb to warm it. When the glue is softened, pull the fin to the proper position and hold it while you blow on it to cool it.

This only works for white/yellow glue, not CyA or epoxy.

 

[GL-P]

try 5 minute epoxy on one fin at a time to get them tacked down

 

[sveinbjorn]

Thanks for the tips! I'm just getting back into this after almost 30 years. Naturally I want to build better rockets than when I was a kid. Back then, the 'F' engine was the big deal. How far we've come...

Ed

 

[Stewart32]

I sometimes put a spent (or new) motor in the fueslage so that I can "eyeball" the fin alignment along the trailing edge toward the nozzel. Its good for a point of reference.

 

[Missileman]

I use a piece of paper.
Draw lines all the way to the edges of the paper at 90 degrees or 120 for three fins.
Use a compass to make a circle slightly larger than your body tube.
Set your rocket in the middle of this circle with your lines on your BT lined up with the lines on the paper.
This only works well with fins that do not extend below your body tube.
I put glue/epoxy on the root edge, line up the fin, put a drop of CA near the middle on one side of the fin/BT joint, then a quick spray of CA accellerator. (The small drop of CA holds the fin in alignment while the adhesive on the root edge sets up)

 

[limd21]

I use one of these:
https://www.a2zhobbies.com/Estes/Rocket_Accessories/EST-2227.html

Using the guide to hold the fin in place, I wick a drop or two of thin CA into the fin-tube joint. It will set very quickly and be perfectly square. Repeat for each of the other fins. I make fillets with 5-minute epoxy. I use epoxy because it's fast and easy to work with for this job, not because of any misguided belief that I need epoxy strength. Though I have nothing against good-old white or wood glue, I can work much faster with CA and epoxy, and be painting within the same evening.

 

[sveinbjorn]

I apologise for not clarifying my problem. The main problem I have is getting the fin to stand straight out from the Body tube as the glue dries. I solved the placement problem by downloading a pdf file from the estes educator site with a fin placement diagram. The Body tube marking "wrap" that comes in kits seems to be subject to a lot of operator error

Thanks again,
Ed

 

[Stymye]

you can try medium cya to attach each fin than follow up with your favorite glue for fillets

or my favorite, a double glue joint with yellow or white glue
it makes a very strong joint and sets up just as quick as cya

 

[Karl]

Ditto , I use Thick or Medium Flash CA to apply a small bead of glue along the root edge , to tac all the fins down , then when they are set , fillet each one with 12Minute NHP Epoxy.

Im not sure if it works but you could tac them down with WhiteGlue/PVA/WoodGlue , then fillet with PVA? I built my first 2 kits with WoodGlue *aka PVA* and it worked fine , and still haven't broke to this date

 

[limd21]

The estes fin marking guide *will* help you align the fin so that it sticks out perfectly square to the body tube. It has a tapered slot which holds the fin and the inside of right-angle portion of the guide lays against the BT. If you're reasonably careful, the result is a perfectly aligned fin .

I use *thin* CA to tack set fin joints because it's fast, i.e. it's set within merely a few seconds. Then, epoxy fillets are all laid, smoothed and set in under half an hour. Primer can be shot on within the hour. I grew up with the good old double glue joint using white/wood glue, and it is time tested and perfectly functional, but it doesn't suit my style anymore - hint: I have a 4-yr old boy running around the house and time is something I have little to spare.

As a side note, for most lightweight LPR models, it's surprising how strong just the tacked on fin joints are. The thin CA soaks into both the BT and the fin, and makes a pretty strong bond even without the fillets. Sure, CA is brittle, but I think it's a lot stronger than some would give it credit for in this application. (BTW, a good technique is to sand or scrape away the shiny finish of the BT where the glue joint is to be, helping the glue - no matter which type - to soak into the fibers.)