Fins

[lipp]

I was just wandering what the best way to get fins alined straight and stay in place while glue is drying??????????

 

[dragonshiprider]

When I install my fins I first make my BT marks with a steel angle iron the full length of the tube.I will then use CA or "super glue" to attach the fins to the BT.I usually place CA all along the root edge of the fin and then place the rear most tip of the root edge where it's suppose to be and then just "roll" it onto the tube.
Most of my fin alignment is done by careful "eyeballing" the top of the fin with the line on the BT.I used to use one of the plastic Estes fin alignment guides all of the time but have come to trust my own judgement more and more.My fin straightness is improving too!

 

[lipp]

my straightness is inproving also,but i was wandering if anyone knew where i could get an old Estes alignment tool? I'm just always looking for an easier way...

 

[Bill]

I presume you are talking about model rockets. I use the double gluing technique. Apply yellow wood glue to the root edge of the fin and press it onto the line drawn on the body tube. After holding it there about a second, pull it off and let the glue set on both surfaces for 30 seconds to a minute. Then apply some more glue to the root edge of the fin and press it into place. The glue grabs almost instaneously, but still gives me plenty of time to make minor adjustments until the fin is perpendicular to the tube.

Like dragonshiprider, I eyeball the fin. I also turn the rocket tail end up and sight across the middle of the motor mount tube to align the fin with the imaginary diameter from the centerline of the rocket to the root edge of the fin to the tip of the fin.


Bill

 

[jflis]

If the design allows, I simply glue a spent motor casing to a piece of cardboard, stand the body tube up on that, set the fins in place and pinch them between two paint bottles. Instant fin alignment jig

 

[phaar]

I have one of those Estes Bt marking tools. Quite handy. PM me if you want me to see if I can get you one. My dad goes to Chicago almost every week and he got mine in a store up there. Let me know!

 

[gerbs4me]

I like Jim's idea, finally a use for spent motors, besides sniffing them, hmmm BP

 

[Karl]

Ahh yes , the old 'Spent Motor Sniff' Carnt get much better then that! I put 1 fin on at a time & keep it horizontal whilst the glue cures.

Karl

 

[limd21]

I used the tried and true double glue method when I started in rocketry back in the early 70's. These days, I use thin CA glue to tack each fin in position - the smallest of drops is all that's required to set a fin in position. If I get one on wrong, it's a simple matter of a little leverage to "pop" it off and try again - though I use one of the simple yellow Estes alignment guides, so that doesn't happen very often. I can get them all tacked on in a couple of minutes and when I'm satisfied with their alignment, I drip a bit more thin CA into the fin-BT joint to get a better bond along the whole edge. Finally, I finish up with a fillet. Again, in the interest of time, I use quick set epoxy, but traditionaly wood glue fillets are fine if you don't mind waiting.

 

[Missileman]

Fin alignment.
Along with gluing a spent motor to whatever (you can still sniff the motor after using it for this) I take a piece of paper and make lines 120 degrees apart for 3 fins 90 degrees for4 and place under the rocket as a visual guide.
On mid and high power I put epoxy on the root and while holding in place I put a drop of CA along the edge and a squirt of excellorator. that holds it in place while the epoxy cures.

 

[Stymye]

a fin alignment tool would be ideal,or something along the line of jim's idea(something to hold the fin(s))
I've had fins go out of alignment while drying more than once
but it never was bad enough to matter

 

[DJ Delorie]

Having a woodshop, I have alternate options. I mill a piece of wood (usually a 2x4) flat, true, and square on two adjacent sides, then route a rabbet (notch) along that corner that's exactly deep enough to position the fin stock when the BT is in the rabbet, and wide enough to just support the BT when all the other fins are in place. The sharp corner is eased so it won't touch the glue. So, I just put the BT in the rabbet, hold it in place with some rubber bands, and just lay the fin on the wood and it's in exactly the right position. I weight it down and let it cure.

 

[sveinbjorn]

Great idea! Simple yet effective...why couldn't I have thought of it!!

Originally posted by DJ Delorie
Having a woodshop, I have alternate options. I mill a piece of wood (usually a 2x4) flat, true, and square on two adjacent sides, then route a rabbet (notch) along that corner that's exactly deep enough to position the fin stock when the BT is in the rabbet, and wide enough to just support the BT when all the other fins are in place. The sharp corner is eased so it won't touch the glue. So, I just put the BT in the rabbet, hold it in place with some rubber bands, and just lay the fin on the wood and it's in exactly the right position. I weight it down and let it cure.

 

[DJ Delorie]

Originally posted by sveinbjorn
Great idea! Simple yet effective...why couldn't I have thought of it!!

Well, I know why *I* think of stuff like that. I have a router table that was built for precision[1] - it's accurate to 0.001" in all directions, so I often use it for precision jigs and stuff. Between that, laser printed patterns, and a really good scroll saw, I've gotten used to thinking about precision jigs. Heck, I can cut my own CRs on the scroll saw and half the time I don't even need to sand them. I also have tools that let me make jigs on the lathe with precision diameters and such.

[1] http://www.delorie.com/wood/projects/router/

 

[lipp]

could you post a picture of your jig in action????????

 

[DJ Delorie]

Sure. Here's the Freedom Forge Missile getting it's rear fins attached...

 

[lipp]

that pretty cool !! i may just copy that if you dont mind..

 

[DJ Delorie]

Originally posted by lipp
that pretty cool !! i may just copy that if you dont mind..

I don't mind. If I did, why would I post it in a public forum?