Fin Alignment help, please

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Jim Rupp

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Hi All,

After 20 years and 4 kids, I am finally ready to take the plunge and get started in rockets again. Of course, the three older ones all yell "Mee Tooooo!", so I picked up a Level 1 kit for each of them, and I splurged for a Quest Harpoon. Figured I'd be able to ram this one together without much problem, since I was making Level 3s when I was younger. :rolleyes:

Yeah, and last night I was checking my son's Baby B, and behold, the fins were misaligned (Yup, I glued them on myself!). Had one fin off vertical by about 5 degrees, and another one was off centerline about 3/16th of an inch. Should take off in a nice circular pattern now. :D At least he was cool with it, 'cause he wants to paint it up really bad.

But that got me thinking. I've got 12 fins to put on the Harpoon, and that makes me 3 times more likely to get a misalignment on my rocket. With my incredible skill, I am guessing I need some help.

Does anyone have a good (and cheap) way of aligning up the fins? Eyeball method, as I am seeing, isn't going to cut it anymore. So I put a halt on getting my rocket together before I make a mess of it, and get some input on how to do things.

Jim
P.S. If anyone in Boise wants to come out and cheer us on, we'll be at Milwaukee Park about 11:30, weather and activities permitting. If you want to join in, bring your stuff! :D
 
Well I will add one bit of advice. Assuming you've used the wrap around body marking guide and you've got them glued on the most important thing you can do is stand the tube on it's opposite end to let each fin dry. If you use tacky glue then the fin will stay on and there will be no lateral pull on the fins so they will dry perfectly straight. I noticed some estes instructions specify this method and others don't. I think they are slowly updating all their instructions. I discovered the idea myself after remembering as a kid how I tried to let them dry with the rocket horizontal between books etc and it was always somewhat of a disaster..I knew that with good aileens tacky glue(silver bottle preferably) that once it grips, the fin will stay on even if it is hanging off the side of the rocket. It's a leverage thing,, when gravity is pulling vertically on the fin it has an entire vertical surface of glue to hold it,, horizontally exerts too much leverage and the fins droop or fall off completely.

Originally posted by Jim Rupp
Hi All,

After 20 years and 4 kids, I am finally ready to take the plunge and get started in rockets again. Of course, the three older ones all yell "Mee Tooooo!", so I picked up a Level 1 kit for each of them, and I splurged for a Quest Harpoon. Figured I'd be able to ram this one together without much problem, since I was making Level 3s when I was younger. :rolleyes:

Yeah, and last night I was checking my son's Baby B, and behold, the fins were misaligned (Yup, I glued them on myself!). Had one fin off vertical by about 5 degrees, and another one was off centerline about 3/16th of an inch. Should take off in a nice circular pattern now. :D At least he was cool with it, 'cause he wants to paint it up really bad.

But that got me thinking. I've got 12 fins to put on the Harpoon, and that makes me 3 times more likely to get a misalignment on my rocket. With my incredible skill, I am guessing I need some help.

Does anyone have a good (and cheap) way of aligning up the fins? Eyeball method, as I am seeing, isn't going to cut it anymore. So I put a halt on getting my rocket together before I make a mess of it, and get some input on how to do things.

Jim
P.S. If anyone in Boise wants to come out and cheer us on, we'll be at Milwaukee Park about 11:30, weather and activities permitting. If you want to join in, bring your stuff! :D
 
Hi Randy!

Thanks for the help. Now why didn't I see that post. A protractor looks great for the off vertical on the end fins. I can just jury rig an alignment block after those are on and stable. That leaves the top to bottom alignment. With 2 protractors, should take care of itself!

:D
Time for construction!

Jim
 
Originally posted by LtSharpe
Well I will add one bit of advice. Assuming you've used the wrap around body marking guide and you've got them glued on the most important thing you can do is stand the tube on it's opposite end to let each fin dry. If you use tacky glue then the fin will stay on and there will be no lateral pull on the fins so they will dry perfectly straight. I noticed some estes instructions specify this method and others don't. I think they are slowly updating all their instructions. I discovered the idea myself after remembering as a kid how I tried to let them dry with the rocket horizontal between books etc and it was always somewhat of a disaster..I knew that with good aileens tacky glue(silver bottle preferably) that once it grips, the fin will stay on even if it is hanging off the side of the rocket. It's a leverage thing,, when gravity is pulling vertically on the fin it has an entire vertical surface of glue to hold it,, horizontally exerts too much leverage and the fins droop or fall off completely.

Hi LtSharpe,

A very good point. Would have never thought that vertical would be less stressful on the root, but it makes sense when I think about it.

We used Elmer's wood glue only, and left it with the drying fin upwards (horizontally) instead of inverting the body. Then we put a piece of masking tape across the leading edge of the fin to keep it upright while in this position. I don't think there was enough tackyness, though, and the fin root slipped out from underneath it. I'll give the tacky glue a shot. We've got enough of it around the house :D
 
I find just closing one eye and looking down the body tube can give you a good alignment if you take your time. Then turn the model upside-down and stand it vertically.

The way you attach fins can make the whole process a lot less clumsy, run a thin film of glue on the root edge, let it dry then run another thin film on top to "reactivate" the glue. Attach this to the rocket and leave it for a while untill dry, then do your fillets.

HTH and welcome to TRF!
 
Originally posted by Mike
I find just closing one eye and looking down the body tube can give you a good alignment if you take your time. Then turn the model upside-down and stand it vertically.

Before doing this trick, here's something else that will help. After you are done marking the tube with the fin-alignment guide (the wrap-around paper thing) and doing the doorframe thing (I've got a completely blackened area on my hobby room doorframe!), mark the end of each of those lines with a felt-tip pen, and mark the end of the tube with it as well. In other words, when you look down the tube like a telescope, you should see on the edge of the cardboard tube 4 little felt-tip pen dots, each 90 degrees apart from each other.

Those 4 dots come into play when you are trying to get your fins aligned and while the glue is setting. By making sure that the base of the fin is centered on your dot, you've got the base positioned properly. By making sure that the imaginary line from the end of the fin runs through the base dot, across the center of the rocket, and hits the dot on the other side, you've got the fin perpendicular to the body tube. Now all that is left is to get the fin centered on the other end of the line, and you're set.

For me, while my glue is setting, I'm constantly checking my angles to make sure it's right. If you look at the fins from behind like you are sighting a gun, you can make sure they all come out straight.

So welcome to The Forum, and get back to building! ;)

WW
 
You could also get one of those Estes yellow marking guides. I use them all the time. You can mark your tubes and then use the angled fin slot holder to hold each fin in perfect alignment.
FWIW
Mark
 
Originally posted by Jim Rupp
But that got me thinking. I've got 12 fins to put on the Harpoon, and that makes me 3 times more likely to get a misalignment on my rocket. With my incredible skill, I am guessing I need some help.

Does anyone have a good (and cheap) way of aligning up the fins? Eyeball method, as I am seeing, isn't going to cut it anymore. So I put a halt on getting my rocket together before I make a mess of it, and get some input on how to do things.


Take a piece of 90 degree angle stock.
Lay it point up an a saw table.
Saw a slot up the center of the angle.

When you place it on a body tune it HAS to be perfectly aligned with the axis of the tube. When you place a fin in the slot, you'll have the small spaces under the angle bracket and either side of the fin to look at and measure to make sure it's even and therefore perpendicular. If you get a small but good carpenter's square that can have the blade moved to either direction or to 45 degrees in the center, you can hold this on the bottom side of the end of the tube and the blade will stick up vertical, so you have something to judge vertical against.
 
Welcome to TRF Jim,

All tried, true and approved methods above here's another one I sometimes use. Stack up enough legos on a a flat lego plate so that the body tube rests on the two stacks.get your fin nicely glue tacked and eyesight centered but not touching between the lego stacks. Look at and center both ends while glue is tacky. Patience, one fin drying at a time and Gravity usually does it's thing to keep the fin straight on. This probably won't work too good on large body tubed models but has worked pretty good for me on LPR diameter ones.

Andy
 
A lot of good methods mentioned. I like to print out a top view of the body tube and fins on my computer. I mark the tube and glue on the fins. The when the glue starts to set I set the rocket on the printout and use the reference lines to adjust the fins for alignment.

Best regards,
Brian
 
Originally posted by BRS Hobbies
A lot of good methods mentioned. I like to print out a top view of the body tube and fins on my computer. I mark the tube and glue on the fins. The when the glue starts to set I set the rocket on the printout and use the reference lines to adjust the fins for alignment.

Best regards,
Brian

Me too, my BSD 3" Diablo came with a fin alignment guide printed on a A4 peice of paper, I always use it, but I chance the circle that the tube sits on to match it's OD. Works a treat.

Karl
 
Another method that I have used is I level my portable workmate and then I hang a plumb bob from the ceiling. Then I tack my fins on and move them around until they match with the string. Also - I've used a laser to project a line down a body tube so that I have something to reference my fin to. Takes a lot longer but the project I was working on was 12" diameter.


Edward
 
Thank you all for your time in responding to me. I think I am well enough versed to continue on. Took timeout today from my own construction, and took the kids to the park to fire off their newly completed rockets after the fog lifted. It was great seeing the kids' looks when things went right, and the "fun" when something went wrong. :D

I'll let y'all know what happened once I get the fins on. Should be early next week. I'm doing the fin prep now, and will get to attachment probably on Tuesday.

Jim
"You must unlearn all that you have learned" - Yoda
 
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