Getting the fins on straight?

[Senior Space Cadet]

I haven't had much luck with fin alignment gadgets. My fins never seem to work with them or maybe it's me. I don't want to keep buying more and more fin guides with the hope of finding one that works.
I've been gluing my fins on freehand. I do an OK job, but it doesn't need to be off by much to make the rocket wobble or worse.
Now, I'm moving toward fins with a shorter root chord. This is going to make it even harder to get them on perfectly straight.
What I was thinking I could try is first gluing the fin to stick balsa the same width as the fin (Do they sell 1/8" inch stick?) but much longer than the root chord. It would be easy to get the fin aligned on the stick and then the longer stick would make it easier to get it perfectly straight on the body tube the same way that a longer sight radius makes a gun more accurate.
If I wanted, I could then sand away most of the stick.
Anybody do something similar or have other techniques that work?

 

[Steve Shannon]

Just buy a piece of aluminum angle that fits your body tube and use it either to draw a line along the tube or to prop the fin against as you glue one side of it.

 

[MOF410]

I agree w the straight line idea. The fin alignment guides work ok but not all on all configs. Laser level or straight edge w slow setting glue gets them on straight for me.

It also helps to have balsa that isn't warped to begin with, as I've had crooked wings that turned out to just be cheap warped balsa from the lobby.

 

[XrayLizard]

practice and more practice. Did without fin jigs for a looongg time.
I have one of Ted Macklins jigs now.. well heck he lives just a few miles from me.. lol
And a couple of home-made ones, made on a milling machine. Will likely build another style soon enough.

But truly just a cradle, well marked tube(carry the line to the end edge of the body tube), and a Starrett ruler/square will get you there. patience

 

[dr wogz]

my trick / tool / jig:

go to post #19

https://www.rocketryforum.com/threads/madcow-super-dx3-patriot-a-build-thread.140215/

 

[jqavins]

I have rather poor eyesight, quite poor hand-eye coordination, and no depth perception. Even I found a way to get my fin's root edges parallel to the center line, but for the life of me I couldn't get them normal to the tube's surface. I don't know what jigs you've tried, but this is the one that changed my life:

Fins on straight and normal darn near every time. It's still possible to mess up, but it's hard.

Without a jig, the best method I had was this:

1. Use a piece of angle to draw the line.
2. Place a drop in thick CA a little bit in from each end of the root edge.
3. Place one corner of the fin next to the line. That's important: keep the line visible.
4. Bring the root down until it's almost touching the tube. The CA won't bond until you "touch down", which is why the drops are a little bit in form the corners.
5. Align the second corner next to the line the same way as the first; this is why you don't want to cover the line.
6. With thick CA, you have about 5 seconds to check that the fin is normal to the body and adjust if necessary. This is the part that I can't get right; no matter how careful I am and how well I think I've got it, I come back and look later and it's leaning.
7. Add a few drops of thin CA along the length of the root edge, which will wick into the joint.
8. Now, you might be thinking, Hey, CA joints really aren't as strong as they're cracked to be; isn't that going to make a weak joint? Yes, it will be weak, because every root edge to tube joint is weak. (The CA bond is - say it with me - stronger than the paper tube.) The real strength of a fin mounting is always in the fillets. This joint will hold more than well enough to get the fillets done.

 

[Spitfire222]

Does no one here use the PayloadBay Fin Guide Tool? Mark fin locations, draw lines using aluminum angle, print out template based on your fin parameters, glue to foamboard, cut out template, glue on fins using rubber band to apply pressure. Couldn't be easier or cheaper, especially compared to a commercial jig. You can even make a second guide to help keep them aligned. In any case, this tool didn't exist when I was younger and even back then, eye-balling it was close enough and yielded rockets that flew just fine.

 

[jqavins]

For a klutz like me, cutting those out with accuracy and precision is about as hard as placing the fins as described above. I have used jigs of that general sort for fins that were too thick for the Estes jig, but those times I used a laser cutter in order to get satisfactory results. Because I need all the help I can get.

 

[Ronz Rocketz]

I’ve heard a lot of complaints about the fin alignment guide but never used one. I’ve been using these a lot or an angled straight edge on occasion.



Others seem to have success with these.
https://www.qualmanrocketry.com/Fin_Guides.html

 

[tsmith1315]

Does no one here use the PayloadBay Fin Guide Tool?
... In any case, this tool didn't exist when I was younger and even back then, eye-balling it was close enough and yielded rockets that flew just fine.

Vince, up until now, all of my rockets have had eyeballed fins. That includes L1 & L2 flyers. TTW tabs make it less error prone. How many of you left pencil or pen marks on your door frames marking fin guides on your body tubes?

I'll gladly download that fin guide for the next build and give it a shot.

 

[BABAR]

You still have to get the lines right, but I find that using “cheaters” (aka “balsa fillets”) helps me get pretty much perfect fin alignment, a much stronger fin/tube bond (at least for non-thru-the-wall fins) and a slightly faster “tack.”

Sand off the outer glassine layer.

Mark your lines, these HAVE to be straight, use a doorframe or aluminum angle or the Estes marking device, whatever.

The “cheaters” are 1/16” balsa. (Or thicker, if you use really big fins.). Cut one for each fin, each is a strip cut with the grain, length is the length of the root edge of your fin (or a bit less is okay.). Width is 1/16”

Glue each cheater with one edge parallel to the marker line. Be consistent, all clockwise to the corresponding line. If they warp away from the tube, use rubber bands to hold in place. Because these are small and light, they should be very easy to place and so light that gravity doesn’t displace them. I like to use a double glue joint— apply the glue to the cheater, put it in place to lay down a bit of glue on the tube, pull them apart and allow to dry for 3 or 4 minutes, then reapply. Because these are straight and light, you should easily be able to get an exact alignment with your marker lines

Once dry, attach your fins, placing the root edge of the fin directly on the tube (not ON the cheater but counterclockwise to it, with one side butted up against the cheater. Assuming you did the above steps right, your fin will be perfectly aligned with the line you drew. Again I recommend the double glue joint. This integrates pretty easily with other fin jigs, so it isn’t an “either/or” proposition. You still need to “eyeball” it to make sure the fin extends directly vertically from the tube, but this is pretty easy AND even if you “leaning” a bit here, the rocket will still fly straight.

Often the balsa strip can be covered by a thick fillet. But if the asymmetry bothers you and/or you want an even stronger fin-tube attachment, once dry apply a cheater to the opposite fin/tube joint.

For Youngster classroom or club builds, the cheaters can be applied ahead of time by the AIC (Adult In Charge) to a bunch of tubes, making a faster and easier and more reliable build for the kids.

 

[Jay Rairigh]

I also make jigs like spitfire explains (I buy the 'fibre' board stock at HL), but I've only used them on TTW fins where the fin slot already keeps the fin aligned to the c/line of the rocket.
It makes the fins SUPER straight without fuss. There's a lot of leeway in cutting the pattern out on the jig. A crooked cut here and there won't matter, but I use a straight edge to cut it with an exacto.

I can't picture using it on surface mounted fins, seems it might be difficult, but I've not tried.

 

[Spitfire222]

I've used it successfully on both surface-mount fins, and TTW fins. The only difference is that it's easier to keep the TTW fins aligned parallel with the body tube. It's still not difficult with surface-mount, just requires a tiny bit more diligence. And yes, using foam board provides some leeway, as the cutouts don't have to be perfect since the foam will deform a bit if too tight.

 

[afadeev]

I haven't had much luck with fin alignment gadgets.
[...]Anybody do something similar or have other techniques that work?

This:
https://www.erockets.biz/semroc-joes-fin-jig-ii-sem-fj-2/
Inexpensive (relatively), highly effective.
Only necessary if you are getting anal retentive about fin alignment, and are motivated to do something about it.
Otherwise, you can eye ball the alignment to within 95% of perfect.

YMMV,
a

 

[Jay Rairigh]

I can see a thicker foam board could hold the surface mount fins much better. My jigs for TTW are rather thin. But as soon as you put even the 1st fin into that jig, it's like everything just locks into place. Amazing.

 

[gna]

I made a stand from a piece of cardstock I marked for 4 fins (90 degrees) and 3 fins (120 degeres), with an 18mm circle in the center. I glued a spent motor in the circle. I used the double glue method with woodglue and eyeballed alignment, put it on this stand, and made minor adjustments to line up fins. It worked ok for the last couple of years.

For larger rockets with TTW fins, it's easier to get them on straight, but I would print out a template from PayloadBay as Spitfire222 recommends.

Someone quitting the hobby dropped off parts, tools, and rockets at a launch, and I snagged a fin alignment guide, the one jqavins pictured. I used it on my last two builds and it works great.

 

[Senior Space Cadet]

Just buy a piece of aluminum angle that fits your body tube and use it either to draw a line along the tube or to prop the fin against as you glue one side of it.

I have both the Estes tools for drawing lines on the body and do do that. I like the idea of using an angle extrusion while gluing. It would have to be pretty small since most of my rockets are BT-50.

 

[Senior Space Cadet]

I made a stand from a piece of cardstock I marked for 4 fins (90 degrees) and 3 fins (120 degeres), with an 18mm circle in the center. I glued a spent motor in the circle. I used the double glue method with woodglue and eyeballed alignment, put it on this stand, and made minor adjustments to line up fins. It worked ok for the last couple of years.

For larger rockets with TTW fins, it's easier to get them on straight, but I would print out a template from PayloadBay as Spitfire222 recommends.

Someone quitting the hobby dropped off parts, tools, and rockets at a launch, and I snagged a fin alignment guide, the one jqavins pictured. I used it on my last two builds and it works great.

I have the Estes marking guides for marking fin spacing. I do this first then use their line marking guide.
I too use the double glue method.
What I really wanted to comment on was your cat.
I like dogs but right now I have cats. They are my children. I have one that can be a little annoying when I'm trying to build rockets. My parents had one that looked like yours. Gone many years now.

 

[Senior Space Cadet]

This:
https://www.erockets.biz/semroc-joes-fin-jig-ii-sem-fj-2/
Inexpensive (relatively), highly effective.
Only necessary if you are getting anal retentive about fin alignment, and are motivated to do something about it.
Otherwise, you can eye ball the alignment to within 95% of perfect.

YMMV,
a

Amazingly cheap for how sophisticated it looks. Might look into it.

 

[Senior Space Cadet]

I’ve heard a lot of complaints about the fin alignment guide but never used one. I’ve been using these a lot or an angled straight edge on occasion.

View attachment 431181

Others seem to have success with these.
https://www.qualmanrocketry.com/Fin_Guides.html

I have all the tools shown. The problem isn't with marking a line. I've got that part. But getting the fin glued perfectly straight on the line is the problem. I think I do a pretty good job, and maybe that's good enough, but I'd like to get it close to pefect.

 

[dhbarr]

I have all the tools shown. The problem isn't with marking a line. I've got that part. But getting the fin glued perfectly straight on the line is the problem. I think I do a pretty good job, and maybe that's good enough, but I'd like to get it close to pefect.

The ultimate is said to be a rose-style jig
https://www.hightechrocketry.com/FinJig.htmlI personally find excellent results with a Macklin guillotine, but I concede I may be a half degree off on orientation and plus or minus a 32nd here and there.

 

[Senior Space Cadet]

The ultimate is said to be a rose-style jig
https://www.hightechrocketry.com/FinJig.htmlI personally find excellent results with a Macklin guillotine, but I concede I may be a half degree off on orientation and plus or minus a 32nd here and there.

Do you have a link to the Macklin? That other jig is for my next lifetime, when I rich.

 

[dhbarr]

https://www.macklinmissileworks.com/shop/mini-fin-jig -- there's larger sizes also

 

[XrayLizard]

Ted Macklin is a first rate guy.
He put a lot of effort into developing the Jig. He puts a lot of the same effort in producing them now. I know because he is a neighbor.

 

[jqavins]

Otherwise, you can eye ball the alignment to within 95% of perfect shoot free throws 95% of the time.

You can eyeball them well enough. Not all of us can. A builder's got to know his limitations (and use tools to compensate).

 

[jrap330]

I have all the tools shown. The problem isn't with marking a line. I've got that part. But getting the fin glued perfectly straight on the line is the problem. I think I do a pretty good job, and maybe that's good enough, but I'd like to get it close to pefect.

It takes time....most times as I hold the fin...it slips, because glue is slippery (yes the Yellow Wood) glue......so try and try and try again.....until it grabs straight. As I mention to "Dee" who was worried about crocked fins....my Black Brant II was my worst...all 3 fins took 4-5 times and I still had to cut one off because angle <120 deg. You are WRONG about slightly crocked fins and and others agreed,......rocket will still fly straight...it may twist on way up but so will rocket with perfect fins. How do I know for all my flights with imperfect fins.
Otherwise keep practicing with your jig.

Keep building and launching and stop worrying.

 

[dr wogz]

Do you glue on the line, or beside the line? I used to try & align my fin 'on' the drawn line. Now, I tend to glue next-to the line, so that I can see the fin and the line, and that (to me) ensure the fin is parallel teh tube's axis.. Just make sure you glue all your fins to the same side of the lines!

To me, the angle iron method has it's own issues: it helps hold the fin in place while the glue dries, but doesn't guarantee the fin is perpendicular to the BT. The fin is begin held at only one point, and unless the vertex of the 'V' angle of the angel iron is directly above the intended glue line, the fin won't be perpendicular. The Estes tool at least holds the fin perpendicular to the 'V', as it has more surface area to hold each side / face of the fin.

 

[jrap330]

The ultimate is said to be a rose-style jig
https://www.hightechrocketry.com/FinJig.htmlI personally find excellent results with a Macklin guillotine, but I concede I may be a half degree off on orientation and plus or minus a 32nd here and there.

FinJig...yeah overkill...$400 buck....that is lot of kits/motors/supplies etc........Just use your hands.... It is part of rocketry building....

 

[jrap330]

You still have to get the lines right, but I find that using “cheaters” (aka “balsa fillets”) helps me get pretty much perfect fin alignment, a much stronger fin/tube bond (at least for non-thru-the-wall fins) and a slightly faster “tack.”

Sand off the outer glassine layer.

Mark your lines, these HAVE to be straight, use a doorframe or aluminum angle or the Estes marking device, whatever.

The “cheaters” are 1/16” balsa. (Or thicker, if you use really big fins.). Cut one for each fin, each is a strip cut with the grain, length is the length of the root edge of your fin (or a bit less is okay.). Width is 1/16”

Glue each cheater with one edge parallel to the marker line. Be consistent, all clockwise to the corresponding line. If they warp away from the tube, use rubber bands to hold in place. Because these are small and light, they should be very easy to place and so light that gravity doesn’t displace them. I like to use a double glue joint— apply the glue to the cheater, put it in place to lay down a bit of glue on the tube, pull them apart and allow to dry for 3 or 4 minutes, then reapply. Because these are straight and light, you should easily be able to get an exact alignment with your marker lines

Once dry, attach your fins, placing the root edge of the fin directly on the tube (not ON the cheater but counterclockwise to it, with one side butted up against the cheater. Assuming you did the above steps right, your fin will be perfectly aligned with the line you drew. Again I recommend the double glue joint. This integrates pretty easily with other fin jigs, so it isn’t an “either/or” proposition. You still need to “eyeball” it to make sure the fin extends directly vertically from the tube, but this is pretty easy AND even if you “leaning” a bit here, the rocket will still fly straight.

Often the balsa strip can be covered by a thick fillet. But if the asymmetry bothers you and/or you want an even stronger fin-tube attachment, once dry apply a cheater to the opposite fin/tube joint.

For Youngster classroom or club builds, the cheaters can be applied ahead of time by the AIC (Adult In Charge) to a bunch of tubes, making a faster and easier and more reliable build for the kids.

So you keep the cheaper on and apply fillets over it?

 

[XrayLizard]

Homemade
Have seen some 3D printed ones here too