Anyone ever use the side of a fin as the stand-off for a Launch Lug?

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

jahall4

Well-Known Member
Joined
Jul 21, 2014
Messages
1,241
Reaction score
217
Anyone ever use the side of a fin as the stand-off for a Launch Lug? … as the stand-off for a 10/10 rail button?
 
The Estes Exo-Skell has one fin that has the launch "lug" (more of a guide) molded into it.
Laying a lug on a normal fin wouldn't be too bad; if you have a second lug, you'd just have to be careful of the alignment, as always.
 
I found a picture. Looks like what I'm thinking of.

What about rail buttons? Anyone?
 
IINM there are some 4" upscales of the Snarky where the builder opted to use rail buttons attached to the fin inside the intake.

Oh, and the Enerjet Egg Crate used a fin mounted LL.
 
Last edited:
IINM there are some 4" upscales of the Snarky where the builder opted to use rail buttons attached to the fin inside the intake.

Oh, and the Enerjet Egg Crate used a fin mounted LL.

Thanks that's a big help. I found pictures of the Egg Crate...
EggCrate.2016-07-04_9-54-50.jpg

... and the Snarky using a lug...
Snarky.2016-07-04_10-02-28.jpg

...but so far no pic of rail button implementation.

Can you link a picture using rail buttons?
 
Yes. Here's a picture of our bowling bowl project from LDRS in 2007. It's not a good photo, but this did work, we launched it twice.

Phil L.
Picture 138.jpg
 
Soooo... is the button mounted perpendicular (tip of fin) to the body tube or tangential (side of fin)?
 
That is a rail button, the screw is screwed into the fin. I don't remember how thick the fin was. We didn't have any problems with it, but as I mentioned, we only launched it twice. Had an 8-lb. bowling ball in the top.

Phil L.
 
Anyone ever use the side of a fin as the stand-off for a Launch Lug? … as the stand-off for a 10/10 rail button?

Yes! I do exactly this on my minimum diameter rockets. It gets funny looks, and sometimes the RSO wants to put me out farther than normal, but it has worked extremely well. Keep in mind that I use a removable bracket for the forward rail button, and I believe that to be critical to the arrangement.

I will try to get you pictures tomorrow.
 
Yes! I do exactly this on my minimum diameter rockets. It gets funny looks, and sometimes the RSO wants to put me out farther than normal, but it has worked extremely well. Keep in mind that I use a removable bracket for the forward rail button, and I believe that to be critical to the arrangement.

I will try to get you pictures tomorrow.

removable bracket? Pictures would be great!

No reason what I'm thinking won't work, but like that RSO I have never seen it done.

thx
 
Yes! I do exactly this on my minimum diameter rockets. It gets funny looks, and sometimes the RSO wants to put me out farther than normal, but it has worked extremely well. Keep in mind that I use a removable bracket for the forward rail button, and I believe that to be critical to the arrangement.

I will try to get you pictures tomorrow.

Any luck finding some pictures?
 
Yes. I decided I didn't want a dedicated stand off with a fin so handy.

That's my thinking to for an upcoming project.

Since this was an upscale using a 1/4 rod... Any specific reason you chose rod (lug) over rail (buttons)?
 
Well, I had the lugs handy from a PS II kit that I put rail guides on.

Guides would have been tricky - it seems to me that the upper one would have to be on a stand off and mounted 90 degrees to the body. And that would be weird. The lugs are co-axial - I just lined the upper one up with the side of the fin, rather than centering it between fins.

I find it easier to get pad time at Bong with guides, rather than lugs. So I'm switching several over. But probably not this one. ImageUploadedByRocketry Forum1468185121.300766.jpg
 
...Guides would have been tricky - it seems to me that the upper one would have to be on a stand off and mounted 90 degrees to the body. And that would be weird.

Exactly! ...and that's where I'm headed, but is "weird" really "tricky" in this case?

That's why I'm pushing so hard to find some pictures where someone else has already done this. It may be less tricky than my alternatives, a very small foward "fin" just large enough externally to attach the button would have zero impact on the CP profile.
 
At last! As promised, here is my bracket, on my heavily modified Punisher Sport or mini or whatever it is called -
pR1pjsy.jpg
 
I realize it looks goofy, and it is probably overkill especially on this rocket. However it works extremely well on my Tomach, which is much longer. I show you this one instead since the shorter size makes it easier to see both ends. Note that the only permanent modification to the rocket is a single hole in one of the fins. Being farther forward, the bracket makes the whole configuration quite stable on the rail. Here are two more shots, focused on the forward bracket -
zofmIPX.jpg

6prHwpe.jpg
 
At last! As promised, here is my bracket, on my heavily modified Punisher Sport or mini or whatever it is called -

Yes! "at last" for me to. Thx! Good Omen too, the Tomach is one of my favs.

So why did you make the bracket removable?
 
Yes! "at last" for me to. Thx! Good Omen too, the Tomach is one of my favs.

So why did you make the bracket removable?

Oh, simple! When I have access to a tower the bracket and fin button come off, and I am hardly any worse off than had it never flown from a rail.

I rarely have access to towers, but they are so awesome. Every time I fly from one I get more altitude than I expected.
 
When I have access to a tower the bracket and fin button come off...

Sure, of course... duh

Then can I interest you in a Fly-away rail guide? :)

I love'em even for the smallest of rockets and if for no other reason than not having to fool with attaching buttons or lugs. It would appear your rockets and MO make you a perfect candidate, really perfect. Why carry 2 buttons and a unsightly, draggy, weighty, band clamp to apogee and back when you can drop those buttons when you leave the rail?

IMG_3342.jpg
 
Sure, of course... duh

Then can I interest you in a Fly-away rail guide? :)

I love'em even for the smallest of rockets and if for no other reason than not having to fool with attaching buttons or lugs. It would appear your rockets and MO make you a perfect candidate, really perfect. Why carry 2 buttons and a unsightly, draggy, weighty, band clamp to apogee and back when you can drop those buttons when you leave the rail?

Oh I get that. I see the appeal, certainly. But after a few bad breaks, arguments with contest judges or RSOs, and other various issues, my little group of rocket friends mostly steers away from fly away guides. Plus, we all know the only real solution is a proper tower!
 
Oh I get that. I see the appeal, certainly. But after a few bad breaks, arguments with contest judges or RSOs, and other various issues, my little group of rocket friends mostly steers away from fly away guides. Plus, we all know the only real solution is a proper tower!

Now you have really Piqued my interest. Care to elaborate?
 
Oh that is most of the story. I think the worst problems were all attributed to the fins not being in contact with the guides, meaning parts would slam together on initial boost. So, chiefly user error, at least excluding the contest official and RSO complications which tend to be subjective and pre flight.

We started to hate going out to the pads to pick up the pieces, too. Either you have to remember to do it afterwards, or you go out there pre recovery when you tend to be all excitable about getting the rocket back, or focused on a tracker.

They work well enough with proper technique, but it never felt like the solution for me. I also think the bracket will hold better as the rockets get heavy.
 
Yep, you don't want the guide to slide, and certainly you have to retrieve them, but what do you mean by "pieces"? Have you had them break on launch?
 
Back
Top