launch Lugs

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Launch Lug

  • One launch lug 1"-4"

  • Two Launch lugs 1/4"-1"

  • Rail buttons

  • None use a tower launcher

  • One or two lugs always on standoff

  • Break away launch lugs (lugs stay on launch rod)

  • What ever the instructions say


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MarkII

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For sport flying, I have never seen that the size, the shape and the number of lugs used has made any real difference in the flight. There are plenty of other factors that produce much more variability in the flight than the launch lug does. I will say, though, that for most larger mid-power and just about all high power rockets, rail buttons appear to be the way to go.

MarkII
 
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luke strawwalker

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Ok so I have been doing some major repairs and overhauls of a number of rockets a friend gave me. I noticed that the launch lugs where 2-4” long depending, and only one.
I have been using 2 launch lugs with angled cuts. Only ¼” – ½” long with great success. Ever since I can remember and have never had any issues but have seemed to gain performance. So I decided I would ask you all what you think. I also like to use standoffs on some modles to protect the paintjob
I agree... on virtually all models, regardless of the instructions, I split the launch lug in half at about a 45 degree angle, and trim the opposite ends off at a 45 degree angle, creating a 'long side' against the tube and a 'short side' out in the wind. I've read that angle cutting the launch lug cuts drag from the launch lug by as much as 50%, and considering that on a clean streamlined design, the launch lug can contribute as much as 50% of the total drag of the model, streamlining the lug can mean some MAJOR drag reductions WELL worth the effort for the tiny amount of work involved!

I'm not real big on standoffs, but if the model has a transition, especially an inverted transition, they're a necessity. I built a 'warp drive' model for our night launches last year; basically a Big Bertha clone, that used one of those LED whirlygig children's toys (clear globe with spinning ring with LED's on the edge making light patterns as it spins) for a nosecone and since it was about 3 inches in diameter, I had to use a roughly inch wide standoff so the launch rod would clear the globe on top. I put the bottom launch lug about halfway out on the fin and filleted it on both sides of the lug. I tapered it fore and aft to reduce drag, as with the standoff lug on the upper body, and streamlined the standoff with a rounded leading edge and tapered trailing edge.

I also like to use launch lugs that are typically one size up than the desired rod size on models, to eliminate any binding on the rod. I've even used soda straws for lugs, which works ok, especially the tougher thicker straws from fast food joints nowdays. The main thing is making sure the glue can stick to them and 'hold onto them'.

Good luck! OL JR :)
 

Solomoriah

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I don't bother with streamlining the lugs in most cases, as I don't build for performance; it just doesn't matter to me.

I can put a rocket higher than I want to already. No need to add a few feet to the altitude.
 

MarkII

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I don't bother with streamlining the lugs in most cases, as I don't build for performance; it just doesn't matter to me.

I can put a rocket higher than I want to already. No need to add a few feet to the altitude.
Exactly my feelings, too. I have to say that I have never really thought much about it. Maybe I should give it some consideration, but I haven't yet. My only two concerns so far have been insuring that the lug doesn't bind on the rod and insuring that the rod clears everything on the rocket. I'm not a real altitude freak anyway; I have enough trouble keeping my rockets from going out of sight as it is, and keeping them within my 2 acre launch field when they come back down.

MarkII
 
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o1d_dude

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I streamline my launch lugs, too.

Mostly because I like the way it looks although I have read that the effect of streamlining is considerable.
 

luke strawwalker

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Yeah I'm with you old dude...

It DOES help performance but it just VASTLY improves the looks of the rocket IMHO... even on scalers it makes the lugs 'blend in' and look like an external camera pod or something... turns something that HAS to be there (excepting alternatives for sake of discussion) into something that looks like it could belong on the side of the rocket.

IMHO of course... :D

Later! OL JR :)
 

MarkII

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... turns something that HAS to be there (excepting alternatives for sake of discussion) into something that looks like it could belong on the side of the rocket.

IMHO of course... :D

Later! OL JR :)
I usually just try to camouflage them with paint, but you make a good point. I'm not as concerned about the aero issues, but the overall appearance? Now that's another matter entirely. :eyepop:

(If the aerodynamics were a major concern of mine, I wouldn't use lugs at all.)

MarkII
 

Micromeister

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Exactly why I really like the "Antenna" ring lugs for the forward lug. Super small footprint, all but go away from a few feet viewing distance and look like they belong on the rocket. your can even add a couple extras as decoration if ya like. while hiding the other in a fin fillet.

I've never really understood way the instructions always centered the lug on the bodytube between fins. Guess it was just the easiest place to put the nasty looking thing.
 

MarkII

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Ring lugs do sound like a neat idea. I wonder why they are not use more often. Maybe they are harder to attach well?

MarkII
 

Micromeister

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Yes, attachment has to be considered during the ring lug fabrication process.

Very thin (.050" and UP") rings can be cut from 9/64" diameter and larger
brass or aluminum tubing for attachment in almost the usual way spot fixed with CA and embedded with epoxy. A sharp Razor Saw or Diamond abrasive saw and miter box make this task much easier.

Super thin (.010" to .030") rings: Can be formed using plain steel or Stainless steel music wire. The trick is working the wire into the proper size ring and leaving some sort of Attachment "feet" or "pins" Some end up looking like a fishing rod Guide eye with a bit of wire extending perpendicular to the plane of the ring. Others will start and end being fasioned into shape with sort of a shoulder and bent inserting pins on the same plane extending below the ring on either side. These "pins" are ment to actually penetrate the model body or body tube as anchor points. This type are particularly useful on PMC's. As a matter of fact thats what first led me to the practice, making aircraft ring antenna details for static models;)
Placement location is all important to which foot attachment method is made and used. On Plastic models I really like the insert pins that allow the entire ring to be heated and "melted" into the models styrene body. This is sometimes reinforced with a tiny patch of epoxy or glassed.

On cardboard, phenolic and other bodytube models one of these Three
Methods work well.
1) If the CG/LL mounting location falls below the forward centering ring of a stuffer tube type model, the same double pin method as above works very well.
2) Using the wide foot "Fishing rod eye" type ring, the Area is prepared for the foot to be imbedded in the bodytube by creating a recess or opening in the outer layer of the tube where the thin wire "foot" can be inserted along a depressed or filed recess in the body tube. After light CA fixing of the foot in the opening the recess & wire are covered by epoxy filling, sanded and restored to the original radius fixing the ring(s) in place.
3) Last: For Plain old sport Flying models using the "Fishing Rod Eye" type rings its possible to simple crease the body tube slightly in the area,align the lug and CA/Epoxy in place smoothing the outer layer to form a slight hump fore & aft of the ring that are small enough to be as acceptable as fillets on a standard Launch lug.
Like most things as we experiment with these applications, experience and practice make the locations and installations quicker and visually pleasing.
 
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MarkII

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I was thinking more of using small wire screw eyes that would be screwed right into centering rings, in the same way that rail buttons are installed. I'm not that interested in the actual details of installation; I'm sure that a way can be devised to mount them securely without too much trouble. I'm more interested in finding out if anyone has ever tried using either screw eyes or some other type of ring lugs in something other than an egg lofter.

MarkII
 
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Micromeister

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I was thinking more of using small wire screw eyes that would be screwed right into centering rings, in the same way that rail buttons are installed. I'm not that interested in the actual details of installation; I'm sure that a way can be devised to mount them securely without too much trouble. I'm more interested in finding out if anyone has ever tried using either screw eyes or some other type of ring lugs in something other than an egg lofter.

MarkII
On man:
Lets see, now your gonna make me have to really think back! Stepping into the Wayback Machine with Mr Peabody there is a very faint glimps of using some Centuri purchased very thin eye screws as lugs (less then 1/16" in wire diameter) on a fairly large clusted model from back in the day.
Didn't use centering rings but used Basswood blocks at the lug locations installed with ambroid cement on the inside surface (after shaping to radius) of the BT-80, .021 wall body tube. I tried to locate a pic of the little beasty last night but couldn't find one. As I recall the model was somewhere around 40" long, 4 fin configuration, 7-18mm motors? early 60's vintage..before D13's;)
As I recall the ID on these screw eyes was almost perfect for use on 3/16" heavy rods of the day. To the best of my recollection thats the only time I personally tried using Screw Eyes as launch lugs. I seem to recall this model made several fine flights with no issues other then the rear lug becoming loose from it's Ambroid glue lock after the second or third flight. I'd really have to go dig thur the flight logs to see if there were any other notes concerning the lugs or placement.
The need for additional INTERNAL support makes this type lug more problematic were other materials could be fashioned into better looking, less cumbersum Lugs that more closely resembled something that should be on the side of a rocket. Semi-open shoes, and/or drop shoes have also been used a good long while as well but again are not a quick and easy fix.
To be sure none of these alternate lug types are as quick as slapping a soda straw on the side of your models but that's really not the intent is it? Not really from my perspective anyway. I'm alway looking for things that look better and can increase performance. As mentioned earlier the LUG thing is really more esthetic then Aero but the aerodynamics can't be dismissed....a 10-20% OA drag reduction is a pretty impressive reduction from such a simple single item.

Most of the other "Ring Antenna" lugs are used on Scale models and PMC's. Lots and LOT's of alternative lug arrangements are used on conversions and we're always Looking to HIDE lugs and other flight required attachments on our scale models. Not so much on sport 3FNC stuff as it does take a little more work;)
 
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MarkII

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Thanks for your reply, John. This is turning into a very interesting thread; it is something more than just a poll now. (Kudos, Charlaine.) I like the idea of incorporating scale versions of the lugs on, say, sounding rockets like the Black Brant II or the Nike Smoke for instance, and have the scale lugs actually be functional. The problem is setting up a launch pad (finding a rail) that would work with the scale lugs. You would almost have to construct a scale model of the real launch pad, too, which would be adding another project on top of building the model, and it would only work with that one model. Scale plans for the BBII pads at Churchill or Wallops or the Sandhawk pad at Barking Sands aren't exactly easy to find (wish they were!), and then there is the problem of fabricating a rail if the model is too small for the existing sizes of T-slot extrusion (80:20 rail).

Regarding ring lugs, the reason that I brought them up was because I had seen plans for competition egg lofters that used them (hand made from thin wire), and I wondered why they weren't used more often, such as on sport rockets. A recent review on EMRR of Sheri's Mercury-Atlas MPR/HPR scale rocket mentioned that she uses screw eyes for launch lugs in her kit, which sounds pretty cool, but that is the only other mention of ring lugs that I have found so far. On sport models, their appearance as scale components wouldn't be an issue; I'm interested in them as a less noticeable alternative to the conventional tubular launch lug. I think that in an earlier post you mentioned something about using fishing rod eyes as lugs, which I find fascinating. Have you actually ever used them on a rocket?

On a fantasy/sci-fi model, using ring lugs disguised as antennae (which you have also mentioned) is also an intriguing idea.

MarkII
 

MarkII

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Another question: how important do people feel it is to have the inner diameter of the launch lug closely match the diameter of the launch rod? Does it really matter if there is some "play" in the fit, even a pretty good amount of "play?" Recently I launched my FSI Hercules clone at a club launch. The Hercules is 33.75" tall, has an OD of 2.34", and it weighed (with a dummy payload and 3 D12-5's in the cluster motor mount) about 770 grams, or 27.16 oz. at the time of launch. My version has 3/8" lugs (13/32" thin-wall brass tubing), but the largest rod that my club had at the range was a 4' x 3/16" rod, so that was what I launched it from. Obviously, there was considerable play in the fit of the lugs over the rod, and the thin rod might have even swayed a little bit with my rocket resting against it, yet the Hercules launched perfectly straight and true, without the slightest hint of rod whip.

I suspect that you would not want to get TOO extreme with using an oversized lug (or an undersized rod), but I am wondering if anyone else has had similar experiences with using lugs that were clearly oversized for the launch rod that you were using. If you did so, did you encounter any problems with them? Since the poll is about the various ways that modelers implement launch lugs on their rockets, this question fits right in with the thread.

MarkII
 

Micromeister

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Thanks for your reply, John. This is turning into a very interesting thread; it is something more than just a poll now. (Kudos, Charlaine.) I like the idea of incorporating scale versions of the lugs on, say, sounding rockets like the Black Brant II or the Nike Smoke for instance, and have the scale lugs actually be functional. The problem is setting up a launch pad (finding a rail) that would work with the scale lugs. You would almost have to construct a scale model of the real launch pad, too, which would be adding another project on top of building the model, and it would only work with that one model. Scale plans for the BBII pads at Churchill or Wallops or the Sandhawk pad at Barking Sands aren't exactly easy to find (wish they were!), and then there is the problem of fabricating a rail if the model is too small for the existing sizes of T-slot extrusion (80:20 rail).

Regarding ring lugs, the reason that I brought them up was because I had seen plans for competition egg lofters that used them (hand made from thin wire), and I wondered why they weren't used more often, such as on sport rockets. A recent review on EMRR of Sheri's Mercury-Atlas MPR/HPR scale rocket mentioned that she uses screw eyes for launch lugs in her kit, which sounds pretty cool, but that is the only other mention of ring lugs that I have found so far. On sport models, their appearance as scale components wouldn't be an issue; I'm interested in them as a less noticeable alternative to the conventional tubular launch lug. I think that in an earlier post you mentioned something about using fishing rod eyes as lugs, which I find fascinating. Have you actually ever used them on a rocket?

On a fantasy/sci-fi model, using ring lugs disguised as antennae (which you have also mentioned) is also an intriguing idea.

MarkII
Working a Launcher into your Scale modeling, can turely be a lot more work but They are OH Soooo KEWL when completed. Especially if you can launch from them as well.
I've always liked Super Scale and Space Systems Competitions but they just aren't flown much anymore because folks have gotten away from building "Scale" launcher to go with their models.

Detachable launch Shoes however don't really require a seperate launcher, rather just an appropriate size beam or rail on which to work. This doesn't always have to be a single piece. We can make our own Rails that are more the strong enough for model and LMR powered models. Materials can be as simple as Basswood or as exotic as you have funds for. The larger the model the more hardware involved in the launcher Rail and shoes. My 13mm Nike Smoke Launcher is built entirely from scrap Styrene, Plasticstruct and various other plastic parts. The shoes for the Smoke are cut from Channels with added pieces to "Make them fit".
Other launchers like the Nike-Tomahawk Wallops Island Launcher I'm building will also be almost entirely styrene with a couple pieces of Stainless steel and Nomex in the Blast areas.
The LaCross Missile is Truck mounted rail launch. I converted a Revell kit for launching it's MicroMaxx powered missle from an incorporated .049" Stainless rod added to the far to short Truck mounted rail. The mode still slides the first few inches on the scale rail and is then guided the rest of the way on the attached rod. Add a little nomex heat shielding to prevent ground fires and it works like a champ. The Truck has to be "parked" on a hill to get the launch angle within code but it still looks pretty kewl sitting on the ground;)

Fishing rod eyes can be a little on the expensive side for Launch lugs but given the cost these days for rail buttons prehaps their time as come again. smaller wire only flyrod eye and the smaller size graphite ring eyes have been used in the past on several clustered models just for fun.
It's also possible to "bend your own" .022" diameter wire, simple inline type rod type eyes that can be installed flush on even standard wall (.021") Estes type tubing with a little care and 1/4oz/yd glass patches. Once sanded and painted they all but disapear. If your using Plain or stainless piano wire these eye types are more then strong enough for any model or LMR model up the the 3.3lb class.
Don't have photos of most of these little things...never imagined anyone would be interested in such. As the Lugs are always the things we try to HIDE in photos, I'll have to see if I any of them still exist from first fleet models....sadly I don't believe so. Heres a couple of those launcher pics.. some converted from Plactic models others scratch built.
I think the main idea is to use whatever type launch lug arrangement that is easiest for your particular need on a give model. One could easily set up a custom fabricated mini rail with drop shoes that could in theory be used on any model you build. Just depends on what your trying to accomplish and if it makes sense for your type of flying?

146b-sm_Mini Bomarc on PMC launcher_10-23-93.jpg
 

Micromeister

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Another question: how important do people feel it is to have the inner diameter of the launch lug closely match the diameter of the launch rod? Does it really matter if there is some "play" in the fit, even a pretty good amount of "play?" Recently I launched my FSI Hercules clone at a club launch. The Hercules is 33.75" tall, has an OD of 2.34", and it weighed (with a dummy payload and 3 D12-5's in the cluster motor mount) about 770 grams, or 27.16 oz. at the time of launch. My version has 3/8" lugs (13/32" thin-wall brass tubing), but the largest rod that my club had at the range was a 4' x 3/16" rod, so that was what I launched it from. Obviously, there was considerable play in the fit of the lugs over the rod, and the thin rod might have even swayed a little bit with my rocket resting against it, yet the Hercules launched perfectly straight and true, without the slightest hint of rod whip.

I suspect that you would not want to get TOO extreme with using an oversized lug (or an undersized rod), but I am wondering if anyone else has had similar experiences with using lugs that were clearly oversized for the launch rod that you were using. If you did so, did you encounter any problems with them? Since the poll is about the various ways that modelers implement launch lugs on their rockets, this question fits right in with the thread.

MarkII
Its been my experience a little play isn't a bad thing but excessive play and I'd say a 3/8" Lug on a 3/16" rod may be getting close to what I'd deem excessive depending on the wall thickness of the lug;)
The purpose for Launch Lugs of whatever configurationis to keep the vehicle moving SMOOTHLY along the guide with a minimum amount of contact friction. the larger the lug the more movement and friction is encountered. Over sized lugs can cause the rod whip you are expecting from to tight a lug as it depends on where the model happens to be riding on the rod at the time it leave the rod. One launch can be perfectly fine while the same model/motor combination can tip off sideway on the very next flight.
General rule of thumb has been At least for models in the 1/8A to G range one size up over the rod size is fine, anything larger can produce undesired results.
Personally I prefer whatever launch lug arrangement i'm using to be pretty close to the size of the rod, rail of beam I'm riding. I like keeping things going it the direction it's pointed. This is particularly true with clustered models as there are many more way for the varience in thrust of the motors, wind gusts, and other factors to alter the way the model travel the rod or rail.
I have seen 1/2"x 1-1/2" lugs torn from the side of a fairly heavy F powered model flying from a 1/4" x 6foot rod. Looked to me like the model was attempting to turn away for the thrust line as it jammed the forward lug on the rod. Model ended up land sharking all over the field. Was this "caused" by the oversize lugs or a malfuncting motor? I'm not sure, but the end result was a failed and somewhat dangerous launch that shouldn't have been.
 
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Micromeister

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Doing a little more digging I did find another photo of a custom made double ring, single piece wire Launch lug. I use this type lug often on PMC's but don't really have many photos of them exactly. ran across this one of my Nephews 1/65th X-15 PMC that shows one of these LL's he made using plain .022" dia Music wire. the rings are formed around a piece of old Launch rod with a pair of pliers. Then worked into the final desired length & shape.
Using a single straight wire between rings gives another place to either heat and recess or as in the photo embed in epoxy. Yes he could have done a much better job of smoothing the surface but hey this was his first PMC and he was an A divisioner at the time;)
Hope this helps.
 

MarkII

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Its been my experience a little play isn't a bad thing but excessive play and I'd say a 3/8" Lug on a 3/16" rod may be getting close to what I'd deem excessive depending on the wall thickness of the lug;)
Yes, I agree. Using the 3/16" rod was certainly not a desired situation, but I went with it because that was all that was available at the launch. My club does have 1/4" rods (and pads that use them) as well as a launch rail, but they are rarely brought to launches because they are so infrequently used. (The rail was brought to a few launches during the first year that the club had it, several years ago, but it has not made any appearances since then.) Of course they will never get used if they stay in the storeroom, but that's not my call. I could bring my own rods and my rail, but members are asked not to bring any of their own equipment to club launches.

MarkII
 

Tom W

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Its been my experience a little play isn't a bad thing but excessive play and I'd say a 3/8" Lug on a 3/16" rod may be getting close to what I'd deem excessive depending on the wall thickness of the lug;)
The purpose for Launch Lugs of whatever configurationis to keep the vehicle moving SMOOTHLY along the guide with a minimum amount of contact friction. the larger the lug the more movement and friction is encountered. Over sized lugs can cause the rod whip you are expecting from to tight a lug as it depends on where the model happens to be riding on the rod at the time it leave the rod. One launch can be perfectly fine while the same model/motor combination can tip off sideway on the very next flight.
General rule of thumb has been At least for models in the 1/8A to G range one size up over the rod size is fine, anything larger can produce undesired results.
Personally I prefer whatever launch lug arrangement i'm using to be pretty close to the size of the rod, rail of beam I'm riding. I like keeping things going it the direction it's pointed. This is particularly true with clustered models as there are many more way for the varience in thrust of the motors, wind gusts, and other factors to alter the way the model travel the rod or rail.
I have seen 1/2"x 1-1/2" lugs torn from the side of a fairly heavy F powered model flying from a 1/4" x 6foot rod. Looked to me like the model was attempting to turn away for the thrust line as it jammed the forward lug on the rod. Model ended up land sharking all over the field. Was this "caused" by the oversize lugs or a malfuncting motor? I'm not sure, but the end result was a failed and somewhat dangerous launch that shouldn't have been.
On my larger LPR and MPR I've been toying with the idea of adding a slightly larger diameter lug near the top of the rocket just to keep it lined up a little better on the rod - especially in the wind. I don't like it when the top of the rocket leans away from the rod as I feel that it puts too much stress on the lug(s) which could lean to binding. By retaining one large lug where designed I won't have to worry about wind induced instability when the top lug leaves the rod and the oversized top lug would reduce the possibility of misalignment with the bottom lug.

Anyone see any problems with my "thinking"?

Tom W.
 

MarkII

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In its launch pads, FSI used to furnish a two-piece launch rod. The bottom half was 1/4" in diameter, and the top half was 1/8" in diameter. There were threads on one end of the smaller rod that enabled the rocketeer to screw the two rods together. Many of their rockets came with one launch lug for each of these diameters. You attached the larger lug near the aft end of the rocket and the smaller lug right up near the forward end. FSI claimed that this arrangement greatly reduced rod whip. Although I don't think that they ever mentioned it, I would imagine that one would have to put the smaller lug on a small stand off in order to center it over the larger lug.

MarkII
 

luke strawwalker

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Another question: how important do people feel it is to have the inner diameter of the launch lug closely match the diameter of the launch rod? Does it really matter if there is some "play" in the fit, even a pretty good amount of "play?" Recently I launched my FSI Hercules clone at a club launch. The Hercules is 33.75" tall, has an OD of 2.34", and it weighed (with a dummy payload and 3 D12-5's in the cluster motor mount) about 770 grams, or 27.16 oz. at the time of launch. My version has 3/8" lugs (13/32" thin-wall brass tubing), but the largest rod that my club had at the range was a 4' x 3/16" rod, so that was what I launched it from. Obviously, there was considerable play in the fit of the lugs over the rod, and the thin rod might have even swayed a little bit with my rocket resting against it, yet the Hercules launched perfectly straight and true, without the slightest hint of rod whip.

I suspect that you would not want to get TOO extreme with using an oversized lug (or an undersized rod), but I am wondering if anyone else has had similar experiences with using lugs that were clearly oversized for the launch rod that you were using. If you did so, did you encounter any problems with them? Since the poll is about the various ways that modelers implement launch lugs on their rockets, this question fits right in with the thread.

MarkII
Well, I've been mostly using soda straws for launch lugs, unless I have some either in the kit I'm building, or left over from a previous kit on a scratchie... I've experienced NO problems flying with them. I just don't see paying $5 or more for a pack of lugs (at the LHS) when I can use soda straws for FREE! (Yeah, I'm that cheap!)

Now, given, the NEW soda straws typically handed out at your fave fast food eatery are quite a bit larger than they used to be (like 1/4 inch or so compared to the old standard straws which were more like 3/16-ish) and I'm flying using primarily 1/8 inch rod (4 foot) and I haven't noticed any problems such as rod whip or stuff like that. The 'slop-induced angle of attack' from the rocket sitting a hair off vertical due to the clearance between the rod and lug isn't large enough to cause any problems, at least from my experience. Usually the wind or the launcher sitting unlevel create WAY more 'off vertical' conditions anyway, and besides a LITTLE off-vertical is usually a good thing anyway. By the time the rocket leaves the rod it's going fast enough that it's usually already straightened up anyway. I've found that actually the oversize lugs solve one problem-- NO rod binding! If you've ever watched slo-mo vids of rockets lifting off, there is usually a 'twang' (to use a term NASA uses to describe the approximately 3 foot movement of the shuttle stack immediately after the 3 space shuttle main engines ignite and come up to full power, which, being off-center, push the shuttle and tank like it's trying to tip over, but this motion is arrested and the stack 'rebounds' back to vertical before the SRB's are ignited and the explosive bolts fired to release the shuttle for takeoff). Model rockets can make this same sort of movement, especially if the rocket is large-diameter, using a smaller rod, and if the lugs are snug or the rod is rough or sticky. The thrust starts to push the rocket up, but the rod friction pulls on the rocket, creating an off-axis tug which causes the rocket to 'twang' ever so slightly against the rod. I've found that oversize lugs actually reduce this tendency, in my experience.

Now, for contest stuff, yeah, ANY motion imparted to the model except STRAIGHT UP is energy wasted that COULD have been used to achieve altitude, but at some point it's infinitesimal.

Later! OL JR :)
 

Micromeister

Micro Craftman/ClusterNut
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Had a bit of an incident a couple weekends ago, Instead of using my normal Micro Launch lugs on a quick build test model I went with an oversized stir stick. fairly large for a stir stick at almost 3/32" ID. This oversize and only using a 1" long piece on the model gave it a good bit of play on the standard .049" launch rod. I was also using a longer then normal rod length since the model was two staged and on the heavy side for the MMX-II-NE booster. I wanted a little longer rod to let the model get up to speed before flying free. Nomally I fly on 9 or 12" micro rods, this is one of my boost glider 16" rods.
At ignition the model jumped up the rod but seemed to wobble around a bit near the top and did tip off a good bit leaving the rod. I'm sure this was due to the combination of longer rod and sloppy lug. Next launch I'm going to use my standard 12" rod to see if I'll have to add a small 2nd lug further up on the model to reduce or remove this problem.
This is another reason on most models I tend to use two small lugs space with the forward lug at or around the loaded CG and the other at or near the forward edge of a fin. This arrangement has always seemed to eliminate the rod whip tendency and smooth out liftoff of most size models even clusters.
 
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