Launch Rods: carbon fibre vs. stainless steel

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BKROSNEY

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Hi all,

First excuse me if this post pops up twice... I seemed to have some trouble submitting it...

Prep'ing for another flying season (flew a couple of days ago and then got hit with a couple inches of snow... yikes... mid-April) so I'm going through the ole Range box and was wiping down and cleaning my launch rods.

I've got a 1/8" stainless rod I picked up a couple of years ago that has become my standard A thru C rocket rod. Basically I just wipe it down with steel wool after every day's flying. Works wonderful. I've got a couple of cheap rods (I think they call them "drill rods" from a local h/w store), that I picked up awhile back for doing multiple group launches, but they have a tendency to rust over time.

I'm thinking of putting together a setup to hold several 1/8" rods for letting the kids drag race some rockets and my first choice for picking up some additional rods would be to use stainless steel. But, in searching the forum for ideas on keeping them slick (i.e. WD40, PAM, Tri-flow... geez I have other bike lubes that would probably work as well) I stumbled across comments about using carbon fibre rod.

I know I've seen the stuff at one of my local hobby stores. I'll have to recheck to see if they have 1/8" and suitable lengths.

So some questions.

For prevention of rod whip, would one (i.e. carbon fibre or stainless steel) have an advantage over the other? I know the carbon fibre stuff is incredibly light. Is it inherently more "rigid"?

Another quick question. Would one have an advantage over the other in the ability to keep it clean and slick? I don't think so, but I'd thought I'd ask as well. But related, aside from stuff like WD40, PAM, etc., what else have others used to keep those rod slick? And any issues with stuff gumming up over time or after hot exhaust gases blow against them?

And finally, failing the hobby shop to carry something, what other sources for carbon rod are there? I know I was at an archery range awhile back (kids B-day party) and I noticed they had stuff like carbon fibre arrow shaft stock. Now I don't know if it would be the right diameter or even the right length. The stuff I saw looked a little shy of 3 feet. Sources for carbon fibre rod if I go that way?

Thanks in advance.

... Bill
 

Handeman

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Bill,
I can't answer your questions about CF rods or even lube for SST, but I can tell you what's worked for me on steel rods and it should work for SST too.

I use all steel rods for my personnal launcher. When I'm done, I wipe them down with steel wool or emery cloth. I then wipe on a layer of car wax and let it dry. The next time I use it, I use a soft cloth to polish up the car wax. The rods are slippery with no build up and don't rust.
 

kramer714

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I don't think you want to use ANY of the lubricants you mentioned on the on the launch rod. They are all good lubricants but what you want for a rod (or a rail) is a dry film lube. these actually 'cure' onto the metal leaving you with a hard, but low friction coating that wont attract dirt or dust.

SailKote Dry Lubricants at a boat store (try west marine) works well, Miller & Stevenson MS-122 is another good one that is actually a mold release for composites. Don't use too much clean the rod and wipe a thin layer on the rod, let it cure and add a second coat. wipe it smooth, works VERY well, and wont gunk up things like the liquid ones do.

On rails, I coat the rail guides or buttons on my rockets, slides right down slicker than ...
 

bigone5500

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Spray silicone lubricant works good on rails...why not rods???
 

ADiehl

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Carbon fiber would be a bad choice for a launch rod. The epoxy binding the carbon would burn away after a few flights.

Also, the carbon is going to be less stiff than a steel rod of equal diameter, and a bit more expensive.

I personally use aluminum rods for LPR. No long term corrosion problem if you wipe em down after use, and cheaper than stainless. If you have heavy rockets, just use a slightly larger diameter rod.
 

STRMan

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Carbon fiber would be a bad choice for a launch rod. The epoxy binding the carbon would burn away after a few flights.

Also, the carbon is going to be less stiff than a steel rod of equal diameter, and a bit more expensive.

I personally use aluminum rods for LPR. No long term corrosion problem if you wipe em down after use, and cheaper than stainless. If you have heavy rockets, just use a slightly larger diameter rod.
Where are you finding those aluminum rods? I haven't found any in the right sizes at either Lowes or The Home Depot.
 

bguff

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Where are you finding those aluminum rods? I haven't found any in the right sizes at either Lowes or The Home Depot.
I can usually find 4' metal rods at Ace Hardware.
 

AX'E

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MAN! I'm even cheaper! Here's what works for me...

I just buy the standard grade steel rods in the bins at Lowe's, Home Depot, Ace-etc- the cheap ones in the steel stock area? Not sure of the exact section... I just see em and grab em. they're around a dollar or so </>
I polish them up with 0000 steel wool, and then oil them with a thin Teflon lubricant like REM-OIL, for storage.
When it's launch time, I just wipe off the lubricant, and rub vigorously with an old t-shirt just to put a final polish on the rod.
Of course- after 2 launches, all the final polishing is nixed.... I bring a few depending on many rockets I want to toss up.
After the launch, I just clean/re coat with the REM-OIL and leave them till next time; polishing again only as necessary.

AX'E
ps- As I was writing this- I see bguff does similar:)
 

hounddawgracing

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Same deal with me, cheap steel rods from HD, gently bend straight, hit with steel wool and then throw a few coats of wax on them. I use a pretty good wax for the cars so I can leave it for however long and then just wipe it off when ready to use.
 

Trip Barber

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The property of a material that determines the stiffness and resistance to "rod whip" of a launch rod made of it is the "modulus of elasticity", which can be found in engineering handbooks. Carbon steel and stainless steel have about the same modulus, so either is equivalent -- one is just harder to keep from rusting in the presence of corrosive exhaust gases. Aluminum has a 1/3 the modulus of steel, and is a bad choice for a launch rod except for very light rockets, unless you move up to a larger diameter than you would use if you were using a steel rod. It stays clean, but it does not do a good job in providing rigid guidance in the presence of wind.

Depending on the materials and wall thickness, I think that a carbon rod or tube is going to be about the same stiffness as steel (lighter weight, but roughly the same stiffness). I don't know how it would stand up in the presence of exhaust gas, never saw anyone use one.
 

Race58

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It works fine on steel rods.:)
Just spray it on a cloth or paper towel wipe down the rod before 1st launch and you're good to go.

Spray silicone lubricant works good on rails...why not rods???
 

Stuck Fingers

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Aluminum has a 1/3 the modulus of steel, and is a bad choice for a launch rod except for very light rockets, unless you move up to a larger diameter than you would use if you were using a steel rod.
Agree with everything Trip said.

It turns out that a 1/4 inch Al rod has the same stiffness as a 3/16 inch steel rod.

I use the 3/16 and 1/4 inch steel rods that Home Depot sells.

I made a storage tube out of PVC Pipe nipples, couplers and caps. I found some 2 foot long 1/2 pipe PVC risers in the irrrigation section. Works great and the rods don't get bent anymore.
 

AX'E

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That's a killer idea with the PVC storage container! I have a bunch leftover from some plumbing work I recently did, and didn't know what to do with it...
Thanks dude!

AX'E
 

Richard Dierking

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The property of a material that determines the stiffness and resistance to "rod whip" of a launch rod made of it is the "modulus of elasticity", which can be found in engineering handbooks. Carbon steel and stainless steel have about the same modulus, so either is equivalent -- one is just harder to keep from rusting in the presence of corrosive exhaust gases. Aluminum has a 1/3 the modulus of steel, and is a bad choice for a launch rod except for very light rockets, unless you move up to a larger diameter than you would use if you were using a steel rod. It stays clean, but it does not do a good job in providing rigid guidance in the presence of wind.

Depending on the materials and wall thickness, I think that a carbon rod or tube is going to be about the same stiffness as steel (lighter weight, but roughly the same stiffness). I don't know how it would stand up in the presence of exhaust gas, never saw anyone use one.
I realize this is an old thread, but wondering if I could quote the above in another thread about launch rods?
I think I recall seeing a tech paper years ago that said that aluminum launch rods may cause less rod whip. Does anyone recall this paper?
 

rharshberger

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Not only has it been dead for 12 years, but all but 3 posters have not been online here for between 9 and 11 years. Handeman, Trip Barber, and one other are active recently.
 

Leo

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I fly all my low power (A to D) rocket with the use of a hollow carbon rods. The rod is always cleaned with a damp (water) cloth to remove motor exhaust residue. It is never "lubed" in any way. I have very good experience using them.
 

Richard Dierking

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Not only has it been dead for 12 years, but all but 3 posters have not been online here for between 9 and 11 years. Handeman, Trip Barber, and one other are active recently.
I was doing some research and noticed that Trip had posted on this (a pretty good source!). I saw he was still active, so decided to give it a try. Also, he had extensive knowledge of the NAR technical base, so I thought he might recall the report I saw so many years ago on materials used for launch rods and rod whip.
 

rharshberger

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I was doing some research and noticed that Trip had posted on this (a pretty good source!). I saw he was still active, so decided to give it a try. Also, he had extensive knowledge of the NAR technical base, so I thought he might recall the report I saw so many years ago on materials used for launch rods and rod whip.
Trip is an execellent source, have you checked NARTS to see if the technical paper is available from them?
 

Richard Dierking

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Yes, I have tried, but every time I get into searching NAR materials I find myself somewhere in the forest. There's a lot of information, and not many search tools for stuff 10+ years. It could even be 15 years ago.

I think it's going to take somebody that says, "oh yeah, I remember that, it's here."
 

o1d_dude

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FWIW, I store my launch rods in a PVC pipe construct mentioned in the 2008 portion of the thread.

That’s where I got the idea back in 2009 when I joined.
 

rharshberger

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FWIW, I store my launch rods in a PVC pipe construct mentioned in the 2008 portion of the thread.

That’s where I got the idea back in 2009 when I joined.
Thats how we store our clubs rods and rails as well, each rail has its own pvc tube and the rods are stored as many as will fit in the tube easily.
 

Bluegrass Rocket

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I’m with Leo, I’ve been using a carbon fiber rod for several years now and it’s far superior to any metal rod that I ever used. Needs no lubricant, easy wipe off clean and seems significantly stiffer than a metal launch rod. Just my 2 cents.
 

rharshberger

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I’m with Leo, I’ve been using a carbon fiber rod for several years now and it’s far superior to any metal rod that I ever used. Needs no lubricant, easy wipe off clean and seems significantly stiffer than a metal launch rod. Just my 2 cents.
Are you launching by yourself or with a club?
 

Leo

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I forgot to add that carbon rods bend back to there original form so the are always straight :)
I've seen some wacky metal rods in my time. Had to cross my fingers the the rocket doesn't get stuck on the way up ..... :oops:
 

Richard Dierking

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I would disregard my suggestion that aluminum may be better to prevent rod whip. At least until I can find that report if I ever do.
Sounds like CF works well, and I like not having to deal with corrosion. But, CF rods when they break can be nasty. I'm careful handling CF when I use it for my rockets.
Also, we are assuming that stiffness is the most significant thing to preventing rod whip, correct?
Sometimes things that seem perfectly logical and are well accepted turn out to be incorrect.
 

Bluegrass Rocket

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Are you launching by yourself or with a club?
I use the carbon rod for personal launches. While I feel it is superior to a metal rod, for the club it’s probably too expensive. I got mine at the local Hobbytown USA and I think it was around 12 bucks. The rod I use is solid 1/8” and 40” long.
 

BEC

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I've dabbled with using CF for 1/8 inch launch rods. I've had no bad experiences with them. I am a little concerned that they might not stand up to the rod clamping mechanism used in many pads (a screw squeezing the rod against the inside of another tube/coupling nut). The rod holders of the good ol' PortaPad and its descendants are better in this regard.

I find a 1/8 inch CF rod to be stiffer than my stainless launch rods, and similar to the good old 1/8 inch music wire rods (a couple of which I have from my first rocketry period in the late 1960s. The formerly ubiquitous K&S rack at the hobby store used to be the source for those music wire rods. 3/16 diameter CF is really nice and stiff.
 
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