[POW]Eagle159
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The title says it...What is rod whip, when does it happen, why?
Thanks for any help...
:handshake:
Thanks for any help...
:handshake:
A final judgement would depend on how heavy the rocket was, but a 36" x 3/16" rod on a stable pad should be able to handle any E motor. I launch stuff on 24mm F motors off of 48" x 3/16" rods all the time and I have even launched G motors from them on a couple of occasions. (Using a 3/16" rod to launch Gs is not something that I would recommend doing routinely, though.)[POW]Eagle159;224126 said:So on the estes maxi 3/16 rod 36'' be bad for the estes SaturnV with some nose weight and an AT E20....That's what im planning to fly soon.
A final judgement would depend on how heavy the rocket was, but a 36" x 3/16" rod on a stable pad should be able to handle any E motor. I launch stuff on 24mm F motors off of 48" x 3/16" rods all the time and I have even launched G motors from them on a couple of occasions. (Using a 3/16" rod to launch Gs is not something that I would recommend doing routinely, though.)
Well if it is any help my Hercules weighed more than 16 oz. empty and I launched that successfully (when all 3 motors lit) on a 3xD12 cluster off of a 48" x 3/16" rod. With something as large as the Saturn V you also need to consider effective rod length, or rod travel. The rocket is longer than the 36" long rod, but as with any rocket the guidance provided by the launch rod is only effective for the distance that the lug is on the rod. If the Saturn on an E20 can get up to speed from a standing start before its lug runs out of rod then you should be OK with that length. You can get a 48" long x 3/16" diameter cold-rolled steel or plated rod at your local hardware or home improvement store and it will provide you with an extra margin of stability. Personally, that is what I would use if I was launching that rocket. The club I belong to uses 48" long rods for its 1/8" and 3/16" rods.[POW]Eagle159;224145 said:With the nose weight its like 14-15oz. or so, on the regular estes pad. It worked well with the E20 and no nose weight but wasn't stable.....:sad: IT WILL BE BETTER NEXT TIME :wink:
[POW]Eagle159;224145 said:With the nose weight its like 14-15oz. or so, on the regular estes pad. It worked well with the E20 and no nose weight but wasn't stable.....:sad: IT WILL BE BETTER NEXT TIME :wink:
[POW]Eagle159 was asking about the advisability of using a 3/16 inch diameter rod for his Saturn V, wasn't he?I think you'll be good to go. One of my clustered Saturn V's liftoff weight is 27ounces. I use a 4' x 3/8ths rod on a camera tripod. No whip at all.
Verna
www.vernarockets.com
Rod whip?
That is when your significant other finds out how much you just spent on rockets and whips you upside da' head with your own launch rod.
Such a frightful experience....
[POW]Eagle159 was asking about the advisability of using a 3/16 inch diameter rod for his Saturn V, wasn't he?
QUOTE]
:y: You are right Mark, I meant 3/16ths. Thanks for the correction!
Verna
www.vernarockets.com
A 3/8" rod is really on the beefy end of the spectrum for mid-power!
The glider launchers that I have seen do indeed have pretty thick rods, now that you mention it. I'm venturing a couple of guesses as to why...[Caution -- completely uninformed excogitation follows]Actually, most F and G powered gliders I fly tend to use exactly that, a 6' by 3/8" launch rod. Regardless of weight, I have found that they tend to fly where I point 'em. Recovery is another matter though :lol:
[POW]Eagle159 was asking about the advisability of using a 3/16 inch diameter rod for his Saturn V, wasn't he?
QUOTE]
:y: You are right Mark, I meant 3/16ths. Thanks for the correction!
Verna
www.vernarockets.com
Everyone else has already posted good advice, yeah, a 3/16th rod would be good, a 1/4inch might be better.
I say that only because you probably need a significantly longer length than 3 feet, and at 4 or 5 feet it is probably time to just go ahead to the 1/4inch size. Especially if you plan to keep working toward bigger and heavier rockets in the future, a 1/4inch is definitely going to come in handy.
As noted in previous posts, rod whip is complicated. It is a combination of rocket weight, rocket pitch inertia, lug placement, thrust axis offset from the launch rod, rod length and diam and material, the structural design of the anchor holding the bottom of the rod, and probably a few more things just make it all confusing. About the only simple thing you can say about launch rod selection is that if you are asking these questions, it's time for you to step up to the next size.
If you have an Estes Saturn V-sized model on a 'medium' thrust motor it will accel more gently and should have less rod whip, but then it will be separating from the launcher at lower speeds and will tend to be less aerodynamically stable. (It needs a longer rod to give it more time-on-the-rod to accel to safe, stable flying speed, and for rods longer than 3 feet you should be using 3/16th or 1/4inch.)
If you have an Estes Saturn V-sized model on a high-thrust motor it will accel better and should have higher velocity at the point where it separates from the launcher, but the higher thrust will tend to aggravate any rod whip problems you might have. (It needs a larger diam rod for more stiffness and less whip.)
And as Mark II pointed out back in #8, the distance by which the model's launch lugs are separated (as well as the position of the last lug) will make a difference on how much "usable" rod length you have before the rocket starts separating from the launcher. Again, longer is better, and anything beyond 3 feet cries for a bigger diam than 1/8th.
The glider launchers that I have seen do indeed have pretty thick rods, now that you mention it. I'm venturing a couple of guesses as to why...[Caution -- completely uninformed excogitation follows]that this because they are pitched so far off vertical and the thickness is to limit any sagging or bouncing while they are in that orientation?Plus, perhaps:
as I alluded to in an earlier post, a large rocket that lifts off slowly due to a low-thrusting motor (or in the case of typical rockets, too little motor or too much mass) can induce rod whip. Since RBGs use long-burn low thrust motors by design, extra precautions are taken to reduce any bouncing or deflection of the guides.Does any of this utter speculation have even a shred of truth?
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