Rail friction impact

[spence]

Has anyone noticed altitude differences due to dirty vs clean rails? If do, what impacts have you seen?

 

[Bat-mite]

I have no data, but I am going to say that there has to be an impact, because I've seen a rocket not be able to leave a cruddy rail.

 

[Zeus-cat]

Well, in contests people prefer launch towers versus a launch rod and lugs to reduce friction. I would assume the same thing applies to rails.

 

[dhbarr]

Well, in contests people prefer launch towers versus a launch rod and lugs to reduce friction. I would assume the same thing applies to rails.

Most of that improvement is due to aerodynamic drag reduction, though; not sticky rails.

 

[Banzai88]

I've had grungy rails hang a launch, and had them tear up rail buttons to the point that they needed replaced after only two launches. It's been bad enough that I bought a new rail for one club that I launch at on the condition that they throw the offender in the scrap heap.

 

[spence]

Has anyone noticed altitude differences due to dirty vs clean rails? If do, what impacts have you seen?

The reason I am asking is I am associated with a TARC team. The team had their altitude really dialed in in practice flights , in different weather, etc. The rails that they used at the local club - are typical local club rails with lots of use. No complaint. At the contest the trails are brand new and nicely greased - pristine. The team overshot their altitude and had controlled for all other variables, other than the launch rail. Several teams actually brought their own rails to the contest. The conclusion, and learning might be that the rail friction on the club rails impacted the calculations and thus the virgin rails gave extra altitude. How likely is this?

 

[blackjack2564]

Very likely.

Small motors especially like TARC uses, in these contest rockets are very touchy when it comes to excess drag. Such as that from dirty rails.

 

[dhbarr]

Yes, I would definitely eliminate the random-rail-assignment variable if trying for precision flying.

 

[rstaff3]

That's interesting. Maybe the teams should be allowed to bring their own rail.

 

[dhbarr]

That's interesting. Maybe the teams should be allowed to bring their own rail.

More scaleable to treat it as a lesson learned and attempt to duplicate the contest conditions as nearly as possible for practice flights.

 

[NateLowrie]

I have found the Chlorox wipes can get normally get the worst of the gunk off the rail easily. It's small insurance to bring the container with you and wipe it down before sliding the rocket on.

 

[mpitfield]

I have found the Chlorox wipes can get normally get the worst of the gunk off the rail easily. It's small insurance to bring the container with you and wipe it down before sliding the rocket on.

I have often thought of bringing something out to the pad to give a quick wipe down prior to loading, assuming this process dos not cause delays, such may be the case at a busy event. What do you guys use to get into the channels?

 

[timbucktoo]

We use steel wool or scotch brite pads and hit it with some wd40.

 

[dcullen]

More scaleable to treat it as a lesson learned and attempt to duplicate the contest conditions as nearly as possible for practice flights.

Actually teams are permitted to bring their own rails or even complete launcher. About a half dozen did so (rails or complete launch systems)

 

[dcullen]

We use steel wool or scotch brite pads and hit it with some wd40.

Likewise, scotch Brite and WD40. This is the same equipment used at TARC nats.

 

[Woody's Workshop]

Does anyone use spray silicone on rails?
I've never used a rail, but the reason I ask is;
I spray the rod before each launch day and kinda buff it.
I also dab a little powered graphite in the lugs before launch.
At the end of the day I use a 3M red scotch pad (3M #7447, 400 grit) and give a quick shot of silicone for storage.
I've never had a sticking problem unless there was paint build up or crushed lug.
I would think a cleaning after each sparky motor would be called for as in my theory, burning sparks would stick to the aluminum rail more than hot burnt power.
But that's me, I'm Mr. Overkill.

 

[dhbarr]

Actually teams are permitted to bring their own rails or even complete launcher. About a half dozen did so (rails or complete launch systems)

Then an adjustable tower would be a pretty sensible investment

 

[Handeman]

I have no data, but I am going to say that there has to be an impact, because I've seen a rocket not be able to leave a cruddy rail.

I've had grungy rails hang a launch, and had them tear up rail buttons to the point that they needed replaced after only two launches. It's been bad enough that I bought a new rail for one club that I launch at on the condition that they throw the offender in the scrap heap.

Very likely.

Small motors especially like TARC uses, in these contest rockets are very touchy when it comes to excess drag. Such as that from dirty rails.

At BattlePark, our rails are 10 years old. They sit in the field from October to April. I don't know that the TARC teams have had any problems with the rails, but if they want their own pad that is allows. If they want to clean our rails, we supply the green scrub pads and WD-40.

What has NEVER happened in the 10 years those pads have been in use is a rocket hang on the rails. With 6 months sitting in winter weather and all kinds of motors, including sparkies, the rails have never been so bad that a rocket got hung on the rails or ruined the buttons. We clean the rails at the start of each season, but that's it. I can't imagine what could possible dirty the rails so bad it would ruin rail buttons or cause a rocket to hang on the pad.
If you can tell me what caused those conditions, please do, because we want to continue to avoid anything like that happening.

 

[DavidMcCann]

Only one way to know. Burn a rail up, and fire two identical rockets off a kicked rail and a new oiled one.

 

[Viperfixr]

Degreasing wipes to clean and this dry lube spray worked really well in a dusty desert environment where wet lube would make a mess and be more of a problem to hang-up a rocket.

 

[Q-Aero]

I'm more worry with the scratches on the rail made by the Skidmark and similar.

 

[Lowpuller]

Back to the OPs original question density altitude also comes into play.

If all conditions are equal you would get a different AGL altitude if you launched in the Rockie Mountains versus at the beach, obviously the extreme case.

In other words if your launch sites are at different altitudes this will affect your overall altitude due to the density of the air, this is also affected by air temperature.

The good news is that you can potentially calculate or at least estimate the affect.

In any case I agree bring your own rail as it eliminates a variable.

 

[boatgeek]

Cleaning rails made a noticeable (like 25-50') difference in altitude for our TARC teams. We mostly use blue motors, so the rail doesn't get too dirty in any given launch. Smoky motors will crud it up in a hurry.

Also, one year at TARC the air was really thick and humid. The team took off just the right amount of ballast to adjust for density. We're pretty much at sea level so altitude doesn't make much difference for us at finals.

 

[spence]

going to try this at next sport launch at club