Nomad near miss

[illini]

Flew my FlisKits Nomad for the first time today and nearly busted the thing. I tried a C11-0/B6-0/B6-6 combo. Liftoff was perfect. Lower stage separated cleanly, but no ignition of stage 2. Ruh Roh!! A *very* fortunate wind gust managed to throw the thing on its side before it smacked the ground and it landed softly without any damage. WHEW! It appears the failure was caused by interstage pressure blowing stage 1 off before stage 2 could ignite. Stage 1/2 ignition is gap staged, but without any vent holes. The pressure blew stage 1 off cleanly, but before the B6-0 ignited.

Anyone had this problem with the Nomad before? Any tips on how to cure the problem short of punching vent holes in stage 1 (which I will gladly do if there is no other choice)?

 

[PWALPOCO]

I dont know this kit at all , Im only allowed to touch Estes at the moment as Im a noobie !! LOL

Anyway , seems from my naive point of view that either the gaps got to dissapear , or the pressure has to get out somehow in order to for the 1st stage to hold on long enough to ignite the next. Either that or the 1st stage section needs some help in order to stay around a little longer.

I take it that the stages are friction fit or something ? Ive not done staging so dont know. If it is friction fit , add more friction ?

If the design doesnt allow you to close the gap , assuming closing the gap is wise , then as you point out , the venting option is next.

Of course , how BIG the vent holes should be is another matter. Too big a hole may cause too little resistance and your motor may try to thrust out via that route than trying to force the first stage off !

The mighty fliskit creator may have some advice for you

Paul

 

[illini]

The stages are fit with a tube coupler...standard issue. The 18mm second stage engine is installed just above the top end of the 24mm motor mount. There is an air gap between them. Gap staging usually requires vent holes to keep the stage on long enough for upper stage ignition to occur. For the Nomad, I think the theory is that the second stage motor is close enough that it should ignite before the pressure buildup is too great. That's theory. In practice, my lower stage blew itself off cleanly with no 2nd stage ignition.

I'm thinking of trying some small strips of cellophane tape on the *outside* joint of the two stages to hold them together a bit longer. Would like to hear from someone who's actually flown a Nomad before trying that, though.

 

[eugenefl]

I've flown my Nomad with all three stages only once. I didn't have any problems with it. The stages held together just fine. Of course, I can't say that might coupler is any tighter on the 2nd stage than yours is. That may be the difference. I know Carl has flown his on 3 stages before and the 1st stage ignited the 2nd stage just fine.

 

[illini]

Okay, so we have at least 2 examples of it working fine. I'm sure the FlisFolks had success when testing it as well or we wouldn't see it as a kit. Must be something to the tightness of the fit. Mine's not loose by any means. The stage "popped" off, it didn't fall off. Maybe it was a fluke, but if it is a problem then I'm thinking small strips of cellophane tape should cure it.

 

[Johnnie]

I have a Nomad but have not started to construct it yet. When they work perfectly, I bet they are poetry in motion. I saw a 3-stage Estes, Comanche 3 I believe, successfuly stage D - C - C yesterday, and all 3 stages were recovered. What a rush.

 

[havoc821]

Yeah, that was the Commanche 3. That rocket had a nice paint job! It went HIGH!! I'm suprised he got all 3 stages back. I can't help anybody here with staging. My first 2 stage rocket will be either the Team America Rocketry Challenge rocket or my scratchbuild HPR rocket staging an I211 to an I211! My motto:

Go big or go home!

I might do an estes two stage kit before my HPR attempt, but I don't think it will help any beacuse they use 2 completely different means of ignition and design, and etc.

 

[KermieD]

Did you line the fins up? It does sound like you might have had a drag separation just before the BP may have lit the 2nd stage.

 

[kelltym88]

Don't know if this will help, but I too have a Commanche 3(2 in fact) And I have never had a problem with any of the stages igniting, and I have recovered all 3 stages sucessfully each time. In fact, the only 2 times that I've had a problem with the 1st stage not igniting the 2nd was:
My Magnum "D" booster CATO'D, flamed out and pushed the 2nd stage off to the side. It was easily repaired and is now ready to launch again.
My Custom Lightnin'-- I had a brain fart during construction and messed up glueing the coupler from the booster to the 2nd stage. As a result I had to modify the coupler, which made it only stick out of the BT about 3/8" of an inch instead of 1'' or so. Thus when the 1st stage went to ignite the second(I had to tape the two together, a little too tight) the result was the booster did not pop off but rather burned right up thru my second stage, MMT and all. Still fixable, but haven't got to it yet.

All in all I would say that with those 2 exceptions, I've never had a problem with my staged rockets performing as expected, and I've had a lot(Apache 2, Omega, CC Express, Commance 3).
I don't have a Nomad, but is it possible to make sure the booster on the 1st stage is butted up against the 2nd stage?
Hope this helps.
Here's a picture of my Commanche 3(the 2nd one)

 

[cls]

Yesterday my Nomad 1st stage D12-0 failed to ignite the 2nd stage. No idea why, I prepped it and launched it the same way as all the other 5 times I've flown it (always 3 stage).

later I used the C6-0/C6-5 successfully on a Renegade. However I burned a couple ignitors to get the C6-0 to light.

I think I remember trouble lighting another C6-0 yesterday. anyone know anything about hard-to-light C6-0s and B6-0s???

 

[illini]

Originally posted by KermieD
Did you line the fins up? It does sound like you might have had a drag separation just before the BP may have lit the 2nd stage.

The 1st stage fins were not aligned -- 60 degrees off from the upper stages. Drag may have been a contributor, but I think the interstage pressure had more to do with it since there was an audible *pop*. The B6-0 was clearly impacted by burning propellant from the 1st stage...the nozzle is slightly blackened. I think I'll fly it 2-stage first (directly igniting the B6-0). When I make another 3-stage attempt I'll align the fins and try a couple of small pieces of cellophane tape on the outside.

 

[wyldbill]

Take a look in the nozzle of the sustainer motor that didn't ignite. Is there any clay in the nozzle itself? It can be a good idea to "clean" these nozzles with a wood toothpick to make sure they're clear before flying them...

FWIW,
-bill

 

[jflis]

hi

I'm back from NARCON and digging through mail and now TRF... whew!

a bit of history on the Nomad. I designed that rocket back in the 80's. I've built 3 and have flown all of them many times in 3-stage configurations and have never had a failure.

I know about vent holes for gap staged models and feel that it is appropriate in many cases. I didn't apply it here because the stages are so close together (patterned after the gap staged Omega which didn't use vents).

Also, for what it may be worth, I *always* have the lower stage fins rotated 60 degrees out (i think it looks cooler )

I would say that two likely culprits could be a loose coupler (in which case a thin layer of tape could help) or a dirty nozzle in the 2nd stage motor.

I would also offer that a vent certainly wouldn't *hurt* anything in this design, it just wasn't felt to be needed based on a *lot* of past experience with the design.

I am *thrilled* that a chance gust of wind allowed for a safe landing and would be most interested in any future flights of this model with either tape to increase friction between stages or a vent hole.

keep us posted!
jim

 

[illini]

Thanks, Jim. I *knew* you wouldn't sell a kit that didn't work. Will give it another go in a couple o' weeks at the next club launch and post the results here.

Yup, surely was a mighty fortuitous wind gust. There were quite a few people at Great Meadow that day (lots of TARC'ers). When the staging failed there was a collective *gasp* from the crowd as the thing keeled over, homing on a piece of turf. I nearly soiled my diaper until I saw the wind blow it on its side and lay it on the grass. I'll probably never see such a kindly wind gust as that.

 

[graylensman]

Originally posted by illini868891
Yup, surely was a mighty fortuitous wind gust... I'll probably never see such a kindly wind gust as that.

It's either clean living or many sacrifices to the Rocket Gods!

 

[illini]

Originally posted by graylensman
It's either clean living or many sacrifices to the Rocket Gods!

I didn't see it myself, but some folks told me they could have sworn Jim Flis was directly underneath the thing blowing as hard as he could. Now *that's* service!!

 

[jflis]

LOL

yea, you know, I had a dream the other day while napping that I was blowing as hard as possible to keep a feather aloft... LOL

I'd love to claim that there is a proximity sensor in the nose cone that fires the pitch motors in these situations....