Zylaxus: a dubious build thread

[neil_w]

Launch Lugs

It's always a small moral victory when I remember to put the lugs on before final painting.

I prepped for the mounting by scraping the primer off the fin at the targeted attachment points. This is something that *would* have been better to have masked beforehand, but I hadn't really finalized how I wanted to do it yet.

The lugs are positioned away from the body enough to clear the plasmasphere with a comfortable bit of clearance.

Lugs were then glued on, nestled against a piece of Al angle for alignment.

Before filleting, I checked the position and alignment of the two lugs. Good clearance over the ping pong ball, and the rod appears to be parallel to the airframe.

Standard fillets finish the job, and now, at long last, the most fun part of any rocket build can begin: fin attachment.

(yes this is a bit out-of-order.... I did all this just before masking the ball)

 

[jqavins]

Launch Lugs

It's always a small moral victory when I remember to put the lugs on before final painting.

I prepped for the mounting by scraping the primer off the fin at the targeted attachment points. This is something that *would* have been better to have masked beforehand, but I hadn't really finalized how I wanted to do it yet.

The lugs are positioned away from the body enough to clear the plasmasphere with a comfortable bit of clearance.
View attachment 635085
Lugs were then glued on, nestled against a piece of Al angle for alignment.
View attachment 635086
Before filleting, I checked the position and alignment of the two lugs. Good clearance over the ping pong ball, and the rod appears to be parallel to the airframe.
View attachment 635087
Standard fillets finish the job, and now, at long last, the most fun part of any rocket build can begin: fin attachment.

(yes this is a bit out-of-order.... I did all this just before masking the ball)

I don't recall from the pictures, but I assume you've planned it so that the cage oriented with the launch rod between ribs.

 

[neil_w]

I don't recall from the pictures, but I assume you've planned it so that the cage oriented with the launch rod between ribs.

Correct. The six-way cage is aligned with the verticals, so the wings are centered between them.

I will need to ensure that the canards are aligned correctly relative to the wings so the rod does not hit them.

 

[neil_w]

First two cage pieces are on. I think two fins per session is going to be about right for this one. So mounting all the fins will take a little while.



It only just occurs to me that this would be a good time to use a foamboard fin jig in tandem with my trusty old 3D-printed jig (shown above at right of picture). I'll have to cut one out before I continue.

 

[neil_w]

And now the four small cage pieces are on, starting to look like something. I'm not always a huge fan of foamboard fin guides but this one proved quite helpful so far.

 

[lakeroadster]

Launch Lugs

It's always a small moral victory when I remember to put the lugs on before final painting.

I prepped for the mounting by scraping the primer off the fin at the targeted attachment points. This is something that *would* have been better to have masked beforehand, but I hadn't really finalized how I wanted to do it yet.

The lugs are positioned away from the body enough to clear the plasmasphere with a comfortable bit of clearance.
View attachment 635085
Lugs were then glued on, nestled against a piece of Al angle for alignment.
View attachment 635086
Before filleting, I checked the position and alignment of the two lugs. Good clearance over the ping pong ball, and the rod appears to be parallel to the airframe.
View attachment 635087
Standard fillets finish the job, and now, at long last, the most fun part of any rocket build can begin: fin attachment.

(yes this is a bit out-of-order.... I did all this just before masking the ball)

I've often wondered what is the optimal approach in regard to the size and quantity of launch lugs? You are using (2) which looks good aesthetically, but is that the "best" way? There's so much "Well here's how I do it." discussions -vs- actual hard data.​

​

Thinking about this rocket:​

​

Statically, on the pad: (2) lugs provide good support,​

​

At Launch:​

Zero Wind​

(2) lugs provide good support until the launch rod is cleared.​

Some wind​

(2) lugs are suspect to rod wip​

Mild wind​

(2) lugs are pretty horrible​

​

Think about the rocket sliding up the rod under power:​

With one lug the rod can whip and as long as it doesn't hit the rocket, no harm - no foul.​

With two lugs, when the rod exits the first lug, the rod whip steers the second lug, at the rear, and things can go wrong real quick.​

Just throwing this out there. Curious about your thoughts.​

 

[neil_w]

In every discussion of launch lug placement, the consensus is always that it's just not that critical, and there are no precise rules.

More often than not, I go with the single large lug somewhere between CG and CP, but that wasn't possible here. Two small lugs is my second choice. The one in back always goes as far back as possible, and the one in front.... is wherever it's convenient. I usually try not to have the forward one too far forward because I don't want it to clear the rod too early. The spacing seemed about right on this one.

I've never had a failure in this area (or even heard about one that I can recall) so I really don't sweat it too much.

 

[neil_w]

Nifty.



Everything seems to be fitting optimally so far. Wings come next.

2 months of tedious prep and now the fun part is blowing by in a few days. Then the *real* tedious parts start: waiting for painting weather, painting, waiting for it to dry, *masking* (oy), more painting. Rockets are fun!

 

[NTP2]

Rockets are fun!

Too true…

 

[jqavins]

Rockets are fun!

Of course they are. Rockets are such a pain in the ass, if they weren't fun no one would build them.

 

[neil_w]

Of course they are. Rockets are such a pain in the ass, if they weren't fun no one would build them.

There's an expression...

 

[neil_w]

Mounting the wings, at last

I had to move my cradle far up the body tube to clear the front mounting points of the wings. And so I stuck a screwdriver into the front to weigh down that end and keep the whole thing from tipping over to the left.



As a final check of tab fit (and first step of double-glue joint), I applied TBII to the fin root (everywhere there would be a glue joint) and inserted it fully. After removing the fin I checked that there was glue everywhere, meaning everything was making contact correctly. This would have been my last chance to adjust the fit, but thankfully it was not needed.


And, at long last, the wings are on.

 

[jqavins]

As a final check of tab fit (and first step of double-glue joint), I applied TBII to the fin root (everywhere there would be a glue joint) and inserted it fully. After removing the fin I checked that there was glue everywhere, meaning everything was making contact correctly. This would have been my last chance to adjust the fit, but thankfully it was not needed.
View attachment 635827

Brilliant!

 

[BABAR]

Looks like you are having a ball!

(Please forgive me, sometimes I can’t help it)

 

[lakeroadster]

As a final check of tab fit (and first step of double-glue joint), I applied TBII to the fin root (everywhere there would be a glue joint) and inserted it fully. After removing the fin I checked that there was glue everywhere, meaning everything was making contact correctly. This would have been my last chance to adjust the fit, but thankfully it was not needed.

As opposed to... "Flood The TTW Openings and Fin Roots With Wood Glue." Oh... the humanity! Clean up on aisle 5.​

​

Looking good Neal.​

​

​

 

[neil_w]

As opposed to... "Flood The TTW Openings and Fin Roots With Wood Glue."​

Honestly, I don't know how well that works. If there's a gap between the fin and the motor mount that is bridged by wood glue, how strong it that?

 

[lakeroadster]

Honestly, I don't know how well that works. If there's a gap between the fin and the motor mount that is bridged by wood glue, how strong it that?

My lame attempt at humor...​

​

Yeah, I know, everybody always says with wood glue you don't want any gaps. But there's always some gaps... the wood glue will fill it.​

It's not rocket science... wait, well, yeah.​

​

 

[neil_w]

My lame attempt at humor...​

​

Yeah, I know, everybody always says with wood glue you don't want any gaps. But there's always some gaps... the wood glue will fill it.​

It's not rocket science... wait, well, yeah.​

​

I got the joke, but it did raise a real question: how important is it for perfect contact on the fin tabs? How does strength vary with gap size?

In this particular case the question is moot, because I seem to have gotten good contact everywhere, and I *assume* that the strongest bond is with good contact and a double-glue joint.

Feels like the gravitational force of a glue thread pulling me in...

 

[neil_w]

Assembly Complete



(minus shockcord and parachute)

 

[BABAR]

Feels like the gravitational force of a glue thread pulling me in...

Don’t go into the light!

 

[BABAR]

Assembly Complete

View attachment 636270

(minus shockcord and parachute)

Some really cool pictoral distortion (or else the taped plasma ball field is doing it.). The wing fins all look warped in the picture. Not sure if it is artifact from the shadow and the sanded paint effect. Be cool if it still had this effect after final paint job!

 

[bobby_hamill]

when I saw the ball it brought back memories of the old superball bounce ball

https://i5.walmartimages.com/seo/Su....jpeg?odnHeight=640&odnWidth=640&odnBg=FFFFFF

 

[lakeroadster]

View attachment 636307Some really cool pictoral distortion (or else the taped plasma ball field is doing it.). The wing fins all look warped in the picture. Not sure if it is artifact from the shadow and the sanded paint effect. Be cool if it still had this effect after final paint job!

It's the plasma of the sphere... warping the rear of the rocket....​

 

[NTP2]

View attachment 636307Some really cool pictoral distortion (or else the taped plasma ball field is doing it.). The wing fins all look warped in the picture. Not sure if it is artifact from the shadow and the sanded paint effect. Be cool if it still had this effect after final paint job!

I think it’s the angle of the shot, probably wouldn’t look like that in person.

 

[neil_w]

I do get a sensation of static electricity in the air when working on the tail end of the rocket…

 

[NTP2]

I do get a sensation of static electricity in the air when working on the tail end of the rocket…

Try rubbing it on your hair.

 

[boatgeek]

It's the plasma of the sphere... warping the rear of the rocket....​

Clearly we’re seeing a gravity lensing effect from the extremely dense material in the plasma sphere. No doubt the RSO will have questions about stability and thrust to weight ratios. That is, if @neil_w don’t need a crane to get it to the RSO table.

 

[jqavins]

It'll be fine once the tape is removed. The space folding field is leaking through the tape, but the leakage is asymmetrical. Once normal operation is restored everything will be good.

 

[neil_w]

It'll be fine once the tape is removed. The space folding field is leaking through the tape, but the leakage is asymmetrical. Once normal operation is restored everything will be good.

That’s an excellent point, one I should have considered when masking. Hopefully the flow of paint when I’m spraying won’t be adversely affected.

 

[neil_w]

I weighed the rocket and measured CG this morning.... unsurprisingly it's quite a bit heavier than my OR model, although the masking around the ball is adding weight to the tail that I can't factor in. I don't think it's *that* much, but in any case it'll make my calculations a bit more pessimistic which is fine.

Minus shock cord, parachute, and eyelet in the nose, I'm at about 2.9 oz, CG at around 20.5". To equalize the OR model I needed to add a 0.85 oz weight 16.25" from the nose. Then I added back the parachute, shock cord, and 1/2 oz in the nose (most of which will be the fairly chunky eyelet that I will be using) and I come up with what should be a pretty accurate model:


Paint will add a bit more weight but I don't think it's going to change much. Either way, this thing ain't hitting 1000' under any conditions and that's fine. 500' on a D12 or 800+' on an Aerotech E should be plenty enjoyable. Drag is the dominant factor here, as evidenced by the optimum delay staying close to 4 seconds regardless of the motor.

I really need to get working on the decal design, since that usually takes a while. I'm still weeks away from painting, due to weather.