ARS Prototype quick build thread

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rockets

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Here is a quick build thread of ARS kit #2.
It's name will remain anonymous until officially announced at a later date.

Anyway, here's all the parts:
IMG_4284.jpg
And these 1/8 inch plywood laser cut fins are a work of art!
IMG_4285.jpgIMG_4287.jpgIMG_4288.jpg

OK, so first off, I draw the lines onto the body tube, to roughly see where these go. Since this is going to be a corkscrew rocket, the fins must be canted.
When my brother designed this years ago, he had 2 of the 4 fins canted.
IMG_4289.jpg
And so the first 2 I put on are going to be straight, and the last 2 will be canted.
Gluing on fin #1:
IMG_4290.jpg
After that dried, on went #2:
IMG_4291.jpg IMG_4292.jpg




I'll go on about this on the next post.




Thanks,
 
OK, now it's time for the canted fins!
IMG_4294.jpgIMG_4293.jpg

And, #4!
IMG_4295.jpgIMG_4296.jpg

While those dried, I started working on the nose cone.
I got the clay, and rolled it into a snake, and using a pen, I pushed the clay into the tip of the nose cone:
IMG_4302.jpgIMG_4300.jpgIMG_4299.jpgIMG_4298.jpgIMG_4297.jpg



I have run out of pictures space.





Thanks,
 

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I put a small amount of CA on the lip of the nose cone insert:
IMG_4304.JPG
Put in in the nose cone, and wiped off the excess adhesive:
IMG_4306.jpg
All done!
IMG_4305.jpg

And now for the shock cord mount:
IMG_4307.jpgIMG_4308.jpg
I used my finger to put it into the tube, but used a pen to push it down and secure it in.
IMG_4309.jpg
All done!
IMG_4310.jpg

And now time for tying the the knots for the shock cord and the streamer:
IMG_4312.jpgIMG_4313.jpg






Thanks,
 
And then I started the fillets:
IMG_4317.jpg



The first flight will be today or tomorrow, not sure yet.


That's all for now! :)





Thanks,
 
All of the fillets are finished.
And the launch lug is mounted on.

It's ready to launch, just debating on whether to do it now or tomorrow.



Thanks,
 
Interesting fins. It has a guitar/violin vibe to it.
For some reason the fins look rather thick, but it's probably just perspective.

Are the fins supposed to be angled like that?
 
Interesting fins. It has a guitar/violin vibe to it.
For some reason the fins look rather thick, but it's probably just perspective.

Are the fins supposed to be angled like that?

The fins are 1/8 inch plywood. They're not very heavy at all.

Yes, the fins are supposed to be angled. It's a corkscrew rocket.


Thanks,
 
Could you show the picture of the compleated rocket

I will when I finish building the rocket.


Prototype #1 didn't do what it was supposed to do. So, I'm now building prototype #2 and this one should corkscrew.



Thanks,
 
Andrew,
I make this suggestion with the sincere intention of being constructive: you need to have more care in your construction. The fins in the first build were all over the place. The fin markings look like they were drawn freehand, and then the fins are not even on the lines.

I'm not sure why you're only canting two of the four fins. If you want it to spin, I'd think you would be best off mounting all fins equally with a slight cant. Make yourself a proper fin marking guide, and mount all fins on the lines equally.

If it's built right, then you can be sure that you're testing the *design*, not the quality of construction.
 
Andrew,

I think Nytrunner is asking about how the look canted over; not perpendicular to the tube (the two horizontal ones do look right in the photo, the two vertical ones are 'falling over') And, I believe we understand they are angled in relation to the axis of the BT to induce a spin.

With the voids in the fins, do you have the area needed to maintain stabability? May I maybe suggest you make the fins a sandwich of the '8' shape you want, but with a clear piece in the middle? You then have the surface area you want for the fin, and the visual of the voids being hollow. Use 1/16" ply, both sides on a piece of 1/16 lexan / acetate film.. You only need a degree or two offset to induce a spin..

The shock cord attachment doesn't look right. Is that just glue onto the rubber cord, on a piece of masking tape?
 
Prototype #1 didn't corkscrew like it was supposed to. I realized there was a small flaw in the design, and I've fixed that, and I built Prototype #2 and it should work, (We'll find out this afternoon! :) )
I didn't rush the build on Prototype #1, I built it in about 4 hours, which is normal for this sort of kit, because it's so simple to build.

The shock cord mount works really well!
Yes, it's a piece of masking tape, Titebond III & the shock cord.
It's super strong. I've built rockets using that method for the shock cord, and it's lasted over 20 flights on some of my rockets without any separations.



Thanks,
 
Andrew,

I think Nytrunner is asking about how the look canted over; not perpendicular to the tube (the two horizontal ones do look right in the photo, the two vertical ones are 'falling over') And, I believe we understand they are angled in relation to the axis of the BT to induce a spin.

With the voids in the fins, do you have the area needed to maintain stabability? May I maybe suggest you make the fins a sandwich of the '8' shape you want, but with a clear piece in the middle? You then have the surface area you want for the fin, and the visual of the voids being hollow. Use 1/16" ply, both sides on a piece of 1/16 lexan / acetate film.. You only need a degree or two offset to induce a spin..


The shock cord attachment doesn't look right. Is that just glue onto the rubber cord, on a piece of masking tape?


My older brother, designed this kit around 8 years ago.
He built a 24mm version, and a 38mm version. He never had a problem with fin strength or stability.




Thanks,
 
Andrew,
I make this suggestion with the sincere intention of being constructive: you need to have more care in your construction. The fins in the first build were all over the place. The fin markings look like they were drawn freehand, and then the fins are not even on the lines.

I'm not sure why you're only canting two of the four fins. If you want it to spin, I'd think you would be best off mounting all fins equally with a slight cant. Make yourself a proper fin marking guide, and mount all fins on the lines equally.

If it's built right, then you can be sure that you're testing the *design*, not the quality of construction.

When my brother designed it, he only canted 2 of 4 fins. His 24mm version works really well. I think it spins every 18 inches.


I drew the lines using a ruler onto the body tube, and after the fact, I realized I messed up one of the lines slightly, and that offset where the fins were going to go. I reset the lines in different areas, and I glued the fins on. So, it may look like I put the fins in the wrong place, but technically, I didn't.



Thanks,
 
One fin off alignment can induce a spin. All the fins at the same offset will have less drag..

Scaling things up or down will not necessarily yield the same results. R/C scale flying plane are a great example of this, the smaller models will have larger tail & control surfaces.. in your case, you've scaled it down, so the relative size & weight of the motor, is much larger than the sample you've scaled from. With that, I would speculate that the CG has moved far enough back to be an issue..
 
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