Scary fast (probably not!) build thread

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Gillard

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Whilst looking on a stricker site for a "William" sticker - for my son's first rocket, i came across the sticker below. Having bought the sticker, i thought i'd better build something to put it on. I'm not going to try and build a rocket like the one on the sticker.

sf sticker.JPG
 

Gillard

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I've opted for a BT70 rocket, with a quad tilted motor mount from sunward. i've already posted a build thread on the mount. photos are from that thread just for completion.

4 mount complete top.JPG


4 mount complete.JPG


4 mount complete bottom.JPG
 

Gillard

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Now the build starts anew.
I decided to make the fins slightly swept back, mainly because of the mass from the motors.
The fins were laminated using fablon, which was a first for me. the fablon plastic went on well.
The leading edge was not bevelled and left square.
The edges were sealed with white glue.

sf fins.JPG
 

Gillard

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the body tube had some spiral grooves in it, where were filled with model filler, and then the BT was spray paint primed, sanded, primed, sanded, primed etc.

as the fins are not TTW, and with 4 x C6 motors, this rocket good move quite fast, i was a little concerned about the strength of the fins., coupled with the fact that swept back fins have a habit of meeting the ground first when landing.
To over come this, i put several holes along the area where the fins were going to be attached, (paint removed first)

sf holes.JPG
 
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Gillard

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fins were then added useing CA gel.
four glue fillets were then added over two days.
hopefully the glue rivets will add strength.

sf fin1.JPG


sffin2.JPG


sf fin3.JPG
 

Gillard

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rocket body was spray primed yesterday.
will probably go for a two colour paint finish, probably orange and white.
off on my holidays tomorrow, so i might get a base coat added tonight.
 

Fred22

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Man that rocket has great lines :) Cant wait to see it going up :)
Cheers
fred
 

sj_h1

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the body tube had some spiral grooves in it, where were filled with model filler, and then the BT was spray paint primed, sanded, primed, sanded, primed etc.

as the fins are not TTW, and with 4 x C6 motors, this rocket good move quite fast, i was a little concerned about the strength of the fins., coupled with the fact that swept back fins have a habit of meeting the ground first when landing.
To over come this, i put several holes along the area where the fins were going to be attached, (paint removed first)
Don't quite understand why the holes were needed, but I really like the canted engines. Can't wait to see the finished model and how it flies!
 

Gillard

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Don't quite understand why the holes were needed, but I really like the canted engines. Can't wait to see the finished model and how it flies!
by putting small holes in the bodytube and then covering them with glue and then applying the fin, the glue dries forming a rivet from the fin, through the BT making a stronger hold.
 

Gillard

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nose cone completed.
used an eyelet for the shock cord anchor. was not certain that it would not come out, even though i had wicked CA into the base. went for three eyelets in the end, all three can't fail - i hope.
the nose cone was balsa and required 5 coats of sanding sealer, three primers and three coats of gloss black to finish.

sf nose base.JPG


sf nose.JPG
 

Gillard

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I was going for a two tone finish on the body, but after much swearing due to masking tape that continues to bleed paint, I went for orange on the whole rocket. The finish is not good, and i'm really disappointed with it.
Sticker has to be applied yet, and i have to add a shock cord, nomex wadding and nose mass.

sf basic.JPG


sf orange base.JPG
 

1584cc

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I was going for a two tone finish on the body, but after much swearing due to masking tape that continues to bleed paint, I went for orange on the whole rocket. The finish is not good, and i'm really disappointed with it.
Sticker has to be applied yet, and i have to add a shock cord, nomex wadding and nose mass.
If you're using normal masking tape, then try Tamiya masking tape instead. It's far better as it doesn't bleed paint.
 

Gillard

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i was using normal masking tape, after it bled, i searched for a better tape on TRF and came up with Tamiya Tape as a possible solution, ordered some of ebay a few days ago. - thanks for the advice.
 

1584cc

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You'll certainly notice a difference from normal masking tape. You'll be tackling those complex roll patterns in no time:)

Don't forget to give us an update on first flight...
 

DexterLB

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Wow this rocket's really cool! Can't wait to see flight pics :p
 

Gillard

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after a long time away from this rocket, i got around to nearly finishing it last night.

15g of lead was added to the nose cone.
Nomex head shiled added to the Kevlar cord
elastic shock cord was added to the kelvar cord, swivel attached to the shockcord.
nose cone attached to elactic cord, via the three eyelet screws.

depending on the conditions, i will be using a 15inch chute for recovery.
 

TheRocketNerd

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you can also use regular masking tape if you seal the edge by spraying it over with the same color paint as your base (or clear coat works, and leaves less of an edge). The go over it with the second color and peel the masking tape off--wala! I do this even when using autobody mask. I shoot a light coat of clear, don't even let it set up, just shake up the second color i want to spray and go to town. Works quite well and is cheaper than the Tamiya masking.

:2:
 

Gillard

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finally flew her today.
only three motors (c6-7) lit, but the rocket went up straight, with a slight kink in the first 10 meters or so, probably as the clips were being yanked free.
on landing she popped a fin, and alot of paint damage, flakes coming off the laminate.
will strip the paint off and the three remaining fins and rebuild.
 

luke strawwalker

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by putting small holes in the bodytube and then covering them with glue and then applying the fin, the glue dries forming a rivet from the fin, through the BT making a stronger hold.
Be sure and let us know how the CA holds up... usually the "glue rivet" method is used with white or wood glues that are used a little more 'liberally' and 'forced into the holes' which I'd think would be rather difficult to achieve with CA.

I've read more than a few people on here saying that CA is very brittle and gets more brittle as time passes. Physically, CA seems to be best for tension joints, and seems fairly easy to break in 'shearing' forces like a fin would be subjected to with a nearly straight-down impact with the ground.

Not saying it can't or won't work, but it'll be interesting to see how your choice turned out and what your experiences are.

Great build! OL JR :)
 

Bignix13

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This is a really cool idea!! I like the idea of the engines canted out. How high do you think it flew to?

Did you fillet your fins? Curious to know if that would make a difference. If anything it would give you that extra little bit of area for your fins to grab onto.

All you guys taking about masking tape...have you ever heard or used something called Frog Tape? Its a green masking tape now sold in Lowes and Target. I saw it on a home renovation show and got some to try, but due to loosing my job rocket projects have been non-existant or slowing down.
 

Gillard

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fins attached with CA, but rivets and fillets (thick fillets) where made with wood glue.
the fin came off as the wood had snapped off, the glue had held fine.
looking at her, me and my dremel are going to be busy sanding everything back to cardboard. i am toying with the idea of having fins that don't stick out the back
 

dave carver

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I had a feeling that a 15" 'chute might be a little small.

I'm sure someone has a chart of size of chute vs. weight of rocket for feet per second of desent. I'm guessing you might do better with a 20" chute.
 

Gillard

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i knew the chute would be on the small side, but there was a fair bit of wind and even with a 15inch chute there was alot of drift. this rocket was the first rocket launch of the day and was used to "test" the winds. It was used because it was the smallest, lightest , lowest powered rocket, and as the other club members pointed out - it has no electronics.
an offering to the rocket gods (although two other rockets were offered up later, including an amazing two stage scratch built skylark scale rocket, which failed to stage)
 

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