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Discussions on mid/high powered model rockets using F powered motors and above.

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Scoop1261
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Postby Scoop1261 » Sun Nov 08, 2009 10:46 am

After a bit of coaxing from some contributors to the project, I was convinced to mark out and cut the fin slots to the booster airframe.

The observant folks here will note that the fin slots do not go all the way to the aft of the airframe, and therefore a traditional method of building the "fin can" may not be employed.

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The fins were marked at 120deg intervals around the airframe (ie 3 fins) and 54mm from the aft end.
The reason we have kept the fin slot from going all the way to the end, is maintain a rigidity in the airframe.

Since we are using a thrust plate on the aft, it is better to keep the airframe in one piece.

"What about fillets?" I hear from those concerned folks.........Well since this is a 6" airframe, we should have no issue in getting inside to run some nice strips of glass along the fin tabs.................Either that or we can inject them in using chopped carbon fibre strand later.

The outside will receive a generous fillet & a tip to tip of a yet to be selected glass cloth weight.

Oh.....here are the slots after they were cut using the Dremel........Damn now I have to vacuum! :cry:

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And here are the fins ready for test fitting.....................

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And here they are again after a quick and dirty test fit............I think we need to trim a little of the bottom of the tabs!.........

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EMiR
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Postby EMiR » Mon Nov 09, 2009 5:55 am

Scoop,

What kind of ply are you using for the fins?

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Scoop1261
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Postby Scoop1261 » Mon Nov 09, 2009 9:12 am

EMiR wrote:
What kind of ply are you using for the fins?


We are using 3/8" or 8.5mm British standard grade marine ply (7ply)

The CR's & BH's are 1/2" or 12.5mm as above grades.
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EMiR
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Postby EMiR » Mon Nov 09, 2009 6:55 pm

nice,

I zoomed in on the piccy, to have a look see, and it looked like 3ply with AA face vaniers, hence I had to ask.

For those looking for good Aircraft/Marine Ply, I found a good suppiler in Syd

http://www.aircraftspruce.com.au/Wood.asp

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Scoop1261
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Postby Scoop1261 » Mon Nov 09, 2009 11:06 pm

I believe many people get all "bent out shape" over ply selection....at least on bigger projects.....you only really need the ply as a core......... coz you are gonna glass over anyway!

As long as is not shitty old warped board or construction ply, pretty much any decent marine ply will do the job. Heck I have even heard of fin cores being made out Luan underfloor board!
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Impulse: A Whole Lot ..So much I've lost count!

bluecurve
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Postby bluecurve » Thu Nov 12, 2009 10:12 am

Hi Scoop and Co,


Good to see you guys are not slowing down for "off season". :wink:

Now seriously thinking of trekking to WA next June - keep us all informed!

What are you planning to fly for the payload? GPS?/RF TX?/Video?

Cheers,

Tom

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Postby PK » Thu Nov 12, 2009 10:47 am

bluecurve wrote:What are you planning to fly for the payload?


HDTV recorder,
GPS telemetry,
DTMF uplink (as a backup to the deployment system).
We'll probably run a data logger or two, for things like accel roll rate (how straight were those fins!) and baro pressure.

Along with the usual:
Altimeter
microMAD,
and probably a timer too!

The more I sand these things, the more I want to be bloody sure we get them back..

PK

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Scoop1261
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Postby Scoop1261 » Thu Nov 12, 2009 11:26 am

PK wrote:
bluecurve wrote:What are you planning to fly for the payload?



We'll probably run a data logger or two, for things like accel roll rate (how straight were those fins!)


I honestly tried to get the slots as straight as I could! :lol: It's not my fault the beer kicked in! :lol:
Why Limit Yourself?

AMRS #4 - L3 |TRA #11080 - L3 |MDRA #263

Impulse: A Whole Lot ..So much I've lost count!

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Postby PK » Thu Nov 12, 2009 11:36 am

I honestly tried to get the slots as straight as I could! :lol: It's not my fault the beer kicked in! :lol:


I won't hold it against you. You've seen the video of my last M flight. I reckon it was doing 1000RPM at burnout.

PK

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Postby whipfest » Fri Nov 13, 2009 11:39 am

PK wrote:I won't hold it against you. You've seen the video of my last M flight. I reckon it was doing 1000RPM at burnout.

PK


Gyroscopic stabilisation ??


:wink:
What were you thinking about as you sat atop the Redstone rocket, waiting for liftoff?

"The fact that every part of this ship was built by the low bidder"

Alan Shepard

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Scoop1261
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Postby Scoop1261 » Sat Nov 14, 2009 10:40 pm

Trimmed fin tab lengths and test fitted MMT, Centering Rings & Thrust Plate.

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Set up Airframe tube between fin alignment guides.

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Oh Yeah!.............One other thing..........Big thanks to matthew at http://www.australianrocketry.org/ for hosting all the pictures we put up on the forum.

Do yourself a favor and check out his site........Some of the other forum members have some cool albums hosted in his Media gallery!
Why Limit Yourself?

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Impulse: A Whole Lot ..So much I've lost count!

hotspot
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Postby hotspot » Sat Nov 14, 2009 11:19 pm

Looks mean love that metal work.

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Postby Wingnut » Sat Nov 14, 2009 11:39 pm


She's looking sweet! Without something else in-shot to give you a sense of scale, it's hard to believe that's a dirty great 98mm motor case sitting in there.

Awesome!


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Scoop1261
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Postby Scoop1261 » Sat Nov 21, 2009 11:01 pm

Well folks, like all good.......No wait!....great projects......there needs to be changes in plans.......and today folks, that is exactly what happened!

We had originally decided to have the Aluminum thrust plate as a removable piece, and the MMT constructed and reinforced with glass strips once inside the airframe.

Today we changed the design by adding a third CR notching the fins, and constructing the "Fin Can" outside the airframe. The fin slots will be lengthened to the aft end of the AF, and the thrust plate will be fitted as a permanent fixture.

The centering rings were grooved and epoxied into place on the MMT and set aside to cure, (unfortunately there are no photographs of this assembly). While the CR & MMT assembly was curing the sanding and filling team set upon the main AF for a session of attention.

The airframe was setup outside in the warmish...yet pleasant conditions...

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The team set about giving the AF a going over with their palm sanders......

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After the bumps and stuff had been sanded smooth....the next team slipped int applying another coat of epoxy and filler......

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looking pretty neato huh???

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Some refreshments were had while waiting for the CR & MMT assembly epoxy to cure......They mostly consisted of red wines and snacky items kindly supplied by the Lamington Lady! :D

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The fins were tacked into place before application of epoxy.......

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The black carbon tubes were used to line up the CR's and will be used as part of the interstage system for future flights.

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Some sections of heavy cloth were cut to size and epoxied into the fin root chord to MMT joint......

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A layer of 200gsm cloth was then layed from fin tip to MMT centre on both sides of all three sets of fins and then trimmed to size.....ish!

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Ohh....hang on..... the fins were wet out with epoxy first!

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And the cloth trimmed around the CR's ......

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Before finally making sure all the leading edges had been sealed.......

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With an end product looking something like this................

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Today's handiwork ended up with these goodies..........and was brought to you by the letter N and the number 2000 ! :D

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And the refreshments .......well lets just say we are all happy! :D

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Why Limit Yourself?

AMRS #4 - L3 |TRA #11080 - L3 |MDRA #263

Impulse: A Whole Lot ..So much I've lost count!

october sky
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Postby october sky » Sun Nov 22, 2009 4:31 pm

What a great buid thread guy's, thank you !! 8)

Did the clothing come out of the line "dust free" considering all the sanding nearby ? :lol:
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