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  #1  
Old 12-06-2008, 07:33 AM
Bravo52 Bravo52 is offline
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Default Scratch built for E9-8

Some time ago I was able to pick up some E9-8 Estes engines at a very good price. I ended up with 6 packs of motors in the $3 a pack range . I just needed a rocket to fly them in. I started a thread over in "Ask the Doctor" for advice on what to build and almost all of the recommendations came back with "light and long" and not complex. There were your basic Estes kits and a couple of recommendations for the Cherokee D (nice rocket), but no one had the right kit. So.....time for a scratch build!

http://www.oldrocketforum.com/showt...79&page=1&pp=10

Because Michael's is so generous with their coupons and they carry a limited range of Estes kits, I challenge myself with using those parts for scratch building rockets. I like the Stormcaster and Patriot a lot as they are based on BT-60 components. The Stormcaster has TTW fin slots and all the components for an E based rocket except the long motor hook. So the challenge was use the Stormcaster and build something that didn't need a hook!
After a few days on the board, someone posted a picture of the Thrustline Arapaho E. What a great design that builds into a beautiful rocket. Hmmmm, unfortunatly, Thrustline is not producing kits and finding someone to sell you theirs is like locating the proverbial "Hen's teeth". Anyway, that was the challenge.
All I had was a picture. I didn't have the .rkt file for the fins so I based my fin design on the pictures and got it wrong! The fins are about 10% too big!. Trying to keep them light, I choose to use 3/32 balsa reinforced with .007 carbon fiber down the length of the fin. The fins are split in half length wise to get the grain right. The tips of the fin are 3/32 bass wood. I then laminated the fins with paper. Plenty strong and I'm too lazy to "fill and finish".
The rest was pretty straight forward. I used the kit BTs, and two nose cones. I bought a baffle from Sunward at NARAM 50 so I used that as the BT coupler. It all came together pretty quick. As I was building the motor mount, I decided to put a hook in and grabbed one from another kit. The reason was that I wanted to use other motors in the kit and thought I needed something other than friction fit for the smaller motors. The problem was the hook looked bad sticking out of the boat tail. So, I got a piece of 1/4 styrene tubing from Evergreen and made a fairing. That turned out to be the best thing on the rocket!
The last thing was to add a little .25 oz glass around the BT opening to help prevent zippers. I figured with this rocket, there was a pretty good chance that might happen on an 8 sec delay. Painted it with Krylon white and Apple Barrel acrylic orange. I loved the orange color and it reminded me of "Dream Sickles" ice cream bars!
The flights......were perfect. Foose4strings was their for the flights and swears it went to 1500". I later sim'd it out at 1467'. Good eye Craig! I've flown it 6 times and the delay is perfect. The only thing wrong is the 16" parachute.......it makes me walk too far.

The rocket is basically a Stormcaster with added nose cone as a boat tail and new fin designs. It's BT-60 based and 26.25 inches long and the fins span about 7 in. Added .25 oz in the NC and the total weight with an E9-8 is about 6.75 oz.
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  #2  
Old 12-06-2008, 08:44 AM
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tbzep tbzep is offline
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Love those fins.

With that heavy duty boat tail and trailing edges of the fins out of the way, you could use a 12" chute with no problem, It would probably be ok with a small spill hole. I have a 12" nylon chute but I don't remember for the life of me where I got it. You could probably fly a couple more rockets during the 16" chute's hang time.
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  #3  
Old 12-06-2008, 09:23 AM
Indiana Indiana is offline
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That's nice Bravo. The engine hook fairing is a nice touch.
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  #4  
Old 12-06-2008, 11:40 AM
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STRMan STRMan is offline
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Quote:
Originally Posted by Bravo52
Because Michael's is so generous with their coupons and they carry a limited range of Estes kits, I challenge myself with using those parts for scratch building rockets.


That is a brilliant idea. It is time for me to start kit bashing.
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  #5  
Old 12-06-2008, 11:53 AM
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barone barone is offline
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Quote:
Originally Posted by Bravo52
The flights......were perfect. Foose4strings was their for the flights and swears it went to 1500". I later sim'd it out at 1467'. ......

If you used RockSim, you mind posting the file?
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  #6  
Old 12-06-2008, 07:08 PM
foose4string foose4string is offline
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Quote:
Originally Posted by barone
If you used RockSim, you mind posting the file?


Don, Bravo52 has a knack for scratching stuff by eyeballing pics, which is what he did with this. The fin profile was nearly spot on, but was a bit oversized. The flights were awesome despite the bigger fins!

Here is the actual Rocksim file as posted through the EMRR review...

Arapahoe E Rocksim

Perhaps Jerry(Bravo52) modified his sim for the bigger fins?
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  #7  
Old 12-06-2008, 07:53 PM
PaulK PaulK is offline
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Quote:
Originally Posted by Bravo52
After a few days on the board, someone posted a picture of the Thrustline Arapaho E.
Glad you liked the idea!
Quote:
Originally Posted by Bravo52
TI've flown it 6 times and the delay is perfect. The only thing wrong is the 16" parachute.......it makes me walk too far.
I use a 4" x 60" Streamer, though my original is probably a tad lighter.
Quote:
Originally Posted by Bravo52
The rocket is basically a Stormcaster with added nose cone as a boat tail and new fin designs. It's BT-60 based and 26.25 inches long and the fins span about 7 in. Added .25 oz in the NC and the total weight with an E9-8 is about 6.75 oz.
Nice bash of stormcaster parts, Bravo. The Thrustline kit used a 2 piece fin just like you did, except with 1/8" balsa.
Quote:
Originally Posted by Bravo52
I loved the orange color and it reminded me of "Dream Sickles" ice cream bars!
Mmm, Dreamsicles...
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  #8  
Old 12-06-2008, 11:11 PM
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Steward Steward is offline
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Walking is the worst part for me...

You could cut a spill hole in the parachute... start small and enlarge as needed.
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  #9  
Old 12-08-2008, 09:30 AM
Bravo52 Bravo52 is offline
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Unfortunatly, I don't have a copy of Rocksim so I didn't use the .rtk file. I just used the pictures of the TLA kit from the web. I did use Thrustcurve.org to help in the design. Great site.
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  #10  
Old 12-08-2008, 10:26 AM
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sandman sandman is offline
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Since the Thrustline Arapaho is out of production and the parts are basically a BT-60 sized V-2 nose cone and tailcone.

How about if we get john at Thrustline (if anybody can still contact him) to get permission to publish the plans.

It's actually a simple kit.

Basically 3 fins (OK, two piece fins) three fin strakes
Nose cone
Tail cone
Body tube

SEMROC should have all that stuff in stock!

Heck I know excelcior makes a decal set for it, or at least they did.

I love that design.

I reccomend a streamer!
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