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-   -   Centuri Fireflash 2X (http://www.oldrocketforum.com/showthread.php?t=3744)

Bob Thomas 08-22-2008 11:23 PM

Centuri Fireflash 2X
 
2 Attachment(s)
Hi gang,

Once again a minor distraction (someone else mentioned one) led me to what is becoming a most rewarding build.

I always wanted a Centuri Fireflash as a kid, but I never got around to it (easily distracted then too). I decide on an almost scale 2X version using available St-10 and 16 tubing and a few workarounds to get the look close enough. I haven't purcased the cones yet as I am still trying to find cheap/free functional replacements. Five cones gets kind of expensive.


Enough suspense, first I tackled the tank connecting rings. There is no scale equivalent to what I assumed were series 7 thrust rings on the original, so I built three upscales out of CR1016, a short section of ST16 and some scrap 1/4 inch balsa strips.
The Fiber rings are glued to the ends of the 3/8 inch wide BT and the strips are cut to short lenghths and glued along the hollow inner circumference like ribs. this strenghthened the fabricated ring to be able to support ejection gas stresses, torque and fin shear.

Here's a photo

Bob Thomas 08-23-2008 12:45 AM

Fireflash
 
9 Attachment(s)
After making the rings I figured on keeping the tube lengths simple at 10 inches for the outboard tanks and 13 inches for the main body tube. I ended up using ST-5 as the ejection port tubes and while planning the port cutting "operation" I decided to make the outboards in two sections, the lower 6 inches and the remainder four. This was the only way I could get access to the inner port intersection to insure a sound connection. I also flared the port tubes inside the St10 a bit to strengthen the connection. I got the three tubes parallel by allowing them to set up on a flat surface with a space for the depth of the spacing ring. It also helped to put a length of ST9 in the main body tube above the connection to run parallel to the outboards. That made it easy to sight anything askew.

Here are other pictures that were made throughout the progression of the build. I wanted to get a coat of primer on it but I am still entertaining the idea of adding tubes between the fins.

I'm heading out of town for a few days so if there is an interest, I will post more of a play by play then.

rosko_racer 08-23-2008 07:37 AM

Centuri Fireflash
 
I always wanted a Centuri Fireflash. It is one of those I have planned on cloning... and now maybe upscale it. I am looking forward to your build. Keep posting pictures.

I noticed that you used a dowel at the top of your fins to anchor them to the MM. What are your thoughts with this technique?

Great build and great pictures. I also noticed your Centuri Orion and the Estes Black Hole Probe.

Bob Thomas 08-23-2008 02:04 PM

Dowels
 
I have used dowels and toothpicks as a leading edge on a few fins in the past and thought it would serve two purposes here. The 3/32 dowel might relieve some of the shearing force on fin, its purpose was to act somewhat like a through the wall fin mount while protecting the soft balsa leading edge. A plus is the paper lamination rolls very well over the even dowel leading edge. I wanted to do a through the wall fin (chickened out), entertained the idea of interchangeable mount (brain couldn't handle it), thought about a static 24mm mount and decided to keep it as a test bed with this design. The dowel nub is sandwiched between two CR710 rings. I used an expanding urethane glue to ensure a good grip. The last ring on the mount is set under the fin end and the rear fabricated ring sits at the fin base to absorb the remaining forces. The design will not fully be tested until the next prototype for 24 mm motors. I will wait after my trip to order the appropriate nosecones and take her for a naked test flight.

space_bus 08-23-2008 04:44 PM

I'm not familiar with this rocket, but it looks awesome so far.

Keep the pictures coming. :)

barone 08-23-2008 06:46 PM

Quote:
Originally Posted by space_bus
I'm not familiar with this rocket, but it looks awesome so far.

Keep the pictures coming. :)

Check it out at......

http://www.dars.org/jimz/km-5.htm

STRMan 08-23-2008 07:38 PM

In those pictures of the engine mounts, I see a spent casing or dummy engine with gold paint on it. Just wondering, could that have been used in the painting of a Golden Scout?

dwmzmm 08-24-2008 01:51 PM

Thanks for starting this build thread; I still have my original Centuri Fireflash "in the bag"
among my unbuilt kits. If I remember correctly, it's a Skill Level - 5 build.....

A Fish Named Wallyum 08-24-2008 04:05 PM

Way cool. I always wanted to do this one 1:1. Somehow the idea of an upscale never occurred to me. :cool:

Bob Thomas 09-05-2008 09:24 PM

Gone to Golden Pastures.
 
Quote:
Originally Posted by STRMan
In those pictures of the engine mounts, I see a spent casing or dummy engine with gold paint on it. Just wondering, could that have been used in the painting of a Golden Scout?


Too observant - The Golden Scout Clone went up on its maiden voyage and never returned. I had two young spotters and we all lost it in the overcast skies. She was not a true Golden Scout as I used Centuri scale tubes and cone. But it was my Homage to the Sky of Gold that I did not participate in. (My sons did not know the difference, and really couldn't appreciate the significance anyway).

The Fireflash is still underway. I broke down to purchase the scale cone equivalants and they are being prepared for finishing. I believe that there will be enough ejection charge to fire both tank cones for a dual chute recovery. That is what I am now planning for and it requires liitle modification of the plans. If it does not work, it will hopefully deploy at least one chute. Otherwise, it will employ the strategically placed front portion of the rocket CRUMPLE ZONE to soften its landing :eek:

I will let you all know after the weekend.


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