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  #1  
Old 09-19-2021, 07:42 PM
rraeford rraeford is offline
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Default Restoring a Centuri Arcon-Hi

I am restoring an old and poorly built Centuri Arcon-Hi. I decided to build a new one along side so I collected the parts from Semroc. When I pulled the fins off the old model I noticed a few oddities. One was the direction of the wood grain on the booster fins. It runs perpendicular to the body tube. These were cut from a printed sheet, which makes them quite old, so I can see they were cut correctly (the lines and printed type are visible on the balsa). I am missing a couple of fins from the original model and thought I could replace them with the Semroc fins. To my surprise, the Semroc fins are really different than the original fins both in size and thickness. The booster fins on the original are 3/32 inch thick and the sustainer fins are 1/16 inch. The Semroc fins are about 1/4 inch shorter than the ones on the original model and are all 1/16 inch thick. The balsa they are cut out of is really soft. I’ve had these Semroc fins for a few years now—going back to the Carl and Sheryl days. Does anyone know if these changed over the run of the kit? Are the Semroc fins just way off? See photo—the pink fins are from the original kit. Any help would be great.
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Last edited by rraeford : 09-19-2021 at 09:51 PM.
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  #2  
Old 09-19-2021, 09:34 PM
Ltvscout Ltvscout is offline
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Quote:
Originally Posted by rraeford
I am restoring an old and poorly built Centuri Arcon-Hi. I decided to build a new one along side so I collected the parts from Semroc. When I pulled the fins off the old model I noticed a few oddities. One was the direction of the fin grain on the booster fins. They run perpendicular to the body tube. These were cut from a printed sheet, which makes them quite old, so I can see they were cut correctly (the lines and printed type are visible on the balsa). I am missing a couple of fins from the original model and thought I could replace them with the Semroc fins. To my surprise, the Semroc fins are really different than the original fins both in size and thickness. The booster fins on the original are 3/32 inch thick and the sustainer fins are 1/16 inch. The Semroc fins are about 1/4 inch shorter than the ones on the original model and are all 1/16 inch thick. The balsa they are cut out of is really soft. I’ve had these Semroc fins for a few years now—going back to the Carl and Sheryl days. Does anyone know if these changed over the run of the kit? Are the Semroc fins just way off? See photo—the pink fins are from the original kit. Any help would be great.

Romie,

I don't have an answer for you but would you mind tracing the old fins, scanning it then uploading them here? I'd appreciate it!
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  #3  
Old 09-19-2021, 09:37 PM
Ltvscout Ltvscout is offline
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Originally Posted by Ltvscout
Romie,

I don't have an answer for you but would you mind tracing the old fins, scanning it then uploading them here? I'd appreciate it!

Forgot to add if you could place a ruler next to the tracing when you scan it would really help.
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  #4  
Old 09-19-2021, 09:49 PM
rraeford rraeford is offline
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I will be happy to.
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  #5  
Old 09-20-2021, 10:25 AM
rraeford rraeford is offline
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I have looked at every photo I can find of the Arcon-Hi and compared it to the Semroc rendering. I now see this has been there all along. The booster fins semi span are much winder on the original design as are the sustainer fins. Now, if only I could find someone with an uncut printed sheet.
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  #6  
Old 09-20-2021, 01:21 PM
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Earl Earl is offline
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Saw your thread last night but have not had a chance to respond due to some other appointments this morning.

Attached are booster and sustainer fin sheets from an original Arcon-Hi kit, circa approximately 1966-67. Also attached is a pdf of the instruction sheet for the kit.

I'll post the early 70s versions of these fins in just after this post, but yes, the Arcon-Hi fins did change between this mid-60s version to the early 70s version (1972 to be exact).

Balsa sheet thickness on both booster and sustainer fins from this kit are 3/32.

Earl
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File Type: pdf Arcon-Hi Mid 1960s-Instructions.pdf (1.26 MB, 30 views)
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  #7  
Old 09-20-2021, 01:33 PM
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And here are the fin sheets for the early 70s (and onward...until about 1975 when the kit was discontinued) and the instructions.

In this version of the kit, the fins, especially the booster fins, are different and somewhat smaller. Also, the sustainer fins are just 1/16 thick. The booster fins are still 3/32.

The instructions are attached also but because the combined pdf would be over 2mb, I have posted the individual sheets.

Earl
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Name:  Centuri Arcon-Hi Fins First Stage-Early 70s.jpg
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File Type: pdf Centuri Arcon-Hi Early 1970s Inst-3.pdf (516.0 KB, 25 views)
File Type: pdf Centuri Arcon-Hi Early 1970s Inst-2.pdf (564.9 KB, 22 views)
File Type: pdf Centuri Arcon-Hi Early 1970s Inst-1.pdf (767.1 KB, 28 views)
File Type: pdf Centuri Arcon-Hi Early 1970s Inst-4.pdf (680.2 KB, 23 views)
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  #8  
Old 09-20-2021, 03:49 PM
rraeford rraeford is offline
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Thanks Earl. I thought you would know and I also thought this would be the case. I think some early staged kit designs had fins that were larger than needed. The booster on the original Arcon-Hi does seem almost a bit cartoonish. Same with the redesign of the Black Widow which changed during it’s run.
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  #9  
Old 09-20-2021, 05:09 PM
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Earl Earl is offline
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Note too that the later booster fins had rounded outer corners whereas the originals had very squared off outer corners.

I built the Semroc version of the Arcon-Hi 7-8 years ago. When I received the kit, somehow the booster fin sheet had been damaged and I had to contact them to get a replacement sheet, which came right away.

But, I did note at that time the relative softness of the booster fin material and sent a message back to Sheryl that, really, the *booster* fin balsa stock needed to be a bit more dense balsa if possible, as material that soft was gonna break and splinter pretty easily when the booster tumbled back to the ground. She said she appreciated the feedback and would discuss it with Carl. But, that may have been only a year or so (maybe less) before Carl so sadly left us.

Earl
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  #10  
Old 09-21-2021, 09:11 PM
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Tau Zero Tau Zero is offline
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Question

Quote:
Originally Posted by Earl
Note too that the later booster fins had rounded outer corners whereas the originals had very squared off outer corners.
Earl,

I noticed the same thing about the Centuri Javelin. I bought my first one in Fall 1971, and it had the silk-screened fin patterns, along with a single ST-79 body tube and the PNC-74 nose cone.

A few years later, I noticed that there were ST-76 and ST-73 tubes, along with the die-crunched (sorry not sorry, "die-cut") fins with rounded corners, as well. (Spock eyebrow)

Dunno what they were thinking, but...

--It was a thing, I guess.

.
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