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Old Mar 01, 2015, 01:42 PM
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Sailplane "CSI":Need help identifying this plane bought in Thousand Oaks, CA

Hi, RCG'ers!

I just wanted to get a little history behind this particular plane that I recently bought. It was sold as a "unknown" plane that was donated to a club. I have a feeling it was a Ron Vann Prism but the tail does not look like it is. It looks like the previous owner was considering converting it from a T-tail to a mid tail stabilizers.
I am just looking for any history on this one model because I am debating whether to proceed with a mid tail installation or to return it to a T-tail config.
Here's what I know:

-The box it came in lists the sender as "Spectrum" from Windsor, CA. Also, on the side of the box it has the words "Prism 15" written on it.

-the wings and fuse look like this http://www.rcgroups.com/forums/showt...m#post29858588

-the wings are obeechi covered foam with aluminum control horns

-this is a used plane

-in most photos of the Ron Vann Prism, the vertical stab has a horizontal extension that is on top of the rudder. The extension is parallel to the fuselage centerline. On my fuselage, there is none.....except for the SLIGHTEST INDICATION of the extension!! (see photo)

-on the vert stab, there is some pencil marks that shows that the prev owner was thinking of putting in a bellcrank for the horiz stabilizer

My questions are:

1) was this a Prism that the previous owner had cut off the fuselage extension and was converting to a mid tail?
2) if so, what his reasoning?
3) if not, do I have a non-Prism that was put in a box that previously carried a Prism?


Any help would be appreciated.

Vincent.....
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Last edited by Phoenix1600; Mar 01, 2015 at 01:53 PM. Reason: one more image and text
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Old Mar 01, 2015, 05:10 PM
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I had a prism at one time. Here are photos. They may be helpful. Looks pretty similar.
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Old Mar 01, 2015, 09:36 PM
MK
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Go to AMA's website and punch in Myles' AMA number to see if he is still active. If so, maybe a phone call to AMA to try to locate Myles' current contact info?
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Old Mar 02, 2015, 09:04 AM
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This looks like a Prism, which was a 118" span version and very similar in configuration and design to the smaller Spectrum. The plane in Ed Anderson's pics is definitely a Spectrum, not a Prism, wingspan is too short for a Prism.

Yours is missing its rudder and the original stab. The stab you show is from something else, the originals were obechi covered foam and were one-piece which bolted to the top of the fin. The original design had a fin-mounted bellcrank to translate the pushrod motion from horizontal to vertical. Perhaps the marks you note are for that, perhaps not.

Also, the "15" designation likely means that the airfoil is an RG15. The Prism was available with RG15, S3021 and possibly SD7037.

This plane has had a hard life judging from the damage in the joiner rod area of the wing. If you are going to rebuild it, it would be worth taking a hard look at this area and repairing properly.

JT
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Old Mar 02, 2015, 02:35 PM
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I no longer have that glider but I believe it was 117". What was the wing span on the Spectrum?

My glider, which I was pretty sure was a Prism, had a SD7037 airfoil. We matched it up to a profile to check. But that is just curiosity, not really relevant to this discussion.

Attached is the Slegers International Prism build document. It may prove helpful in identifying the glider or setting it up.
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Old Mar 02, 2015, 04:20 PM
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JT, thanks for your help! I didn't even think about the bellcrank being used for a T-tail.

Aeajr, thanks for your input as well and the file. I will open it up tonight on my home computer.

Now that I look at it, the horizontal stab does not look the same as a Prism's. I'm going to look at the Slegers International Prism build and see about making another horizontal stab.
Will post my progress.
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Old Mar 04, 2015, 04:34 PM
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Does anyone out there have any idea how I could get a horizontal tail for this Prism?? I would like to restore this bird to her former glory
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Old Yesterday, 11:17 AM
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Let me look in my shop. I may still have the stab from my Prism. Strangely enough, I bought it from Myles Moran who probably is the previous owner of your Prism!
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Old Today, 05:14 AM
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George........the name listed on the sticker is "Myles Moran"!!! Let me know if you find the old stab! Thanks!!!
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