I've been spending a lot of time on Vikings lately and have run into something a bit confusing with the Viking 2. The 1971 catalog at Ninfinger http://www.ninfinger.org/rockets/ca...71/71fsi10.html gives the Viking 2 length as 16", but the 1990 catalog appears to give 23" as the length. http://www.ninfinger.org/rockets/ca...i90/90fsi8.html The 23" length is also closer to the length you'd get if you follow page 9 of the Viking 2 pdf at YORP, but page 1 of this same pdf gives the lengths of the main body tubes as 9" and 4", which would make the finished product around 16". I'm guessing that I'd be right in going either way, (leaning toward the shorter one because it just seems like it would look more solid,) but I was wondering if anyone had ever seen either version fly.

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Bill Eichelberger
NAR 79563

http://wallyum.blogspot.com/

I miss being SAM 0058

Build floor: Centuri Design Contest F-150 Hurricane Estes - Low Boom SST Semroc - Marauder, Shrike, SST Shuttle

In paint: Canaroc Starfighter Scorpion Estes F-22 Air Superiority Fighter, Multi-Roc, Solar Sailer II Semroc Cyber III

Ready to fly: Estes - Solar Sailer II Semroc - Earmark, Groonie Der V 1/2

16" is the length that used when I built mine. I have wondered about that longer dimension too. I did use some of the dimensions in the YORP plan appendix in my first Viking II clone, but the completed rocket didn't look anything like the pictures in the catalogs. I ultimately concluded that the 23" dimension was a typo. That is the length of the Stargazer, and no other FSI rocket had that overall length. The SG uses the same RT-8 body tubing and the same HNC-101 nose cone as the Viking II, and at 23" long, it looks like a bean pole; very long and skinny. None of the photos of the Viking II show a rocket that is anywhere near as lanky, yet that is what you would get if you tried to make one that was 23" long. A 16"-16.5" long Viking II looks correct from every angle.

One other issue with the YORP plans: the close-up photo of the tube stabilizer and finlet (page 6 of the PDF). It shows a stabilizer whose beveled length is approximately 3/8" to 1/2" longer than the root edge of the finlet. Yet in every photo of the Viking II, and even in every illustration of it in the instructions, the length of the tube between the bevels matches the root length of the finlet. In fact, the angle of leading edge of the finlet also matches the angle of the bevel. Essentially the leading edge continues the bevel angle outward until it meets the trailing edge at a 90° angle. When you look at the stabilizer from the side, the addition of the finlet seems make the combination of tube and finlet into a rectangle at the tip edge; it "squares" it off. If you use the stated length of the stabilizer from the Appendix, it won't work; 5" is too long. The finlet won't fit exactly in between the upper and lower bevel of the tube. Instead you'll get a stabilizer that looks like the one in the photo. I reduced the length of the stabilizers in my second Viking II build to 4.25". With 29° bevels on the tube, that length works out just right.

Also note that when you mount the stabilizers onto the main body tube, align them so that the high end (upper end) of the lower bevel is even with the aft end of the main body.

The first two attachments are of my completed Viking II clone. The third photo is of my Stargazer, which may give you some idea of the proportions of a 23" long rocket made with ST-8F. The fourth photo is of my first Viking II clone, which has 5" long stabilizers and is 18.375" long overall.

Oddly enough, the Viking II is the only one from that series that I have not launched yet.

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SAM # 0011

This is what mine will look like. The stabilizer tubes and fins are the only things I have finished at the moment. I wanted to get opinions on the length discrepancy between the two catalogs before I cut any more tubes and I think your explanation sounds plausible. I'm going with the shorter bird.

__________________
Bill Eichelberger
NAR 79563

http://wallyum.blogspot.com/

I miss being SAM 0058

Build floor: Centuri Design Contest F-150 Hurricane Estes - Low Boom SST Semroc - Marauder, Shrike, SST Shuttle

In paint: Canaroc Starfighter Scorpion Estes F-22 Air Superiority Fighter, Multi-Roc, Solar Sailer II Semroc Cyber III

Ready to fly: Estes - Solar Sailer II Semroc - Earmark, Groonie Der V 1/2

FSI changed lengths of tubes several times, and I wouldn't be surprised if things like the angles of tube fins has changed.

I'm on vacation and can't measure or photograph my built Viking II. I bought it in 1988; it was in old-style packaging.

Also, after I return, I will post photos of my Viking II upscale project. I need to wet-sand the tube fins, mask and paint the red parts, and then glue them onto the main body tube.

What Stephan said. Mine is straight out of the bag, old style packaging. Hard to see from the photo, but that's an 18" ruler. Viking II measures in at 17-1/4": main tubes 9" and 3-3/4", nose cone 3", the stabilizer tubes are 4.5", fin root edge is 2-9/16".

Observation: I think the stab tubes for the Viking II were probably originally shorter and matched the fin root but at some point FSI decided (either for stability issues or just to cut down on inventory) to make the stab tubes the same length for Vikings I - IV.
Vikings I, II and IV in the second photo are all built from early style packaging kits, mid-eighties or there 'bouts.

S.

Addendum: I measured the parts in another 'Olde Style' Viking II. The lower airframe tube is 4", the nose cone is 2-13/16" and the fin root edge is 2.5".
All other measurments aere the same as above. So I guess as far as FSI was concerned, close enough was good enough.

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