Having been so accustomed to Semroc's outstanding quality standards, I find myself questioning my sanity, having started building two recent releases and finding what appear to be MISTAKES !

Thunderchief--Step 9 fin marking guide is oversized, does not match the tube. One more reason I dislike templates and prefer wrap-around guides, which are easy to tweak if sized wrong. Also, while not necessarily a mistake, a bit of a design flaw--kevlar/elastic combo is waaaaaaay too short for the 27" frame--barely 7 inches extends beyond the tube. Finally, fins are mounted 1/4" from rear. Not sure if that was on purpose or not, but seems to be a cut/paste relic intended to support external tape motor retention for a minimum diameter design. As released, the motor tube extends down about a 1/4" and has a metal hook, so fins aren't exactly in the way.

Spartan--Looks plenty stable on its own, but parts diagram shows a heavy washer anchored to nose cone held in place by a screw eye. The washer isn't called out in the directions anywhere, and the screw eye head is smaller than the ID of the washer, so won't hold it on anyway. Can't imagine this would need nose weight, especially with 4 larger fins and only about 11" of body tube.

I'll have to take this up with the board of directors next time I see 'em. Ever since they went global and bought out Estes back in April, their design department and QC have really shown signs of strain .

--Chan Stevens

Thanks for the feedback, Chan!

We noticed the wrong fin guide a day after the release, reprinted the instructions and opened, fixed, and resealed about 130 kits. A few leaked out to a lucky few. The online PDF is correct.

We have had less luck with the wrap-around guides. Laser printers are not exactly 100% as offset presses are. For the few kits we do with wrap-around guides, we have received the most complaints about fins being off by about 1 degree or so. We print on 5 different laser printers so it is impossible to match them exactly. The end guide is less affected by printer "scaling."

The Kevlar is tied to the upper coupler so it should stick out about 7-8 inches. The 18" shock cord should extend the combo to about 24 inches.

The offset of the fins is a "Thunder" trait. All of them were offset up from the end of the tube for no apparent reason except for aesthetics.

The Spartan washer weight has gone back and forth several times over the past few years of development. It is not required and was not completely removed from the final version. The online PDF is correct and future runs will not have the washer.

Chan, you know we make mistakes! Some are intentional, to keep you on your toes. You want to see strain! Next time you are at your alma mater's reunion, stay here a few days and you will see strain!

Thanks again for the feedback. We might not get it right the first time, but we will keep trying until we do.

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Carl McLawhorn
NAR#4717 L2
semroc.com

+1 for wrap-around marking guides. The stand-on-a-circle guides are just too easy to move around accidentally, not to mention align properly in the first place.

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Roy
nar12605

Wow, you mean I've got a rare collectible, and I opened/built it? Drat!



D'oh! Me and my mass production tendencies--I was building them side by side, and of course not reading directions, so attached the Kevlar to the motor mount just like on the Spartan. Going to the coupler makes more sense, though at least I can claim I was trying to hide that unseemly bulge, and now have something to do with a little of that 500 yards of elastic I picked up last year.



Oh man, and here I am building another rare collectible . There goes the retirement fund...



I wouldn't want to wait that long (8 years), would love to find some other excuse to visit sooner. Since I'm an unemplyed bum at the moment, doing odd jobs and volunteer work here and there, I figure if you need some part time help kitting and packing Saturn V kits I'd gladly pitch in .

Back when the Orbital Transport was released, I was sure I'd caught Sheryl in a shipping error, not sending me a numbered kit. She was polite but adamant that she'd got it right. I had to shake the bejeebers out of the bag, but eventually the label slipped out from the middle of the instruction booklet. It really does take a pretty good effort to track down a Semroc mistake, and that search is part of the reason it's so much fun building and flying all your stuff, just waiting for that one moment when I can say "gotcha".

I guess I'm weird. I just make my own wrap around guides for most rockets, even if one is printed in the plans. That way I don't have to cut up the plans or try to keep a tube sitting perfectly on an end guide. No measuring is needed for four finned rockets unless you use thick paper. A quick mark and a couple of folds and you are done. Only minor measuring and division skills are needed for other fin numbers.

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I love sanding.

You can also use a software tool to print a fin wrap such as the one at:

http://www.payloadbay.com/index.php...action=FINWRAPS

You may run into problems with the print-out not scaling correctly, but this hasn't been a problem when I've used the tool. When you print the template make sure "Page Scaling" is set to "None." The print-out has a "one-inch" scale at the bottom of the printed page to make it easier to judge the accuracy of the print-out.

-- Roger

That's the way I do it.

I also make my own fin jig out of 2 sections of foam boards from Hobby Lobby. I just print out the templates from AutoCAD, attach it to the foam board with 3M Super 77 spray adhesive, cut out the fins & BT area from the template. Line up the boards with the lug reference line on the BT, tack the fins on with CA, remove the jig. Then I add the structural fillets.

In the interest of full disclosure, this idea is not original with me. On one of his instructional videos, I saw Dave Triano do this for one of his HPR airframes and adapted it.

Greg

You *might* be weird, but I do the same thing when I need a fin guide.

Luckily I have an Estes fin alignment jig (the gray one) that somebody gave me, and that's what I use whenever I can.

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John Thro, NAR #84553 SR
I was too old when I started! Now I'll *never* become a BAR!

I print mine out from VCP. I have found that entering the nominal tube diameter into the appropriate box in the Fin Wrapper tool produces a wrapper that is too small. So now I keep a document on my computer containing a list of tube sizes that I have used and the correct VCP Fin Wrapper Tool tube diameter settings that I have worked out for them via trial and error. I have had to do the same thing in order to get perfectly-sized tube miter guides using Matt Stum's Template Widget. The tube diameter setting for the Template Widget is usually different than the diameter setting that works for the same tube in the Fin Wrapper tool, and both settings differ from the nominal tube diameter provided by the supplier.

MarkII

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SAM # 0011

Might I suggest a new thread related to printing wrap-around guides rather than hijacking the Semroc-goofed thread?