They do, I agree. But I'm not sure it's a suitable skill to teach kids - I'm afraid they'll be as likely to damage the rocket as they are to get the motor to stay in during ejection. Heck, too many of the adult fliers I've seen on the web complain about friction fitting being a PITA

I consider myself quite proficient at it now, thanks to being an avid multi-stage flier who does it out of necessity. But, for newbs, I can see lawn darts and broken fins being more common than good flights. And there will be a few ham fisted fliers who bend the airframe or crush it while trying this. I know I'd be crying if I did that.

That's why I prefer kits with motor hooks for newbs, young and old. Even if the hooks mount on the outside of the (minimum diameter) airframe, it's much easier to prep the rocket (IMNSHO).

That said, I do encourage folks to put a wrap or two of tape on the motor to ensure a good seal (for ejection gases).

Anyway, I agree friction fitting is a good skill for accomplished fliers to have on their resumes, but I just don't think it's a good to require it of beginners.

Doug

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YORF member #11

...And yet all or nearly all of us learned it from the start. I'm reluctant to "easify" everything, because it lowers competence (and slows down advancement in competence) by setting low expectations from the start. I'm not suggesting that a neophyte model rocketeer (whether a child or an adult) should be expected to start with a Skill Level 5 kit, but friction-fitting motors properly isn't fundamentally any more difficult than packing a recovery system properly (it can also be done too loosely [causing nose cone separation due to differential drag as the rocket coasts, resulting in a "shred"] or too tightly [causing the body tube to burst at ejection, or resulting in a "lawn dart"]). Also:

If it's done similarly to threading a screw or a bolt into place, by using masking tape that's helically-applied to the motor in a "coarse"--high inclination--spiral (this thread [see: http://www.oldrocketforum.com/showt...ht=friction-fit ] discussed friction-fitting motors in this way), it's quite simple, and the tightness of the fit is even easily adjustable. If it's taught in a matter-of-fact way (not in a way that might make newbies nervous), they simply pick up the technique as being a normal part of preparing such a model rocket for flight, as we did. Even in G. Harry Stine's "Handbook of Model Rocketry" and Stuart Lodge's "The Model Rocketry Handbook," friction-fitting motors is treated in this way ("If your model has a motor clip, secure the motor X way; if it doesn't, use the Y [friction-fit] method, which is done as follows...").

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Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see:
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http://www.lulu.com/product/cd/what...of-2%29/6126511
All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com.
NAR #54895 SR

You know, there is an easier way, especially with a rocket like the Viking. Mount the fins 1/4" forward of the back end of the body tube and put the motor mount in at 2-1/2" - motor sticks out 1/4". Now, put a wrap or two of GOOD masking tape (Tamiya Masking Tape is good for this) around the base of the motor, wrapping around both motor and body tube. Burnish down with your fin get and you're ready to go. Since the Viking is a mutable design anyway (mount the fins in many configurations), moving them forward 1/4" fits in the design parameters.

That said, you have to be careful with some fin configurations on either the old Centuri or newer Estes versions - 3 fins mounted with either of the longer sides of the fins as the root edge CAN be unstable with larger motors - you might need some nose weight in that case. But I consider the Viking to be an excellent starter kit.

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Greg Poehlein

Member of Launch Crue - http://launchcrue.org/

Hint #1: Do not use magician's flash paper for recovery wadding!

Hint #2: Clean your shoes after flyin' in that cow pasture - that ain't no dirt clod on the sole!

That definitely works, and in fact it is a little easier to do--and it's aerodynamically slightly "neater"--with the Estes Viking than with the Centuri one, because the motor has more of a "sleeve fit" in BT-20 tubing than in the #7 tubing (and the external taping works very elegantly on BT-5/#5 size minimum-diameter, mini motor-powered rockets). Also:

The short rearward-protruding length of body tube (as well as the rear end of the motor) behind the fins acts as a boat-tail, serving to help straighten out the airflow aft of the fins, which reduces the turbulence and thus the base drag, even though the amount of taper is only very slight (due to the protruding end of the motor). The tape tends to counteract this (aerodynamically speaking), but if the tape is applied neatly, it doesn't add much drag. Plus, this forward-mounted fin arrangement helps to protect the fins from landing impact damage (a BT-5 size, down-scaled "Mini-Viking" with fiber fins and the 4:1 tangent ogive Gnome/Quark plastic nose cone would be even more resistant to landing damage to its [smaller] fiber fins, even if they were mounted in the "longest-span" configuration).

__________________
Black Shire--Draft horse in human form, model rocketeer, occasional mystic, and writer, see:
http://www.lulu.com/content/paperba...an-form/8075185
http://www.lulu.com/product/cd/what...of-2%29/6122050
http://www.lulu.com/product/cd/what...of-2%29/6126511
All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com.
NAR #54895 SR