Fin marking guides that don't fit

[wwattles]

Have you guys ever gone through the steps of building a kit, and when it comes time to wrap that little cutout around the body tube to mark the fin placement, it doesn't seem to quite fit?

About 75% of the kits I've built seem to have this problem. It's almost like the kit makers draw out their marking guides thinking about inner diameters, not outer, or they somehow shrink the scaling just a touch.

Anybody else have this problem???

WW

 

[not a lib]

That's why I like the fin marking guides that have you place the body tube on an out line of the body tube diameter & mark the fins that way. It's like an Estes tube marking guide. Rocketpad does it that way & it works. I hate the wrap type!
not a lib

 

[Stymye]

WW I noticed the same thing . I use the round marking guides from the estes alignment kit.

 

[flying_silverad]

I usually pack kits in small lots depending on what I need for orders, inventory etc. Anyway, I had a couple of runs of different kits that the guide was off by 1/8th of inch or so. The originals were fine, of all the copies that I made a few, for whatever reason, were smaller.

So, I can speak from both sides of the fence. I know what it's like to get one and unfortunately, I know what it's like to give one.

As always, if you ever have problem with my kits, you can always e-mail and I will always make things right, I think most of the other vendors would do the same.


As a builder, I actually never use them anymore unless it's a strange fin set-up (Shrox Stiletto for instance). It's just easier to use an Estes guide. The other cool thing you can do is get a copy (it's free!) of the VCP program and you can make any fin guide you want!

 

[wwattles]

Unfortunately, the current build IS just one of those "unusual" fin arrangements. On more than one occasion I've broken out my digital calipers, measured an tube's OD, and used the famous Matt Stum Template Widget to print out a new fin wrap template! But alas, that won't work with this kit. It's not a HUGE difference, only about 2mm difference, but it may be enough to possibly throw something off!

If your kits were sent out with slightly shrunken marking guides, were the other templates (fin cutting, etc) slightly shrunken as well?

WW

 

[flying_silverad]

Originally posted by wwattles
Unfortunately, the current build IS just one of those "unusual" fin arrangements. On more than one occasion I've broken out my digital calipers, measured an tube's OD, and used the famous Matt Stum Template Widget to print out a new fin wrap template! But alas, that won't work with this kit. It's not a HUGE difference, only about 2mm difference, but it may be enough to possibly throw something off!

If your kits were sent out with slightly shrunken marking guides, were the other templates (fin cutting, etc) slightly shrunken as well?

WW

2 things. One, I wold try the VCP program. You really shouldn't need the calipers...if it's BT55 then it's 1.325" etc,.

Two, the kit that I had a problem with had a seperate fin guide wrap. Fins were fine, it was on a different sheet. And, they have been corrected (Thanks to Nick!! )

 

[jflis]

We've had this problem on a few of our kits. You will notice that this problem is becoming less and less common.

Initially, our printer didn't realize that these sheets needed to be *scale* and we didn't realize that we needed to tell them that, so there was some shrinkage, which is normal.

Even with that said, there are occations where there is some change in scale when doing printing. We do our best to catch this and react quickly when someone finds such a case.

THat is why we have posted our Fin Marking Guide online (under free stuff) at: https://fliskits.com/products/free_dl/fin_marking_guide_template.pdf

This way if you find something amiss with your fin marking guide, you can download one and use. Of course, this only works for evenly spaced fins...

When I'm building a rocket, I've done so much scratch building that I just wrap paper around the tube, mark and cut then fold it into 3rds, or 4ths, as needed and I have an instant marking guide

Oh, one other thing that nailed us. We used about #60 stock for our fin marking guides. Someone commented that it seems as though some kit makers used the *inside* diameter when making them, well what may be happening is what happened to us... We used the OUTSIDE diameter, but THAT is incorrect too. You need to use the OUTSIDE diameter of the FIN MARKING GUIDE when wrapped around the tube. The thickness of the card stock may not seem like much, but you will be surprized at the effect it has on circumference

jim

 

[DynaSoar]

Originally posted by jflis
Initially, our printer didn't realize that these sheets needed to be *scale* and we didn't realize that we needed to tell them that, so there was some shrinkage, which is normal.

Even with that said, there are occations where there is some change in scale when doing printing. We do our best to catch this and react quickly when someone finds such a case.

IIRC, there are/were some photocopy machines whose "100%" copy size was actually 98%. These were older ones that did a few sizes, not every 1%+/- across a wide range. Not sure if newer ones still do this. Not on purpose anyway. They can easily be misaligned and get the size slightly off.

I agree with the comment about the old Estes style circle with radiating fin lines. Even if the size is slightly off, the angle is still right.

 

[powderburner]

You need to consider that these instruction sheets (and the wrap-around guides for fin spacing that are on those sheets) are reproduced by a process that seldom ever delivers a 100.0%-sized copy. Most copies vary by a fraction of a percent (both larger and smaller) and some copies by much more than that.

And if they copied a new batch of their instructions from an old copy . . .

Last but not least, remember that these are just people who put these kits together, and people do have a tendency to occasionally make mistakes.

 

[cls]

this used to bother me more than it does now. instead: cut a strip of paper to exact BT circumference, then fold in thirds (3 fins) or quarters (4 fins). mark the fin lines at the folds and you're done!

I am sure I learned this tip from TRF.

I used to do it the hard way, printing a wrapper in SpaceCAD.

of course, if the fin marking guide is wrong then the fin templates are probably wrong too.

 

[flying_silverad]

Originally posted by powderburner
You need to consider that these instruction sheets (and the wrap-around guides for fin spacing that are on those sheets) are reproduced by a process that seldom ever delivers a 100.0%-sized copy. Most copies vary by a fraction of a percent (both larger and smaller) and some copies by much more than that.

And if they copied a new batch of their instructions from an old copy . . .

Last but not least, remember that these are just people who put these kits together, and people do have a tendency to occasionally make mistakes.

What could make matters worse is taking the bad copy and making more copies then everything just snowballs!

 

[jflis]

Yep, copying can compound any problem. We don't *copy* our documentation, it is all printed fresh from an electronic document RIP'd to the printers.

Also, if the fin marking guide is off, say, 2% on (for this example) a BT-70, then it is off by more than a tenth of an inch (.139") which would be unacceptable (at least for me ), however the corrisponding 2% error on the fins (assuming a standard 3F or 4F model) really wouldn't matter all that much.

 

[Stymye]

some may do with making the wraparound guide to the tube OD rather than the wrap od, thicker paper/cardstock would compound the difference.
and as you wrap ever larger tubes the surface area will increase and produce a wider gap
almost always in my case the wrap is too short

 

[wwattles]

Originally posted by stymye

almost always in my case the wrap is too short

So what do you do when the wrap is too short and it's an unusual fin pattern (uneven fin spacing)?

WW

 

[Stymye]

one way,you could draw the "end view" on paper , set the tube on it and mark the positions around the tube.

 

[Stymye]

this is a quicky example but it shows the idea

 

[flying_silverad]

I still say even if you are involved with an unusal fin pattern, you could use the VCP program and just pick your on degree poiints for each fin. It's pretty easy. I set my nightfighter up that way, worked fine. And that model has fins all over the place!

 

[jflis]

What I have done in the past (set the way-back machine to 1980...) is to run the fin marking guide through a copy machine set at 101% or so and click the size up till I got one to fit...

 

[DJ Delorie]

Ok, I'm a computer geek. I had the computer print a wrap with a gauge at the overlap. I wrapped it, and read the gauge. Then I used that measurement to adjust the size of the wrap, and the next print fit perfectly.

 

[wwattles]

I've discovered a possible source of my problems: My very own copier!

I always copy my wraps, templates, etc, onto cardstock and keep the originals in a file folder in case I screw up the cutting. When I checked my copy size against my original, sure enough, it was just a touch reduced in size. That's enough to cause my marking guide error!

Guess I'll be doing it at a professional copy center from now on, and not the cheapo desktop copier (complete with briefcase-style handle) at home!

WW