Less is more?

[cncdoc]

The one thing I enjoy about reading other builder's experiences is that when there is a common thread of one kind or another, I can use that information as a way to make improvements or alter the way (the plans show) I should build.

Mr Slade and I had a short discussion about a particular area where there was a seeming mistake.

Did you ever notice how the amount of spar cap tape is almost always too little when used to fill the spar gap when using plans specifications depth?

Is it Wicks or AS shorting us (ususally the same amount)?

John didn't necessarily think so. But he did offer an alternative explanation:

 

When the plans were developed, EZ-poxy was being used. It is much thicker than the new and improved MGS product. Using the newer, stronger(?) thinner epoxy leaves more room between plys. Right? IF so, that leaves a few questions:

 

1. Is it better to keep the original amount of spar cap plys and raise the floor of the cavity so that no additional (weight) material be added to keep the wing surface smooth?

2. Is the additional spar cap tape necessary or is it better to have the additional strength the extra tape affords?

3. Has anyone got any "hard" numbers on what the depth would be taking into account different epoxy?

4. Could the plans be wrong?

5. Could John's observation be wrong?

6. Is it quicker to Chicago than by bus, or should I take a lunch?

 

See as Chapter 10 is looming ominously on my horizon, I'd like to get some additional info....even though spar cap tape isn't that $$$! and I could use it later....

 

 

Thank y'all...

[Wayne Hicks]

For the canard, yes. Order more than the plans require, like about 4 plies worth (4 x 12 feet = 48 feet extra). You can always use the extra on the wings. Why? Two main reasons - (1) The plans don't tell us a specific number of plies to put into the troughs, instead saying simply to fully fill the troughs; and (2) The depth of the spar cap troughs varies from builder to builder. A really hot hot-wire will result in deeper spar cap troughs. (A really hot hot-wire burns/melts the surrounding styrofoam more than necessary.....) A colder wire results in shallower troughs. So the amount varies from canard to canard.

 

For the wings, the plans specify the exact length and number of spar cap tapes. I found the plans-specified amount to be just about correct. (But I ordered extra in case I screwed up.)

 

I cannot comment of being shorted by ACS or Wicks. I wasn't anal enough to roll out the tape and measure it. It seemed like they got it right. That being said, when it came time to build the spar caps for the 2nd wing, I did roll out the remaining spar cap tapes and cut them to the right lengths to ENSURE I had enough spar cap tape to do the job.

 

====================

Wayne Hicks

Cozy IV Plans #678

http://www.maddyhome.com/canardpages/pages/waynehicks/index.html

[dust]

mmmmmm, seems to me the required number of layers filled the trough about right, maybe we added a layer here or there. I don't know if we orderred exactly the correct amount of tape or not, but we did end up with extra, i think it is in IOWA.

 

And thanks for enjoying the "dust"

 

enjoy the build

 

dust

[rmaddy]

I was never short on any of my spar caps (all 8 of them). I always made sure I ordered enough extra for at least one more layer than specified incase my troughs were too deep. After I finished the second wing, I had some 3" tape left. Not sure how much but it seemed to be about enough for an extra layer.

 

Make the troughs per plans. If you manage to get all the layers in place but still need more - add the extra to fill - better a hair low than a hair too full. It's easier to sand the foam down then to fill up around an overfilled trough.

 

Like others said, just order some extra. Actually, I'd order all called out for in the plans in one shot, plus an extra 8 yards or so. This stuff is like gold and there is one machine in the world that makes it. Get it while you can. I've heard of 6 month outages before.

 

Personally I don't buy the thinner vs. thicker epoxy argument. It takes a certain amount of epoxy to wet out glass. Then again, John may be right and I'm just using too much MGS

 

Enjoy