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Practice Layup


Gothic-crow

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I did the practice layup and dont understand what I'm looking for.

the dry layup came in at 2.3 ounces. but the book says thats the wieght for the correct layup.

the correct layup one is 2.5 ounces which is suppose to be the heavy one but looks better than the dry layup. what gives?

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GC, I'm guessing that you're referring to a "practice kit", which I don't have. The practice layup in the Cozy plans calls for a 6-BID layup that is 12.5" x 18" and then cut down to 10" x 16". The final weight is expected to be anywhere from 10.5 to 12.5 ounces, with 11 ounces being ideal.

 

I wouldn't knock yourself out over it. You could try it again, and squeegee even more agressively to see what happens with the next practice weight.

 

The important point is that it's really hard to judge too heavy or light on such a small scale. Assuming the precision of your scale is accurate to 0.1 ounce, you're talking about 0.16 to 0.24 ounces difference. That's just a few paper clips.

 

I'm in chapter 4 (bulkheads), where it's more important to worry about structural integrity than it is part weights. You get to practice there several times over, and compare your part weights with other builders. See http://www.cozybuilders.org/ref_info/part_weight.html

Jon Matcho :busy:
Builder & Canard Zone Admin
Now:  Rebuilding Quickie Tri-Q200 N479E
Next:  Resume building a Cozy Mark IV

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No, this one called for 4 plies of BID cut to 7X7". O-well, I've done fiberglass on boats before so I have an idea of what to look for. I ordered Chapter 4-7

but having shipping troubles. But atleast I've took step #2, Ordered the material. Step #1 was the plans. So I'm half way there right!!??

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No, this one called for 4 plies of BID cut to 7X7".

That's what I thought -- you did a different piece than what is in Chapter 3 of the Cozy plans.

 

I ordered Chapter 4-7...

Congratulations!

 

So I'm half way there right!!??

You're definitely more than halfway to somewhere better than before, at least. :)

 

Jump right into Chapter 4 Step 1 when you get the material -- you'll do fine.

Jon Matcho :busy:
Builder & Canard Zone Admin
Now:  Rebuilding Quickie Tri-Q200 N479E
Next:  Resume building a Cozy Mark IV

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Well I've done neither...

 

What you have is the original book by Burt Rutan, the daddy who adapted fg sailplane construction to something you can do in your shed. It may have been revised, but the materials may still be different now. As Jon said, the tolerances on weighing such a small sample would take you either side of the desirable target! Look at it, bend it, compare it to a piece of aluminium that weighs the same, nail it over your workshop door and show it to the missus & your mates, but don't draw too many conclusions whether you have learnt the method yet. The plans will do it.

 

I see the book and the accompanying kit are still in the ASS & Wicks catalogues and was tempted to get one myself before I had a go myself on another bloke's project. Keep it to proselytise others who like the boat you're building...

Mark Spedding - Spodman
Darraweit Guim - Australia
Cozy IV #1331 -  Chapter 09
www.mykitlog.com/Spodman
www.sites.google.com/site/thespodplane/the-spodplane

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