Gettin Redy to Rebuild

Share your thoughts, photos and general help to all builders

Postby Lspav8r » Fri Feb 01, 2008 10:02 pm

I am so happy I found this forum. the help so far has been invaluable in my decission to take on this task. I am really looking forward to getting this Lazair in to the air and I am sure with all the help and parts available in this forum it will be a smmoth job.

Jim
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Postby Chappy » Fri Feb 01, 2008 11:10 pm

Early Lazairs were assembled using the cheap United Shoe Machine style POP Rivets. Later on, Ultraflight switched to a much improved blind rivet made by Avex (this applies to the aluminum blind rivets only). An Avex blind rivet works a little differently than a Pop style blind rivet. When you pull a Pop rivet, the center mandrel deforms the blind end of the rivet and creates a bulb against the back of the material. It supplies (only) clamping force in the process (that's why you want to make sure the rivet head is snug against the work when you start pulling it). The Avex, on the other hand, expands to fill the hole as you pull it, then forms a bulb on the end (expand, then clamp) to finish the job of forming the rivet. The great advantage of the Avex is that it is much better suited to hand assembly where holes may be less than perfectly drilled, and especially when doing rework and repairs where a rivet has to be drilled out and replaced, and the hole gets beat up and is no longer perfect, and even somewhat oversized (within reason). I would strongly advise using only Avex blind rivets on wing spars as a replacement for Avex, and particularly for cheap old Pop Rivets. The Avex cost a little more, but are well worth it! Here is one supplier: http://www.aircraftspruce.com/catalog/h ... indriv.php

In removing any blind rivet on a Lazair, I always use a vey small punch to drive out the remaining mandrel in the center of the rivet, then drill the rivet out. Many times the mandrel will make it hard to drill the head, and can cause the drill to walk off center and cause damage. This is especially true on the few places stainless steel blind rivets are used. When drilling out the stainless steel blind rivets, use a very sharp drill, and run the drill much slower that you would on aluminum. Also, keep more pressure on the drill. The idea is to get it to cut without burning and over heating the drill. 5 or 10% Cobalt drills make removing SS rivets much easier, and they last much longer. I buy mine here (this is an exapmle):
http://www1.mscdirect.com/CGI/NNSRIT?PM ... O=37085257

There have been cases where owners substituted stainless steel rivets where aluminum rivets were called out for in the assembly manual and it caused problems after many hours of operation!

None of the above has anything to do with the solid, bucked rivets used in a few places on the Lazair.

One more thing. Spend a few bucks and get a copy of the Standard Aircraft Handbook. It will become your guide to using aircraft hardware and tools, and is especially valuable if you are making repairs.
http://www.aircraftspruce.com/catalog/b ... achdbk.php

Chappy

PS Edit: Sorry, I missed the first few posts on this thread so please excuse me for repeating some of the info in them.
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Postby shorty_ » Sun Feb 03, 2008 6:05 pm

Axex rivets for the most part are 3/8" long grip
some are 1/2 "
plus some SS rivets

I buy mine in bulk right from Textron by the pound.
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Postby Chappy » Mon Feb 04, 2008 12:48 am

Yea, I love these rivets. I have something like 10,000 crappy Pop rivets in stock, but I always go for the Avex rivets when I building or repairing something that's better than junk. Aircraft Spuce only carries the two shorter grip ranges; I think there are actually 4 ranges made in the basic aluminum/steel 1/8" size. Another nice thing about Avex rivets is that they have a wider grip range per size.

For the guys that haven't used these rivets before, I found a nice little article on blind rivets and Avex use in airplane construction at:

http://www.zenithair.com/kit-data/ht-87-1.html

Avex rivets Manufacturer: http://www.avdel-global.com/avex.asp

Some nice basic stuff on light aircraft construction at Chris Heintz On-line Design College:

http://www.zenithair.com/kit-data/ht.html

Chappy
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Postby shorty_ » Wed Feb 06, 2008 8:12 am

Chappy ,another issue on AVEX is the head of the riveter should be a concave one so that the rivet will form a nice rounded head.
regualr " pop rivet guns" just havea flat suface and makes a sloppy looking head.
you can "machine" your own with a drill bit sharpened on less of a angle than normal . I do it in my lathe.
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Postby Chappy » Wed Feb 06, 2008 11:30 pm

Shorty,

I'll try it!

BTW, what lathe do you have? I have a small 9" South Bend with quick change gears and Aloris tool post. I bought it and learned how to use it way back when I had decided to build the reduction drives I have on my Pioneers. If it wasn't for the Lazair, I probably never would have owned one or learned how to run one. I've never been much good at cutting treads on it though.

I'm still jealous of the big husky bending brake you built last winter! I had scrounged some big angle for one myself years ago, but it got diverted to another project. I got the steel out of a huge building that they aged Virginia Gentleman Whiskey in when they tore the building down. Wish I could find some more.

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