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Old 09-21-2006, 11:27 PM   #1
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Honeycomb Aluminum Panel As Sub Floor, the adventure...

Yes I got my hands on some, yes I'm using it for my sub-floor and yes it is totally aluminum honeycomb panels!
Ok, people have spoken about this before, like some sort of legend or something their friends neighbor had done. Now for better or worse it will be done, posted and talked about, here in this thread.

Within a larger total remodel, I will be retrofitting the sub floor of my darling 1971 Caravel, using 1" Aluminum Honeycomb sandwiched panels. Details of the product start in post #16.
This is being done for a few reasons...
  • Weight reduction, my goal with every step of this remodel is to explore new materials and techniques to greatly reduce the total weight on my twinkie
  • Durability to the elements and stress of trailing. moisture, dry rot, mold, animals and all the other things we struggle with will presumably addressed
  • Exploration, if nothing else we are a group of adventurers. This was a curiosity and challenge I could not bear to let sit untouched.
This is a long term project and will be going into quite a few uncharted territories, this is half the fun. Sharing the process and final results with everyone will be the other half, stay tuned....
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Old 09-22-2006, 02:20 AM   #2
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Really hoping to get some info before morning....
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Old 09-22-2006, 07:07 AM   #3
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Im not much help but that honeycomb stuff is great, best of luck !!!
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Old 09-22-2006, 07:29 AM   #4
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Exclamation Go for it!

Just do it! (no - not a Nike commercial)

If you have the knowledge & talent to work with the material, then get your hands on the inventory and go for it.

If you haven't fabricated or assembled with this material previously ... then you may be setting yourself up for a grand & intricate adventure!

Be aware that the adventure will include not only a complicated process, but also the interface of dissimilar metals.

If you do not have the knowledge & experience, you may be better served to construct light weight furniture with the stuff, and stay away from structural applications.
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Old 09-22-2006, 07:53 AM   #5
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Hi Rivka; Buy a horse before you buy a whip. I think that you are to anxious to get going. I reccomend that you make a plan first. You need to know the details first, and than plan your repairs step by step. My first concern would be the contact area's of dissimilar metals, steel to aluminum. Steel rusting or the trapped moisture will always try to bridge the contact area's first. This is where the moiusture will hang and cause the aluminum to oxidize. You will need some form of barrier, perhaps PVC strips between steel frame and alum floor. Aluminum is harder to work with and pending what the thickness is it may not handle the compression load under the heads of attaching screws to the frame especialy if the screws fall in the center or honeycomb. I am not sure either if under extensive towing they would not loosen up causing aluminum fatigue. I think you should get some imput on that from metalurgy experts. Good Luck. "boatdoc"
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Old 09-22-2006, 08:37 AM   #6
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Look at the VAP -

http://www.thevap.com in the "archieves" section - see episode 16.

They have an illustration on how the various year Airstreams where put together. I do think that you have C-channel to connect, but it rides ON top of the floor (per these pics). The only problem would be if you're using your bannana wraps again - since you're doing a frame off, I'm assuming you're making new ones, right?

Happy hunting! Wanna race? Tee Hee - no, I'm not pulling the floor out of the Argosy.
Tell us how it goes! The honeycomb would work well for cabinets, walls, and counters too!
Marc
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Old 09-22-2006, 09:15 AM   #7
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Rivka, We use the honeycomb panels rot the fuselage structure of our UAV,s. A 4X8 sheet of 1/2" normally costs $ 700. When you expose the edges you need to microballon and epoxy the newly exposed area, And the 1/2" is not structuraly strong for you floor, Have to bump up to 1". You would be starting a nightmare, Not to mention that everywhere you needed a fastenint point you would need to epoxy in a support capusule- remember the panels are hollow! Compression load..If you really want to go down this road why don't you go the boat route and use edge grain balsa encased in epoxy cloth. I would hate to see you get discouraged and give up on your project. Me I would replace the the floor with marine grade plywood and get a bigger motor in my tow vehicle. Tim
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Old 09-22-2006, 11:19 AM   #8
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i think a number of you are jumping to a few conclusions that i don't know what i'm doing. I do. I have over a decade of working with metal and years of schooling in the same. I have been studying the use and issues about honeycomb for a while now. what has come up for me is that i just jumped a decade in my main trailer so have a bit of catching up on a trailer whose construction differs in a lot of places. I have a warehouse, i have the tools, i have a plan. I would not be buying material if the rest of this had not been done already.

as for the VAP archive, can someone confirm what is in photo "B" there is the "U" channel with the open end facing up, is there also a "C" channel open side facing in and there for capping and restraining the thickness of the flooring?

Yes i will be redoing the belly pan and banana wrap, mine is pretty bashed up.
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Old 09-22-2006, 11:24 AM   #9
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Quote:
Originally Posted by doorgunner
Rivka, We use the honeycomb panels rot the fuselage structure of our UAV,s. A 4X8 sheet of 1/2" normally costs $ 700. When you expose the edges you need to microballon and epoxy the newly exposed area, And the 1/2" is not structuraly strong for you floor, Have to bump up to 1". You would be starting a nightmare, Not to mention that everywhere you needed a fastenint point you would need to epoxy in a support capusule- remember the panels are hollow! Compression load..If you really want to go down this road why don't you go the boat route and use edge grain balsa encased in epoxy cloth. I would hate to see you get discouraged and give up on your project. Me I would replace the the floor with marine grade plywood and get a bigger motor in my tow vehicle. Tim
not sure what you base you strength data on, the companies i have spoken to seem to indicate the overwhelming strength of these panels. and fyi i don't give up, and my T/V is not up for option.
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Old 09-22-2006, 12:19 PM   #10
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Me thinks the strengths you note are best case scenarios - the spar spacing on the AS may not be adequate for the live loads encountered. However the honeycomb is worth the effort for weight reduction in gauchos and bed support sheets, custom built-ins, etc..
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Old 09-22-2006, 04:56 PM   #11
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What type of honeycomb are you looking for? Alot of the honeycombs out there would NOT be a good choice for a floor. The tension load that alot of honeycombs can carry isn't very good. Just as long as you know that you will have to install threaded inserts to attach anything to it and that it will delaminate for no reason at all, losing all compression strenghts. I,ve been using it for years in the avaition buisness and couldn,t begain to guess how much I've removed and replaced with conventional construction. It is extreamly easy to damage and extremly difficult to repair. I would use it for cabinets and interior bulkheads and furnishing though. I just don,t think that your application for this product is going to give you good long term results. If you can get your hands on some boran grafite faced and phenalic core or fiberglass face with phenolic core sheets it would be better then aluminum faced with aluminum core, but also much difficult to work. Composite sheets do not work well with metal cutting tools. They like diamond tooling and expensive resins.
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Old 09-22-2006, 08:11 PM   #12
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Red face My apologies to Rivka

Hi Rivka; Please accept my apology for comment made in reply to your post. I was only commenting on the use of alum. honeycomb sheeting for such application, not on your ability or capability. We all know that anyone who is willing to tackle such job, must be confident in their ability and I admire you for this. I merly wanted to point out that while honeycomb has a ultimate rigidity because of it's design, but on the other hand pending on the thicknes of skin it has very little compression value when considering a very small contact area with head of the screw. Head of the screw can easily tear thru the thin skin in the center of honeycomb. Recessing screw heads is a problem. Using flat head screws and driving them down flush will cause tears under the heads. While you may not notice them at first, they will show up later especially if the frame flexes. If you use hex head bolts, you will have heads sticking up. There are some other issues with such application as "Doorgunner" has mentioned. The truth Rivka is, that it was not our intent to destroy your entusiasm. I guess it is in our nature to be concerned for others and cannot help ourself to share our knowlede with fellow airstreamers. Thank you, "boatdoc"
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Old 09-22-2006, 09:45 PM   #13
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Here are some answers to some of your questions. I hope they are not too late.

Unfortunately I am not sure if the 1971 models had the "C" channel along the bottom of the "U"channel at the base of the walls. They definitely did for 1973 models. If it does not have the "C" channel on the bottom then the "U" Channel is sitting on top of the floor material which would give you less of a constraint.

If it is like the 1973 then the space for the sub-floor material is constrained to 3/4" material. If you had to you could cut off the bottom leg of the "C" to fit a thicker floor panel I suppose but that would be a lot of work in my opinion. The cross-members in the frame are typically at 24" on center. The lengthwise frame members are about 60" apart.

If I recall correctly the width of the floor at the bottom of the walls is about 84" inside the walls plus about another 1-1/2" at each side under the wall for a total of about 87" or so. The original floor panels were 4' wide sheets typically mounted with their lenghwise dimension from side to side. The frame cross-members are located so that the joints at the 4' points fall on cross-members. On my 1973 the cross-members at the 4' joints are about 5/8" shorter in height than the rest so that a 5/8" thick plywood spline could be added at the joint of the plywood sheets.

As a pretty rough rule of thumb solid wood weighs in at about 50 lbs per cubic foot. If I am calculating right then a 4' x 8' x 3/4" sheet of plywood would weigh in at about 100 lbs.

I have been to the Boeing yard and it is a pretty fascinating place. I hope you find what you are looking for.

Malcolm
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Old 09-22-2006, 10:09 PM   #14
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Some threads in the Archives make reference to certain Argosy Minuets that had a honeycomb floor. I don't know if the top & bottom membrane surfaces were aluminum or a resin matrix of some sort. You might want to ask overlander64 (Kevin Allen) about that -- as well as history of how they held up. I don't know. Bimetallic reaction should be lessened if the shell-belly transition is properly sealed to exclude moisture. Airstreams have always had aluminum and steel in direct contact.

The proper floor thickness is about 9/16". 1/2" is just a little shy of OEM. I couldn't resist using some solid core 19/32" plywood underlayment for some partial floor replacement on my Argosy -- that was definitely over original spec and was tight getting it between frame and C-channel. These numbers shouldn't be so critical if you were doing a full shell-off restoration.
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