Drawer Decking Alloy or Timber

Submitted: Wednesday, May 09, 2012 at 20:58
ThreadID: 95464 Views:6139 Replies:8 FollowUps:13
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I am working on my canopy fit out. I have made drawer frames out of alloy angle.. I plan to use nally tubs in the frames as drawers. I have made the carcase for the drawers from 20 x 20 square alloy. The deck frame has spacings of 350mm between them on the top.
I was planning to use alloy for the deck and secure it with nutserts and carpet over the alloy. My question is what thickness alloy should I use over the heavy goods part being cartons of drink and what size over the light goods part such as chairs table beach shelter etc ?
My other question is timber predominately used for decking because of cost or is there a good reason why alloy is not the popular choice for the deck in both professionally and home built drawer / false floors. ?
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Reply By: jacent - Wednesday, May 09, 2012 at 21:18

Wednesday, May 09, 2012 at 21:18
My brother made my drawers out of MDF, I'm assuming they use timber to keep costs down, alloy may possibly vibrate or dent if not thick enough!? my drawers have had a thrashing over major corrugations around australia and havent fallen apart. They were only a quick knock up before a long trip but have stayed there for years. sorry I cant be of much help! good luck!
AnswerID: 485400

Reply By: Member -Pinko (NSW) - Wednesday, May 09, 2012 at 22:15

Wednesday, May 09, 2012 at 22:15
I have a ute with a canopy fitted. The two drawers go across and can be accessed one side or the other..
I first made the carcass and the drawers from MDF and sealed it with three coats of diluted estapol (recommended). I got water in and the carcass began to swell and the drawers began to tighten up.
The carcass was spaced off the floor giving an air space to ventilate.
I have remade the carcass from 16mm construction ply from Bunnings and sealed it with bondall multi surface waterproofer.
I have exposed the ply offcuts with sealer applied to constant wet weather and it is obviously waterproof.
Drawers have a lot of weight in them over very rough terrain and are fine.
I think there is a degree of flex in the construction and it is probably a plus.
www.drifta.com.au make elaborate camper kitchens from ply and they are successful.
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AnswerID: 485408

Follow Up By: kwk56pt - Wednesday, May 09, 2012 at 23:30

Wednesday, May 09, 2012 at 23:30
Sounds like a pretty strong set up. Can I ask what thickness ply you have used on the deck ? I was trying to make mine as light as possible, I guess the trouble with DIY is that I may have to beef up the design once I have put it to work. Looks like you have a good camper and ute. Out of interest did you do the canning towing without any assistance ?
Cheers Peter
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Follow Up By: Shaker - Thursday, May 10, 2012 at 07:55

Thursday, May 10, 2012 at 07:55
With 350mm centres, 10mm marine ply will be adequate. It will also be more resilient than aluminium.
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Follow Up By: Member -Pinko (NSW) - Thursday, May 10, 2012 at 08:45

Thursday, May 10, 2012 at 08:45
Peter
The drawer setup is all 16mm. ply. includes the deck as at times heavy stuff gets loaded on to it. If it were 10 mm. the clearance between drawer and deck may have to increase as the flex may bind the drawer.Both drawers are 450mm. wide with a vertical between.
Incidently I did not use commercial drawer runners, instead went to the Plastics Factory and had them saw 25mm.X 4mm.X 2400mm. strips of HDPE which I counter sunk and screwed to both corners vertical and horizontal,of the drawers and carcass. HDPE has a very low friction coefficient and makes the drawers so slippery.

If weight is your concern go to Bunnings lift a 1200 x 2400 sheet of 10mm. then lift a sheet of 16mm. and compare.

As for the Canning S.R. Peter, we traveled alone as we do most places and had no trouble at any time and thoroughly enjoyed the journey. Pay strict attention to Jol Flemmings method of arriving at the optimum tyre pressures to get equal footprint on every tyre and you cannot go wrong.
Cheers
Stan
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Follow Up By: Shaker - Thursday, May 10, 2012 at 21:03

Thursday, May 10, 2012 at 21:03
At 350mm centres 10mm wouldn't flex, you can use 15mm plywood for house flooring with joists at 450mm centres.

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Follow Up By: kwk56pt - Thursday, May 10, 2012 at 21:33

Thursday, May 10, 2012 at 21:33
Thanks Stan for the Jol Fleming tyre info, makes sense to work off the footprint which covers the different weight variable. The strips of hdpe is another worthy suggestion. I did buy drawer runners 900mm which are a bit heavier than I thought they would be but I may still try the hpde elsewhere yet.
Glad you enjoyed the canning and managed it alone without dramas. My plan is to stop dreaming and start doing.
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Follow Up By: kwk56pt - Thursday, May 10, 2012 at 21:39

Thursday, May 10, 2012 at 21:39
Shaker, I will clamp some 10mm ply over my frame and put a load on it to see the difference between using the heavier ply. thanks for the information. So many variable such as the weight, is the load tied down so it cant jog and the carcase design used,
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Reply By: Geoff H (Q - Thursday, May 10, 2012 at 08:58

Thursday, May 10, 2012 at 08:58
Hi,
I built a set of drawers from 12mm construction ply from Bunnings, I used Liquid Nails and quad in some corners and small screws to hold it together until the glue set. They made the trip to the cape full of gear and held their shape very well.
Regards
Geoff
AnswerID: 485427

Reply By: GT Campers - Thursday, May 10, 2012 at 09:13

Thursday, May 10, 2012 at 09:13
Yep 12-15mm (I can't recall) ply/timber is pretty good stuff, easy to cut/work and strong enough within reason and is quiet when in transit - no rattles or buzzes. Set things up right and you won't need separate framing
AnswerID: 485429

Reply By: Member - John D, Wandong (Vic) - Thursday, May 10, 2012 at 09:39

Thursday, May 10, 2012 at 09:39
I built a false floor in the tub of my Rodeo, there seems to be some similarities in what you are doing, you can check out the results here...tub modifications.
AnswerID: 485433

Reply By: The Bantam - Thursday, May 10, 2012 at 09:56

Thursday, May 10, 2012 at 09:56
If you get to the sharp end of the pencil, the strength to weight ratio of good ply and aluminium is pretty damn close in this sort of application.

Generally the engineering of draw systems is very crude, and people tend to use material that is way too heavy.

If you step away from the hardware store and start buying ply from a decent source you can get some very strong light material.

If you want to step up from there a single sheet of 200GSM woven glass mat and marine epoxy on the underside will increase the strenght out of sight..then you are leaving the aluminium sheet way behind in strenght for weight.

I used to build equipment cases for a living, and even without the glass mat, you would be surprised hwo strong 8-10-12mm ply can be if you attach the edges well.

AND this is your limitation, how well you can support the edges.

Ply will be quieter and carpet will definitely bond better to it.

cheers
AnswerID: 485436

Follow Up By: kwk56pt - Friday, May 11, 2012 at 20:51

Friday, May 11, 2012 at 20:51
Your reply was appreciated especially as you seem quite knowledgeable on the subject. Seems you may be correct in using the woven matt. Google tells me it is much stronger than the chopped stuff I once used to reinforce a sagging fridge slide base that I had made some years ago. It did soak up a lot of resin which is not light so I was a bit surprised to hear you say it would be light. Its probable the woven matt does not need as much resin. When you say attach the edges well at what intervals would you space the edge screws. I am going into 20 x 20 x 1.6mm alloy tube so I will probably use nutserts to fix it with ?
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FollowupID: 760840

Follow Up By: Shaker - Friday, May 11, 2012 at 22:14

Friday, May 11, 2012 at 22:14
You can buy purpose made pop rivets to attach timber to a metal frame.
It is good to see somebody else agree that most amateurs build their drawers way too heavily. I am guessing that The Bantam may have a background in boatbuilding as do I. Personally, I think that sheathing the underside would be overkill in your application with 350mm fixing centres.
You could coat it both sides with Everdure which will add some strength as well as preservation, you can also epoxy glue it to your alumni framework if you want maximum strength, but that would be unnecessary.
A top quality 10mm marine ply, maple or gaboon would be more than adequate, avoid cheap plywood or plybrace!

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FollowupID: 760849

Follow Up By: The Bantam - Saturday, May 12, 2012 at 09:45

Saturday, May 12, 2012 at 09:45
Yes, I've done little bit of fiddling with boats, a bit of a late starter for the son of a shipright.

I note that shaker is an "evidure man"...there are a couple of schools in wooden boat circles I come more from the "west system" school having defected to "boatcoat"

there is not a large difference between chopped strand and woven mat in strenght....but woven mat is available in thinner material and is better to work with.

woven mat is also better on wood in a single layer with epoxy, chopped strand is more intended for building in glass and resin alone.

the trick it not to try and lay too much resin on at once....epoxy is very much different to work with than polyester and is far far better with wood.

the trick is to use a foam roller and do several thin coats wet on tacky.

the epoxy will wet out the ply and the mat far more redily than polyester, but it takes a few minutes to do so, so ya have to be patient and hold ya nerve.

Put on too much epoxy in 1 coat and the mat will float off the surface of the wood. same if you don't wait enough between coats.

If I am working with sheets, I will tend to apply mat to one side of the board before I cut it up working on up to half a sheet of ply at a time.

The amount of strength you can get out of very thin light material is just stunning.

The optimum coverage of epoxy is considered to be arround the same weight of epoxy as glass.....so with 200GSM matt you are adding arround 400 grams per square meter total.
so adding a single layer of 200GSM mat to a sheet of ply adds arround 1.2Kg to the sheet.

Just laying up a couple coats of epoxy alone on ply improves its strength and certainly its surface stability and abrasion resistsnce...particularly in the thinner materials.

A good quality light weight ply can be half the weight of radiata or luan and just as strong...go the other way to european burch, you gain a bit of weight, but a heap of extra strength and surface resilience.


Ordinary pop rivets work quite well in plywood, the problem with any fastener as the ply gets thinner is the fastener holding in the ply.
Rivets tend to compress the ply where screws tend to chew a hole.

Pulling rivets thru ply into metal, can be quite strong and in the softer plies the rivets will sort of flush in.....100 to 150mm spacing & between 25 & 50mm from corners..... that ply wont be going anywhere

I used to use extrusion that took the ply in a slot and that was incredibly strong

A length of roadcase angle or stair nose across the exposed edge ofthe unit is a good idea...stay away from plain aluminium angle it tends to bur up when it cops a hit, and will open you up like a jam tin.

If you riveted and put a bead of sicaflex on the rails before you fix and that will be realy solid and wont rattle or drum.......hard work if you ever want to pull it up though.

no need for nutserts

cheers
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FollowupID: 760860

Follow Up By: Shaker - Saturday, May 12, 2012 at 14:40

Saturday, May 12, 2012 at 14:40
Everdure is a very thin epoxy sealant that deeply penetrates & rot proofs timber, it used extensively in both new boats & rebuilding old boats.
Epoxy resin cannot be used with chop strand mat.
To be honest, I think it would unnecessary to sheath his timber drawers deck.
My boatbuilding background is with timber boats.

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FollowupID: 760879

Reply By: Crackles - Thursday, May 10, 2012 at 18:59

Thursday, May 10, 2012 at 18:59
I'd be inclined to use 12mm marine ply (Not MDF, construction or form ply) which is the strongest for it's weight, will not bend over time like alloy, not drum or bang & is water resistant compared to other timbers. On mine I recessed the ply top into 20mm angle, frame made of 15mm RHS with alloy tubs & mesh sides for fridge ventilation & to minimise weight.








AnswerID: 485466

Follow Up By: kwk56pt - Thursday, May 10, 2012 at 21:02

Thursday, May 10, 2012 at 21:02
Thanks for all the great replies. Recessing the ply deck in the angle was a great idea. I assume you have found the locking slides stay locked ok ?.The ones I bought have a small amount of back and forward movement when locked which I thought might be a problem on corrugations.. I was wondering how to secure the fridge and the what looks like a chain link cut in half is a idea to consider.
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Follow Up By: Crackles - Thursday, May 10, 2012 at 21:31

Thursday, May 10, 2012 at 21:31
These cheaper locking slides do move slightly but a rubber pad at the rear took the slack out. There are some more expensive yellow handle slides available that are very solid. Non locking slides with a pad bolt may be a better long term solution. The chain link is actually an alloy finger pull handle from Mitre10 which is screwed on & I use a friction strap to secure.
Cheers Craig.........
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FollowupID: 760758

Reply By: Member -Pinko (NSW) - Friday, May 11, 2012 at 16:20

Friday, May 11, 2012 at 16:20
Plywood ute canopy setup.
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Follow Up By: kwk56pt - Friday, May 11, 2012 at 20:30

Friday, May 11, 2012 at 20:30
Thanks Stan for going to the trouble posting the pictures. The drawers look good and the plastic drawers are another good idea. My canopy came with a built in water tank at the front and the last owner had a lpg tank for diesel gas fumigation installed at the rear of the canopy so I have had to work around that. Fitting out is taking a lot more time than I thought but I will get there in the end.
Seems like the wood deck is my best bet. Enjoy your travels...........Peter
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