OT Wood strength question

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dlovett
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OT Wood strength question

Post by dlovett »

So to make the floor for the bike trailer I need to put a piece of wood on to of the metal frame which is approximately 90cm x 70cm. It needs to support a max weight of 60kg. Can anybody suggest what would be the lightest wood to use and how thick it would need to be.

Many thanks

D
Lazarus
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Re: OT Wood strength question

Post by Lazarus »

is the frame supported underneath - ie is the one piece of wood all that provides support?
Either way not very thick - look how thick the wood on a pallet is and what weight they can support.
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Re: OT Wood strength question

Post by Mariner »

Cant help with dimensions but I would be looking at constructing a 'T' shaped beam possibly from a laminate like marine ply.
Use the direction of sag in one to counter act the other.
If you google around looking for wood strength figures I am sure you could come up with a mathematical model. You are dealing with span and load points.
Me I would just build it. Get some off cuts if it stands my weight its good. If it breaks go thicker.
I am not a structural engineer. :oops:
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dlovett
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Re: OT Wood strength question

Post by dlovett »

I was guessing at 10mm think marine ply?? The frame only supports the wood on the edges so perhaps I do need some kind of extra battens on the underside of the wood between the frame.
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Re: OT Wood strength question

Post by Bearbonesnorm »

If you've got some sort of support / framework beneath, then 9mm marine ply will be fine.
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Re: OT Wood strength question

Post by psling »

Sorry to be a pedant but when most people refer to "marine ply" they are generally talking about exterior grade ply. Exterior grade ply will be bonded with waterproof adhesives (WBP) and I would recommend sealing any cut ends with a waterproof varnish to help delay delamination. 'Marine Ply is bloody expensive; exterior grade ply is much less so!
I would agree with others though that to help support sheet materials such as 9 or 12mm hardwood ply you will need some sort of cross-frame support to reduce bowing under 60kg load on a 90 x 70cm area.
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Re: OT Wood strength question

Post by Bearbonesnorm »

Absolutely Peter ... exterior ply :wink:
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Re: OT Wood strength question

Post by psling »

Bearbonesnorm wrote: Fri May 31, 2019 10:55 am Absolutely Peter ... exterior ply :wink:
:grin:

(I've been holding myself back from writing an essay on some of the other recent threads - you can probably guess which ones!! - so I thought just a very small rant on this one would be Okay! Either that or chuck the computer and shun soshal meeja :smile: )
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Re: OT Wood strength question

Post by Cheddar Man »

You don't ever really need a belt and braces, unless you are parachuting.

It's only a small area, it's a static(ish) weight, put a light strip of whatever wood you have lying around underneath as a support, bingo. 6mm will be more than enough, you could probably get away with a piece of that stuff that Ikea make the back of bookcases with! You are in danger of towing your body weight around if you use 12mm ply, a baby trolley and a 50+kg dog.
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Re: OT Wood strength question

Post by whitestone »

Domestic flooring uses 400mm centres between joists so a couple of battens equidistant along the long axis should be more than enough.
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Re: OT Wood strength question

Post by dlovett »

Its actually a fair bit smaller than I thought, 55cm x 72cm. I've been to Jewsons and they Kindly gave me some offcuts but boy is it heavy. I'm guessing it's 12mm thick and weights a ton. They also gave me some softwood in 5x55cm to make two cross battens. I think I will try to get a anti main piece a bit thinner to keep the weight down as it was noticeable. I have also leant that the trailer won't fit on either Sonder due to the way it clamps round the chain stay. It looks like the modern Thule Chariots with their QR mounts, have kept the same connection bar and ball joint, so I be able to get one of those and use it with the Camino. It might even be possible to drill one out for the fat bike's through Axel. In the meantime I had to dig out the old road bike that isn't disc and it clamped on ok. 6kms ridden so far and it wasn't too draggy, however I would think that 25km/h will be about the top speed if that when fully loaded as per it's maximum spec.
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Re: OT Wood strength question

Post by Al »

If you find a reasonably priced source of those ball joints can you let me know - our kids trailer doesn’t fit on anyone’s bike now as they’re all disc brakes.
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Re: OT Wood strength question

Post by dlovett »

This seems to be the cheapest one I have found.
https://www.deporvillage.net/kit-comple ... eTEALw_wcB

I am hoping though that I can get away with just getting the we hitch mount, although with all the bits you get the first one might be a better deal overall. Still I have a floor to sort and a dog to test ride it before I buy any other bits for it.

https://m.bikester.co.uk/397465.html?_c ... AfEALw_wcB
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In Reverse
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Re: OT Wood strength question

Post by In Reverse »

Cheddar Man wrote: Fri May 31, 2019 11:26 am You don't ever really need a belt and braces, unless you are parachuting.

It's only a small area, it's a static(ish) weight, put a light strip of whatever wood you have lying around underneath as a support, bingo. 6mm will be more than enough, you could probably get away with a piece of that stuff that Ikea make the back of bookcases with! You are in danger of towing your body weight around if you use 12mm ply, a baby trolley and a 50+kg dog.
I'd just like to say that I completely disagree with the above - do NOT put your dog on "that stuff that Ikea make the back of bookcases with". :lol: :lol: :lol:

12mm marine ply weighs just under 7kg per square metre, so a 0.9 x 0.7m piece should weigh 4.4kg. It should be strong enough without any further supports - I can probably do the calcs to check if you really wanted. Waterproof it with yacht varnish or similar - you'll be able to pick up a small tin from Screwfix/B&Q etc.

edit - having read your post if you want to go lighter you can use lats (like under a mattress on a bunk bed) spaced out. You'd need to fix them at the edges and put some sort of foam or whatever over the top, but it would be lighter.

Awésome dog anyway Duncan :-bd
Last edited by In Reverse on Fri May 31, 2019 6:28 pm, edited 3 times in total.
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Re: OT Wood strength question

Post by Bearbonesnorm »

Waterproof it with yacht varnish or similar - you'll be able to pick up a small tin from Screwfix/B&Q etc.
Yes and buy that stuff that does exactly what is says on the tin - that way there'll be no nasty surprises or dogs stuck to bits of wood :-bd

I buy a lot of yacht varnish as I'm trying to convince the girl in the DIY shop that I'm an eccentric millionaire.
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Re: OT Wood strength question

Post by dlovett »

Yes I am thinking that that is the best idea after all I really need to try and keep the weight down.

Cheers, he is a top dog!
In Reverse wrote: Fri May 31, 2019 6:13 pm
Cheddar Man wrote: Fri May 31, 2019 11:26 am You don't ever really need a belt and braces, unless you are parachuting.

It's only a small area, it's a static(ish) weight, put a light strip of whatever wood you have lying around underneath as a support, bingo. 6mm will be more than enough, you could probably get away with a piece of that stuff that Ikea make the back of bookcases with! You are in danger of towing your body weight around if you use 12mm ply, a baby trolley and a 50+kg dog.
I'd just like to say that I completely disagree with the above - do NOT put your dog on "that stuff that Ikea make the back of bookcases with". :lol: :lol: :lol:

12mm marine ply weighs just under 7kg per square metre, so a 0.9 x 0.7m piece should weigh 4.4kg. It should be strong enough without any further supports - I can probably do the calcs to check if you really wanted. Waterproof it with yacht varnish or similar - you'll be able to pick up a small tin from Screwfix/B&Q etc.

edit - having read your post if you want to go lighter you can use lats (like under a mattress on a bunk bed) spaced out. You'd need to fix them at the edges and put some sort of foam or whatever over the top, but it would be lighter.

Awésome dog anyway Duncan :-bd
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Re: OT Wood strength question

Post by Cheddar Man »

In Reverse wrote: Fri May 31, 2019 6:13 pm
Cheddar Man wrote: Fri May 31, 2019 11:26 am You don't ever really need a belt and braces, unless you are parachuting.

It's only a small area, it's a static(ish) weight, put a light strip of whatever wood you have lying around underneath as a support, bingo. 6mm will be more than enough, you could probably get away with a piece of that stuff that Ikea make the back of bookcases with! You are in danger of towing your body weight around if you use 12mm ply, a baby trolley and a 50+kg dog.
I'd just like to say that I completely disagree with the above - do NOT put your dog on "that stuff that Ikea make the back of bookcases with". :lol: :lol: :lol:

12mm marine ply weighs just under 7kg per square metre, so a 0.9 x 0.7m piece should weigh 4.4kg. It should be strong enough without any further supports - I can probably do the calcs to check if you really wanted. Waterproof it with yacht varnish or similar - you'll be able to pick up a small tin from Screwfix/B&Q etc.

edit - having read your post if you want to go lighter you can use lats (like under a mattress on a bunk bed) spaced out. You'd need to fix them at the edges and put some sort of foam or whatever over the top, but it would be lighter.

Awésome dog anyway Duncan :-bd
Yep vaguely exciting dog!

But don't over-engineer the solution to this problem. If you don't believe 4mm plywood is strong enough, you are welcome to come and have a paddle in my 4mm Marine ply canoe anytime. And I am much more than 50kg. I don't jump and down in it, just sit calmly and paddle along

Image
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Re: OT Wood strength question

Post by In Reverse »

Nah you're alright mate :grin:
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Re: OT Wood strength question

Post by Cheddar Man »

In Reverse wrote: Fri May 31, 2019 6:58 pm Nah you're alright mate :grin:
It's essentially a packraft :grin:
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Re: OT Wood strength question

Post by In Reverse »

If it was made out of cheddar I'd definitely be interested :-bd
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Re: OT Wood strength question

Post by dlovett »

Cheddar Man wrote: Fri May 31, 2019 6:41 pm
In Reverse wrote: Fri May 31, 2019 6:13 pm
Cheddar Man wrote: Fri May 31, 2019 11:26 am You don't ever really need a belt and braces, unless you are parachuting.

It's only a small area, it's a static(ish) weight, put a light strip of whatever wood you have lying around underneath as a support, bingo. 6mm will be more than enough, you could probably get away with a piece of that stuff that Ikea make the back of bookcases with! You are in danger of towing your body weight around if you use 12mm ply, a baby trolley and a 50+kg dog.
I'd just like to say that I completely disagree with the above - do NOT put your dog on "that stuff that Ikea make the back of bookcases with". :lol: :lol: :lol:

12mm marine ply weighs just under 7kg per square metre, so a 0.9 x 0.7m piece should weigh 4.4kg. It should be strong enough without any further supports - I can probably do the calcs to check if you really wanted. Waterproof it with yacht varnish or similar - you'll be able to pick up a small tin from Screwfix/B&Q etc.

edit - having read your post if you want to go lighter you can use lats (like under a mattress on a bunk bed) spaced out. You'd need to fix them at the edges and put some sort of foam or whatever over the top, but it would be lighter.

Awésome dog anyway Duncan :-bd
Yep vaguely exciting dog!

But don't over-engineer the solution to this problem. If you don't believe 4mm plywood is strong enough, you are welcome to come and have a paddle in my 4mm Marine ply canoe anytime. And I am much more than 50kg. I don't jump and down in it, just sit calmly and paddle along

Image
That sir is a rather beautiful watercraft.
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Re: OT Wood strength question

Post by dlovett »

Of course when not carrying a dog, the trailer will carry things like a proper sized tent, a proper size stove, a proper sized inflatable kayak and other proper non ultralight race kit for camping trips. I try not to use my car for anything other than long journeys and not anything on the island now, so the ability to carry more stuff will be welcomed.
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Re: OT Wood strength question

Post by RIP »

"I buy a lot of yacht varnish as I'm trying to convince the girl in the DIY shop that I'm an eccentric millionaire" - :lol: . Just walking through the door instantly convinced her about one of those two attributes. Not sayin' she was right 'cos first impressions can be deceptive. Especially with bikepackers.
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Re: OT Wood strength question

Post by middleagedmadness »

If you have no or little support use a piece of wisi-deck will more than support 60kg is weather proof both sides and about 8-10mm thick
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Re: OT Wood strength question

Post by Cheddar Man »

Another low cost and low weight solution would be to use webbing like in the bottom of a chair? A bit of clever weaving and you would be left with a very sturdy base, extremely strong and tremendously light.

Webbing is cheap to, you could proof it quite easily with a bit of something or other.
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