Lightweight walls

[GPW]

Quote: "saying particle board is crap just shows you don't know squat.. " ... Hmmm??? Perhaps !!! Not the first time I've been told that !!!

re: gussets ... I'd rather have the extra margin of rigidity ... just my preference ... been using them for 50 years ... Absolutely no argument about the skin strength... Maybe I was just thinking too light !!!

[afreegreek]

Quote: "saying particle board is crap just shows you don't know squat.. " ... Hmmm??? Perhaps !!! Not the first time I've been told that !!!

re: gussets ... I'd rather have the extra margin of rigidity ... just my preference ... been using them for 50 years ... Absolutely no argument about the skin strength... Maybe I was just thinking too light !!!

diagonal braces or corner gussets can add some strength to skin/frame panels.. it all depends on the direction the stress is applied. they say leaving screws in doesn't add anything either but it does.. it stops a failed glue bond from getting bigger. a gusset can help prevent that failure by giving something other than the glue joint to take the stress..

[kennyrayandersen]

plywood this and particle board that.. bla bla..

there's many different types particle board just like there's many kinds of plywood.. saying particle board is crap just shows you don't know squat.. there is WATERPROOF particle board, as well as many different densities, glues, and wood fibres to choose from.. there's a few that would be just fine for building a TD out of.. and a few that are not.. just because it isn't at Home Depot doesn't mean it doesn't exist. try thinking outside the big box stores..

We are not worthy… There may indeed be some exotic particle board out there that you could use, but I guarantee it will be heavy, and it likely won’t be cheap. There are so many good, relatively cheap materials to build with; I can’t see too much reason to go gallivanting off on a quest to find the grail, so to speak. Big-box = availability.

diagonal braces or corner gussets can add some strength to skin/frame panels.. it all depends on the direction the stress is applied. they say leaving screws in doesn't add anything either but it does.. it stops a failed glue bond from getting bigger. a gusset can help prevent that failure by giving something other than the glue joint to take the stress..

In a composite panel the skins react the loads and the core transfers the shear between the facesheets. Unless the skins are woefully undersized or you have a complete bond failure (if that happens you got a lot of problems), the diagonal braces will only affect the stiffness insomuch as they change the overall core stiffness (G13, G 23 terms in the stiffness matrix). It’s not that they won’t affect it, but why bother – the skin/core combination is rightfully sized to react all of the structural loads. As Andrew [rightfully] points out, we only need to make accommodations for local attachment loads (local load introduction) which can be accomplished with either buried 1X1s (or so depending on the design) or really the way it’s done is with inserts, which could be, depending on the applied load a 2 inch circular plywood disk the same thickness as the core. The internal gussets or ‘stringers’ /sticks are not needed – they’re put in there to make us feel good about it.

Last year I worked on an 18 foot long helicopter cowling that was made from very light-weight honeycomb (1.8 and 2 Lb per cu. ft. core and graphite, but for a wee bit of weight fiberglass could have sufficed. The thickest core was 1 inch thick, but much of it was only a ¼ inch thick! Except for local load introduction areas, there wasn’t anything buried in the sandwich. For local areas there was either potting compound (solid epoxy with some fillers), or inserts, that were potted into the core (most of those being only 1 inch in diameter). The core you get at bigbox is about the same density, but around ½ the strength (it’s OK, we just won’t drive the tear faster than 150 mph!). I think most people would be quite surprised how strong 2 layers of fiberglass on either side of some foam core can be. The only caution is that when going this light-weight care has to be taken to make sure that the facesheets stay attached (like poking regular small holes in the surface of the foam core etc.).

For most people it might be a bit easier to use the 1/8 ply over the 1 inch thick core than it would be to work with the thin skins and since the plywood has a lot of thickness it actually quite a bit stronger in compression than the thin fiberglass. Still, the fiberglass is going to be the lightest solution this side of graphite ($$$).

[diy4life]

Hi
I was at a show recently and came across this caravan (brit for trailer, lol).

I reversed my car up to it so I could see what it would be like as I'm getting too stiff in the joints to be able to dress in a tent. Apart from the axle, wheels and ball joint it's all wood and coated fabric, so only weighs 5cwt - 560UK lbs @ 16 ozs to the pound.
It set me thinking I could make something similar and came across T&TTT from Google. And here I am.
I am thinking of making a small folder rather than a tear.
I was interested to find that most of your tears seem to be about 1000lbs; my car wouldn't pull that weight as its only 19BHP and weight about 1200 lbs.
Sorry - this rambling is leading to...
I got a stick and hardboard wardrobe door out the loft today - I made 40 years ago. It's 48"x15"x3/4". It weighs 7lbs, so a full 6ft floor would only be about 30lbs if made in the same way. The battens are 1x1/2" along each edge and one across the middle. I placed it on 2 supports 24" apart and stood on it. It barely flexed,so I recon you are still over-designing.
Obviously I would use marine or exterior ply but on a very quick calculation think a complete trailer would end up at under 300lbs.

edit to say the trailer is a 1926 model and a couple of spilling mistales.

[afreegreek]

plywood this and particle board that.. bla bla..

there's many different types particle board just like there's many kinds of plywood.. saying particle board is crap just shows you don't know squat.. there is WATERPROOF particle board, as well as many different densities, glues, and wood fibres to choose from.. there's a few that would be just fine for building a TD out of.. and a few that are not.. just because it isn't at Home Depot doesn't mean it doesn't exist. try thinking outside the big box stores..

We are not worthy… There may indeed be some exotic particle board out there that you could use, but I guarantee it will be heavy, and it likely won’t be cheap. There are so many good, relatively cheap materials to build with; I can’t see too much reason to go gallivanting off on a quest to find the grail, so to speak. Big-box = availability.

diagonal braces or corner gussets can add some strength to skin/frame panels.. it all depends on the direction the stress is applied. they say leaving screws in doesn't add anything either but it does.. it stops a failed glue bond from getting bigger. a gusset can help prevent that failure by giving something other than the glue joint to take the stress..

In a composite panel the skins react the loads and the core transfers the shear between the facesheets. Unless the skins are woefully undersized or you have a complete bond failure (if that happens you got a lot of problems), the diagonal braces will only affect the stiffness insomuch as they change the overall core stiffness (G13, G 23 terms in the stiffness matrix). It’s not that they won’t affect it, but why bother – the skin/core combination is rightfully sized to react all of the structural loads. As Andrew [rightfully] points out, we only need to make accommodations for local attachment loads (local load introduction) which can be accomplished with either buried 1X1s (or so depending on the design) or really the way it’s done is with inserts, which could be, depending on the applied load a 2 inch circular plywood disk the same thickness as the core. The internal gussets or ‘stringers’ /sticks are not needed – they’re put in there to make us feel good about it.

Last year I worked on an 18 foot long helicopter cowling that was made from very light-weight honeycomb (1.8 and 2 Lb per cu. ft. core and graphite, but for a wee bit of weight fiberglass could have sufficed. The thickest core was 1 inch thick, but much of it was only a ¼ inch thick! Except for local load introduction areas, there wasn’t anything buried in the sandwich. For local areas there was either potting compound (solid epoxy with some fillers), or inserts, that were potted into the core (most of those being only 1 inch in diameter). The core you get at bigbox is about the same density, but around ½ the strength (it’s OK, we just won’t drive the tear faster than 150 mph!). I think most people would be quite surprised how strong 2 layers of fiberglass on either side of some foam core can be. The only caution is that when going this light-weight care has to be taken to make sure that the facesheets stay attached (like poking regular small holes in the surface of the foam core etc.).

For most people it might be a bit easier to use the 1/8 ply over the 1 inch thick core than it would be to work with the thin skins and since the plywood has a lot of thickness it actually quite a bit stronger in compression than the thin fiberglass. Still, the fiberglass is going to be the lightest solution this side of graphite ($$$).

right! that's the million dollar question.. are the skins properly bonded to the core? well, most people are not going to get a good bond to foam core. unless they get some proper foam, prep it properly, get the correct adhesive and put it in a vacuum bag to laminate it all together.. most people are going to but XPS foam and a few sticks of solid wood to build your basic foam filled, plywood clad stud wall. in that case gussets will ad plenty..

waterproof particle board is no more expensive or heavy than an equivalent size sheet of baltic birch.. it's made of long strand pine particles and phenolic resin glue. it hold screws very well, even in the edges and... it's water proof.. I wouldn't use it but that doesn't confirm the wives tale that particle board is crap. some is, some isn't. just like plywood, foam, and core-bond.

[teardrop_focus]

diy4life

Hi

I was at a show recently and came across this caravan...

Apart from the axle, wheels and ball joint it's all wood and coated fabric...

Hello! and Welcome to T&TTT.

I'd like to see more pics of this caravan, or pics of similarly-constructed trailers! Can you help by suggesting any more search keywords?

Thanks!

[diy4life]

One of the few places I came across is http://www.historiccaravanclub.com/
I have emailed asking if the member who owns the caravan can contact me. Like an idiot I didn't get his details at the show, even though he showed me the plans for it.
Anther place that has occasional items is http://www.oldclassiccar.co.uk/vintagecaravan.htm
But that is about all I've found apart from tears, Romanies(a bit heavy for small cars!) and airstreams. Traction Engines etc tend to pull large Living Vans - solid wood construction weighting a couple of tons! and definitely not air-smoothed.
I will put the pics up in due course and let you know where.
Dave


Hello! and Welcome to T&TTT.

I'd like to see more pics of this caravan, or pics of similarly-constructed trailers! Can you help by suggesting any more search keywords?

Thanks![/quote]

[kennyrayandersen]

waterproof particle board is no more expensive or heavy than an equivalent size sheet of baltic birch.. it's made of long strand pine particles and phenolic resin glue. it hold screws very well, even in the edges and... it's water proof.. I wouldn't use it but that doesn't confirm the wives tale that particle board is crap. some is, some isn't. just like plywood, foam, and core-bond.

The OP was asking about light-weight construction. I still suggest that the particle board is quite heavy (I looked on the manufacturers website of the product you posted -- it's still pretty heavy). I agree with you that no matter what you use you could screw it up, but making a composite sandwich isn't that difficult and its probably a third the weight. I'm not trying to dis you or anything -- like I said there are special products out there, but for weight, there is not any advantage to it and MOST particle board is still pretty much crap.

[angib]

Can you help by suggesting any more search keywords?

Something very similar you may have found already is the Raven Argonette:
http://www.oldclassiccar.co.uk/ravencaravan.htm

Andrew

[S. Heisley]

Whats especially interesting about this Raven Argonette is that the even the sides are curved. It states that the width is:

Ends, 4'6"
Centre, 5'6"

However, knowing how tight my bench beds are at 5'1" wide, I can't imagine how they got two cots and an aisle in that one.

The plans on this one would be a delight to see.

[kennyrayandersen]

Argonette = cool , thanks for the post Andrew!

[BillZ]

However, knowing how tight my bench beds are at 5'1" wide, I can't imagine how they got two cots and an aisle in that one.

Your average person was much thinner back then.

I was thinking that I may need to go on a diet before I finish my tear just so the wife doesn't get mistakenly squished during the night.

[Shadow Catcher]

Filon composite panels.

[kennyrayandersen]

Filon composite panels.

Do a search on the forum for that... some interesting reading, and it ain't all good...

[oicu812]

Does anybody know or have an estiment of what these different
construction methods wiegh per Sq. Ft. of finished wall?
Thanks in advance.

Tony.