Epoxy/Styrofoam Test Panels

[eaglesdare]

Last go at explaining.....

In Eagles build http://tnttt.com/viewto ... sc&start=0 they built a bulkhead at the rear



and for such a small TD thats all i think is needed.

In the build of pat g http://tnttt.com/viewto ... sc&start=0 this is what they did



Its not very high but its a bulkhead that stops the shear forces

It does not have to be huge or take a lot of pressure just simply stop the initial movement that could break the T2.

i also have a small spar in the front. can't get a pic of that because the mattress is in there now. but its just like the above pic, in is on the floor and the front curve and both side walls are attached to it. so that one piece will stop the front and sides from the moving.
you are right, in my size that is all that is needed.

[starleen2]

perhaps a solution for the sliding factor / inertia principle can be found in the traditional teardrop building methods - adapted to the foam method of construction. In a conventional build - the walls can be secured to the floor via screws from the bottom into a cleat. All that is holding the wall to the floor is some adhesive and screws coming up from the bottom.

Now stay with we - the sliding factor / inertia principle applies here equally - the only difference is the addition of the screws and their shear strength. But as we all well know - screws directly into foam do not really hold all that much! So what to do?

Once the wall panels are glued to the floor, one could drill under from the floor and insert dowels - maybe 4 inches in length - around the perimeter of the floor up into the walls - then secure with the foaming action of the gorilla glue through the entire length of the dowel

[GPW]

Edited for Content ...

[GPW]

S2, Thinking that dowel through the floor is a GREAT idea!!! done along the floor at specific intervals , it would literally stitch the foam to the plywood... eliminating any thoughts of this silly sliding business... Combined with the other reinforcing methods , it would provide the ultimate in security for this somewhat controversial area... Best thing , it's Thrifty too ...

[Conedodger]

GPW:

Wow, come on, that was un-called for, its a discussion and to be fair all along i have said that IMO the join between the foam and the floor is the weakest spot and in fact you have agreed with me. You even thought it a good idea to use an alloy storage box as a bulkhead.

IMO = In My Opinion

Now all of a sudden i'm made out as being negative and my ideas are ridiculous, i dont think thats fair at all, in fact its downright rude.

I am in no way trying to cause a crisis, and i still dont think there is one, i have been very positive all along. These are home built so people can do what they want and make them how they want.

If I made one I would put in a bulkhead and items to stop any possible shear but thats up to me, others will not bother and thats up to them but its better to at least be aware of it, even if you feel its silly.

You have no idea who I am or what I do. Part of my experience is 40 years as an engineer. I have had trailers all my life and towed them many thousands of miles with all sorts of loads including several race cars.

I have seen a race car (not mine) break its straps under breaking and land up in the trunk of the tow car. I have seen a large plastic tank that was strapped on come off on a motorway with a police escort.

I am sure you are aware that Trailers have this knack of losening fixings and that loads that seem to be well strapped down when you leave, are loose a few miles down the road.

So, the questions are

1) Which is stronger, foam, cloth and PVA or the same with a bulkhead and key point fixings?
2) Is foam, cloth and PVA 100% safe to use to secure a TD on the floor?
3) Do you want me to stop posting?

I think until that post the whole thing was very interesting and gave all forum members food for thought about how one should be build, and thats what i thought the forum was for.

If i have upset you for asking questions and giving ideas or for any reason I am truly sorry but to be fair i still cannot see anything I have said thats wrong.

[GPW]

1. who knows ... that's up to you to test ...
2. Maybe ???
3. of course not ... everyone is entitled to their opinion ... and we most welcome your ideas and input !!!

[Wobbly Wheels]

A couple things - first...just a thought here as an alternative to dowels...if you ran a length of flexible pipe like pex in place of the dowels, you could use a long screw and fender washer through the pipe and into the ply. The washer holds the foam and the pex prevents it cutting in.

An added advantage came from installing porcelain heads in boats...whiuch requires a short story that someone can hopefully use in a similar application :

The flange on the bottom of the heads I was installing had mounting holes cast through it, one on each side. Now, in order to get that to sit tightly without rocking, it took a careful torquing to get it JUST to the point where the head didn't rock back and forth when a 250lb fitter sat on it ;^)
A 1/4 turn too much and you hear a "tink" and have to order another because you just busted the flange...
You can't use any kind of adhesive as a 'helper' because you need to be able to get at the pump inside to service it, ideally every year.

It didn't take long to figure out that I could cut a piece of pex so it sat on end inside the cast hole and stood proud of the flange about 1/16". When you run the screw/washer in, the washer compresses the pex and it bows out ever so gently and 'grabs' the inside of the hole. I think something like that would work well here because you wouldn't exceed the compressive limit of the foam and split it.

Just a thought (albeit a long one!)

Also: since I started the thread I figure I should get my .02 in here.
I appreciate the perspective of those who have been there and done that.
GPW - please continue to share your thoughts, especially since you seem to know your way around this stuff pretty well. Being new to this, I'm as interested in Cone's concern about that joint as I am in the arguments for your lack of concern.
Conedodger - I think we are alike in that it's FAR easier and more productive to exhaust a line of thought rather than figure out why something broke. I agree that shear loading on the wall/floor joint is a force that absolutely does need to be considered though we are of varying opinion on its priority.

Now can't we all just get along ?
Lol

[Conedodger]

1. who knows ... that's up to you to test ...
2. Maybe ???
3. of course not ... everyone is entitled to their opinion ... and we most welcome your ideas and input !!!

Answers are IMHO
1. Using a bulkhead or dowel fixing is a must and will be stronger, and it does not need a test. I just brought up a safety issue, and I am sure you will agree its better to over engineer while building than it break.
2. You say "Maybe ???", and that was my point, maybe is just not good enough.
3. You say everyone is entitled to their opinion ... and we most welcome your ideas and input !!! - however you called my ideas and input "Negative, Ridiculous" and since "silly", yet you praise the dowel idea. This i cannt understand, if there is no problem why do you need the dowels

The one thing is Safety is not silly and anyone who thinks it is needs to think again.

T2 clearly states its not for structural joints, and thats not because its does not stick, its because it has no give at all, when under strain it can snap all of a sudden. Using dowels, bulkhead as the structural fixing all the T2 is doing is holding the joint together rather than structural

[Conedodger]

Now can't we all just get along ?
Lol

Please

[GPW]

Cone , you have a very good point of consideration ... Lets try to work it through... together...

[Conedodger]

Still feel a bit shell shocked at your post GPW but will carry on posting.

Below is a link to a video, now before you comment please ( be nice ) read the following twice.

The video is little to do with a TD, the guy in the tow car is stupid and it would only happen if you were stupid. Its nothing to do with foam or our construction discussion.

It does show what happens when a normal caravan fails at the weak point where the floor and box meet and i admit these are the most exceptional circumstances. This one looks like its built using more traditional methods and it takes a lot to make it shear. It does not have a flat floor so has to lift first.

So why show it? (Other than it made me laugh )

Well the video does show the floor staying put, bolted to the chassis and the box parting at the join. Now I am not saying this will happen just what would happen if this structural joint failed and I also feel it highlights how little structural jointing is needed to make this point safe.

http://www.youtube.com/watch?v=iEHHkx929T8

IMO the joint on this trailer was safe before the driver went stupid but here in the UK we regularly see news reports of caravans turning over on the motorways in high winds and most keep their integrity intact. Here is one ftom the USA

http://www.youtube.com/watch?v=kwOqARlw1EI

Now thats what you call a standy.........

[GPW]

That was Funny !!! What an Idiot !!!
video#2 .. That was Scary .... hopefully our smaller trailers will offer less wind resistance than that Huge Box... Top of the hill ... bad spot for wind... food for thought... Thinking too a lot of those RV's are Top heavy , with appliances, AC mounted high up ...
I had more thoughts about your cargo box idea... Was going to go over to my friends little guitar factory , he's got some thin "diamond plate " aluminum ... Thought of this fixed to the front with Mike's inset dowel idea , mostly as a stone guard ... but if we had a nice Aluminum cargo /storage box, and bolted all that together , that should really strengthen the front ...an aluminum bulkhead ... What do you think ???

Ps .Please excuse my curmudgeonly ways, just an old fart living in the woods trying to build a trailer before hurricane season ... It sometimes gets a bit wet here, have to leave for a while ... Trying to do this "on the cheap " (retired)

That and everybody has a Bad day !!! Sorry to take it out on you ... and the dog ..

[Conedodger]

GPW:

I think i already said sorry and I agree we all have off days and as I get older there are more and more.

No problem, All forgotten

Your alloy box sounds like a great idea, 3 birds with one stone, bulkhead, stone guard and storage.

I spoke to my 91 year old dad today and he has been a carpenter all his life. I asked him about PVA and he said "I always used just PVA on wood joints, thats why the legs fall off after a few years". He was told that you make a structural joint that will hold on its own and use the PVA to stop it moving.

When i talked to him about the dowel idea he said they used that idea years ago on some foam injected panels for a building job but he went on to say "remember to put the dowels in at different angles rather all drilled straight in or it will simply lift off". He explained its structurally better as the panel could never lift as it could with them all straight in, he said think of a dovetail joint, if it was cut straight it would pull out.

He also said they cut a slot in deep into each dowel, glued them in and then put a long wedge in each so they were solid in the core and the ply floor. Then when all dried they cut them flush

Sounds like a good idea to me.

Now go and pat your dog.....

[GPW]

Nothing like the voice of experience eh !! Dad knows all the Good tricks ... I'm writing that down ... !!! Thanks !!!

The dog won't have anything to do with me ... unless I have Food ... Dogs ..

[starleen2]

"remember to put the dowels in at different angles rather all drilled straight in or it will simply lift off". He explained its structurally better as the panel could never lift as it could with them all straight in, he said think of a dovetail joint, if it was cut straight it would pull out.

He also said they cut a slot in deep into each dowel, glued them in and then put a long wedge in each so they were solid in the core and the ply floor. Then when all dried they cut them flush