That floor to wall join ...

[GPW]

Now there have been several comments that our floor to wall joinery might NOT be sufficient We always assume we'll be operating under normal conditions, but should some odd thing happen ( bumps, potholes, streets/roads that are like an off road course), that must be planned for ... And there have been several Good and valid ideas to help cure this problem ...
1. Bulkheads... we know that works from previous builds... and the sage recommendations of others. The novel idea of using a storage box on the tongue mechanically attached to the front to "serve" as a bulkhead Is just another brilliant solution ...
2. Pinning the foam to the plywood with dowels ... another Good idea! Thrifty too
3. Fiberglassing that whole area.. Messy but effective...
4. Attaching inner structure to the floor (beds cabinets,etc.) and then anchoring the foam to those , through the cabin.
5. Using inner skins of plywood and a "board " mechanically attached to the floor , the foam glued to that...
6. Using a combination of all of these ...

This is the place to work this out ... We Don't want anyones trailer falling apart for lack of reinforcement ... Since this is all new , we're all still learning ... Any ideas on this ... ??

[GPW]

Now Cone's Dad has straightened us out about the dowel method... He says to put the dowels in at an angle , opposing angles down the line , like a dovetail joint ...

"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 " - Cone'

An even More secure method !!!

Keep this up and we might just find something Bear Proof yet ...

[mikeschn]

I'm at the point where we are evaluating the wall to floor joint now. Granted it's just dry fitted, and you can't compare foam to wood in this state... But the foam sure seems weak.

So my first thought is to laminate the inside with wood, which of course would substantially improve the strength of the wall to the subfloor joint. And being that the wood is on the inside, we are still not increasing the risk of wood rot.



Mike...

[Conedodger]

I think your design is a first for foamie Mike and sorry to say has an inherant problem. Foam has very little if any structural strength from what its constructed of, it does however have amazing compressive strength. With this in mind any stress needs to try to compress the foam, and as such the foam needs to sit on the floor so all the stress compresses into the floor. In your design where the foam goes past the floor all the stress will be on your fixings. I cant see how the foam could stand the pressure of the wall moving side to side or downwards without a good really skin to take all this stress. Basically the only way i can see that working is a sandwich of wood or wood and alloy sheet making it a normal construction with foam insulation.

The look you are after can still be achieved using foam as this build http://www.goldbrand.info/motorcykelhusvagn2.html shows

About half way down the page you will see he adds a foam filler under the floor but the top wall is still on top of the floor.

I will be very interested to see what folks come up with on this one

Very interesting problem so its thinking cap on............



Now all i have to do is get my brain to work .........

[GPW]

Mike , I'd sure put some paneling on the inside of the foam ... Nice woody interior, much stronger walls ...

Saw on a home show , a guy was saying that even untreated wood lasts just fine indoors ... guess the same goes for trailers with a protective shell on the outside ...

It would be interesting to know what the Old Time Trailer builders thought of their materials , several years down the road ... They covered everything with canvas... Yet I've never seen any really old trailers ...

[starleen2]

Just musing around with the dowel idea and came up with this – how about routing a ¾ inch strip in the foam and gluing in a ¾ strip of wood. You could glue and screw the wood strip to the floor – then attach / glue the foam – then add the dowels horizontally?

[mikeschn]

Sometimes it good to sleep on these things. I now have a new idea for mounting the walls to the floor, that puts the walls into compression.

I'll start by gluing a 2" key to the sides of the subfloor. Then I'll cover the subfloor with 1/2" plywood. Next I'll cut a hole in the sidewalls equal to the size of the key and plywood. I'll slip the sidewalls over the keys and set them on top of the floor. Voilà! Compression!!!

Mike...

P.S. If you can't picture that, swing by later, when I have some photos for you to look at!

[Conedodger]

Just had a talk with my 91 year old dad, I think if he was younger he would love to build one. He sees it like builting a huge canvas canoe. The canoe frame would is the structure and the canvas keeps out the water while at the same time keeps the joints in place.

He came up with one very good point. he said:

"If i was building one, i would design all the joints so the whole thing would hold together on its own without its coverings or using glue, that way all the canvas and glue is doing is holding the joints from moving as extra security."

I think he has a point and as long as we all remember that Wood glue (PVA) is not suitable for structural joints we should design accordingly.

[Conedodger]

Sometimes it good to sleep on these things. I now have a new idea for mounting the walls to the floor, that puts the walls into compression.

I'll start by gluing a 2" key to the sides of the subfloor. Then I'll cover the subfloor with 1/2" plywood. Next I'll cut a hole in the sidewalls equal to the size of the key and plywood. I'll slip the sidewalls over the keys and set them on top of the floor. Voilà! Compression!!!

Mike...

P.S. If you can't picture that, swing by later, when I have some photos for you to look at!

The way i see what you are doing sounds good, basically you will be making 2" slots in the foam and putting 2" keys on the floor. Maybe you 2" keys could also be cut at differing angles so the act like dovetails. Angles one way screwed to the frame first with a matching slot and then others angled the other way screwed on after the foam is on into thier matching slots. It would still need a lot of slots so most of the forces are compression but the whole thing could key together nicely.

[GPW]

Question: If T2 is not "structural" why has it worked so well (for me) in the past... I've made Furniture , which gets sat on ... Take my rocker , 3/4" ply , T2 and a few brads .... been rocking on it for 11 years now ...it doesn't even make those "cricking " noises...
Been building guitars with T2 for many years ... never had one come apart , even after soaking for a month in toxic waste water during Katrina ... And they endure much abuse on stage and with X lbs. of compression on them All the time ... I
We even made many English Longbows with T2 for the laminations... Never a problem , even with the extreme bending of the wood (wooden spring)... Regularly thump the competition at Archery shoots with these...
So What exactly do we mean by "structural "

Cone' I think Dad would have really enjoyed making the more vintage aircraft style trailer ... all strip and stringer woodworking , laminated steam bent profile ribs... covered with the canvas... (think AVRO) I'll bet he could have made a real Beauty !!! All advanced woodworking... like a Canoe/kayak

TDs are merely inverted boats eh ??? Sorta'

[mikeschn]

Here's the key on the side of the subfloor...



and here's the hole in the foam for the key...



Mike...

[Conedodger]

In joints its all to do with area and having no movement on any right angle joint. Bonds with large surface areas are more difficult to break.

Titebond II has amazing strength when used on materials its designed for and remember foam is not one of those listed.

Lets take it as read that you are a good woodworker so your joints before the brads would be tight in the first place and no doubt the chair design is not all right angle joints in the same oriontation. PVA will not fill a hole, well it does but it will have no strength. It works on a tight joint where the PVA bond just helps the mechanical joint and stops the movement.

Your guitars are wood to wood bond and thats different as its what PVA is for and no doubt they will have really tight joints over a large area

As to the longbows, again thats wood to wood so the joint is stronger than the wood and no doubt the wood was clamped tightly together.

Clamping the parts together make the joints stronger and we cant clamp the cloth as far as i can see.

I think this explains:

http://www.titebond.com/Download/pdf/HowStrongisYourGlue_FWW.pdf

And this

http://www.titebond.com/download/pdf/ww/PremiumIITB.pdf is about Titebond II and it clearly states under limitations "Not for structural or load bearing applications" as does all PVA glues

Titebond II / cloth should not work as the foam is not porous but it seems to work, but I think thats just because its bond is over such a large area that the load is spread so it just does not move.

By the way we should refer to it as TiteBond II as T2 is a polyurethane glue made by Sika. (Which may well work better.....)



Maybe we should have a post with links to product spec sheets so people dont get mixed up.

--------------------------------------------------

As to my dear old dad well he cant remember what dod of the week it is, what he had for lunch or that i called him 10 minutes ago but he can remember the war and all his working life and i am sure he would have made an amazing TD

[mikeschn]

By the way we should refer to it as TiteBond II as T2 is a polyurethane glue made by Sika. (Which may well work better.....)

How about TB2?

Mike...

[Conedodger]

Here's the key on the side of the subfloor...

Great cutting Mike, that may well work

[GPW]

That key and slot is pretty ingenious!!! do you plan on covering the inner wall first ? Seems that would only make it stronger spreading the load ... Great solution Mike !! IMHO...
Cone thanks for the glue tips ... so much yet to try !!!