Mechanical Fasteners

[alftinc]

Has anyone built a teardrop with just glue, and no mechanical fasteners like screws and nails? I know the hinges and etc would need them, but i am talking about floors, walls framing, etc.

[madjack]

I can't even imagine doing that...your camper is going to be subjected to hurricane force winds and severe G shock loadings...put some fasteners in any thing structural...PLEASE........
madjack

[Miriam C.]

My take on it---if you glue you are bonding the veneers of each layer to the other. If the veneer fails I used the daylights out of screws. And even put some brads in the trim.

[Steve_Cox]

NO SCREWS, NAILS or STAPLES??

Both of my trailers the 1/4" plywood sides and top were put on without putting holes in it. It was attached with thickened epoxy. But, there were more than a few pounds of screws holding everything else together.

Even my doors are put together without fasteners... except on the hinges and latch

[kennyrayandersen]

It is certainly possible, but requires a firm understanding of the engineering principles involved. Adhesives are very good in shear, but poor in tension (generally). Designing so that there are only ever shear load in ALL of the joints is challenging, though not impossible. Typically, screws are used to assemble and hold the structure whilst the glue sets up (yellow glue or epoxy). The shear capability of most modern adhesives rivals the strength from mechanical fasteners, and certainly the base material itself; however, the adhesive would be especially superior in material that have low bearing strength. My build will have fasteners that join the parts together, but the joint strength will be due to the adhesive (plus there will be fiberglass fabric plies on the inside and the outside of the joint (the interior of the joint reacts the shear and the fiberglass plies react the joint tension on the outside of the joint)).

[wannabefree]

What they said. If you have infinite time, infinite patience, and a near endless supply of clamps go for it. It would be a challenge. I started my tear in October, and after 6 months of spending every weekend on it, nails and staples are acceptable shortcuts.

[kennyrayandersen]

To clarify a bit. Screws don't come loose like nails or staples. Nails or staples are good for tacking the material together while the glue you put on before you tacked them together dries. Joints that are glued and screwed are going to be the strongest and last the longest. The point I was making is that the glue, in the end, is where most of the strength comes from unless you got a LOT of fasteners (which seeing some of the final weights I'm inclined to believe that there was no shortage of fasteners used.

I mostly use drywall screws when I screw everything together. Even on the composite build I'm scheming on, I will have 1x1 strips buried in the panel that I will use to biscuit, glue, and screw. Stuff usually breaks at either fasteners or local load introduction points (often they are the same location). Once the joint dries though, I think that the real strength comes from the biscuits and glue. IF you crush the part after is sets up the joint won't be the spot that breaks -- it should be the basic material.

[Rock]

I'm using Miller Dowels.

http://www.millerdowel.com/

These things go in tight, are self aligning and you really don't need clamps but I use them. If you try to pull one out right after installing it you can't. (I know - I installed a birch dowel on the exterior by mistake and it sticks out like a sore thumb but it ain't coming out short of drilling it.)

I don't have any data, but I bet they're stonger than drywall screws in shear and bending, and with Titebond III I bet they're stronger in tension. (Due to pullout of the substrate.)

I'm using Black Locust flavor which is a wood that can stand in the ground as a fence post for 50 years before it rots. And the wood seems to have the tenacity of Hickory.

I'll let you know if it falls apart.

Eric[/quote]

[aggie79]

I'm using Miller Dowels. http://www.millerdowel.com/

I've been interested in these for a while and can see where they have their advantages. Keep us up to date on how they work for you.

[RichAFix]

When I first read this I was thinking "why"? After a few postings I am starting to understand. On the inside of my roof I have will have any issue as the wood will have to attach to the spars but I don't want to see the fasteners from the inside. This is very much a concern as being on the inside of the curve the wood will not hold until any glue could possible set up. This however is nothing structural. I am intentionally using hard wood rather than plywood in some areas (when a fastener is going into end grain) as I know that plywood and screws/nails don't play nice together.

I guess I never really thought much about screw vs. nails much before, just always used screws when they would be hidden and brads when I was trying to conceal them.

This posting has been very informative, thank you all. Maybe I knew it all along, but I feel like I learned something today. It is a good day.

[Mark McD]

I've also used Miller dowels for joinery, but always in conjunction with adhesive. The joints are rock solid and look nice.

Like Aunti M. said...

The problem with foregoing the use of mechanical fasteners lies in the strength of the materials being fastened. Most glues, including yellow glue and epoxy and poly glues will have a stronger bond than the materials being bonded,especially when using cheaper grade "Chinese box store plywood". Next time you go to Home Depot, look at the Chinese products; they aren't rated because they aren't sheathing/flooring- they're "construction panels". Ply seperation and delamination could cause serious problems given the bond will only be on the surface of the materials, in most cases, a face veneer that is thin as paper.

Now a product like Baltic Birch, while still not rated, is far superior to the Chinese ply and would be better suited to all adhesive construction. For my piece of mind,and 25 years experiance in building trades, I 'll use fasteners when needed.

[halfdome, Danny]

I mostly use drywall screws when I screw everything together.

Drywall screws are not for building things as they are weak and can snap while screwing them in. It would be better to use a screw like Home Depot sells under the Western States brand. They are black square drive multipurpose screws with a coarse thread. They go in fast and really pull things together. As far as using staples with glue it's the glue that holds the joint together. I staple and glue two layers of Baltic Birch for my roof that becomes a very strong formed roof. Danny

[Senior Ninja]

Hi TD Builders,
I used mechanical fasteners where ever I thought they were needed. Trailers are towed into some very strong winds and subject to torsional and vibratory stresses. I think fasteners are well advised. I positioned them where they are covered as much as possible. I was introduced to pocket hole screws and made good use of them in areas such as joining the rafters to the sides. I also used yellow glue liberally in the build.
Steve

[Walt M]

I've been building modular classrooms for about 11 years. Everything we assemble is both glued and mechanicly fastened. I have had a time or two when something had to be changed the nails pull out be the adhesive just doesn't let go. I've learnd it's cheaper to build a new wall than try and dissemble the old one. All that being said. On my tear. I used mostly PL urethane adhesive. no fasteners in the head liner or on the walls, both inside and out. I used fasteners and adhesive to apply the 5'x5' balitc birch to the floor framing. I used the cleat between the panels method to fasten the walls to the floor with coarse drywall screws (I also used pl glue. and I glued the 1/8 roof ply (two layers) and finish stapled it down till the glue dried. Walt

[kennyrayandersen]

I mostly use drywall screws when I screw everything together.

Drywall screws are not for building things as they are weak and can snap while screwing them in. It would be better to use a screw like Home Depot sells under the Western States brand. They are black square drive multipurpose screws with a coarse thread. They go in fast and really pull things together. As far as using staples with glue it's the glue that holds the joint together. I staple and glue two layers of Baltic Birch for my roof that becomes a very strong formed roof. Danny

The reason they make a torque setting on the drill is so that you can set it not to rip the head off the screw or spin the fastener in the hole. There are better screws and better screw systems out there -- no argument from me on that; but, the drywall screws are fine when assembling stuff together as the strength comes from the adhesive, as I and you both noted, and not due to the screws. If a person has a pile of them laying around there is no reason not to use them. I've build dozens and dozens of loudspeaker boxes, tooling, forms etc using them. To keep the head from busting a #6 (or #8 also works) countersunk bit is used first, then the screw. I manufactured speakers for a while and got quite good at using them. I'll probably switch to the square-drive type when I run out, because they are a bit better, but I have a 25 Lb box that I might be using for a while.

The big thing is that I think most people underestimate the power of glue, but it works especially good in wood as the wood is porous and so you get penetration on both sides of the bond as they suck up the glue. The resulting joint is stronger than the wood itself.

It's personal preference, because either dowels or biscuits will work, but I prefer biscuits to dowels as they are much easier to line up. You can make all the biscuits before hand with out having to do a drill on assembly-type procedure. If you are letting something show from the outside, as with the trim on a woody, then the Miller dowels look good, but that procedure is IMO more time consuming and the biscuits will be strong enough for internal-type joints.