A Trailer Without Fasteners?

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A Trailer Without Fasteners?

Postby nbcarey » Sun Oct 10, 2021 7:36 pm

Using structural adhesives to build trailers with far fewer fasteners.

https://www.assemblymag.com/articles/86 ... r-assembly

https://www.henkel-adhesives.com/us/en/ ... ailer.html




Structural adhesives help assemblers of trucks, trailers, buses and other specialty vehicles reduce costs, boost throughput and improve aesthetics.

Manufacturers of specialty vehicles, such as trailers, truck bodies, buses and construction machinery, are increasingly using adhesives and sealants to assemble frames, panels, booms and cabs made of metal, plastic and composites. By building these components with adhesives and sealants instead of welds, threaded fasteners or rivets, engineers can reduce assembly costs, increase throughput, distribute stress more uniformly and improve aesthetics.

To prove the efficiency, durability and cost-effectiveness of adhesive assembly, we acquired a trailer frame-7 feet wide and 10 feet long-and constructed a work trailer almost exclusively using adhesives and sealants. The few fasteners that did make it into the trailer were used to temporarily hold components in place while the adhesives cured. No fasteners were used to provide structural stability.

Some adhesive applications on our trailer have already been tried and tested in the field. However, we also tried many new applications for adhesives and sealants. The end result is a tougher, more reliable, better-looking trailer that cost less to build than a conventional model.

Step by Step

Bonding bed to frame. In traditional trailer construction, the floor is attached to the frame using mechanical fasteners, a time-intensive process that leaves the trailer susceptible to water damage.

In our project, we bonded the wood floor to the frame using Loctite 5570, an elastic adhesive and sealant that distributes the load evenly over the entire frame and prevents water from leaking in through the floor panels. Only four screws per panel were required to install the entire floor. All totaled, we installed the floor in just 10 percent of the time that would have been necessary had we used fasteners alone.

Loctite 5570 is a one-part adhesive based on a modified silane polymer. The adhesive cures by reacting with atmospheric moisture. Skin formation and curing times depend on humidity, temperature and joint depth. Under normal conditions, the adhesive develops functional strength in 24 hours and fully cures in seven days.

This odorless, noncorrosive adhesive does not contain solvents, isocyanates, silicones or polyvinylchloride. Besides wood, it adheres to stainless steel, galvanized steel, aluminum, glass, fiberglass and plastics. It is compatible with most paint formulations. Resistant to ultraviolet radiation, the adhesive can be used for both interior and exterior applications.

Bonding skins to frame. The sheet-metal skin covering the sides of a trailer are usually riveted or bolted onto the frame.

Instead, we used two fast-fixturing structural acrylics: Loctite H4500 and H8600. During the cure process, we used screws to fixture the skin in place. By bonding the skins to the frame with adhesive, 90 percent fewer fasteners were needed for assembly, resulting in a better looking, stronger, more leak-resistant trailer. This same process was used to bond the door and roof skins.

Loctite H4500 is a highly thixotropic, two-part methacrylate adhesive for bonding metals, such as steel, stainless steel and aluminum. It also bonds epoxy-coated metal, sheet-molding compound and many plastics. The adhesive bonds to metals without a primer. It contains a corrosion-inhibiting additive to ensure long-term bond durability even when exposed to moisture. Mixed at a ratio of 10-to-1, the adhesive reaches fixture strength in 15 to 20 minutes at 70 F.

Loctite H8600 is two-part methacrylate for structural bonding of galvanized steel. Mixed at a ratio of 2-to-1, it reaches fixture strength in 55 minutes at 72 F. This toughened adhesive has a high peel strength. A thick material, it can be applied to vertical surfaces without sagging.

Seam sealing the frame and skins. On standard trailers, polyurethane or silicone caulks seal gaps and prevent water penetration. These sealants work well, but they will yellow over time and do not last long in the harsh environment of the road.

On our trailer, we used Loctite 5510 to seal gaps in the frame and all the skins, including the door and roof. Like the adhesive we used to bond the floor, Loctite 5510 is a one-part adhesive based on a modified silane polymer.

Free of isocyanates, solvents and silicones, this low-odor, highly flexible sealant resists vibration, movement and impact. Because it is impervious to UV light, the sealant will not degrade or crack over time. It fixtures quickly and can be color-matched to the skins for seamless assembly.

The adhesive cures by reacting with atmospheric moisture. It develops functional strength in 24 hours and fully cures in seven days, but these times can be shortened by increasing exposure to moisture.

. . .

The Results

The trailer was completed in April 2008. Since then, it’s been on the road, hauling a motorcycle and an all-terrain vehicle throughout the country. The exterior of the trailer is decorated with graphics that were applied without concern for the placement of metal fasteners. As of January 2009, the trailer has logged 7,000 miles and experienced no problems with structural integrity or leakage. In early February, the trailer started a tour of manufacturing locations along the East Coast.
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Re: A Trailer Without Fasteners?

Postby Shadow Catcher » Sun Oct 10, 2021 8:20 pm

I can see this, considering what you can do with 3M VHB tape...
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Re: A Trailer Without Fasteners?

Postby MickinOz » Wed Oct 13, 2021 5:05 pm

I've done a few experiments trying to see for myself just how strong adhesives only joints are.
I've also seen a few websites where manufacturers put RV;s together with nothing but adhesives.
I've formed an opinion and it's this, as best as I can articulate it:
I think these adhesives are perfect for what they are designed for - adhering metal panels to metal frames, and stopping the wings from falling off your aeroplane.
But it seems to me adhesives only construction is not for the DIY'er building with timber and ply wood in his driveway or garage.

A couple of reasons.
1) Cleanliness is very important when gluing things together in any application, but it seems to me to be beyond vital when relying only on adhesives. Beyond critical. Its a level of cleanliness I doubt my ability to achieve at home.

2) Despite being promoted as primer free, many list specific situations where a surface prep product of some sort is recommended. I dunno what is like in the US, but here in the Great Southern Land, those surface prep products are almost never sitting on the shelf alongside the whizz-bang super glue.

3) When you rely on adhesive only, the connection is only as good as the next one.
Some examples of what I mean:
Us home builders are generally building to a painted trailer chassis. If we were to emulate many an RV builder and glue our panels straight to the chassis, the
strength of the connection is actually only as good as the adhesion of the paint layer to the underlying frame.

When relying solely on the glue to affix plywood to a timber frame, the strength of the connection is only as good as the glue between the face veneer being glued and
the next veneer. I've found this with several "stronger than wood" adhesives. Yes it is, but its also much stronger than the A-Bond phenol formaldehyde resin used in
marine and structural plywoods. So it just tears the first layer of veneer off.

There's a reason why wooden boat builders put in so many nails when putting hull sheets on the frame, or tape the seams and sheath the whole lot in a layer of glass and epoxy.
Unless you are doing the whole stitch and glue with epoxy thing, I think it best to use fasteners to back up your glued connections in our situation.
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Re: A Trailer Without Fasteners?

Postby DrewsBrews » Thu Oct 14, 2021 6:41 am

@MickinOz, My thoughts exactly.

Cleanliness of the joint and material quality become prime importance.



When gluing wood I tend to use screws primarily for clamping the joint. Then it is just added insurance, after the fact, to hold the joint together if glue failure occurs due to inferior bond... hopefully buying some time to notice before dominoes start falling on total structural failure.

For my build, on my floor top layer I removed all screws after the construction adhesive cured. I figured there was plenty of surface area on the inner skeleton and perimeter to have a more than adequate bond.

The roof spars I'm counting on TBIII mostly; using a single 3" screw through the plywood into the end grain of the spar. Not the best method, but its easy, and I'm lazy. I'll leave the screw in to bolster the glue joint.
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Re: A Trailer Without Fasteners?

Postby MickinOz » Thu Oct 14, 2021 1:23 pm

I don't see your roof spar connection as a problem. I did it that way too.
A 50mm screw through 17mm of plywood into a pilot hole is the perfect backup for a glued end grain.
I dunno if you've noticed, but a lot of technical data sheets for glues say they tested the joint strength on end grains - the glue can get into the end grain pores and its very strong.
One thing I do though - the inner plywood layer is glued and stapled structural ply.
My double layer roof is a torsion box. The sheets and the spars are reinforcing each other.

Re: surface area, I was watching a video from the Tips from a Shipwright series on Youtube, when I noticed something I've taken up myself.
He was affixing a panel to a frame. Traditional planking. He spread the applied bead of glue so the entire surface was covered before he laid the plank on.
He didn't rely on nailing the plank down to squeeze the glue over the whole surface. I've been doing that ever since I noticed it.
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