adhesives for long stiffeners, "glueing stiffeners on" Options

[charliew]

I know we don't build horse trailers but glueing structures and panels on makes a stronger structure and it's a lot easier and cleaner and seals better. Scroll down and read about the trailer doors.

http://www.lordfulfillment.com/upload/RE3024.pdf

I know it's a wierd name of a glue mfg but so what?

http://www.lord.com/Home/ProductsServices/...65/Default.aspx

crash tests http://www.lord.com/Home/ProductsServices/...06/Default.aspx

It looks like fusor is the brand name used in the local auto body supply places around me.

I've been reading, it looks like if you ever did want to remove a "glued on" piece it is removable with high heat just like the anerobic thread lockers, ie seperate it after heating, and scrape the residue off.

It also looks like a acrylic is the best one for my application.

I covered two of my painted plywood deer stands several years ago with painted steel I bought from a local metal building supplier. It was off of big rolls of painted steel intended for the sheets of r or u panel that goes on metal buildings. I just had them shear the sheets the sizees I wanted. I screwded and glued it with NP1, a urethane caulk. I used corners on the edges. You cannot seperate it without destroying the metal at the seams. Of course this isn't a car but I bet the np1 would even work on the 914. I also used it for seam sealer on my jeep truck but it did shrink and the paint cracked where the np was in the seam like in the roof gutters. But the np1 didn't crack.

[brant]

I would advise against this
I've glued non structural pieces onto a 914
they do fail over time

your not starting with fresh, clean, perfectly flat metal

[McMark]

My biggest question: How will vibration and flex affect the glue? Too stiff and it may crack. Too soft and it may not achieve the same rigidity increase as welding.

I haven't heard of anyone doing it yet. If you're serious about trying it, I would try to get ahold of the glue co. engineers. They'll have the absolute best information about their product, and aren't trying to get your money (as much) as the sales guys.

[sean_v8_914]

several modern cars like Ferrari and Lotus do this. there are adhesives specifically designed for this application. prep and primer is key. the fixtures to squeeze it together PROPERLY WOULD BE A CHALLENGE

[charliew]

I can tell some of the repliers have not read the links. I think livestock trailers get way more structural twist than any car.

[PeeGreen 914]

Interesting read. YOU should try it and let us know (IMG:style_emoticons/default/beerchug.gif)

I don't mind jumping off cliffs as long as someone else goes first (IMG:style_emoticons/default/happy11.gif)

[strawman]

Hi Charlie --

I believe this is a solution to a problem that doesn't exist. If you're looking for better sealing for the interior long-stiffeners, don't let water into the cab of your teener. And unless you're running without an interior, the carpet will cover the welded-on stiffeners anyway. Finally, if it fails you'll probably never be able to completely clean that snot off to be able to correctly weld the stiffeners on... just my $0.02

Geoff

[Root_Werks]

Interesting read. YOU should try it and let us know (IMG:style_emoticons/default/beerchug.gif)

I don't mind jumping off cliffs as long as someone else goes first (IMG:style_emoticons/default/happy11.gif)

(IMG:style_emoticons/default/agree.gif)

I also think that's the worst advice I've ever given. (IMG:style_emoticons/default/wacko.gif)

[sean_v8_914]

I used laminate steel adhesives on an anchor trolley frame system for an oil rig. under sea water and stress beyond imagination. this is proven technology. welding is easier for our cars. the prep work and fixturing requires training and knowledge beyond the scope of commitment of your average car enthusiast.

[rsrguy3]

Sean is dead right. Structural bonding is very dependable. It has aerospace roots, many aircraft are still flying after 25 years with no signs of de-lam, in many applications, bonding is preferable. Where these cars are concerned I actually believe bonding would be perfect(better than welding), reason being, if you can get all the metal properly cleaned, prepped, and coated, you would end up with less unprotected metal and stiffer results(more bonded surface). Another bennie is not having the ability for capillary action to take place, common in laminate welds. Now that I've covered all this and defended bonding, am I gonna do it to mine? Nope, I just don't have time to re-invent the wheel, or build fixtures to accommodate the process. Those interested in doing this should look to SEM for the proper bonding adhesives.
http://www.semproducts.com/

[Katmanken]

Charlie,

We've beaten this one to death more than once.

Here's a clue.

Aluminum aircraft can use aircraft structural epoxies and rivets to create lightweight rigid structures.

914's use mild steel that can form rust cells...

Rust cells create high pressure bubbles, bubbles create delamination areas that reduce glue area and glue bond integrity- usually when you don't want it- ie when subjected to a shock load. Does Lord recommend use on ferrous metals???

What are your livestock trailers made of????

[charliew]

I'm pretty sure with the slow curing epoxy or polymer that screwing or riveting the panels together will work. I'm sure I need to study it a little further but I know the car will be better if this works because the heat from welding will cause the inside of the longs to rust sooner and the risk of warpage will not be there and the worries of the rust forming inbetween the panels is less. I am a good welder but I also know what welding does to metal.

[Katmanken]

MIG welding reduces the heat applied to the panel and reduces the likelyhood of rust. Oxyacetelene gas welding tends to heat a large area and create a lot of rust.

My guess is the livestock trailers and truck trailers are aluminum to save weight. Aluminum is excelent for use with a structural adhesive. Lotus uses aluminum extrusions and structural adhesives to make the chassis/frame of the car.

That tan cavity wax is good to spray inside of longs and other enclosed areas with a spray wand. It even has rust inhibitors.

In my younger days in Florida in a high salt beach environment, I tried fiberglass on steel and glass putty on steel. Cleaned the rust with a sandblaster and used Ospho as a prep. Pretty bummed out when the glass delaminated from the metal (from the rust growth), and the rust bubbles kept on growing and popped out the putty. Thats when I realized the rust pits in steel are conical and the sand blaster can only drive the sand so far into the conical pit before it stops. That blasting didn't remove the root of the rust cell and that's what regrew. A materials expert at work told me the hydraulic pressure in a rust cell is surprsingly high, and popping the glass and putty was what he expected. Down there, rust is known as "Florida Cancer"

[sww914]

The first cars I encountered with glued panels were Fords. I haven't been too impressed with Ford cars longevity as a whole. How long has it been since you saw an old Taurus that was still a good car? An old Fiesta? Pintos are the same age as our cars, how have they fared?
I weld them on.

[Joe Owensby]

I have a glider that I built about 28 years ago. It has lots of structural components that are glued together with epoxy. In this plane, I have the South Carolina altitude record for gliders- 17,600 feet. I could have gone higher, but 18,000 was as high as I could go legally per FAA rules. Not too bad with no engine.

The epoxy holds very well, as long as the base material is perfectly clean and prepped. Anything less than perfectly clean, then all bets are off. Welds are more forgiving- if they are also done correctly. JoeO

[Porcharu]

The first cars I encountered with glued panels were Fords. I haven't been too impressed with Ford cars longevity as a whole. How long has it been since you saw an old Taurus that was still a good car? An old Fiesta? Pintos are the same age as our cars, how have they fared?
I weld them on.

I see a Pinto wagon almost every day - when was the last time you saw a stock Vega?

[charliew]

Ok these are some good points. And yes the trailers are aluminum.

I have grown old doing mild steel body repair and I am still learning. I learned 20 years ago to clean the rust off completely, treat with metal prep, put down a good coat of non-sanding epoxy primer and then put the filler on. That will seal the metal and you can't beat the primer off, it will only mash where the hammer hits it. If I use this sealer as a base I feel that the metal will never rust inbetween the lamination. I also know the other side is no worse for getting rust started. I know from learning to weld, the true heat applied in penetration can be judged by looking at the back side of the welded piece. I also know any time metal is heated enough to change it's color the properties of the base metal has changed, usually it's more brittle right next to the weld. Why fool with this if there is another just as strong if not much stronger way to laminate two sheets of metal. I like the stiffeners but I don't like all the heat on a good tub that really may not even need them and have never liked the thought of making a thing worse after I work on it.

[sww914]

The first cars I encountered with glued panels were Fords. I haven't been too impressed with Ford cars longevity as a whole. How long has it been since you saw an old Taurus that was still a good car? An old Fiesta? Pintos are the same age as our cars, how have they fared?
I weld them on.

I see a Pinto wagon almost every day - when was the last time you saw a stock Vega?

There are 2 across the street from me. I've never seen either of them move. (IMG:style_emoticons/default/smile.gif)

[Katmanken]

Here is what the materials expert also taught me.

A glue joint is no better than the surface you are bonding to. If there is a fingerprint or any other contaminant on the surface, you are gluing to the contaminant. For aircraft and spacecraft parts, he had a really involved cleaning process starting with 409 cleaner. He wouldn't recommend bonding steel for other than a non-structural home project of limited duration.

Question:

Which is stronger for a unit of attachment area?

1. A weld

2. A glue joint applied between cleaned bare metal plates

3. A glue joint applied between bare metal plates with a coat of oil applied to one of the plates right before gluing.

3. A glue joint applied between cleaned plates with a coat of paint on each one.

Answers:

For 1. you are loading the weld which has the highest strength value per unit of area both in shear and tensile loading

For 2, the glue is the weak link and is nowhere near as strong as a metal weld.

For 3, the retention qualities of of the oil film is all you got. Can you say easy separation????

For 4, the weak links are the paint or the glue, whichever is weaker. Usually, the paints are a LOT weaker. Glue a bracket to your painted hood and one to a clean I beam. I bet the paint joint separates at a much lower force than the I-beam. Neither is as strong as the same area of metal or weld.