Adhesives Vs Welding (of Metal Boats?)

[brian eiland]

The state-of-art in adhesives has advanced dramatically in the last ten years. I've often wondered where and when we might see it really infiltrate the metal boatbuilding community. It certainly could help eliminate the warpage associated with the heat required during welding, and the joining of dissimilar building materials. At one time I was very interested in the possibility of a copper-nickel alloy hull bottom with a fiberglass topsides.

Here is a short article sent to me recently:

Specialty Adhesives Put the Squeeze on Welding
For more than 20 years, 4-Star Trailers has welded the components of their aluminum trailers together, so they were initially skeptical about using an adhesive process. However, after learning that several major automotive manufacturers including DaimlerChrysler, General Motors, and Ford, have used structural adhesives on more than 10 million cars, 4-Star Trailers decided to evaluate the adhesives’ merits.

Testing the technology
“We chose adhesives formulated by LORD Corporation after reviewing the motives of these large automotive corporations for choosing them for bonding roof and door panels,” says Butch Patchell, manager of research and development. “Attributes such as impact resistance, vibration, and noise dampening as well as superior strength were among those cited, which is exactly what our customers want.”

For a two-year period, the company conducted extensive testing to develop fixtures and test the strength of their bonded designs. The door shop was the ideal place to try the adhesives.

...illustration...
4-Star employees apply the adhesive to the trailer doors in preparation for the testing

.

Two doors were created for the testing process — a traditional welded door (with taped and riveted outer panels) and one constructed entirely using adhesives, both of which were hung to a heavy steel frame. A hole was drilled in the lower corner of the door to simulate where a horse may kick and the panel would experience the most stress. Then, the chain from a 3/4-ton winch was threaded through the hole.

On the welded door, at 40 lbs of force, the door pulled off the frame. At 950 lbs of force, the door pulled out 5.5 in. and broke apart.

In contrast, at 1,000 lbs of force from the winch, the bonded door had only pulled out 1/2 in. The team was so amazed with the results that they bought a 3-ton winch, hooked it up, and performed the test again. Only when 2,500 lbs of force was applied did the bonded door move 1 in.

....illustration...
During 4-Star’s testing, the adhesive withstood 1,600 lbs of force. Welds did not measure up.

The same test was repeated again at a later date for the non-believers. This time, the welded door was irreparably damaged at approximately 960 lbs of pressure. Because the team never broke the adhesive door on the first test, they set out to find the breaking point by adding 800 lbs per stroke of the winch. Somewhere between 4,000 and 4,400 lbs, the door popped loose, but when they released the winch, it went back to its original position and laid flat with easily repairable damage.

Another test involved using adhesives on small feed doors and placing them in a freezer maintained at minus 20°F. The doors, which were shuttled from the freezer to the outdoor sun and back several times over the course of a week, experienced no change with the temperature difference. This test was important as thermal expansion problems are common with welded components.

Yet another test involved the use of a high-powered vibrator hooked to the door. Although the welded door quickly failed, the adhesive door never fell apart though the hinges eventually wore out from the heavy vibration.

The results showed that the bonded doors outperformed welded, taped, and riveted doors in every test. Therefore, it was determined that the bonded doors were four times stiffer and possessed double the impact resistance of the welded doors. This stiffness prevented the door from flexing as easily and provides excellent security for cargo.

“The doors were frozen, baked, dropped, pulled, and hammered,” says Patchell. “We conducted these tests repeatedly because we could not believe how much stronger the bonded door was when compared to the welded door. Our welded doors were considered the best in the industry because the frames were welded and then the skins were taped onto them using double-side acrylic adhesive tape as well as riveted for good measure. This is why we were initially skeptical when we were shown an adhesive that was more effective than all those measures.”

Unlike welded doors, a bonded door cannot warp out-of-plumb because of its superior stiffness. As such, the company developed a new process for attaching doors to the trailer. The new approach involves pre-assembling the door to a doorjamb and then attaching the pre-hung door assembly to the trailer. This design maintains a uniform gap between the door and its sealing surface all around the door, which allows the rubber seal to have equal compression with no gaps. Further, the lack of gaps contributes to better water resistance than previous designs.

Proof is in the numbers
Although strength and durability are key, 4-Star also sought a more efficient and cost-effective solution. This goal was achieved by integrating adhesives into their door assembly. Not only has the company been able to reduce labor by 50%, but the switch from rivets, adhesive tape, and welding also results in savings, enabling reinvestment in improved designs for their hinges and doorjambs. Because of this success, 4-Star is experimenting with bonding the floor panels. In addition, the adhesives are expected to be a quieter solution, which is important in reducing the stress horses experience during transport.

Designfax OEMeNews article with illustrations

Lord Corp.www.rsleads.com/601df-108

[MarkC]

A Sensation!?!

This is the first info I have had to read on the subject.From reading the Lord Corporations web site I understand that the glue is being used by car-makers for attaching panels. I wasnt clear if it was being used for more heay-duty framing purposes.

Firstly - I feel for those who have invested much time and money with welding - what should people investing in welding machines and learning to weld do now? Wait and see if the glue becomes popular or accept the change and test it out?

The poor welders! It must be unsettling news.

But I guess it all hinges on the price of the glue. What is the price of the 250 mill glues???

The glue likes a 2.5cm overlap. Doesn't like to stick to Zinc Phosphate so galvanising frames before plating is out. Lord corp even offer a baked enamel to replace the galvanising.

I wonder what thickness of panel can sucessfully glued - perhaps some frames as well.

I hope framed steel or aluminium boats see a rise in popularity now that the very lightly skinned boat-hulls (say 2mm or 1mm steel) can be done without distortion and done relatively quickly.

The end of the Strongall system?

An interesting development.

[MikeJohns]

Have great caution in their use with catastrophic failure in mind. If you had a bad batch of glue……..

Adhesives have been touted for years as a replacement for mechanical fastening, in wooden construction they have been highly successful but in metal construction I suspect that the application will be limited to use in non critical components.

The problem is that the properties of most adhesives change over time, in high stress situations long-term failure probability is high although they may exhibit very good performance in the shorter term. They do work well in conjunction with mechanical fastening but again long term viability means that the join is still fully riveted. Look at the aircraft industry.

[safewalrus]

It looks very exciting BUT i certainly wouldn't want to be the FIRST guy out in a force 9 in a boat stuck together glue alone!

There again we're starting to use 'water based' paints on the outsides of boats these days

"Stick your boat together with wallpaper paste and paint it with emulsion!" As I said a brave man!

Still as Mike Johns sez above for non structual componants why not; then ; eventually; later!

[MarkC]

I still think it is a positive development.

Have great caution in their use with catastrophic failure in mind. If you had a bad batch of glue……..

Adhesives have been touted for years as a replacement for mechanical fastening, in wooden construction they have been highly successful but in metal construction I suspect that the application will be limited to use in non critical components.

Boat-builders have had bad batches of Aluminium - which the smelter had to pay for rebuilds (as I had read here on this very site). There probably have been bad batches of epoxy too - bad batches of bronze screws, faulty welding rods, mis-labeled welding rods. Has this hurt anyone? It is hard to tell. This would probably be more of a factor in Aircraft than boats IMHO - hence the 'belt and braces' approach.

Didn't people express doubt about the longevity of wooden cold-molded monocote-structure boats in the USA? I believe that Brooklin Boat Yard warantee their strip-planked and cold-molded yacht-hulls for 22,000 normal cycles - about 2 -1/2 years of weekend use (if I remember correctly from the book 'A Unit of Water, A Unit of Time').

BUT i certainly wouldn't want to be the FIRST guy out in a force 9 in a boat stuck together glue alone!

Well why not??

Fine - then find a French catamaran racer, offer him / her / them a boat to thrash and keep in regular contact... Isnt this the way it has always been done?

I hope this glue is successful - and I hope it heralds the return of the small steel/aluminium yacht.

[boltonprofiles]

Sounds good in theory and I think we should grasp modern technologies whenever possible - but not when they first come out or not until they have been tried and proven and become an accepted alternative. The 'catch 22' is how do they become this accepted normal if no one adopts them in the first place.
OK on a trailer perhaps where lives are perhaps not so at risk. On a boat though where it could kill many, not so sure.
We tend naturally to be too staid in our ways but with good reason with tried and tested methods.
It would always be at the back of my mind as I was sailing, especially as the boat grew older, whether everything was still ok, so for that reason alone I will continue to weld my boats thank you very much.
Good idea though for the future but I will let others try it first.

Paul

[MarkC]

It would always be at the back of my mind as I was sailing, especially as the boat grew older, whether everything was still ok

This could apply to many boats of differing construction techniques.

That is why there are surveyors... you do have your boat regularly surveyed dont you?

In addition - it would be good to see the results of any 'Artificial Ageing Destructive Testing' that has been done by the car manufacturers - especially the Germans.

[sal's Dad]

One approach would be to use the new technology in highly visible, but non-critical applications at first.

I have long wanted a skiff or small launch of welded aluminum, with integral flotation chambers. The bottom and lower panels would be of 1/8" plate, while upper gunwales and air chambers (seats) could be of a much lighter material. Unfortunately, light gauge aluminum is impractical to weld in a backyard shop. And building the entire boat of thick plate would result in a very heavy craft.

So how about welding up heavy plate for the lower portions of the hull, and gluing on the topsides (above the waterline only!), decks, and furniture? Failures of the adhesive would be visible, and reparable (rivets?).

I would expect this approach would work just as well on a larger boat.

An obvious question is how the adhesives would work below the waterline. On my Bolger Diablo, I have been experimenting with gluing "skid plates" to the ply/epoxy bottom. Epoxy lasted about 3 years of heavy use; the 1/8 plate wore more than halfway through before the glue failed. I am now coming up on one year with 3M 5200; so far so good. A metal skeg glued onto a welded boat would provide a good test of its suitability for hull construction.

Sal's Dad

[safewalrus]

So we combine Bolton's retinance with Sal's non critical areas and Marks exhauted surveyor. Weld the hull and deck, glue on the extra bits, ventalators, tabernacle, lockers etc and check it regularly! Sounds good so far, all we want now is a 'volunteer' to take the 'ship' to hell and back for a few days - Sydney and back round the 'Horn' will do!

Well the idea holds water will the boat? Quite frankly I believe we have a viable system, maybe not quite like that but something similar has definate promise - after all welding is only "electronic glueing" when all said and done

[boltonprofiles]

I don't agree that welding is only 'electronic glueing' as such Walrus but I do think you have a excellent point of compromise and I would be willing to try a bit of glueing on the boat I am building at the moment for some 'add on' pieces, no, on second thoughts I have changed my mind I don't even want to do that. Maybe someone will build a test rig and monitor it over time - even then would you belive it?
I am perhaps too cynical as perhaps money will be involved from too many interested parties, as you say Walrus I would't like to be caught in a force 9 with a glued together boat.
I still say however that it is the future for these types of leaps forward (or perhaps not) in any kind of construction thinking. I still think we need to embrace these concepts whenever possible.

I keep thinking of the tiles on one of the space shuttles which came adrift which as I understand it were glued. If I am right and NASA can make this kind of, shall we say perhaps, error of judgement what chance have we?

The designers, who I genuinely think should be the only authority on this type of 'radical' build, will perhaps let us know what they think.

Another good thread from Brian, thought provoking and interesting.

[safewalrus]

yeah I know what you mean Paul, My next project (steel hull again!)will most certainly have adhesives used in many more places than the last! But most definately NOT the main part of the Bucket!

Now the name plate, that may be diferent! As for the rest, we'll see!

[brian eiland]

Originally Posted by sal's Dad

...I have been experimenting with gluing "skid plates" to the ply/epoxy bottom. Epoxy lasted about 3 years of heavy use; the 1/8 plate wore more than halfway through before the glue failed. I am now coming up on one year with 3M 5200; so far so good.

What a great product that 5200 is, not only its tenacious bonding power, but the fact that it remains somewhat plyable rather than brittle, promoting a resilent longer life.

I'm surprised no one has brought up the subjects of how a number of these 'superyacht' powerboats, and some military vessels, are attaching their dis-similar material hulls and superstructures??

[MikeJohns]

polyurethane adhesive/sealant makes a good glue. Bonds excellently with weathered aluminium and I have seen aluminium patches stuck on dinghys as a temp patch still functioning 4 years later.

There is another one called Sonolastic ULTRA that I specify for high bond hard wearing adhesive/sealant. I have specified this as a coating over epoxy paint in steel anchor wells and it has performed admirably in work boats.

Some building industry polyurethanes sealants go soft on the surface in a marine environment after a couple of years, I suspect all the brands will eventually break down, this demise can be put off if sealed with paint. This sort of observation makes me cautious as does the manufacturers life estimate eg 20 years for the sonolastic product. They do not last forever.

If you use it note that it can takes one to two weeks to cure to full strength depending on the exposed surface area.

Brian
Are you refering to the bonded strips ? Bar Al on one half and steel on the other. There is actually an alloy zone where these are sharing electrons.

The older way was always bedding compound/gasket and isolated bolts and this is still often used in commercial boat building.