OT: Difference between Epoxy vs. Fiberglass Resin

[BRENT in 10-uh-C]

I am working on a set of reproduction Top Iron Sockets that need reinforcing inside. My 'go-to' epoxy company for the past 5 or so years has been TotalBoat by Jamestown Distributing which I have been very happy with their products. Several days ago I called them to ask for recommendations where I plan to insert a 0.750" aluminum rod into the top socket and then pour Epoxy into the socket surrounding the aluminum rod as a method to reinforce the socket and keep it from bending due to the weight of the top.

After a lengthy discussion they asked if I would send them pictures of what I am planning and what materials. One of the tech guys (Brian) called me back yesterday and said "After some thought, they do not offer a product for my needs." Apparently what makes 'epoxy' strong is it being able to soak into wood and that penetration is what makes it strong. Naturally I can fab a piece of 18" long piece of wood to insert however that does not allow the epoxy to soak into the metal Top Iron Socket which he claimed is what will make this strong.

I began wondering if using a panel bonding adhesive would be a good solution for this but I understand those adhesives are very flexible when they are dry, ...which is not what I am after. I need rigidity. So what are some thoughts on the best product to use when trying to pour into a socket that will give rigidity and reinforcement over the 18" long area? Should I just use Fiberglass Resin??

[Badpuppy]

Resins would be similar if not the same, I believe. Not a good adhesive to metal. How about a press fit?

[608bill55]

Brent,

You might want to consider this: 3M 38315 Panel Bonding Adhesive. I am not associated with 3M but have used this type of adhesive for multiple antique airplane non structural repairs. This type of adhesive is used heavily in the automotive manufacturing industry.
It would be worth considering and build up a "prototype" sample to give you the assurance of the repair.

Bill Liimatainen
Model A Pietenpol builder and flyer.

[rich b]

I would think your original idea is sound; the epoxy will act as a filler capturing the aluminum rod within the tube with no real load or stress on the epoxy.

[JayJay]

Brent - you might look into the West System epoxies and fillers (westsystem.com). These are epoxies that, with special fillers, are used extensively in the marine restoration industry. They have recommendations specifically for bonding to metals. I’ve used these epoxies for over 30 years with great success. The only other epoxies I use are the JB Welds when I need high compressive strength (epoxies without the metal filler of JB Welds tend to creep under constant load).

I would not go to polyester resin for this application, I don’t think you would get the strength of bond to the metal you are looking for. No data to back that up, just a gut feeling.

An issue I see with aluminum is the propensity for aluminum to form an oxide layer on the surface. This can inhibit bonding. You might want to roughen up the surface of the aluminum immediately before inserting it into the socket. Or perhaps even turn some grooves in the aluminum on the lathe, before inserting it into the epoxy. Otherwise, I think your approach seems sound.

[Kurt in NJ]

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Make a tapered sheet metal piece like a axle shim and glue it inside with panel bonder— it could be a gauge of metal similar in thickness to sheet metal ductwork— wouldn’t increase weight much and the strength would be increased considerably.

[johnneilson]

Brett

This sounds similar in application to a process of bedding precision rifles

Basically it is a metal filled epoxy to form a void free connection between different materials

Back with wood stocks aluminum pillars are placed for fasteners to compress along with areas of stress free connection of action and barrel


Check Brownells on line for bedding materials

John

[Wick]

When installing electronics on boats if you don't want something to move or flex we would use
5200 I think it's made by 3M. I've see transducers gluded with this stuff in boat hulls, after 20 year's you have to use a hammer and chisel to break it loose.

[nkaminar]

I am going to go with what Jay Jay said, Post #5. The West System has different fillers such as short fiberglass strands that add a lot of strength to epoxy. My experience with the West System is when making repairs and changes to my boat. I second his idea of roughing up the surface of the aluminum.

Another option is two part polyurethane and an adhesion promoter primer. These are used for bonding body panels on trucks. Do not use the air cured one part polyurethane unless you have a year to wait for it to cure.

[oldspert]

Remember fiberglass resin alone will shrink as it cures if it is of any thickness at all.
Ed

[RDVAARK]

Hi Brent,
I've run into a similar situation in the past with English car tubular steel seat frames. Even if the seat covers and stuffing are good the seats sag back as people contort and brace themselves into a small car. The tubing is usually 3/4" mild steel and runs around the edges of a single sort of bucket seat, making a 90 degree turn between the seat cushion and the back. The seat reclines eventually and is often discarded. (In high school my 1960 Hillman station wagon was well known and admired for its single driver's seat and full floor mattress for the passengers.)
The solution, even on seats to be roughly used, was to thread, if possible, a flexible stiffener, such as a fibrous cord completely into and through the tube. Plug the end and fill with resin. Roll the thing over, shake it, vibrate it with a sander, etc. to fill completely the voids. If, as in your case, there are cross bolts or shape changing features, tapers, curves, to lock it in place, all the better. Use a slow curing mix of the resin to allow for a good thorough fill. The result is a fiber-reinforced, steel cased shaped solid rod that will resist bending. Fiber/resin-filled fishing rods and sports equipment are similar in design. Weight of the product is high, but worth it for the strength.
In your application, the aluminum rod could be inserted as far as possible, with a gripping or knurled surface, or a sleeve could be installed, before the resin sets. Shrinkage seems negated by the fibrous filler, the tapered shape, cross bolts and slower curing resin.
I've used a good quality commercial liquid resin (Evercoat), and for fiber I use braided cord. My preferred 'cord' was braided Aramid (Kevlar) tubular insulation that is used on high spec wiring, like military or aerospace. It can be stretched to be skinny, stuffed in to be fat, is high tensile, and won't rot like cotton.
You get the general idea. Modern materials, like carbon fiber and new resins come to mind. Imagination and ingenuity could also improve on my ideas.
Good luck,
Russ

[BRENT in 10-uh-C]

Originally Posted by 608bill55

Brent,

You might want to consider this: 3M 38315 Panel Bonding Adhesive. I am not associated with 3M but have used this type of adhesive for multiple antique airplane non structural repairs. This type of adhesive is used heavily in the automotive manufacturing industry.
It would be worth considering and build up a "prototype" sample to give you the assurance of the repair.

Bill Liimatainen
Model A Pietenpol builder and flyer.

My experience (-which is limited) is that panel bonding adhesives have some elasticity to them, ...which I don't think I want. My experience with panel bonding was using a product called Lord Fuzor which their rep was working with us to start installing patch panels with. Do you know is the 3M product you mentioned is similar in characteristics?

Originally Posted by JayJay

Brent - you might look into the West System epoxies and fillers (westsystem.com). These are epoxies that, with special fillers, are used extensively in the marine restoration industry. They have recommendations specifically for bonding to metals. I’ve used these epoxies for over 30 years with great success. The only other epoxies I use are the JB Welds when I need high compressive strength (epoxies without the metal filler of JB Welds tend to creep under constant load).

I would not go to polyester resin for this application, I don’t think you would get the strength of bond to the metal you are looking for. No data to back that up, just a gut feeling.

An issue I see with aluminum is the propensity for aluminum to form an oxide layer on the surface. This can inhibit bonding. You might want to roughen up the surface of the aluminum immediately before inserting it into the socket. Or perhaps even turn some grooves in the aluminum on the lathe, before inserting it into the epoxy. Otherwise, I think your approach seems sound.

I will look at West Systems product line.

As for aluminum, I would think the rod being encapsulated in the Epoxy or Resin would be shielded from moisture, etc. I can just as easily substitute some hot rolled steel in the place of aluminum. To create a sort of gripping surface, I could knurl the outer surface of the rod in the lathe which might add some gripping surface.

[JayJay]

Originally Posted by BRENT in 10-uh-C

I will look at West Systems product line.

Available retail at West Marine (no relation), closest to you is likely Knoxville.

To create a sort of gripping surface, I could knurl the outer surface of the rod in the lathe which might add some gripping surface.

That would work I would think.

Pls see above

[rotorwrench]

Weight is likely the reason for use of aluminum. Adhesives can also be heavy in large enough quantities. There is a multitude of different structural epoxy adhesives used in aerospace composite construction. I used several types of Hysol epoxies for structural modifications and approved main rotor blade repairs over the years but they can get expensive. It seems the strongest types like to get really hot during the application after mixing. I've had the plastic sim kit containers melt on me during the process if I didn't dispense it to the work fast enough. One caveat to use is air bubbles. It has to be fluid enough to run all the way down to the bottom of a work project and then fill all the way up without getting air pockets in it, otherwise it will slowly bubble back up. 3M 2216 epoxy was used a lot to seal around main rotor blade leading edge nickle abrasion strips. It's a gray color and is considered a structural adhesive. I used to purchase it in pint containers to make a quart of the part A & B mix. I haven't priced it in years but it's likely more expensive than JB Weld. It's slow to cure so a person has to contain it so it won't run but it's strong stuff. Only the old Hysol types are stronger once cured.Those were used to glue the main rotor blades together then heat cured in an autoclave.