In the 1970's, when I started building my KR-2 there was 2 flying. I built my KR with epoxy resin and don't know of any KR's that was built with polyester resin.Many commercially made items use polyester resin. Its use in objects that stay submerged for a long time, like boats, has its problems but usually they appear long after the warranty has expired. I am pretty sure the KR series planes were built with fiberglass and polyester resin. It was really when Rutan started using extruded polystyrene foam where Polyester resin was an issue because it would dissolve the foam core. Thus the VariEze and LongEz had to use epoxy resin since it would not harm the core material that was being used.
The other thing to watch out for is whether the resin contains wax to help cure it. This is usually used on the last layup. The previous layups may use a bonding resin without wax which remains tacky for a long time to promote a bond with the next layer. But if you used the resin with wax so that it fully cured and had no tackiness, it would be very difficult indeed to make a secondary bond to that layer because it is so difficult to remove the waxy layer and then one would also need a mechanical bond.
Lots of education needed if one is not to screw it up.
Just picked up a West Systems kit fro Aircraft Spruce prior to holiday weekend, the gallon with fast hardener. It was $168 up from $144 in the prior catalog....Sigh ..I hate supply chain issues LOLAircraft grade glass has fiber bundles (tow) of controlled size woven into a cloth with relatively the same number of tows in both directions. The smaller the tow size, the stronger the laminate. Normal 7781 glass has a tight, orthogonal weave and is approx 10 mils in thickness, dry.
It is the standard woven material in structural designs. It has epoxy sizing for good matrix adhesion.
Polyester resins used on boats are cheaper than epoxies so boatbuilders use plenty of it because they are building up mass and want to keep costs down. Epoxies have higher temp resistance and provide a stronger laminate than polyesters. If you are making an aircraft structural part or repairing one, always use an epoxy matrix. Aeropoxy from Spruce is a good 2-part system with high mechanical properties at reasonable cost. The West Systems work also.
Test it first. Some of the "boat cloth" I have seen do not conform well to compound shapes and layup heavy. We do a lot of compound shapes, corners, fillets, etc with glass, so it has to go around corners and conform. Laid up weight with many boat cloths tend to have a larger fraction epoxy than the 50-50 (by weight) we generally achieve with BID and UNI. WEIGHT IS THE ENEMY in airplane construction. Excess epoxy or vinylester resin does nothing for strength or deflections, only makes your bird heavier.Can I use boat fiberglass on aircraft? I am thinking it has humidity, fire and low temp/high temp resistance.
Thanks, but I idn’t find any vinyl ester gel coat there.
Couldn't find any vinyl ester gel coat there.
MGS was designed as a composite strucural epoxy. West was designed as structural resin for composite reinforced wooden boats. Both have failure strains exceeding those of common woods and fiber reinforcements, have similar moduli, handling, wetout, and cure. They both also have similar reputations for long lived structures in service.Just poking for fun but West System is on the packaging. I think West wins because of accessibility not because it’s the best. Stuff like MGS you have to be in the know. Most homebuilders, although we think we know, really just follow the crowd, which usually means easy to get ahold of and instructions that hold your hand.
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