Re: Fiberglassing the edge of plywood?
Prep is key m8 ..
If the edges of the ply is not properly 'prepped' with resin then it will almost be impossible to wrap..no matter what method you try.
The edge needs to be completely Sealed before you even think about applying mat. In fact ANY surface that you want to laminate on has to be completely Sealed for proper glassing.
#1 reason for air bubbles is improper 'prep' of the wood. .. it has nothing to do with tools or resin .. Prep IS key.
YD.
I respectfully disagree with parts of this statement.
Im only pointing this out so it cannot lead people to think they have to resin coat and let cure before doing a layup.
Yes, prep is the key to everything.
However sealing the surface before laminating will lead people to believe that they resin coat, cure, then laminate. This is incorrect and will create a very weak bond.
I am referring here to polyester resins and not epoxy resins.
In order to do a first lay up on wood. sand the surface, as yd mentions, prep is the key.
The real trick is to get the first good bond to the wood, if this is not a good bond, the rest of the laminate is no good.
Studies by resin manufacturers have found that a cured resin layer on top of a substraight will create a weak bond.
In this case the substraight is new plywood.
You can test this by looking at your resin bucket that has cured poly resin in it......bend the plastic bucket, and you will see a thin film of poly resin around the inside of the bucket.....take some out and crumple it in your hand....this proves that poly resin by it self is very brittle.
This very brittle resin rich layer is what is between your substraight and your laminate layer.
According to resin manufacturers data, this is the correct procedure for laminating (for the first time) on a new piece of plywood.
First, make sure your wood is dry. Plywood that comes form lowes or home depot is not dry. it usually contains a large moisture content. To absorb resin, the wood has to be moisture free. (you will never get wood that is 100% percent free of moisture as the ambient humidity in the air will be in the wood). In areas that have high humidity, use a de humidifier in the room.
To dry a piece of plywood, get a fan on it, and possibly a space heater and leave it for a good week or longer. Possibly as long as 2-3 weeks.....(This is usually the time it takes a new builder to gut a boat any how) so get your wood first and start it drying.
After its dry, sand the wood with 120 grit....even the edges, and round off the edges, as glass does not like a 90 degree corner. You just want to remove any surface burs and get the wood cleaned....Wipe, vacuum or blow the dust from the wood.
Prep your unwaxed poly resin by mixing the mekp at 1.7 % resin to mekp ratio, (if you use the metric system, this is really easy to do , and you don't need to be a math major to get it exact.) Do not use thinners for the resin like acetone...just regular resin. If you use a thinner, you will ultimately weaken the resin, there for, all your hard work will be in vain.
Taking a fuzzy roller, roll the resin onto the plywood...be very liberal with the resin, fully saturate the wood. (just the area to be glassed) Take a bondo spreader and remove any resin pooling on the surface of the wood.
Then leave the wood alone for a few minits....let the resin soak into the wood and let it get tacky, almost to cure.
(be careful here, unwaxed resin will remain tacky for a week after its cured, you should still be able to slide your fingers across the wet resin....but feel a tack).
Mix your next batch of mekp and resin at 2% mekp as per normal.
Now we do the lamination. Take your fuzzy roller again and wet out the plywood,,,,,but this time, twist the direction of the roller, and slide it across the surface of the wood.
If you take a real close look at the resin as it is rolled on to the surface, you will see that the resin tends to pool or bead. You are trying to eliminate those beads...this will cause micro bubbles in the layup.
If you have ever seen a lay up with a gazillion little air bubbles all over the place and wonder what the heck happened, this is the cause, a bad wet out.
You must work quickly due to the curing resin that you layed on the plywood.
Now add your matt and using your fuzzy roller, roll the resin into the matt..
Now take a bondo spreader and remove any excess resin..
Then take your resin roller and roll out any air bubbles in the laminate.
If you are doing multliple layers, add them now. but no more than 3 1708 layers (with csm between) as the resin will get too hot during cure, cook and become brittle.
You can do several layers of csm alone, but remember that csm soaks more resin than 1708 !
What you are doing here......is first saturating the wood with resin, and while that is soaking into the dry plywood, and starting to cure, you are adding the next layer of csm and resin. This causes the laminate to achieve a chemical bond with the resin soaking in the top layer of wood. the laminate actually intertwines with the wood.
In laboratory testing......they actually take a pair of pliers and try and pull the cured glass from the plywood.
They measure the resistance needed to pull the two apart.
Then they look at the glass....in a properly prepped and applied laminate, the resin will actually pull the wood up with it when torn apart.
There will be chuncks of plywood all over the glass..
This means that the plywood had actually broken before the bond between the glass and wood gave way.
If you let the resin cure first, then add the csm.....it is easily torn apart, with little wood on the glass, this is due to the weak resin rich layer cured between the wood and the glass..
In this case, the resin has failed, and the bond poor.
For the edges, the same principal applies. however, you have to prep the csm like woodie explained above.
This really sounds like a lot of work......but in actual fact, its not...but just every day glassing. the only extra step, is the initial wet out of the wood, and semi cure. You will still need a wet out, but not a wood saturation.
For glassing into a hull, where the glass has been cured for years, the same basic principals apply.
However the initial wet out and semi cure in not used.
The grinding (sanding is the same) you remove the top layer of resin and get to the glass.
You further prep the surface farther by cleaning with acetone.
Now.....LOL.....The reason I typed that whole thing is not to be argumentative, but to further help first time glassers to avoid some possible miscommunication's, and to insure a good first bond between plywood and a first laminate layer.
I hope this helps some of you.
Cheers
oops
