Confused on the order to do layup

A great debate, but I will give you the best answer I have...

First of all, laminating is counter intuitive. The strength is in thickness; not length. This is critical.

There are a number of reasons to go from largest to smallest and I almost always follow that rule.

1. If you lay the largest glass first; you are less likely to sand through longest bond in fairing.

2. You are less likely to entrain air into your laminate if you lay longest first. And thus it is easier to laminate longest vs shortest first because shorter first always results in air at the overlaps in the absence of thixo. Otherwise it is a real battle to get air out of smallest first work.

There are a few times I went shortest first, but it usually had some solid thought behind it.

I have a glass patch on the boat where it was a little convex by mistake. It is sort of longest first 101. If I had done the smallest first; it would have had lots of air. Sorry this is under peelply.. each black line is another layer of glass with the smallest on top..

 

Also, a structural failure is not preventable by the last layer holding and all the rest failing. The structural failure is prevented by the thickness and a quality-air free job.

And my drawing of glassing over the motorwell was semi accurate to longest first laminating...

 

The other line of thought is you don’t want a bend or curve in the glass, applying the smaller pieces first leaves the longer pieces straight, resulting in better strength.

It really doesn’t matter that much because if you did a have decent job it won’t fail either way. The materials you’re using are better than than original.

Is the last 1708 is mat side up then you don’t sand into the glass supplying the strength.

 

I had not considered laying the last layer of 1708 upside down. I think I have some better clarity now! Thanks fallguy & ondarvr! So, does one vs the other make for easier fairing? I will be honest, I was trained years ago to do this, but I've forgotten everything. I should probably go back for training!

 

There is no difference in fairing, but if you develop a hump that must be sanded; the underlying laminate might get damaged. So avoid sand through, which is also a good general rule.

I like the idea of last glass mat up for tapes.

But my hulls are done the other way as we finished our last structural work yesterday.