Super Jet Squarenose build - layup thickness question

[MrBlack]

I'm in the process of re-building my '92 square nose SJ. I'm turning it from a square to round nose, widening the tray, and adding my own custom footholds.

After reading up on some other builds the common theme was 2 layers of 12oz biaxial fiberglass and one thinner layer of 6oz e-glass all layed with epoxy resin.
I decided that I wanted to make sure this thing wasn't going to break on me so I ordered 17oz bias with mat, 12oz bias without mat, and 6oz e-glass.
I ordered enough glass for 2 layers of 17oz, 2 layers of 12oz and 1 final layer of 6oz for both the nose and for the tray/footholds.

My question is:
Is this going to be overkill? Is it just right? or is it not enough?


I don't care all that much about weight (if i did I'd buy a different hull) - I just want it to to be be strong enough but not more than it needs to be.
Also one last question - what do you guys use to finish before paint? I was going to go with US Composites SM Fairing compound

Thanks

 

[SuperN8]

Do a sample layup and check out the result, only need to do patch that is only a few square inches. It will show you the overall thickness, how it will layup, and also allows you to check the rigidity, flex and strength. I am by no means a composite expert. You may only want to do one layer of the 17oz with mat because the mat is going to hold a lot of resin and it is better to double up the layers of material then it is to have layers with a lot of resin in-between. Having a lot of resin between layers can lead to delamination, and a loss of strength.
Maybe 1 layer of the 17oz w/mat, 2-3 of the 12oz and a layer of 6oz.

 

[DAG]

I'm laying up my SN rocker with 4 layers of 12oz biax in the thinnest spots and nearly double that where all the overlap is. just 2 layers of biax is hard to believe. I'm making a hoodliner with 2 layers of 12oz biax and it flex's a ton.

 

[Byeai]

17oz is kinda hard to wet out I did three layers of 12oz on my build I'm still not done but it's solid 12 with mat is way to go

Sent from my SAMSUNG-SGH-I727 using Tapatalk 2

 

[SuperN8]

if you do a layer of 1-17oz, 3-12oz and 1-6oz should give you an overall thickness of about 1/6"
2-17oz, 3-12oz, 1-6oz thickness of about 13/64"
(this is based off uscomposites material thinkness for these fabrics: 6oz = 0.0093", 12oz = 0.037" and 17oz = 0.044")

If you check with the manufacturer they can tell you the thinkness of each cloth and then you can determine how many layers of what will give you the thickness you are after.

 

[brandox2]

How thick would you recommend for a sn rocker build?

 

[SuperN8]

How thick would you recommend for a sn rocker build?

Depends on what and where you are talking about, some areas do not need to be as think as the others. I used most of the stock SMC hull for the rocker on my SN and used 3-4 layers of 17oz to build the new nose of the top deck, feels extremely strong and rigid.
now in the the hull where i chopped 3 inches off the back I rebuilt it with about 5-7 layers of 17oz and it turned out to be just about a 1/4" thick.