Cruisers Forum
 


Join CruisersForum Today

Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 26-03-2020, 11:13   #1
Registered User
 
Madehn's Avatar

Join Date: Nov 2014
Location: Kemah Tx
Boat: Gulfstar 51
Posts: 189
Best Way to Fiberglass

I am in need of a fiberglass panel- roughly 6 feet by 3 feet that will become a new deck over a well in the aft part of my boat- it will be supported all around the perimeter as well as having transverse support structure underneath. I am planning on making the decking with a 3/4 inch 20 density closed cell foam core followed by 2 layers of biaxial cloth on each side followed by 3 layers of fiberglass cloth on each side with epoxy resin. is this the proper order of the two types of cloth or should I alternate between biaxial and cloth? also trying to figure out how much allowance I need to leave on the sides for the added layers of cloth? the panel fits down into a lip on three sides so I would like to get it close both for appearance and to get maximum support from the lip structure- lip is probably an inch and a half tall and an inch and a half wide. also for the strengthening transverse members I was told to just cut one inch strips of the foam and fillet and glass them to the underside- I was going to use 2/4 with the vertical side being 4 inches but like the idea of no wood anywhere to rot- advice?
__________________

Madehn is offline   Reply With Quote
Old 26-03-2020, 12:12   #2
Registered User

Join Date: Nov 2019
Posts: 922
Re: Best Way to Fiberglass

I canít visualize your engineering

To stiffen panels Prisma Preforms are widely used in the marine industry

They save much time

https://www.jamestowndistributors.com/mobileportal/show_product.do?pid=57770

Do some googling
__________________

slug is offline   Reply With Quote
Old 26-03-2020, 12:16   #3
Registered User

Join Date: Oct 2011
Location: East Coast, Canada
Boat: Big C Marine, 15 metre Catamaran
Posts: 685
Images: 2
Re: Best Way to Fiberglass

I'm not sure I'm getting this right. First of all, what weight of glass are you using. And what weight of foam? 20 what? I don't think 20kg is available, and it would be very weak in any case. So 20lb foam is my assumption, which is very heavy for such a small piece. If 20lb foam, then you'd only need a very light coating of biax on each side. Not near what you're suggesting. Say 400 gsm on each side, and maybe a 300gsm uni. but 20lb foam is very strong, and heavy, all by itself.

I don't know what you mean by fiberglass cloth. There are many weights of cloth.

Here's what I'd use, and you can perhaps extrapolate from that.

3 feet wide by 6 feet long. I'd use 80kg (5 lb) foam, and two layers of 600gsm uni, and one layer of 600gsm biax. The uni would go in the 3 foot direction, and the biax doesn't matter. I'd put the uni first, only because the biax is usually easier to fair. Do this on each side.

With this layup, I'd be surprised if you need any ribs.

Cheers.
Paul.
__________________
If you can dream it; with grit, you can do it.
GRIT is offline   Reply With Quote
Old 26-03-2020, 12:49   #4
Registered User

Join Date: Oct 2011
Location: East Coast, Canada
Boat: Big C Marine, 15 metre Catamaran
Posts: 685
Images: 2
Re: Best Way to Fiberglass

As an addendum. Putting a rib transverse, on the layup I described, will not help much, except directly above the rib. If using my layup, and you really want a rib, put it longitudinally, across the uni, and that'll help spread the load. Be sure your biax is 45 degrees each way to the uni.

If you don't want to use uni, and are using 0/90 glass, then I'd not bother with the biax, as it's just going to add weight. Use a total of about 2000gsm of 0/90, on each side, and install your rib, and you'll be fine.

Resin infusion gives 1mm thickness for 1000gsm of glass. Hand layup is about 1mm thick for 600-750gsm of glass, depending on how much you squeegy.

1000gsm is about 34oz (someone correct me here)

My apologies if you're not familiar with the metric system, but that's how we built our boat. 1mm is 1/25th of an inch.

Cheers, and good luck.
Paul.
__________________
If you can dream it; with grit, you can do it.
GRIT is offline   Reply With Quote
Old Yesterday, 03:52   #5
Registered User

Join Date: Dec 2009
Location: Australia
Boat: building Roberts Mauritius 43ft
Posts: 1,502
Re: Best Way to Fiberglass

I just skimmed through the comments but I would not disagree any advice given, BUT I definitely wouldn't use epoxy, vinylester would be better but as it won't be immersed in water I would consider Polyester the way to go.

There's quite a few threads on this very topic.

https://www.thehulltruth.com/boating...-building.html
coopec43 is offline   Reply With Quote
Old Yesterday, 05:44   #6
Registered User

Join Date: Jul 2010
Location: Oriental, NC USA, Sailing Capital of Eastern North Carolina
Boat: None presently
Posts: 104
Re: Best Way to Fiberglass

Per: coopec33 This is correct. Epoxy is a waste of money and you would never see the strength of the epoxy used to its potential. Vinylester is great but polyester will be fine for this application. Easy and inexpensive. For a panel this size, any directional glass on the underside would work fine. Even 24 oz. woven roving would be fine and much less costly. Fiberglass mat is good in compression and a few layers should be used on the top side. I started using fiberglass professionally in 1978. Since that time, I have almost never found 'cloth' to be worthy of inclusion in any laminate. Exception being very thin, very light weight layup. Like the top of a kayak. Stay away from the stuff as it has potential to delam and peel. Doubling the core section gives 5X the stiffness. If you can use thicker core do so. Ribs glassed under will be beneficial. I would not use less than a 7.5 lb per cubic foot foam. Heavier solid urethane foam panel would be good and stiffer and easier to work with if you are trying to make a flat panel. don't over think this project. Use simple, inexpensive materials and don't get talked into vacuum bagging or infusion or anything complicated. This boat will not feel an extra 20 lbs in the weight of this repair.
FPNC is offline   Reply With Quote
Old Yesterday, 12:39   #7
Registered User

Join Date: Dec 2009
Location: Australia
Boat: building Roberts Mauritius 43ft
Posts: 1,502
Re: Best Way to Fiberglass

FPNC Absolutely spot on!


Couldn't have said it better myself.
coopec43 is offline   Reply With Quote
Old Yesterday, 12:48   #8
Registered User

Join Date: May 2008
Posts: 45
Re: Best Way to Fiberglass

Forget the cloth, just use uni in both directions on each side and a layer of peel-ply to aid fairing and bonding. Transverse framing at 2ft intervals will make it nice and stiff so little flexing to compromise the bonding to the lip. I am assuming the panels to be fixed permanently in which case I would prefer epoxy but if not any of the resins will be fine
Slainte1 is offline   Reply With Quote
Old Yesterday, 14:24   #9
Registered User

Join Date: Nov 2019
Location: Gold Coast
Boat: Farr 43`
Posts: 31
Re: Best Way to Fiberglass

When making panels I either taper the core at the edges to bring the skins together or remove core material at the edge and fill with filler /reinforcement as appropriate.

For a 25mm core I would fill with a laminate equal to the combined skins.
If fasteners were required (hinges?) there would be some hi density filler involved e.g. mineral talc.

Techniques can be combined e.g. bevel cut and fibre fill.

Avoid laying cloth around (tight) corners.
- Dimensioning is difficult.
- Strength is reduced.
- Laminate failure probability at the corner is high.
Rucksta is offline   Reply With Quote
Old Yesterday, 23:42   #10
Registered User

Join Date: Dec 2009
Location: Australia
Boat: building Roberts Mauritius 43ft
Posts: 1,502
Re: Best Way to Fiberglass

If it is possible to fiberglass a rib (or a number of ribs) into the panel it would stiffen it (The same principal as corrugated roofing iron or a rib in a motor car body panel)

I put a rib in the lids of my water tanks and they are tremendously strong and won't bend. Maybe I should have put some corrugations (or ribs) in the walls of the water tanks too?
Attached Thumbnails
Click image for larger version

Name:	Screenshot_2020-03-28 Holding tanks.jpg
Views:	9
Size:	70.4 KB
ID:	211437   Click image for larger version

Name:	Screenshot_2020-03-28 car body panel rib - Google Search.png
Views:	7
Size:	273.9 KB
ID:	211438  

__________________

coopec43 is offline   Reply With Quote
Reply

Tags
fiberglass

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Best way to modify fiberglass? TooCoys General Sailing Forum 29 22-03-2017 20:51
Best Filler for Repairing Screw Holes in Fiberglass cabo_sailor Construction, Maintenance & Refit 17 17-04-2011 16:23
Best Fiberglass Dinghies unbusted67 Product or Service Reviews & Evaluations 20 08-03-2011 12:29
Best Tool for Cutting Fiberglass Deck ? bazzer Construction, Maintenance & Refit 62 21-02-2011 15:56
Fiberglass Dinghy Stowed Solidly on Foredeck is Best; Bernie Eskesen Auxiliary Equipment & Dinghy 22 23-02-2009 05:51

Advertise Here


All times are GMT -7. The time now is 23:48.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.