urathane foam core?

[rapscallion]

http://www.magallanesboatbuilding.co...e%20method.htm


what do you think of this?

[War Whoop]

The main problem with urethanes is "peel" strength like they have none until around the density of granite.

[dereksireci]

We use urethane cores all day every day for transoms. Coosa makes a product with some fiberglass in it. Michigan composites makes a molded product that you can easily add details to compared to something cut out of a sheet.

War Whoop, what do you use? and what is peel strength?

[rapscallion]

Originally Posted by dereksireci

We use urethane cores all day every day for transoms. Coosa makes a product with some fiberglass in it. Michigan composites makes a molded product that you can easily add details to compared to something cut out of a sheet.

War Whoop, what do you use? and what is peel strength?

Do you use exoxy with urathane or poly?

[dereksireci]

Polyester

[rapscallion]

Can you use urathane for a sailboat hull?

[JEF]

It is a very interesting idea for me looking for a core which has this thickness, 100 mm, to act both as a stable core and insulation at the same time. I am lookin at high density XPS instead of urethane and if you look at the shear strength it is between H60 and H80 Divinycell so I believe the problem with delamination as you can get with Urethane will not be a problem any more.

[jimslade]

Ive read Hankinsens book and I think he would not advocate this type of building. Peel strength is the force required to separate the glass layer from the foam.

[JEF]

Jimslade, the peel strength as you refer to, isn't that how good the bonding is made between the core and the skin? The negative thing with urethane is the bad shear strength but with this method the shear forces are reduced so that is why it seems to work well.

[AVMan]

Standard urethane foam cores, in high densities, can be used for hard points and transom cores along with sufficient fiberglass skins. While peel strength does come mainly from the bond between the skins and the core, it also depends on the friability (how easily the foam crumbles or degrades when rubbed) of the foam. Low density urethane foams are notoriously friable and therefore not well suited for dynamic applications such as boat hulls, decks, etc.

[War Whoop]

Originally Posted by AVMan

Standard urethane foam cores, in high densities, can be used for hard points and transom cores along with sufficient fiberglass skins. While peel strength does come mainly from the bond between the skins and the core, it also depends on the friability (how easily the foam crumbles or degrades when rubbed) of the foam. Low density urethane foams are notoriously friable and therefore not well suited for dynamic applications such as boat hulls, decks, etc.

Bingo! We have a winner

[SamSam]

Below is a site and a short blurb about polyisocyanurate foams. They are a standard item at commercial insulation suppliers and are usually used under hot tar roofs. The boards can be gotten in different thickness up to 9", in different densities to the point of withstanding a moderate amount of foot traffic with no damage. It can be gotten without the fiber facing and some brands have short fiberglass fibers in the foam itself. Inexpensive also.

http://www.alliedbuilding.com/produc...uctID=12221110
Our PIR (polyisocyanurate) foams are manufactured according to international standard. PIR foams are chemically similar to but higher performing than polyurethane foams. Outstanding thermal (flame resistance classification B1) and moisture resistance make PIR products highly effective insulating materials. PIR is also widely used in composite sandwich construction due to its light weight, cost efficiency, and compatibility with most resins and adhesives. Carving and sculpting can be done with PIR products as well due to its machinability and dimensional stability. Our PIR are produced in a variety of densities and sold as blocks, sheets, and fabricated parts according to customer's needs.

[rapscallion]

Originally Posted by SamSam

Below is a site and a short blurb about polyisocyanurate foams. They are a standard item at commercial insulation suppliers and are usually used under hot tar roofs. The boards can be gotten in different thickness up to 9", in different densities to the point of withstanding a moderate amount of foot traffic with no damage. It can be gotten without the fiber facing and some brands have short fiberglass fibers in the foam itself. Inexpensive also.

http://www.alliedbuilding.com/produc...uctID=12221110
Our PIR (polyisocyanurate) foams are manufactured according to international standard. PIR foams are chemically similar to but higher performing than polyurethane foams. Outstanding thermal (flame resistance classification B1) and moisture resistance make PIR products highly effective insulating materials. PIR is also widely used in composite sandwich construction due to its light weight, cost efficiency, and compatibility with most resins and adhesives. Carving and sculpting can be done with PIR products as well due to its machinability and dimensional stability. Our PIR are produced in a variety of densities and sold as blocks, sheets, and fabricated parts according to customer's needs.

Do you know what resins and adhesives are compatible with this foam?

Epoxy? Polyester?

[SamSam]

I used it with polyester. Locate a small piece at a jobsite or an insulation supply co. and put some resin on it and see. Maybe the manufacturer can tell you. Sam

[rapscallion]

Originally Posted by SamSam

I used it with polyester. Locate a small piece at a jobsite or an insulation supply co. and put some resin on it and see. Maybe the manufacturer can tell you. Sam

Interesting!

what were you building? How well has it held up?