Fibreglass materials

[Sangster21]

I have tabbed in my transom, and am ready to start on my stringers. 18oz roving is 8$ a yard, 1-1/2 oz CSM is $6.30 a yard and 1708 is $15 a yard. As I understand it, you need to layer CSM in between layers of roving. This totals $14.30 a yard and is only slightly less than using the 1708. Seems to me the logical choice is to go ahead and buy the 1708. Having to lay csm in between the roving is an extra step that is not needed with the 1708. What would you do?
Alan

 

[tpenfield]

Re: Fibreglass materials

The 1708 is the better choice for a high stress application (such as tabbing stringers) regardless of the price.

 

[Georgesalmon]

Re: Fibreglass materials

For what it's worth I made some small boats for the US Navy. Specifically the 7 meter RIB's that are replacing the old motor whalers. They were made with 7 layers of 24oz woven roving with no CSM in between. I questioned the contract specs on this because I was always taught that you must use CSM between WR or it won't stay together. The Navy SUPSHIPS people produced test results proving that the the interlaminar shear strength did not get better with the addition of CSM between WR. In fact, the tensile strength was slightly reduced. The flexural modulus would of course increase because of increased thickness.

 

[oops!]

Re: Fibreglass materials

For what it's worth I made some small boats for the US Navy. Specifically the 7 meter RIB's that are replacing the old motor whalers. They were made with 7 layers of 24oz woven roving with no CSM in between. I questioned the contract specs on this because I was always taught that you must use CSM between WR or it won't stay together. The Navy SUPSHIPS people produced test results proving that the the interlaminar shear strength did not get better with the addition of CSM between WR. In fact, the tensile strength was slightly reduced. The flexural modulus would of course increase because of increased thickness.

this test result is not what the manufacturers of the glass and resin have found. they test the stuff all the time.

the reason is that resin is brittle.....very brittle...the bond between each layer of woven will have a resin rich area between each laminate.
the reason for the csm in between is to soak up the resin rich layers between the laminate. this is especially due to the thicker woven glass. the thicker the glass the deeper the resin rich pockets.

the csm, with its shorter and multi directional strand pattern soaks the resin well and will make a far stronger laminate.

btw.....the prices you are quoting are really really spendy.

1708 should be around 6-9 bux a yard. and the chopped is around 3.

did you look in nanamio? i can probably buy here and ship to you greyhound for cheaper than what youre quoting

 

[rickryder]

Re: Fibreglass materials

US Composites 1708 is $6.60 a yd and csm is $2.75 yd

 

[Sangster21]

Re: Fibreglass materials

The prices quoted are from Industrial Plastics here in town. I think it is the only game in town to get bulk materials. It may be one of those places that without an account you get worked over on pricing. I want to get my stringers in this weekend, and I am out of cloth.
Oops, is there a place in Nanaimo I should be contacting?
Alan

 

[Yacht Dr.]

Re: Fibreglass materials

For what it's worth I made some small boats for the US Navy. Specifically the 7 meter RIB's that are replacing the old motor whalers. They were made with 7 layers of 24oz woven roving with no CSM in between. I questioned the contract specs on this because I was always taught that you must use CSM between WR or it won't stay together. The Navy SUPSHIPS people produced test results proving that the the interlaminar shear strength did not get better with the addition of CSM between WR. In fact, the tensile strength was slightly reduced. The flexural modulus would of course increase because of increased thickness.

Just to add to oops ..

Shear strength is not really an issue with FRP boats. There are few instances where Shear would be involved.

Tensile strength is not really an issue with FRP boats. There are almost no reasons to pull your boat side to side or for and aft ( stretch your boat ).

Flex strength ( what I call Compressive strength ) is Very Important in boat builds IMO. You Need this type of hybrid strength in your hulls for impacts and such.

You need the mat between Woven. .. before and after..

Another thing .. Have you ever tried to Lam 4-7 layers of just woving ? .. Think Air bubbles .. and lots of them ( unless you resin rich which is like Oops said is not a good idea ).

Back on the OP ..

Sangster .. If you need to buy now..then you have to bite the bullet.

1708 would be your best bet.

If you have to do it now and the overcost is going to be 40 bucks..then you gotta do what you gotta do.

Happy boating

YD.

 

[Sangster21]

Re: Fibreglass materials

Thanks for the input, I went ahead and bought another 10 yards of 1708, and some CSM to coat the deck. I did talk to the manager about prices. I did get %15 off, so that helped a bit. He suggested that some of the cheaper materials may be offshore made and the quality may suffer. If I were to take on another big project, I think I would look into ordering materials online.
Alan

 

[Cadwelder]

Re: Fibreglass materials

Another thing .. Have you ever tried to Lam 4-7 layers of just woving ? .. Think Air bubbles .. and lots of them ( unless you resin rich which is like Oops said is not a good idea ).

Air Bubbles that are near impossible to get out too..... I tried to laminate 3 layers of woven on a mold once without the CSM.....never again.