3/4 or 1.5 oz mat for a layup shcedule?

[rpuchowicz]

I am doing a stringer job on a 1987 21 foot Cheetah. The plan is to remove the wood, leave the stringer hollow, and reinforce/cap the stringer with mat and roving. I will be using polyester resin. From what I have read the standard layup schedule for glassing stringers seams to involve the use of 1.5oz mat between 18 or 24 oz roving. My question is, can use ? oz mat to conserve resin. Since I can get more strength out of the roving, I would rather maximize the amount or roving and limit the use of the thicker mat which takes a lot of resin. Please through in your 2 cents. Thanks.

 

[oops!]

Re: 3/4 or 1.5 oz mat for a layup shcedule?

the thinner the layup. the more layers you use......but you use less resin on the whole. the big roving or bi ax will drink, but over all the work load will be greater with the multiple layups. the total resen saved will be a gallon or two. so the trade off, is 10 x more work for 2 gallons of resin.

the current standard is 2x24 oz layers. i did that, as well as adding two layers of matt, one 1oz and one 10 oz. the smaller layers underneath.


i would also add foam or other substance to the stringers, instead of just leaving them empty....with a good glass job. even canned foam eek will last for 20 years.

i hope i explained that right

 

[rpuchowicz]

Re: 3/4 or 1.5 oz mat for a layup shcedule?

the thinner the layup. the more layers you use......but you use less resin on the whole. the big roving or bi ax will drink, but over all the work load will be greater with the multiple layups. the total resen saved will be a gallon or two. so the trade off, is 10 x more work for 2 gallons of resin.

the current standard is 2x24 oz layers. i did that, as well as adding two layers of matt, one 1oz and one 10 oz. the smaller layers underneath.


i would also add foam or other substance to the stringers, instead of just leaving them empty....with a good glass job. even canned foam eek will last for 20 years.

i hope i explained that right

I was planning on doing 2 layers of 24 oz roving. I guess what I am trying to ask, is can I go light on the mat but heavy on the roving. From everything that I have read, the mat is not where the strength is (at least when compared to roving) but is mainly there to create a resin rich layer to allow the roving to properly adhere to the substrate. So my thinking is to put the resin to use where it is most effective (in the roving). For this reason I am wondering if I can go with ? oz matt instead of the thicker 1.5oz or 2oz that seams to be more typically used in this kind of layup and save on the resin. Do you even really need mat between the layers of roving once the first layer of mat and roving have been put down?

 

[oops!]

Re: 3/4 or 1.5 oz mat for a layup shcedule?

yup and yup

matt toving matt roving.

the short strands in the csm will help the woven to adhere to each other, without it it will be harder to get a bond.

this is one of the reasons bi ax is such a good product. the csm is allready woven and stiched into the fabric, you want to try to do the first layer of csm and the woven while the resin is still wet, but youll have to wait a bit before the mext layer, just a bit of cure time, so the resin wont get too hot while curing, just an hour ot two

 

[ondarvr]

Re: 3/4 or 1.5 oz mat for a layup shcedule?

The mat is there to reduce the resin rich (resin only) layer between the layers of roving and is needed between each layer, this increases the strength of the bond. I've never seen any data to show whether there's much of difference between 3/4 and 1.5oz mat, but any amount will help.

I don't know how much glass will be left after you remove the wood, but your new layup will need to add back the strength lost from not having the wood inside the stringer.

 

[fixb52s]

Re: 3/4 or 1.5 oz mat for a layup shcedule?

When I did my stringers, I used 2 layers of .75 mat/24 oz roving with great results. You can do what Oops suggests and just use bi ax and not need to layer the mat/roving. I would have gone this route, but at the time, my supplier was out of bi ax.

I will tell you that the 1.5 mat just sucks the resin. I glassed a firewalll last week using 1.5 (left over from when I did my deck last month) and used more resin than I wanted. It made the wall strong but added a lot of weight. In hindsight, I should have used .75 because I just glassed it more for waterproofing. It didn't really need the strength​

 

[Coors]

Re: 3/4 or 1.5 oz mat for a layup shcedule?

I am doing a stringer job on a 1987 21 foot Cheetah. The plan is to remove the wood, leave the stringer hollow, and reinforce/cap the stringer with mat and roving. I will be using polyester resin. From what I have read the standard layup schedule for glassing stringers seams to involve the use of 1.5oz mat between 18 or 24 oz roving. My question is, can use ? oz mat to conserve resin. Since I can get more strength out of the roving, I would rather maximize the amount or roving and limit the use of the thicker mat which takes a lot of resin. Please through in your 2 cents. Thanks.

Just stick some composite in the stringers(not plastic) to take up space.
Then pour in an epoxy slurry of sawdust and glass fibers;installing some roven etc, every 1/4 inch.
Then close the top of the stringer. After that, it doesn't matter what size material is used on the top.

 

[salty87]

Re: 3/4 or 1.5 oz mat for a layup shcedule?

The plan is to remove the wood, leave the stringer hollow, and reinforce/cap the stringer with mat and roving.

this plan makes the assumption that the existing glass 'shells' are going to survive the wood being removed and also that the builder built them good enough to even keep for your project. have you taken a look under the old foam yet?...all depends on what you've got to work with but it can be a gamble to re-use some of it.

 

[rpuchowicz]

Re: 3/4 or 1.5 oz mat for a layup shcedule?

this plan makes the assumption that the existing glass 'shells' are going to survive the wood being removed and also that the builder built them good enough to even keep for your project. have you taken a look under the old foam yet?...all depends on what you've got to work with but it can be a gamble to re-use some of it.

I think I will be able to get the plywood out without destroying the case. From the test holes that I drilled, it appears that the plywood strings have delaminated from the fiberglass and are just floating in their fiberglass cases. The orginal stringers were glassed all the way to the top and should make for nice forms for an overlay.

 

[rpuchowicz]

Re: 3/4 or 1.5 oz mat for a layup shcedule?

Just stick some composite in the stringers(not plastic) to take up space.
Then pour in an epoxy slurry of sawdust and glass fibers;installing some roven etc, every 1/4 inch.
Then close the top of the stringer. After that, it doesn't matter what size material is used on the top.

What core material would you suggest? My plan was to keep them hollow because I am not sure if I could get a good secondary bond on the inside of the stringer (even with epoxy). Its kind of hard to get in their and really clean them up and rough them up.

My current plan is to keep them hollow and build up the outsides with 1708 until I achieve a thickness of about 3/8. Doest this seem like enough?

 

[Coors]

Re: 3/4 or 1.5 oz mat for a layup shcedule?

Oh, my 4winns stringer shells are 3 inches wide. I had plenty of room to dig out rot. I was thinking yours might be close to the same; I hade a 1x in there, covered by foam, to lay up f/g to. And 3/8" f/g.
I cleaned out with acetone and white vinegar- it stuck.