woven roving too heavy?

[MercMark]

I've been looking to buy supplies to do transom and stringers in my boat.<br /><br />It's a 15 thundercraft wildcat (looks like a small checkmate) with a Mercury 850, straight four cylinder 85hp outboard on the back.<br />It's a small boat used for pleasure touring at speed, and water skiing on only inland lakes (the Kawarthas in Ontario Canada, Trent Severn system)<br /><br />One supplier has told me that 1.5 oz mat, 18 oz roving, 1.5 oz mat, 18 oz roving, as I've seen recommended here is waaaay overkill, and it would add hundreds of pounds to he weight of the boat. He said that kind of construction is the kind of thing you'd find in the bulkheads of a large sailboat.<br /><br />He suggested using two or three layers of 6 oz cloth with West System. <br /><br />I have "runabout renovation" on the way, but I'm having trouble with the courier (don't use amazon.com and DHL courier). I'm losing time and need buy materials by tomorrow, Saturday at the latest.<br /><br />This is coupled with the fact that nobody carried roving around here, and most stores haven't heard of a mat specific for use with epoxy.<br /><br />I've been dealing with Boater's World Canada out of Peterborough (very helpful) and two marine specialty stores in Ottawa (also both very helpful).

 

[prockvoan]

Re: woven roving too heavy?

18 oz is not over kill for stringers,its what you should use.Matting,use 2 oz,you can get away with 1.5.Weight will not be that great for the amount that you will be using.

 

[ondarvr]

Re: woven roving too heavy?

Use the 18 oz, most boat builders don't use cloth for anything. It's all mat or chop and roving or other nitted (combination non woven glass and mat stitched together)products.<br /><br />Are you using epoxy or polyester resin? you mentioned epoxy but didn't say if that's what you were going to use.

 

[MercMark]

Re: woven roving too heavy?

I have suppliers in one ear telling my I'm crazy to use that much material, and I have boat builders in the other telling me I'm crazy not to.<br /><br />It's weird because I thought it would be the other way around. I thought the suppliers would be the ones trying to sell me extra material. I really get all turned around when I get this unexpected sort of feedback.<br /><br />So if I use woven roving what about one layer of cloth and one layer of roving?<br /><br />I'm also a bit ticked off because I shelled out for "Runabout Renovation" and at first glance he doesn't mention cloth type or weigh at all.

 

[ondarvr]

Re: woven roving too heavy?

You didn't say if you are going to epoxy or poly. If you have the cloth you can use it, but cloth works better with epoxy. Are you still going to use mat? <br />If this boat is only 15' long, the difference in weight between the to methods won't add up to much. <br /><br />Mat, roving and poly will work just fine.

 

[MercMark]

Re: woven roving too heavy?

I'm planning on using epoxy because I don't know if there have been repairs done in there before. I'd rather not run into a situation where there's some expoxy in there and the materials I've bought won't stick. I'm also counting on being able to add layers while the first coat is in the gel state and have them chemically bond.<br /><br />I plan on using west system with the 205 hardener.

 

[ondarvr]

Re: woven roving too heavy?

Epoxy will work fine, but I don't think they would have used epoxy to do any of the earlier repairs if there are any. Not that many people use epoxy on repairs and almost no boat builders use it to make boats, 99.999...% use poly. If the money is not a issue use epoxy, if it is, use poly. In this type of repair you won't really see much of a difference.

 

[snapperbait]

Re: woven roving too heavy?

MercMark.. Epoxy and mat don't work together.. <br /><br />Mat must be specifically for epoxy, otherwise the binder that holds the mat together will not disolve in epoxy... In other words, you'll have a big mess...<br /><br />You might look into biaxial cloth (biax) with mat stitched to the back.. I think it would serve you better..

 

[BillP]

Re: woven roving too heavy?

I'll just say it bluntly...epoxy or not, the supplier telling you to use 2 layers of 6 oz for stringers and transom is wrong...off the map wrong. NOBODY in the boat building business does it that way because it is WAY too weak. Even the cheapest POS boats made don't build that light. <br />Please don't tell me WEST is saying that.<br /><br />"1.5 oz mat, 18 oz roving, 1.5 oz mat, 18 oz roving" is accurate for stringers and around the transom. The "field" of the transom only needs one or two layers to protect the wood from dings that would let moisture in. Many boat builders use 3oz mat and 24 oz woven rovin with the same lamination schedule.<br /><br />Don't feel bad about the Runabout Renovation book. It is lacking a lot of specific info but is better than nothing if you don't know what to do.

 

[SuzukiChopper]

Re: woven roving too heavy?

Just to add my 2 cents...<br /><br />I used 2 oz mat, 24oz roving, 2oz mat, 24oz roving, 2oz mat and a layer of light cloth on my transom, didn't add hundreds of pounds to my boat. I also used the SAME layup on all of my stringer and half that on the floor. the boat if anything is a couple hundred pounds lighter and about 30 times stronger than it was before I did any of it. All done with vinylester resing (5 gallons). <br /><br />I was told though, that if you plan on using heavy roven for your layups, plan on using double what I used with the vinylester. I was told it takes quite a bit more to wet it out properly.

 

[BillP]

Re: woven roving too heavy?

Weight:<br /><br />Resin weight is all in ratios of lbs per oz of glass.<br /><br />Woven rovin is measured in oz per SQ YD and is calculated at 1oz resin for 1oz of glass. 20 oz of glass uses 20 oz of resin.<br /><br />Mat is calculated in oz per SQ FT...2oz resin for every 1oz of glass. 20oz of glass uses 40oz of resin.<br /><br />Do the math on your project and see what each weighs.

 

[MercMark]

Re: woven roving too heavy?

Runabout Renovation, as I was reading last night says to use bare wood stringers, and maybe put in a layer of mat if the builder did. I was a little suprised.<br /><br />Like I said in another post, I plan on cutting into the boat and seeing what it's made of and using the same materials. It's so shallow that I'd be suprised to see anyting bigger than a 2x4 as the center stinger.<br /><br />If 18oz roving is so common, then why am I having so much trouble finding it, and why do marine specialty store owners look at me like I'm on crack when I say any of the following:<br /><br />-I want 20-30 yards of woven roving (they don't have it and can't imagine why I need that much)<br /><br />-I need mat made for epoxy not for polyester resin. (neverheard of it)<br /><br /><br />I've already bought a size B set of West System, But I'm considering switching to polyester resin for control over the kick time. If if find the kick time is too fast with the west, I have to go buy an new can of the slower hardener. Does polyester resin have a gel state the way West System does, where the next layer will still bond chemically. I've always sanded between layers of polyester resin, but I'm hoping to cut that sanding time out of this project to get more done. One reason to spend the money on West System.

 

[prockvoan]

Re: woven roving too heavy?

With poly resin,you can put more that one layer of glass and then wet it out,or lite sand when adding a second coat.No need of washing like epoxie resin if you had started a lay up and not able to complete it till the next day(bluing).<br />Poly in my book is very easy to use compared to epoxie,less then half the price too!When using poly resins,one must use it with care,its a must.

 

[MercMark]

Re: woven roving too heavy?

Originally posted by BillP:<br /> Weight:<br /><br />Resin weight is all in ratios of lbs per oz of glass.<br /><br />Woven rovin is measured in oz per SQ YD and is calculated at 1oz resin for 1oz of glass. 20 oz of glass uses 20 oz of resin.<br /><br />Mat is calculated in oz per SQ FT...2oz resin for every 1oz of glass. 20oz of glass uses 40oz of resin.<br /><br />Do the math on your project and see what each weighs.

I don't know what's under the floor. For estimating purposes I had assumed (worst case) four stringers, 6" up the side and 6" onto the hull. So that's a 24" wide strip per stinger per layer. Rolls of woven roving are usually 50" wide around here, so I need eight 15 ft (5yd) lengths to do two layers on four stingers. sor that's 40 yards of a 50" roll.<br /><br />If I look at that realistically, by boat isn't 8 ft. wide. The stringers themselves aren't as long as the boat, so there's a lot of waste in that estimate.<br /><br />I probably only have three stringers which would mean three 24" wide strips at 5yds. but unfortunately to get the length and because of the width the rolls are I still have to buy the same amount of roving as if I had four stingers. Or, I buy 30 yards and divide the width of the roll by the number of stringers. The second layer isn't as wide as the first layer because of feathering back the edges of each layer to avoid stiffness lines in the hull. Maybe 30 yards will do.<br /><br />Or I use only one layer of Roving if the existing stringer coverage indicates thats how much was in there to start.

 

[MercMark]

Re: woven roving too heavy?

I've just has a builder from CA suggest using 12oz cloth with biaxial fabric (not sewn together with another layer just the fabric) for use with epoxy.<br /><br />Any thoughts?<br /><br />Seems like this is not an exact science, everyone has a different way. I'm hoping to find a middle ground.

 

[swimmin' for shore]

Re: woven roving too heavy?

Back to the subject of "Runabout Renovation". Don't be upset about his methods. They're not bad. Keep in mind that he's providing you a basic overview of boatbuilding, and he does that well. Also, his book is written in the early 90's, and we've come a long way since then. Epoxy, as I understand it, was unheard of then. So was vinyl ester. There are a lot of newer books out there, and you can read them also. There are also a lot of sites like this, and as far as I've seen, the information given and shared here is more up to date than what I've learned from marinas. Go with the heavier roving. It'll be worth the effort.

 

[SuzukiChopper]

Re: woven roving too heavy?

The roving shouldn't be hard to find. US Composites has it, Iboats may even have it. The mat is almost not necessary when using epoxy, the mat is used to help poly and vinylester resins bond. It also helps fill the voids in roving providing more strength. Because epoxy is so much stronger and is a glue, the matting between layers can be elminated, that's why it's hard to find. It sure wouldn't hurt using it though.<br /><br />The thing with advice too, is you have to use some common sense when accepting it. With most builders that do it for a living, especially when there are more than one around, will do what they were taught or what they see as the best, but because even shabby work can last 10 years, may never see the results after any period of time. <br /><br />The builders/hobbiest on this forum that have repaired and built boats, have a vested interest in the integrity, saftey and strength of their work. They use their boats frequently and SEE first hand the results of building one way or another. I would say that if the majority of people are suggesting a method on this forum, you should tend to lean towards it. It's been proven. But this is just my opinion and I'm not meaning to discredit anything told to you. Only you can decide what's best for you. Someone may look at you like you're on crack, or you're crazy, but they aren't the ones that are going to be in the boat.

 

[MercMark]

Re: woven roving too heavy?

Fair comment Suzukichopper.<br /><br />I have also purchased West System's fibreglass boat restoration guide. BTW far better info for much less money that Runabout Renovation. Save your cash, buy the West System guide.<br /><br />In the guide from West Sys. they have a table which shows what thickness any given weight of fabric will give you cured with epoxy. They say match the thickness of what was there. From what I could tell, they don't suggest what to build it up with, just give you the tools know how many layers, of whatever you choose to use, that you will need to match the thickness you measure at the time of demo.