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Old 15-08-2007, 03:26   #16
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Generally
, you describe an accepted technique, but I wouldn’t use a “general purpose” ortho’ resin anywhere on a boat. Stick with an Isophthalic (ISO) resin system, throughout.
You’re addressing a very complex technical subject, with a very broad query.
Can you be more specific?
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Old 15-08-2007, 05:39   #17
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Not all epoxies and vinyl esters are equal. Although there have probably been recent advances in resin chemistry, several years ago I could not find a low viscosity epoxy with a high heat distortion temperature. Thin room temp epoxies had HDTs around 150 - 170 F. Epoxies with HDTs over 200 F were quite thick, and to achieve the best properties need to be post cured or high temperature cured, just like pre-preg epoxies. Strength properties also vary with the specific resin system, with high temp cure epoxies usually coming out on top.

I found premium vinyl ester resins (Dow 8084 being one of the best) to be equal to or better than room temperature cure epoxies for just about all physical properties, although the prices are just about the same. I believe vinyl ester resins were developed partly for making tanks and other water and chemical reisistant structures, so it makes sense that they would be better for boats.

I built a lot of specialty small boats with thin skins using vinyl ester, Kevlar and carbon. Hulls made with vinyl ester resin were just about as good as high temp cured epoxy hulls; and vinyl ester is much easier to use with MEKP as a catalyst and the ability to adjust gel times. I am still using vinyl ester building my 32 footer, unless I just need to glue something together, in which case I use epoxy.

Regular polyester? Good for lower strength structures using glass reinforcement that will not be in constant contact with water or chemicals.
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Old 15-08-2007, 05:56   #18
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I'll still stick to me guns and say if you are using a timbercore (balsa is timber) the only resin to use is epoxy.

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Old 18-08-2007, 15:36   #19
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epoxy and polyester resins

i'm with cat man do, if you are bonding or glassing wood use only epoxy. Polyester does not bond well to wood. I have been able to pull complete sheets of glass off wood boats that were skinned using polyester.
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Old 18-08-2007, 16:08   #20
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Quote:
Originally Posted by Red Horse
i'm with cat man do, if you are bonding or glassing wood use only epoxy. Polyester does not bond well to wood. I have been able to pull complete sheets of glass off wood boats that were skinned using polyester.
Rich
A little aside (not meant to drift the productive and great thread):

ALL glass treatments of wooden boats should be done with *mechanical* fasteners that bind the mat to the to the wood, which in turn binds the epoxy/mat fiberglass to the wood. It's the only way to ensure the fiberglass skin coating doesn't delaminate from the wood. Some get lucky, but this is the only way to be sure - be it vinylester, polyester or epoxy.
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Old 18-08-2007, 16:24   #21
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I'm not sure what you mean by mechanical fastners
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Old 18-08-2007, 18:16   #22
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Quote:
Originally Posted by Red Horse
I'm not sure what you mean by mechanical fastners
Rich
Well a mechanical fastener is usually a screw, bolt, nail, clip, clamp or similar. Sorry I don't know exactly what Sully had in mind when he said that.

I'm looking at "Raptor Nails" which are plastic if I need to fasten the fiberglass to our ply hull before it's wetted out with epoxy.

Raptor Nails and Staples - UCI Raptor
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Old 18-08-2007, 22:03   #23
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mechanical fastners

Bolts, nails etc was my first thought, but wasn't sure I might have missed something in translation. Resistance to peel is far superior with epoxy than polyester when using glass over wood. It is generally not a good idea to use mat in a layup with epoxy as the binder in the mat inhibits addhesin.
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Old 18-08-2007, 22:34   #24
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so this has been an informative thread. Reading all these posts it seems like a basic requirement not to use polyester resin yet the majority of boats I'm doing research on, still use it.

It sounds like the process has a impact on the quality and level of strength. So you can offset some of the negative aspects of GRP whether its by heat curing or using more material. Do I have that right?
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Old 18-08-2007, 23:37   #25
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Reading that post of yous for the third time Sulli, definetly want more info on this.

I have Never seen or heard of a boat with screws bolts etc to hold glass on.

If the resin matrix fails and your are left with a couple of screws to keep things together, I think your boat is rooted.

Steel staples to hold glass on are a problem as they have been knownt to rust and cause small rot spots.

I heard of plastic staples once on a strip plank project, leave em in, sand em off, but cant find anything about them.

Bare in mind that today, composite boats have no fsteners at all in them, everything is bonded.

Dave

PS:Good on ya Rick, all the wankers in OZ at all the tool shops thought I was on Drug's.

Just goes to show that the tools on the shelf are'nt the only ones in the shop.
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Old 18-08-2007, 23:47   #26
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polyester vs epoxy

There seems to be some misunderstanding regarding the use of resins. Epoxies are best used for wood or foam cored construction and when using glass skins on said wood boat. Polyester or vinylesters are generally used when building an all glass boat, or a foam cored boat, and is preferred by production builders for cost effectiveness. My experience with epoxy comes from working in a small aerospace company. Epoxy is preferred in aerospace for its superior adhesion and strength.
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Old 19-08-2007, 00:10   #27
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fastners and fiberglass

My boat was built in strip plank usingn a male mold inside out. No "mechanical" fastners what so ever. All parts were vacumn bagged. My resin system was Shell 821 resin. I can't remember the hardner, My resin and hardner were from EV Roberts in Los Angeles. All the custom boats I know of have been built in epoxy. Epoxy is prefered for one offs because you don't build a female mold as is generally done when using polyesters,also one offs are either wood or foam cored.I hasten to add I am not up on construction methods used by production builders, so my info may be dated. I will stand by my statement that polyesters do not bond well to wood This discussion could easily lead off into the different build methods
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Old 19-08-2007, 05:36   #28
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Ok... and sorry for the thread drift. This is a great thread. I'm especially enjoying the differences between the various types of "goo" that can be used with the mat/woven roving. It does seem most boats have used polyester in the past.

Here goes:

The secret to taking a wooden boat (timber) and putting on a fiberglass skin is mechanical fasteners. What are mechanical fasteners? One of the most common would be staples. Here's how it works:

You wet out an area with your polyester, vinylester or epoxy resin. Next, you apply the first layers of roving and mat - or just mat depending on your taste (mat is necessary). Wet that.

Now, after *some* drying, but not too much, take a staple gun and use heavy galvanized, bronze or monel staples and staple the layers you just put up to the boat at approx 2" intervals all over the entire surface area. (LOTS of staples)

Once this layer is *mechanically* fastened to the hull, you are free to add as many extra layers as you like, building on this mechanically fastened layer.

The staples are best because they allow the wood to move below the fiberglass *without* cracking the fiberglass or popping out of the wood. They give/bend just a bit, but hold on tight.

This is the secret to how the guys up here in New England have taken old wooden boats (that were weak, half rotted and headed for the graveyard) and gotten another 20 or 30 years (and going) out of them.

It's no small amount of work, but it's the only way to be sure your fiberglass over wood boat won't delaminate. The bar of the staple becomes an intrinsic part of the fiberglass (bonded right into the middle of it, holding down several layers of mat/roving, which are cured to the outer layrs it is not holding down in every spot except where the bar of the staple is. So... no way to separate it and no delam. The staples keep the fiberglass on the boat, rather than relying on luck and hoping your resin/epoxy holds to the wood.

That's how to do it so it won't delaminate.
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Old 19-08-2007, 16:28   #29
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OK Sulli, that's what I thought you meant.

Might be the go on an old wet half rotten loose planked boat ( still sounds dodgy as) but on a new clean core of a modern timber cored vessel , this is deffinetly not the way to go.

On an old wet rotted hull the best method IMHO will still be DRY the hull, CLEAN the hull, SAND the hull, CLEAN the hull again and then EPOXY resin soak and glass.

I believe that on a traditional planked hull one will always have problems as each plank needs to be edge glued to prevent movement and the interior of the vessel needs to be sealed with epoxy to prevent moiture ingress causin swelling/movement

What you are saying is that the strongest part on your method is a pile of staples, and the glass and resin is a secondary.

What evidence have you got that new epoxy hulls have the glass delaminate from the timber core?

How many have you done?

I think your advice is incorrect and would not be recomending this method to anyone.

Dave
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Old 19-08-2007, 20:59   #30
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Quote:
Originally Posted by Redbull addict
so this has been an informative thread. Reading all these posts it seems like a basic requirement not to use polyester resin yet the majority of boats I'm doing research on, still use it.

It sounds like the process has a impact on the quality and level of strength. So you can offset some of the negative aspects of GRP whether its by heat curing or using more material. Do I have that right?
For what it's worth, 20 years ago 6 amateur boatbuilder blokes got hold of a yacht mould and hand laid up 6 hulls (decks etc). Five were done in polyester and one was done in vinylester. None of these boats have experienced any problems and are still sailing strong today.
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