Fiberglassing Assistance

[DestinDave]

The cloth basically acts the same as a wire mesh does in a concrete pour - it provides strength across a larger area. Spread a little epoxy over a piece of plastic. After it's cured, flex the plastic and you can crack the epoxy sheet into splinters. But if you have a layer of cloth embedded in it the whole piece will lift off the plastic, staying intact. When applying it to wood the epoxy soaks into the wood fibers and bonds to the wood so there is little chance of the whole piece lifting off the wood. However there is still the chance of tiny cracks. On a wooden torsion box such as the teardrop bodies how much flex there is probably depends on the design and construction. 1/8 ply will flex more then 3/4 ply. I'm no expert though and it would seem in these cases to be a personal choice thing.
Heikki - osmotic blistering is when water penetrates the surface of the epoxy (normally a gelcoat finish) on a boat hull and begins to delaminate the finish from the substructure causing a blister in the epoxy and fiberglass layers. I have never seen blisters above the waterline. In other words, the teardrop would have to be immersed in water quite a while for osmosis to occur.
As far as smell - brands differ. Most that I've used have a fairly strong odor comparable to Acetone, Toluene, or Xylene. The odor dissipates quickly when curing though. We recently used Epiglass epoxy which has a strong ammonia smell to it. Personally I'd rather smell Acetone all day. Steve has recommended this before and I do to - get a respirator if you're working in a confined area. I'm not so concerned about killing brain cells or ruining my lungs. It's the damned headaches I can't stand.
Dave

[Arne]

I'd be reluctant to not glass a tear if it wasn't being uniflexed or covered in aluminum. My thinking is that with just resin, surface crazing will occur much faster with no glass..... I've seen it on decks that have been coated with resin.... I believe it has to do with the heat from the sun and maybe uv rays, and probably lack of maintenance in keeping the surface intact....

The glass also creates a more solid surface less prone to expansion and shrinkage from moisture....

The additional cost of putting glass on just isn't a budget killer, and it gives a lot of bang for the buck in appearance and durability down the road (hmm, a pun).

[Guy]

Dear Heikki,

This is a LINK to a previous thread on this topic that some interesting info and link on it.

[angib]

Here I go repeating myself again:

A month ago I was doing some repairs on a plywood dinghy I built 7 years ago that has lived outside all its life at a rented holiday house, so it hasn't had an easy life. It had two good layers of epoxy, no glass except on the side/bottom corners as scrape protection, and two good coats of high quality two-pack varnish. After 7 years, the varnish has suffered but the epoxy is completely undamaged (except by being rubbed on rocks!). The ply is 1/4" sides and 3/8" bottom so there's been no shortage of flexing.

So I'd say adding cloth to the epoxy is completely unnecessary.

On epoxy 'smell', it is nowhere near as bad as polyester as it doesn't have the volatile components. Some brands do smell a bit, but it is never strong (and you may like it!).

Once again let's add: do not get epoxy on your skin - it can cause a skin reaction something like eczema, though only in a few people. It does no long term harm but isn't pleasant.

Andrew

[Arne]

Andrew, I understand everything you said..... In my case, if I go to the trouble of building a tear, I'm not going to take the chance. A layer of glass will not cost that much, will use only a bit more resin, and add little weight. Even if it just gives me peace of mind, it's worth the $50.00 extra it might add to the cost... and I still think it makes a more stable surface. but, that's what makes the tear world go round.... and this is the same type of thinking that made me put a 15amp circuit breaker in my tear and not depend on the c/g's working.

[Classic Finn]

Well I checked with a local sailboat builder and they said for me to bring in the walls of the tear and they said for about 60 USD they would spray
the sides with epoxy... plus the clear for UV protection...Marine products they will use on it..

Also they informed me as did also a few here that fiberglass is not necessary.. they have also sprayed wooden boats so it will be just as durable..as the boats they cover...

Curiosity drove this company to assist since they have not dealt with any
kind of a trailer or teardrop. They were very interested to see what we are building....

So next week we,ll bring the sides there.. For 60USD I guess I cant go wrong...

Classic Finn

[TomS]

$60 USD sounds like a bargian to me. You'd probably spend at least that in materials to do it yourself.

[Arne]

C/F.. that is a bargin. Figuring materials (latex gloves, resin, squeegees, rollers, brushes, etc.), time, finish... go for it...!

[Nitetimes]

Surface integrity. Same reason you don't use finished plywood for a counter top. You cover it with a laminate. It makes it more durable.

Not necessarily true. I have seen lots of countertops that were nothing more than finished ply and they held up as well or better than some laminate. I have also seen some gorgeous bar tops that were nothing more than finished ply and they take some serious abuse and still look just as good as new after a lot of years of heavy use. There are a lot of ways to do things, just because one person feels it is a must for them doesn't automaticaly make it the way it has to be.
When you build a wooden box the way most of these trailers are built with interior framework even without the insulation the flex is minimal, so unless you are doing like Steve did with multiple sheets the structural integrity you believe you will gain is negligible at best.
All the resin really does on the sides is help you get a smooth finish to shoot your clearcoat or spar varnish on.

[Classic Finn]

C/F.. that is a bargin. Figuring materials (latex gloves, resin, squeegees, rollers, brushes, etc.), time, finish... go for it...!

They have a giant spray booth or room to do this in ... so it will be done with some other work at the same time so they said it wont be that much work to get it done on the side.... so we lucked out...


Classic Finn

[Arne]

Don't think so. The resin locks all the individual wood fibers into one contiguous mass. Many becomes one. If you take a piece of thin ply, which is what most of us use, the resin saturates and toughens the wood noticeable... it isn't just about creating a flat surface, though it makes the surface able to be much smoother when sanded and provides a better finish foundation.

[Nitetimes]

Opinions vary

[CncMan]

Finn, If I were you, I would use 4 oz. cloth on your panels. Depending on your ply quality, most will check, and if you do not use cloth the epoxy resin itself will crack when the ply checks. High quality european marine plywood (ie. BS1088 Okoume, Sapele etc) has less tendancy to check as it is actually considered a soft hardwood, the BS1008 grade ply can not have patches, open knots or veneer joints on the faces. US domestic fir ply checks easily. Once the ply checks and moisture gets in the ply you've got a problem, rot, discoloration etc. Any good quality resin will work, West, Raka, Sys III, most manufacturers have a few grades available. Generally the higher price resin is somewhat harder and clearer than the general purpose, but the GP will give good results. The GP gives a slight amber tint. Keep in mind the resin itself has NO uv inhibitors, so you have to do finish coat(s) of a high quality Marine Spar varnish after glass work is completed and finish sanded. It is best to do a test pc. on some scrap ply, before you jump in with both feet. I am a System Three Resin dealer and boatbuilder.

Neal

[Arne]

This kind of my final word on this topic. I just got off the phone with a friend who deals with Morris (yachts).... his take is, given the environment (outside, sun damage to underlayment) and the flat plate area (wall size) with no bulk heads over a large span and the door cut out in the middle, he recommends glassing it.

He said though it sounds strong, there are enharent weaknesses because the wall is not thick, it rides over rough surfaces for long distances (potential twisting and viabration), lacks mid-line support from front to back, and has a large hole in it... the door.

So, do what you all want.... glass is cheap insurance.

[Nitetimes]

This kind of my final word on this topic. I just got off the phone with a friend who deals with Morris (yachts).... his take is, given the environment (outside, sun damage to underlayment)

How is this happening? I do believe this is what your paint, varnish, clearcoat, etc. is there for. Properly coated and maintained sun damage won't be an issue.

This kind of my final word on this topic. I just got off the phone with a friend who deals with Morris (yachts)....the flat plate area (wall size) with no bulk heads over a large span and the door cut out in the middle

Large span? My door is no more than 2 feet from a bulkhead at either end. Hardly a large area, average length is only 8 - 10 feet and less than 4 feet high. Again, not much of an issue.

This kind of my final word on this topic. I just got off the phone with a friend who deals with Morris (yachts)....
He said though it sounds strong, there are enharent weaknesses because the wall is not thick, it rides over rough surfaces for long distances (potential twisting and viabration), lacks mid-line support from front to back, and has a large hole in it... the door.

Mid-line support? It sits on a frame, plenty of support even on a light frame. Twisting and vibration? That's why you have suspension, the simple box built construction pretty much negates that as has been covered here many times.
If I were building a 40' yacht I might be inclined to take his advice but since this is a small trailer that will never see the water I'll stick to my earlier posts.
Just my varied opinions.