how many layers of epoxy??? [Archive]

Daddles

17th July 2005, 12:32 PM

I'm not a great fan of epoxy coating because it's a rigid layer that can be cracked, allowing water in. It is tougher than paint but harder to repair if you get moisture in hence allowing rot. Paint also 'breathes' so scratches, etc aren't as much a problem as glass or epoxy.

The epoxy isn't going to add any strength, but will be a tougher surface than paint.

Personally, and this length boat is in the same category as what I play with, I'd buy a good, professional quality enamel and use its primer. Prime the timber well and a few good, top coats. The trouble with enamels is that while they dry in a couple of days, it takes a few months for them to achieve full hardness, so you'll find yourself touching up a fair bit in the early days, but they work well and are long lasting.

If you've got the money, one of the very thin, epoxy timber preservatives is the way to go. These ghastly creations are like water and soak into the top layer of plywood, this protecting it, but the fumes are horrendous so do it outside and with protection.

Normal epoxy (West, etc), just sits on the surface - try sanding it and seeing how quickly you get through it. You can thin it and it will soak in further, but if you thin it enough to soak in like a specialist preservative, the thinners will evaporate as it cures leaving worm holes in the epoxy - it's not water proof. Not a problem if you are putting another coat of unthinned epoxy on top.

If you do go the epoxy coating route, and many do for the added toughness, use a roller. Just a cheap, foam roller (the dense foam, not the squishy foam) - cheap because it's going to be a throw away job. Put a plastic bag over your roller tray so that clean up consists of just chucking the bag away. Roll on one coat. Next day, roll on another - if you do it the next day, the epoxy will still be green and you will get a chemical bond between the layers. Leave it longer and you'll have to sand the first layer to give a mechanical bond between the layers.

Once the second layer is on, sand it within a couple of days, while the epoxy is still green. You'll find it sands exceeding easily and you'll have to watch you don't go through it - you'll also have to wear a face mask as that epoxy dust is still curing and you don't want it doing that in your lungs. If you leave it a week before sanding, it'll be like rock, but still quite sandable.

Personally, I've found that epoxy coating a boat is expensive, time consuming and doesn't produce a result I find satisfactory. A good enamel will be needed anyway, so let that do the work. Any surface, even a glass one, will get breached and once moisture gets under a layer, you're in trouble. Paint breathes and so the problem isn't as bad - it's also easier to fix. When stripping back my 12' yacht earlier this year (it's for SALE if anyone wants it), I pulled off the old fibreglass tape on the seams - under one piece of tape, I copped a very strong, musty smell as it came off. That tells me there was rot starting under that tape and no sign of damage to the tape.

BUT, others have different views so ...

Now, time for a gentle reprimand. The description '11ft boat' provides no gratuitious gratification. We want BOAT . Piccies. Piccies. Piccies.
Please :D
What is is?

Cheers
Richard

bitingmidge

17th July 2005, 01:34 PM

Sorry about the long post, but I have a different view and I'll put the reason behind each of Richard's quotes, note that both of us are "right" it's just that I think I am the most right!! :D:

I'm not a great fan of epoxy coating because it's a rigid layer that can be cracked, allowing water in.

I am a fan, it is not so rigid that normal panel flex will cause crack, and if the epoxy cracks, generally I reckon you will have lost the paint only finish long before!

It is tougher than paint but harder to repair if you get moisture in hence allowing rot. Paint also 'breathes' so scratches, etc aren't as much a problem as glass or epoxy.

You are only likely to get rot in areas which are constantly damp, or between mating surfaces. Repair on a "normal" scratch means sanding back, drying and dobbing on epoxy, the only tough bit is that it is one more step than just painting, but the process is the same. You would only be using glass in a structural situation, and paint can't overcome that.

The epoxy isn't going to add any strength, but will be a tougher surface than paint. Wrong! The epoxy will add considerable stiffness to the ply, if you don't believe me, grab three bits of 4 or 6mm ply, leave one uncoated, coat one on one side with two coats of epoxy and one on both sides and compare the stiffness.

Personally, (snip)..., I'd buy a good, professional quality enamel and use its primer. ...(snip)... so you'll find yourself touching up a fair bit in the early days, but they work well and are long lasting.

If you've got the money, one of the very thin, epoxy timber preservatives is the way to go. (snip)...
Note all of Richard's advice re use of epoxy is sound and I won't repeat it, however to an extent the material depends on how you are going to use your boat. I would (and do) go the diluted route every time, with a purpose bought diluent, and use a second full strength coat (sometimes three) depending on where on the boat it is.

My skiff is 10 years old, and I am about to remove all the varnish and do it again (it's been carefully kept under cover when not used) and the hull is two-pack over epoxy and unmarked (almost!).

My old canoe on the other hand was house paint over epoxy. It didn't stick very well but the epoxy never wore through on beaching. My next canoe will probably be waterbased poly over epoxy.

I think if you add up the total cost of the boat, the additional life the epoxy will give you is a tiny percentage of the cost (and extra $30 or so?) and well worth it.

Personally, I've found that epoxy coating a boat is expensive, time consuming and doesn't produce a result I find satisfactory. A good enamel will be needed anyway, so let that do the work. Any surface, even a glass one, will get breached and once moisture gets under a layer, you're in trouble. Paint breathes and so the problem isn't as bad - it's also easier to fix. When stripping back my 12' yacht earlier this year (it's for SALE if anyone wants it), I pulled off the old fibreglass tape on the seams - under one piece of tape, I copped a very strong, musty smell as it came off. That tells me there was rot starting under that tape and no sign of damage to the tape.

This is where I seriously disagree. Moisture will only travel under an epoxy layer through the substrate itself, not between the substrate and the finish, so it is relatively easy to find and fix.

You should be looking for those sorts of scratches anyway, and fixing when they occur, NOT relying on paint or epoxy to keep you out of trouble.

The removal of fibreglass tape was almost certainly a boat built with polyester resin. Most stitch and tape boats were until relatively recently. Polyester does not have anything like the same properties as epoxy and many people are confusing failure of Poly with epoxy.

Typically one can simply lift off failed glue joints, and often they have cracked and allowed water under giving the symptoms that Richard has described. THIS IS NOT AN EPOXY FAILURE!

Dunno if I've been helpful or not, but that's my somewhat contrary view:

In summary, if you are going to use the boat often, or keep it for a long time: go two coats of epoxy, one of the diluted with the recommended product.

Cheers.

P (who hates epoxy, but uses it while wearing one of every known saftey thingo!)

:D

Daddles

17th July 2005, 02:39 PM

Before we confuse the new bloke too much, we should point out that this argument is one of those perennials and there is no 'right' answer and in many cases, possibly depends on use.

You are going to have a safe and servicable boat whichever route you take.

One thing to consider, says he as he looks at the Mouseboat he's building that now has gunwales, top decks and awaits only a seat and skeg, is the amount of timber that's been covered with epoxy through the stitch and poo ... err, glue process - IF that's been the method of construction you've used.

By the time you prime the surface for the tapes, glue the tapes on, have over runs (coz I'm a messy builder) and generally dabbed at areas spreading the drippage instead of wiping it up, you often find that much of your boat has been epoxy coated by default. That's certainly been the case with my 8' Mouseboat, but I'm also using 100mm wide tape (it was cheap in the hardware ... and I won't be repeating THAT experiment). As a result, epoxy coating the rest of the boat would be tempting if I were doing a 'good' job. Sadly, Toad is a budget special and so I won't be.

On the other hand, my Yellowtail is lapstrake and will be done 'properly'. Once it's cleaned up, there will be little epoxy on the surface of the timber. She'll get the timber preservative and enamel treatment.

Interestingly, Iain Oughtred is firmly against epoxy coating his boats, even against things like the timber preservatives. His designs are all glued plywood lapstrake, a method that is more modern (in that it was developed later) than stich and glue, so it's not because he's an old traditionalist. The proponents of epoxy coating tend to be stich and glue specialists and working with wider, flatter areas of ply. Perhaps there's something in there. Perhaps there isn't.

The thing to remember la Huerta, is that this is one area where there aren't any rights or wrongs, so don't stress on it - if in doubt, follow the designer's instructions slavishly. It does make an interesting discussion for a sunday arvo while the epoxy sets, even if Midge is wrong :D

Cheers
Richard

bitingmidge

17th July 2005, 05:18 PM

By the time you prime the surface for the tapes, glue the tapes on, have over runs (coz I'm a messy builder) and generally dabbed at areas spreading the drippage instead of wiping it up, you often find that much of your boat has been epoxy coated by default.

My sentiments too.. so it's not much to do the rest!

How do you seal the watertight compartments Richard? Just curious?

Cheers,

P
:D :D :D

Daddles

17th July 2005, 07:12 PM

The two Mouseboats have had their floatation chambers sealed with epoxy. The first because I was new to boat building and wanted to seal everything with poxy. The current one was done with 100mm wide tape (an experiment with cheap tape from a hardware store that I won't be repeating) and the chambers are only small so by the the time I'd done it all, it was easier to seal with poxy than mess about with paint. I use inspection ports on all sealed chambers and release them when the boat isn't in the water.

Redback was sealed with poxy from the first plank down. When I started her, I thought you coated everything so I did. But by the time I got to the second plank, I'd given up so half of her is coated and half isn't. The outside of the hull is all enamel. There are hardwoord rubbing strips along the bottom and another runs the full length of the hull along the centreline (and hence along the bottom of the skeg). Interestingly, the paint that's needed touching up has been on the sides where I dug it against things like trailers ... and there is a suspicious red stripe from the first day Dean had Scrat on the water with me (Scrat is red, Redback a sand colour).

I'm still not sure how I feel about Redback. All that work, all that money, for a boat that was hard to build ... but taught me a lot about lateral thinking, using four different methods for four apparently identical tasks, lousy plans, dodgy designs and getting the use right first. I'd be more forgiving if it did the job ... but even that's compromised (and not just by size). Grrrr. I'm grumping again aren't I.

Can't wait to start me new row boat :D :D :D (no excited smilie so I've got to use three green ones)

Cheers
Richard

la Huerta

17th July 2005, 08:14 PM

i seemed to have opened up pandoras box on this subject...ok need to straighten some things out...first , it is similar to stitch and glue, the question is , instead of using fibreglass and chopstrand mat on the outside , it is recomended to use epoxy and mat as it is stronger and binds to the ply creating a solid unit , ok , so how many layers should be built up , if it was just fibre glass 3-4 layers would be pretty strong, should the same amount of layer be used with the epoxy...and yes i will take some pics ...

bitingmidge

17th July 2005, 08:27 PM

Not really a pandora's box! :D

Don't use chopped strand mat, it doesn't do anything structurally in this sort of structure.

How thick is the plywood?
What did the designer recommend?

You shouldn't need more than one layer of woven glass in anycase, but the weight will depend on the structural requirements.

Cheers,

P

la Huerta

17th July 2005, 08:47 PM

ok lets start at the begining the ply is 6mm and is just used to get the shape of the boat and then to fibreglass around the whole boat(ply)y inside and out , fibreglassing as normal with chopstrand mat , this should make a very strong boat (a 9.9 outboard will be used ) perhaps about 3-4 layers each side (remember the ply is just for getting the shape, nothing else)...but would epoxy be a better choice than traditional fibreglass or is 3-4 layers of fibreglass strong enough, will the fibreglass bind to the ply ok to form a solid mass...

bitingmidge

17th July 2005, 09:26 PM

I understand what you are saying, but fear it won't necessarily make a very strong boat at all sadly. It will still need frames and strengthening ribs, and the inner and the outer skins will contribute very little to the structure.

My guess is that it will make a very heavy boat for less strength than a properly designed and constructed ply one, or a more orthadox glass moulded one.

Epoxy would be wasted on such a construction in my view, you may as well use polyester resin and save some bucks. From memory, the binders used in Chopped Strand Mat are designed to dissolve in polyester, and may not do so in epoxy?

Why have you decided on that method of construction?

Not only will it be structurally inefficient, and difficult to build, in order to get a fair (smooth) finish you will have an incredible amount of work as well!

I don't want to sound like a smarty, but I think you would save a lot of money buying a decent set of plans from a recognised designer, and you will have a safe and good looking boat to boot!

Cheers,

P

la Huerta

17th July 2005, 09:40 PM

ok yes there will be ribs , thats all worked out, and infact i am actually helping a very good mate to do this boat , he has done a lot of fibreglassing in the past ...the funny thing about this project, is it used to be a 8ft tender and it was cut in half and a 3ft section fibreglassed in and 8 in added to the height, it has just kind of evolved on it's own , yes if i was building a boat from scratch i would do it propely, but the show must go on and this boat has got this far and it is almost ready to fibreglass , if infact fibreglass would be fine and strong enough to bind everything together ...

bitingmidge

17th July 2005, 09:45 PM

It's getting more interesting by the post! ;)

No doubt the strongest solution would be to use woven mat, and epoxy, stay away from choppies.

I don't know anyone in Sydney who can give you advice, suggest you go to FGI, or the WEST System agents and get some recommendations. They are used to these sorts of projects and won't give you advice which will get you into trouble. (Like I might ;) )

Take some dimensions and details of the frames with you.

I'm really keen to see some photos!

cheers,

P :D

la Huerta

17th July 2005, 11:42 PM

la Huerta

17th July 2005, 11:46 PM

that's odd when i refreshed my browser i sent the post again...sorry

la Huerta

17th July 2005, 11:58 PM

i will give these companies a ring this week , i think the woven mat and epoxy is the way to go for this rig...i won't keep everyone in suspence to long , i'll get some pics of the project so far, it's really cool, kind of a short stocky deep barra boat...but i can't take credit i'm just helping my mate...

sinjin1111

18th July 2005, 09:59 AM

On the outside i would use 1 layer of 6-10oz cloth, and then epoxy. Use more if you like, and if it was a hard work boat i would, but seeing your just having some fun and can afford to look after it a bit just go for one layer.
I really don't understand the talk about hard to repair at all. I've always found sheathed boats easy to repair. Unless of course people has used Polyester resin instead of epoxy. Polyester adheres poorly to wood generally compared to epoxy.
Sinjin

la Huerta

18th July 2005, 10:05 PM

thanks mate , thats would will be done, one of the companies mentioned earlier said epoxy is the way to go to...infact doing 1 or 2 layers inside and out should make a very strong boat, is that right?...it will be used at lake macquarie and it can get really rough there real quick, so it has to be supa strong...

sinjin1111

19th July 2005, 09:09 AM

Hello La, you come from a great part of the country. I really don't know the construction of yr boat. But if you’re in the early stages and this is a little hard to explain. But I’ve sheathed boats upside down and before the gunwales have been put on. The reason being you can get a much better job when sheathing. It’s very important to understand when applying your cloth/epoxy to wet the surface of your boat then apply the cloth and scape off all of the excess resin. You want the cloth totally wet but at the same time you want as little resin as possibly between the ply and the cloth. It’s the same technique making surfboards. Scrape all the resin all the hull. The surface will be very flat also. When the resin has gone off then apply another coat to fill the cloth totally.........After that you wait till it sets nice and hard and I sometime used a cabinet scraper to scrape off some of the small high spots. Give it quick sand. Then another coat maybe 2 coats with epoxy and filler...the choices for fillers to add to epoxies are many. Then let that set and cure. Sand the hull till you are either sick of it you are happy with the result. Then give it one final coat and mum's the word.
The reason I liked leaving off the gunwales was it just made life allot easier. To one, put on the cloth and paint resin everywhere and no have to worry about runs all over the gunwales...then have to clean up before it sets. 2 it give a much better finish. 3 if you need to repair the gunwales at some stage you not worried about the joint between the cloth and the gunwale. I know for some boats you can't not leave off the gunwale before glassing but most of the time you can. As for sheathing the inside....dead set prick of a job really but I used to try and do the same thing leave out what you could without any compromise the integrity of the construction.
The one thing I can't emphasise enough is the importance of getting the cloth down dead flat onto the ply surface. Epoxies are not the easiest to work with compared with Polyester. So don't be scared to mask out areas with plastic where you don't want runs etc for go.
Good luck...
PS I have epoxy poisoning....luck me you get to keep this for life...SO....safety. Wears gloves wear a mask wear a suit and wear glasses make sure you have plenty of ventilation. And you will be fine.
Sinjin

delamaree

20th July 2005, 10:55 PM

Hiya all, just to add my bit (5yrs with epoxy BB systems now) to this intruiging line of thought.

1. A strong boat is defined by the choice of materials and method of design and joinery, not its protective coating. The discussion seems to revolve around protecting the timber, not strengthening it.

2.Epoxy will add stiffness at about 2.5 times its weight so on 9mm ply a 10% by weight coating of epoxy will stiffen it up to the equivalent of 12mm ply (roughly). So this is a 0.9mm coating all over. Depends on the number and quality of laminations in the ply really, as 5 laminations is far superior to 3 but will hold less thinned epoxy.

3. Epoxy is 99.5% water and moisture resistant, poly about 45%, paint about 20%. Yes paint breathes - air, chemicals, water vapour and any number of fungal spores.

4. Judiciously used chopped strand is STRONGER than woven glass as it works in a stiffness plane of 360 degrees and not just 90/180 degrees. Woven just looks cleaner.

5. HIGHLY RECOMMEND applying a thinned epoxy to bare ply to soak in - just keep putting the stuff on until it can soak no more in. Incidentally a little goes a long way and as far as price goes, Wattyl makes an excellent product for about $10 litre (2 part) in a 50/50 mix available from AA Fibreglass in Hemmant, Brisbane (worth paying the freight for their prices). It is thinned with toluene so a mask is a must if you want to live or breed successfully.

6. You must paint the epoxy exterior to protect it from UV exposure. I have had the best success in terms of application and life from good old 2 pac car paint with a final spray of thinned epoxy that is then cut and buffed to a mirror shine. I guess almost any good 2 pac will suffice, but I find car paint takes the weathering well. For all the research and expense in the marine paint world I have not found a marine 2 pac that is any better and many that are much worse.

7. You cannot rely on epoxy alone to compensate for poor joins etc. Epoxies soak well into fibreglass mat or thin film provided they are thickened first with either microfibre, a blend of same or other such fillers. It is imperative that the filler achieves 100% soakage or the soundness is seriously compromised (so wood dusts, talcs etc are a no no). Again AA Fibreglass (aafibreglass.com.au) sells a microfibre/microballoon/blend for about $30 for 4 litres. Jeez, I sound like an ad for them now but really, they are good and taught me plenty.

Hope this all helps anyway.

sinjin1111

21st July 2005, 08:52 AM

Well, i don't think chop strand matt is at all stronger. As what the product says it is .....ie chop strand matt the actual fibres are short and more easily torn apart. As you know when working with chop strand you can tear the sheets up very easily and even split sheet of chop strand. I have never been able to to even get close to tearing cloth. So i don't agree at all about the strength part...i think thats stretching it pretty far.
Sinjin

la Huerta

21st July 2005, 10:12 AM

looks like i'v started a small war over the best solution...ok, my mate spoke with one of the fibreglass co. and they said epoxy and mat was the way to go...but ! that's if you want the boat to last for the next 1000yrs or plan to use it in space exploration, if using it just as a fishing boat with a 9.9 , then fibreglass would be fine , first roughing the ply up with 40 grit , apply one coat to soak in and act as a binder for the rest...

bitingmidge

21st July 2005, 10:48 AM

4. Judiciously used chopped strand is STRONGER than woven glass as it works in a stiffness plane of 360 degrees and not just 90/180 degrees. Woven just looks cleaner.
delamaree is completely correct on all but #4!

Sorry, but this is just not correct. I can't think of a situation on a boat where the forces run in 360° unless one is talking about 360° in one plane, in which case a triaxial glass would be the most efficient by far.

Choppies are nothing more than a bulk binder for a polyester matrix, usually used these days with fabric each side (if the structure has been engineered at all) and do little more than add weight, and give water the opportunity to penetrate the structure by wicking (osmosis) down the strands which are at angles to the surface.

There is lots of misinformation bandied around, and as I have said in a previous post, most CSM manufacturers use a binder which disolves in polyester (NOT epoxy), because that's what it's designed to do.

Cheers,

P
:rolleyes:

STEPHEN MILLER

24th July 2005, 12:01 PM

Chopped Strand is basically way is used in all commercial fibreglas boat building the strand comes off a roll, goes through a chopper gun, is mixed with resin and sprayed into a mould to produce a hull etc so one would imagine it does hve some strength qualities about it. :rolleyes:

bitingmidge

24th July 2005, 02:14 PM

would imagine it does hve some strength qualities about it. :rolleyes:
Yes indeedy Stephen :rolleyes: :rolleyes: but when was the last time you saw a commercial boat built by gluing chopped strand to each side of a permanent plywood mould??

Ever wondered why not??

:rolleyes:

P

la Huerta

24th July 2005, 11:40 PM

we're going the fibreglass way with the mat , some big boats have been built this way with a plywood core...

bitingmidge

25th July 2005, 10:30 AM

Don't forget to post the pics of the process! (and the finished boat of course)

I'd also be interested to see if you can have it accurately weighed after it's finished, it'd be good to have some of that sort of info recorded for future comparisons.

Cheers,

P
:D

la Huerta

25th July 2005, 12:38 PM

not sure about the weighing but will post some pics soon...

Boatmik

4th August 2005, 03:26 PM

Boatmik

4th August 2005, 03:29 PM

200gsm glass woven cloth on the outside. It is very unusual to glass boats on the inside - I would suggest seeing how stiff it is after the outside is done and then decide whether it needs it on the inside as well.

MIK
YOu may get away with just glass taping the seams and joins with 50mm glass tape on the inside if the outside is pretty close.

Also any external timber structure that is added - skegs, gunwales, bottom skids - will stiffen the area which is loaded by your feet.

MIK

smee

20th July 2006, 05:08 PM

Yes indeedy Stephen :rolleyes: :rolleyes: but when was the last time you saw a commercial boat built by gluing chopped strand to each side of a permanent plywood mould??

Ever wondered why not??

:rolleyes:

P
Hi, I have a ex- commercial 27' flybridge cruiser that i'm about to start work on. It's going over onto it's side so it will be uncomfortable to work on.
It has some hull damage and am going to sand back to bare timber.
The boat is hardwood planked hull with ply over and fiberglassed.
I was thinking of just using poltester & glass (pictured) after reading this thread I'm concern about the matt types ie for poly or epoxy
I dont know what type the matt is (bought 2nd hand shop) as you can see its heavier the normal stuff in chanderies.
what is the best plan of attack I am faced with?
should I reply the surface again. the timber doesnt have corking inbetween planks but is fairly close fit.
Dan

Boatmik

20th July 2006, 07:46 PM

Hi, I have a ex- commercial 27' flybridge cruiser that i'm about to start work on. It's going over onto it's side so it will be uncomfortable to work on.
It has some hull damage and am going to sand back to bare timber.
The boat is hardwood planked hull with ply over and fiberglassed.
I was thinking of just using poltester & glass
Dan
Polyester doesn't stick to wood very well - epoxy does.

If current glassing was done with epoxy then polyester won't stick to epoxy.

Epoxy will stick to just about anything that boat hulls can be built of including polyester.

Also the glass you have looks like woven rovings

(MIDGE - HELP)

If it is then they are too coarse - you should use either woven cloth or a stitched multiaxial fabric.

MIK

bitingmidge

20th July 2006, 10:04 PM

(MIDGE - HELP)
Crikey that's a big call! :eek:

smee,

Firstly read and believe what Mik said on the epoxy, (you'll see sinjin also posted similar advice earlier in the thread) it's all true.

So epoxy it is!

There really isn't quite enough information to provide any constructive advice, so I'll pike by explaining why!

Hi, I have a ex- commercial 27' flybridge cruiser that i'm about to start work on. It's going over onto it's side so it will be uncomfortable to work on.

If you are talking about chocking it over at 90°, make sure you have batteries and engine(s) somewhere else while you do it won't you? There's nothing comfortable about working on a boat hull, but there are risks involved in subjecting them to this sort of load, so make sure you've got the thing well supported structurally or you may well end up with a bigger repair than you thought. I'm guessing that the damage is in the bottom of the hull, or you wouldn't be contemplating this, but is it REALLY necessary?

It has some hull damage and am going to sand back to bare timber.
The boat is hardwood planked hull with ply over and fiberglassed.
More info on the damage would be nice, as would more info on the structure.

I can interpret your description that it was a carvel planked boat that was sheathed with ply then glass, (which seems odd in my experience) or is it a hardwood FRAMED boat with ply hull?

Either way the odds are that the glass was a heavy duty sheathing rather than a structural component. THAT IS A VERY DANGEROUS ASSUMPTION ON MY PART, DO NOT BASE ANY OF YOUR WORK ON IT UNLESS YOU CAN GET SOME ADVICE TO CONFIRM IT.

A lot of boats built of timber were sheathed in Dynel, which is a polyester mat used for abrasion resistance or as a matrix to carry resin for waterproofing, and contrary to popular myth is not a structural component.

I think before you do anything else, you need to get some advice on the design and the construction method employed, if you are making a structural repair in a critical area, people could die if it isn't correct!

I was thinking of just using poltester & glass (pictured) after reading this thread I'm concern about the matt types ie for poly or epoxy
Use epoxy for all the reasons outlined.

See if you can find out whether the structure of the boat depends on the outer layup, or if it is just a sheathing.

See if you can get a bit of the old laminate off. Odds are if it was done in polyester, you will be able to free a chunk using a chisel, then take it to a specialist glass supplier to see if they can guess what the original layup was!

I dont know what type the matt is (bought 2nd hand shop) as you can see its heavier the normal stuff in chanderies. Mik's on the money. From the pic I wouldn't use it as a top laminate on a timber hull, it would soak up a lot of resin and there'd be a real risk of delamination I reckon. This sort of mat is used in solid fibreglass construction, often between two layers of Chopped strand mat, to give the structural reinforcing layer.

I'd also be very wary using it in a structural spot, it looks quite dirty and any grease or dust in it will prevent proper bonding.

what is the best plan of attack I am faced with?
should I reply the surface again. the timber doesnt have corking inbetween planks but is fairly close fit.

I think we'd need photos at least, but really, your best plan of attack would be to get some advice from someone who can crawl over the hull. A marine surveyor would charge you for this advice, but you should be able to rely on it, and develop a plan.

It is very dangerous receiving (or giving) advice of this nature over the internet, from people who may or may not know what they are talking about and who haven't seen the boat. Your damage, may have far reaching consequences, or may have been caused by another problem you haven't told us about (or maybe aren't aware of), so we really can't give detailed advice.

Sorry! Please keep us informed though, we are all interested in finding out now!

Cheers,

P
:)

smee

20th July 2006, 11:20 PM

If you are talking about chocking it over at 90°, make sure you have batteries and engine(s) somewhere else while you do it won't you? There's nothing comfortable about working on a boat hull, but there are risks involved in subjecting them to this sort of load, so make sure you've got the thing well supported structurally or you may well end up with a bigger repair than you thought. I'm guessing that the damage is in the bottom of the hull, or you wouldn't be contemplating this, but is it REALLY necessary?
It will lean over not quite 90 maybe ~70deg onto truck tyres
batt and things out, diesel was going to say,-strapped to winch strap holding boat to recover it back to the other side.
Its necessary for a full strip a few damage points from beached on rocks (not me! ;))
& previous owned has done the most bodgiest patch job you have ever (or likely) to ever have seen.

More info on the damage would be nice, as would more info on the structure

I can interpret your description that it was a carvel planked boat that was sheathed with ply then glass, (which seems odd in my experience) or is it a hardwood FRAMED boat with ply hull?
will get hull photos tomorrow, I was told :rolleyes: it was plywood sheath under glass- yet to be seen
its only for sealing, its timber beam and stringer framed structural hull > (ply?) > glass (epoxy?)
boat was built built 1980 by crestcraft (goldcoast) - now closed down

Dan

viking

21st July 2006, 12:15 AM

mate for thuis boat id use 225grm csm glass and poly ester resin on bare ply but use un waxed resin for good adhesion and be neat and use what we call in the trade a hot coat [resin, acetone30% and cobolt blue1%.] b4 you start with the csm it acts as a priner

bitingmidge

21st July 2006, 12:28 AM

Viking,

With all due respects how can you say that? Glass over ply over carvel?

If that's what it is, you could use artists water colour and it'd work!

On the other hand, if it's a glass reinforced ply skin over relatively light framing (Jim Young style?- I can't remember!) and if the damage is over a compound curve area which is providing a substantial part of the structural form, whacking a bit of csm on a repair of unknown magnitude could constitute a recipe for complete disaster IMHO.

Or if I am way off beam, could you please explain the reasons for your succinct summation?

It must be this thread, I just can't stop getting into trouble on it. Or maybe I'm just old enough to have seen a few bits of well intended advice go badly awry over the years so I'm too conservative for my own good!

Cheers,

P

Daddles

21st July 2006, 12:01 PM

Viking, again with all due respect, but you are a new bod to the forum and completely unknown while we've already had advice from known experienced boat builders to use EPOXY, not polyester. I'm not saying your advice is wrong, I lack the experience to do so, but I'm afraid that in this case, you'll need to tell us something about yourself so we know where you're coming from ;)

Richard

bitingmidge

21st July 2006, 12:10 PM

will get hull photos tomorrow,
Cool, pity I didn't read this post earlier, I could have dropped in yesterday (but I only got as far as Sexie Coffee on the highway! :cool: )

Cheers,

P

Boatmik

21st July 2006, 03:29 PM

Midge

The pic looked like rovings didn't it - that was my question.

Would be a bugger to fair up.

But good point about the construction - it could change the nature of the repair method - I wasn't watching the ball.

Viking

CSM (chopped strand matt) is a right bugger to fair (smooth up) - a woven fabric or stitched biaxial cloth will save lots of labour and general stuffing around. Surface finishes more or less flat.

Epoxy will stick to timber - polyester generally doesn't consistently then traps water between the timber and the glass in the delaminated areas. Then comes rot.

I have done too many repairs to someone elses repairs over the years simply because they used polyester.

MIK

viking

21st July 2006, 03:57 PM

well on boats in water of large size epoxy all the way using peel ply for a fair surface .;)
even vynal ester as a cheaper alternative.
as for my last post i was describing what i would do on a small dinghy in dry store.
if you put poly on wet timber you are right it peels off.:confused:
but dry ply thats new. different kettle of fish.
done with modern techniques works well the key is to start dry and keep out the water by encapsulation.
im a boat builder shipwright and have been for 25yrs :cool:
somtimes it realy hard to diagnose on forums and you have to take lots of different perameters into account ie cost ,labour and is it worth the time and efort .
i see this all the time .
amatures doing over kill to rot boxes whats the piont in using top notch materals when you have a repair that will last 50 years when the rest of the boat is compost
im not rought just relistic if i had my way id do it old school
stuff the itchy cap.:D :eek:

bitingmidge

21st July 2006, 04:29 PM

im a boat builder shipwright and have been for 25yrs :cool:
somtimes it realy hard to diagnose on forums and you have to take lots of different perameters into account ie cost ,labour and is it worth the time and efort .

Firstly, let me say that having a shipwright round here is a welcome addition to the clan.

Then I will agree entirely with the rest of the quote, it's a trap we've all fell into, (I still do regularly!) It pays to understand the problem first!

i see this all the time .
amatures doing over kill to rot boxes whats the piont in using top notch materals when you have a repair that will last 50 years when the rest of the boat is compost
im not rought just relistic if i had my way id do it old school
stuff the itchy cap.:D :eek:

Yes, but then I could say the same for any boat restoration/repair.

Teaching amateurs the right way to go about things is a very important part of the hobby mentality. Most don't care about how long it takes, they want to do a good job and understand how to do it next time. If we advise them to simply bog up a problem, next time they'll think that's the right solution, or worse, some innocent (like yourself as a newcomer) will stumble on the thread, and take it all out of context, and the next thing you know we have an accident on our hands!:eek:

To my mind, show us the short cut by all means, but firstly tell us it's a short cut and describe how to do it right. That way, the person asking the advice will get a proper understanding of the task, and can decide for himself how they want to approach the repair.

Now: you are needed on bitofascallywags thread http://www.woodworkforums.com/showthread.php?t=34852

Cheers,

P
:D

viking

21st July 2006, 04:41 PM

i agree totally

smee

21st July 2006, 05:03 PM

Fair dunkum there's some unscrupulous operaters around :rolleyes: (that should not even be allowed to buy fiberglass)
pics...

smee

21st July 2006, 05:06 PM

This craftsman couldn't even be bothered to take the antifouling off :eek:

smee

21st July 2006, 05:08 PM

got more than I bargained for :(

viking

21st July 2006, 05:52 PM

throw it out the glass that is its been wet and is that green mould mate its no good
Hi, I have a ex- commercial 27' flybridge cruiser that i'm about to start work on. It's going over onto it's side so it will be uncomfortable to work on.
It has some hull damage and am going to sand back to bare timber.
The boat is hardwood planked hull with ply over and fiberglassed.
I was thinking of just using poltester & glass (pictured) after reading this thread I'm concern about the matt types ie for poly or epoxy
I dont know what type the matt is (bought 2nd hand shop) as you can see its heavier the normal stuff in chanderies.
what is the best plan of attack I am faced with?
should I reply the surface again. the timber doesnt have corking inbetween planks but is fairly close fit.
Dan

viking

21st July 2006, 06:05 PM

good luck mate best thing i sujest is you get a shippy to look at her
i dont think you will find any one who will be able to quote this one
prob is if its that extensive you end up replacing usualy 3to6X area to get back to good wood if you dont this will be same the reult in less than 12 months time
rot never steeps
no miricle cure either
this is why you find boats with bogy work because its beond most and very costly say i do it on an hourly rate not un comon to cost 15k and you end up with1/2 a new boat sorry mate but this is it.

smee

21st July 2006, 06:17 PM

is that green mould mate its no good
If you refering to the bulge it's only spray paint overspray
can re hull be (re)repaired with ply etc cheaply?- to get me a few years?

viking

21st July 2006, 06:22 PM

If you refering to the bulge it's only spray paint overspray
can re hull be (re)repaired with ply etc cheaply?- to get me a few years?
no on the glass cloth yes you can do it your self but under the guidence of som body in yhe to hard to do from photos

bitingmidge

21st July 2006, 07:07 PM

I'd take a real guess and say it appears that the fibreglass isn't structural, so that bit's easy to fix (but as viking says not with the glass you've got).

The timber repair needs to be done through the whole depth of the hull, you can't really just bung a bit of three ply over it.

Without wanting to repeat what viking says, I will anyway: get someone who knows a bit to supervise, or at least show you what to do. It's not hard, but you need to know just a bit.

Cheers,

P

smee

21st July 2006, 07:22 PM

Yea ouch, thanks all esp midge and viking for the info you have supplied
Got the whole picture now
Dan

viking

22nd July 2006, 11:02 AM

Yea ouch, thanks all esp midge and viking for the info you have supplied
Got the whole picture now
Dan
its not the amatures we wory about its the pros :cool: :mad:behaving less than :eek: amatures and being payed lke pros:mad:

smee

26th July 2006, 10:36 AM

Viking, just say I was crazy enough to take this on, what type of timber planks should I look for and where would I find 8m lengths?
Im in SE Qld
Dan

viking

26th July 2006, 11:04 AM

well id find out what you have in the boat first by asking a shipwright
TO LOOK AT THE BOAT FOR YOU
could be any thing from king billy pine to pacific maple as for the length you will not find a lenth that long you need to scarf it[join]
why do you want to replace the whole plank any way ? if you need to replace all of the plank the wood you need will fit in a small cardboard box the size of a match box.joke.
seriously mate i canot do any more for you via a web forum if i can help in any way i will but the help your asking for and need is more hands on than this.
regards viking

smee

26th July 2006, 01:18 PM

why do you want to replace the whole plank any way ? if you need to replace all of the plank the wood you need will fit in a small cardboard box the size of a match box.joke.
seriously mate i canot do any more for you via a web forum if i can help in any way i will but the help your asking for and need is more hands on than this.
regards viking
Yea thanks mate, I appreciate your help, I'm considering getting it fixed (BIG maybe-and looked at by a shippy - the whole top was going to have to replaced aswell from dry rott) just getting further info 1st. I thought the whole planks - for end to end had to replaced-it doesn't seem that's the case now (by scarfing?) so the timber has to be replaced with the same or equiv (is this for expansion or weight reasons?
about the green mold in glass- is this going to be a problem if the glass is sanded off the boards between them and glass?
Thanks again
Dan