Fiber Cloth on new Wooden Hull

[teoman]

Fiber on wood is ggetting quite common..

I am currently building a 36' lobster boat. The hull is made from 2 layer of strip plank chestnut wood (each 0.5 inch width), nailed and epoxied together.

People over here recommended that I should epoxy the inside without cloth.(not required for structural reasons, just to protect the wood they say.)
And they recommend a fiber glass sheating of the hull on the outside with cloth.

I am worried a little doing it on both sides. Can anyone give an idea ??
The boat is being built brand new.
Also the fiber coathing on the outside is not reuqired for structural reasons.

thanks for your help..

:?:

[lewisboats]

What does the designer spec for coatings?

[gonzo]

A cloth of 10oz or so will make the surface more abrasion resistant. If you epoxy one side you should do the other too.

[teoman]

Actually the designer, neither the planss reflect any need for fiber coating inside or outside. It would be purely for protecting thee wood, if does really protect ??

I understand that an old boat may need it, but is it still the case for a new hull ??

[alan white]

Can you better describe the construction? Is this a typical double-planked carvel hull?

[Ilan Voyager]

In fact as the planks have been glued with with epoxy (excellent glue, but it does not stand wood swelling) epoxy "encapsulation" inside and outside to keep the wood dry is mandatory.

Inside 3 coats are sufficient, outside it's better to add resistance abrasion with glass 6 or 10 oz. The glass has another advantage; it permits to control the thickness of the epoxy coat.

[alan white]

How wide are the strips? and do the strips simply stagger seams (both fore and aft, but offset), or does one layer go at some different angle? And what kind of framing lies against the hull? How closely spaced, what fasteners, and so forth. In other words, if you are going to get some advice that makes sense, you'll have to carefully describe the construction method.

[teoman]

Thanks for your feedbacks. Here are some pics of the boat, and the construction type. The thickness of each layer is 0.5 inch. Epoxied togetheer.

[alan white]

This is a kind of updated double-plank method combined with a variation of cold molding, with the frames as the tensile element. The right wood (I know nothing of your planking material except to say chestnut must be like oak (?), and I'd not use a hardwood in such a construction, but rather pine or cedar or some similar softwood. the softwood could be made into wider planks than hardwood---- if using hardwood planks, how wide are you going?
Maybe it's my ignorence, but is this an accepted method in Turkey? Again, I can't comment on Turkish wood varieties.
obviously, glassing the inside is not feasable, but the exterior could be done for abrasion resisance and some tensile contribution in addition to the frames. This is based on the total encapsulation of the planking in epoxy, with epoxy between the layers as well.
Not a bad method with the right wood.

[teoman]

Thanks. Yes chestnu is like Oak, it is quite hard compared to pine. It has a much longer life.
It is quite expensive, and used mostly on large wooden yacht. It gives very low humidity.
It is mainly used here in Turkey.

May I ask one more thing. If I glass the outside, with time, isn't it going to crack and maybe alow water to go through and create problem ??

[alan white]

Well this is what I'm talking about. I've asked what the planking width is, but you haven't said. I would not be comfortable using chestnut as a planking material on that construction. As I said, I would prefer a wood like cedar.
I don't think chestnut is a good choice for an encapsulated planking material of any width but especially for normal plank widths of over 100mm.
I can well imagine using chestnut where the planks are allowed to swell and shrink. Hardwoods have successfully been used for hundreds of years for planking material.
However, it sounds like you've been thinking about taking a tried and true construction method and attempting to modernize it by encapsulating it with epoxy.
While some hardwoods might work in this situation, an oak-like wood is probably too hard to carry over into an encapsulated hull design. Spanish cedar or luan or various other cedars would be more ideal, and the hardness of the hull could be achieved by a couple of layers of heavy glass cloth.

[alan white]

Thanks. Yes chestnu is like Oak, it is quite hard compared to pine. It has a much longer life.
It is quite expensive, and used mostly on large wooden yacht. It gives very low humidity.
It is mainly used here in Turkey.

May I ask one more thing. If I glass the outside, with time, isn't it going to crack and maybe alow water to go through and create problem ??

Regarding cracking, this is what I mean when I suggest a soft wood, as softwood are far less apt to crack the glass skin. I'm sure the chestnut lasts well when caulked in the traditional way, but you are talking about using epoxy, so it's possible that the epoxy/glassed hull would last a very long time with very little maintainance. that is, if you use the right core wood.

[Ilan Voyager]

The boat is made, so a discussion about the wood to use is pointless now. I do repeat, the epoxy as glue on wood has a major drawback: the glue lines do not withstand the stresses made by wood changes of dimensions by the effect of humidity.
It's why epoxy glue cannot be used on laminated beams left unprotected (or just painted) in exterior conditions.
Resorcinol has not this problem, and it has been used successfully on simply painted boats.
So the boat must now be completely coated with epoxy, one of best known water barriers, for stabilizing the wood.

You'll find very useful information in the Forest Products Laboratory internet site
http://www.fpl.fs.fed.us/search/index.php
and make a search with the word epoxy.

To get the task done you have 2 directions:

1-Use a a true naval epoxy resin for wood with 2 main characteristics;
-About 1000 centipoises of viscosity with only reactive diluent. Thus you won't never use solvents that degrades the impermeability of the epoxy. And the resin is fluid enough to penetrate the wood without need of dilution. Heating is the best solution to lower the viscosity of a resin. Such fluid resins are a pleasure to use.

- A minimum of 5 % of max elongation so the resin won't crack or to be prone to micro-fissuration.
A lot of epoxy resins have only 2% elongation; that's not enough, the resin will crack.
As the resin is used as "sealer" the ultimate resistance is of little importance, but no-brittleness is of great importance. The no-blushing quality and the easiness of sanding are primordial. They do save a lot of hard work. Greasy surface and clogged sanding paper are a pain.

The inside of the boat will be too difficult to cover with fiberglass. 3 "thin" coats on all surfaces are a good measure. An extra coat in the bilges is not a luxury. It's better to leave the epoxy resin without finishing paint in the bilges, so any infiltration of water in the wood will be immediately visible as the wood darkens when wet.

Outside you can use fiberglass (but it's not mandatory) 6 or 10 oz, in satin weave so it's highly deformable to follow the contours of the boat without wrinkles and the weave is very small, easy to fill. It's pretty expensive but 2 coats of a 6 oz satin is very effective and long lasting.

The glass has 3 main advantages; better resistance to small knocks and abrasion, impedes the cracking and checking, and more important it permits to control the thickness of the epoxy coat. It's primordial to have an even epoxy coat on the outside. It's highly counseled to use at least 4 to 6 coats of epoxy under the waterline.

2- To be sure and eventually to improve the adhesion of the epoxy on the wood as your planks seem to be rather large.
I have no idea of the behavior of the wood you have used with epoxy as I have no experience with it.
I would check the adhesion of the epoxy by using 2 simple and cheap tests: one of peeling with fiberglass, one similar to the test used for the adhesion of paints on a substrate.

It's very probable that the results will be satisfactory.

If not, you may have four causes (separate or combined)
- too nice and fine sanding. The pores of the wood are clogged with a very fine dust and the resin won't penetrate. Easy solution; rougher sanding, open pores and a good vacuum cleaning. Epoxy needs some teeth to grasp on the wood.
- wood too dense. That seems unlikely, but it happens with some very dense tropical woods.
- wood oil or resin. For example Teak is a wood known to be difficult to glue. A good cleaning with a suitable solvent will probably solve the problem.
- very acidic wood like some oaks. Epoxy resin is very basic, I mean the PH is pretty high and sometimes on a very few woods the chemistry between a very acid wood and the basic resin is not good. That's more difficult to solve.
A cleaning with monoethylene glycol diluted at 50% with water gives often good results.

In short words the advice given by your fellow countrymen was good: resin inside, glass and resin outside.

[alan white]

I didn't get that the boat was already planked,Ilan, but if so I apologize to the builder for misunderstanding the situation.

[Ilan Voyager]

Alan, I made almost the same mistake... when I saw the pic of the planking I understood that the planking was already done. I doubt that in Turkey (very beautiful country, excellent food and the Izmir wines are marvels) Teoman would find the soft woods at a affordable price. So he used a local and affordable wood.

After seeing the Model (1).pdf I would suggest to use the fiberglass cloth with a angle of around 45°. That improves the strength of the glass-epoxy coat, as two stands of fiber will cross on each glue joint.

The delicate point is the chine where glass fiber is mandatory with great care. Epoxy resin alone won't last. Such angles around 90° are delicate to finish.

If using a 5 to 6% elongation resin the finish will last without problems, the resin being enough flexible. Most good European naval epoxy resins are of this quality.

The lines, and structure shown in the PDF look very similar to Italian runaboats made in the 60's in plywood.

A "brutal" but strong way to cover the angle is to use stainless steel sheet 0.45 to 0.6 mm thick glued with polyurethane and screwed. It asks for some good craftsmanship to get a nice result.

[teoman]

wooww thanks guys. That is a lot of good informatşon for me. Thanks a lot.

Actually yes it is allready planked. So no way out on that :)

but thanks for the valuable information. I will go that way. I have to reasearch those products and cost. Hope it will not be too expensive...

Can wait to have it finished and enjoy a good wine here in Istanbul.

Just one last thought: isn't it good just to leave the wood without glassing on the outside and inside ?? So it can bread, have contact with air on the inside and just normal coating for paint preparation on the outside ??

Just wondering.... thanks a lot...

[alan white]

I assumed the picture of the planking was another boat, an example. In any case, I agree that glass on the bias is the way to go where flex is expected. And if chestnut is the only wood available, I understand. I'd like to hear from others about using oak-like woods under glass/epoxy, maybe some experience with older boats originally done that way.

[apex1]

Thanks. Yes chestnu is like Oak, it is quite hard compared to pine. It has a much longer life.
It is quite expensive, and used mostly on large wooden yacht. It gives very low humidity.
It is mainly used here in Turkey.

May I ask one more thing. If I glass the outside, with time, isn't it going to crack and maybe alow water to go through and create problem ??

The species used in Turkey is "Castanea Sativa" , not as hard as Oak, but a hardwood. The reason that it is so common especially for building Gulet´s, is the fact that there are hughe chestnut forests in Turkey.
The timber is by no means the best choice for boatbuilding (the average Gulet does not get old, to prove that).
It is acidic, which corrodes fasteners, it is susceptible for warping and difficult to dry.
Though it is fairly rot resistant.

Due to the choosen building method, you have no other choice than sheathing the entire outside, and to saturate / encapsulate the inside with at least three layers of resin. The rest was already said by Alan and Ilan.

Go to Tersaneler Caddesi in Tuzla, about 300 meters behind RMK Tersane is a small road with some 40 yards and boatshops, almost all building in wood epoxy (most to a very crappy quality), ask them about their experience, which resin on chestnut did / do they use! You will find, that most of them are using Mahogany, but there are some still working with Kestane.

If in doubt: "West systems" should do the trick.


Regards
Richard

[Ilan Voyager]

Apex thanks for your precision: I know this wood, very used in old roof carpentry and some fishing boats. Very acid, like the european oak it "eats" the screws. Tendency to warp and split if old tree wood is used.
The West System price will be prohibitive, West makes you pay the name, and, very personal opinion, it's not worth the price.
You have Sicomin ( http://sicomin.com/prod.asp?scat_num=12#product25 ) in France with the very good SR 5550 which will be probably cheaper.
There are surely some epoxy formulators in Turkey. I used myself a formulator who provided me excellent resins at fair prices during years in France. An acquaintance of mine solved his epoxy problem in Colombia using a local formulator of epoxy resins for tanks and pools in concrete and steel. The requisites are very close to those of naval boat building.
In fact a good epoxy resin for permanent immersion and good chemical resistance would do the job if it's fluid, flexible and softens above at least 70 degrees Celsius. An easy task for a formulator starting from a Derakane 33 for example.
All the naval epoxy brands are simply formulators, having their personal recipes.

Teoman; You're welcome. The tests of adherence are mandatory on an acidic wood.
1- Peeling fiberglass;
Cut 4 strips 25 cm long, 5 cm wide in a 10 onz (300 gr m2) cloth fiberglass. Put tape on the last 2 cm of the glass, so it won't glue and you can grip this loose end with pliers.
Prepare 4 samples of your planks.

a- 1 plank sanded with 120 grit. 1 coat saturation. Resin the glass strip, just to cover the weave. Let it harden 3 days.
b- 1 plank sanded with 80 grit. 1 coat saturation. Resin the glass strip, just to cover the weave. Let it harden 3 days.
c- 1 plank sanded with 80 grit. Clean it with Xylene and let it dry. 1 coat saturation. Resin the glass strip, just to cover the weave. Let it harden 3 days.
d- 1 plank sanded with 80 grit. Clean it with monoethylene glycol diluted a 50% with very soft or distilled water and let it dry. 1 coat saturation. Resin the glass strip, just to cover the weave. Let it harden 3 days.

Now you take the glass strip with the pliers and peel it out. Look at the resin remaining on the wood.
If the resin is gone with the cloth, totally or partly leaving the bare wood, it's no good at all. Failed. No adhesion.
If the resin stays on the wood, having the print of the cloth weave, that means that the bond between the resin and the wood is stronger that the bond of the resin and the cloth -I simplify, I won't enter in the details of fracture mode of the resin-. Good.

2- Prepare another 4 samples of wood, sanded and cleaned as for the first test.
Put three coats of resin; first saturation, light sanding, two normal coats. Let it harden 3 days.
Take a good cutter and with a ruler, make a square grid of cuts every 1.5 mm through the resin.
If the resin falls from the wood at this state it's not good at all. But that's not all.
Take a good tape, very adhesive like duct tape, brown tape something that glues ferociously. Put it on the resin grid, squeeze well to get a total adhesion of the tape and peel it out.
More than 20% of the 1.5*1.5 mm squares stay glued on the tape and left the wood; failed. Between 10 and 20 % not too bad but can be better. Less than 10%, more than 5 % very good: acceptable. Less than 5% excellent.

This test can be used also with paints to test the adhesion on the substrate.
Be not afraid, epoxy resins glue very well on Western Red Cedar which is also a very acidic wood. It's just a good and necessary precaution.

With a wood like this chestnut YOU MUST USE glass fiber cloth outside. At 45° it would be better. With the tendency of the chestnut for checking, 2 coats of fiber would be a plus. Douglas fir has the same defect and it's used with epoxy resin and glass fiber with reasonable succes.

White or very light color final paint mandatory. Dark paints and epoxy resin under the hot Turkish sun won't last.

[troy2000]

With a wood like this chestnut YOU MUST USE glass fiber cloth outside. At 45° it would be better. With the tendency of the chestnut for checking, 2 coats of fiber would be a plus. Douglas fir has the same defect and it's used with epoxy resin and glass fiber with reasonable succes.

????? The old lumber schooners that plied the West Coast of the US were made of the same Douglas Fir that they carried for a cargo. According to what I've read, they used it for framing, planking, decking and spars. And there were certainly no epoxy resins or glass fiber available at the time.

The C.A. Thayer, a three-masted schooner built of Douglas Fir in 1895, carried lumber until 1912. She then became a salmon packet, and later a Bering Sea cod fishing vessel. Her last voyage was in 1950, according to a web page devoted to her. But it refers to a picture of codfish being salted down in her hold in 1953, so apparently she was still earning her keep even after that.

http://www.techprose.com/Samples/SFMaritime/thayermoreinfo.htm

Maybe they just didn't worry as much about checking in those days, on a working vessel?

By the way, the C.A. Thayer was bought by the State of California in 1957, and restored as a museum ship. She's still around, berthed in San Francisco.

[apex1]

Thanks Ilan,

yes there are formulators in Turkey, but not worth talking. I import all my stuff from Germany and at several hundred TONNES per annum that is still worth the extra cost!
The Turkish sun is not soo dramatic for a appropriate resin (dark colour), Florida is much hotter. But I sell my boats even with dark blue hulls in Florida. Although we are using the right resin (high Tg) and postcure the entire boat at 80°C.

"West" is just very common in the small boatshops in Turkey, of course you pay mainly the name, rather than the stuff.

Troy

if this boat would have been built as a classic wooden boat in carvel planked manner and caulked, it could do without epoxy treatment, sure. But it is already a "wood / epoxy" build (done improper to save some pennies), now he has NO CHANCE, he MUST encapsulate the entire wooden structure in epoxy and he MUST apply at least two layers of glass at the hull (outside).

Regards
Richard

[teoman]

Hey,
Actuallly the goal is not to save money, I wasn t told of any implication created by having the two layeer epoxied together. I appreciate and thank you for giving me a way out of that. I think we all agree that I should glass inner and outer.

Richard if I understood correctly, you do import all the product needed for glassing from Germany. I am also looking for the same things. do you sell it as well ?? please let me know.

I am wondering something. They do a lot of laminated yachts around here 3-4 or even 5 layer. If I am coorect all those layers are epoxied together. So all those yachts would need to have the inner and outer glassed as well ??

[apex1]

Hey,
Actuallly the goal is not to save money, I wasn t told of any implication created by having the two layeer epoxied together. I appreciate and thank you for giving me a way out of that. I think we all agree that I should glass inner and outer.

Richard if I understood correctly, you do import all the product needed for glassing from Germany. I am also looking for the same things. do you sell it as well ?? please let me know.

I am wondering something. They do a lot of laminated yachts around here 3-4 or even 5 layer. If I am coorect all those layers are epoxied together. So all those yachts would need to have the inner and outer glassed as well ??

NOT THE INNER SURFACE !!!

Glassing the outer surface is mandatory, but inside you are fine with three layers of pure resin (apply them wet in wet).

No, we do not sell our imported products! (that would be very complicated due to the customs regulations)
But if you follow my advice and go to Tuzla you will find everything you need.

The boats you are referring to are built "cold moulded", yes every layer of veneer is fully encapsulated in epoxy. In fact every single piece of wood has to be encapsulated. If that is properly executed you have a boat which is as mainenance free (I claim it needs less maintenance) as a GRP boat.

But too late, your hull is done, so live with it and do the rest proper!

Regards
Richard

[alan white]

'Glass is not required, inside or out. The process is called "cold molding". The layers are laminated at angles (the outer sometimes is run fore and aft for appearance).
Two layers, both going fore and aft, lacks the strength across the grain. The fiberglass is then required inside and out, but glassing between frames inside is a huge amount of work.
A true cold-molded hull (5 layers, several angles) requires far fewer frames.
In your case, it appears you are thinking of mixing traditional double-plank with strip-building with a little cold molding thrown in.
Any one of the methods will work fine (carvel double planking, strip build, or cold-molding), but mixing those methods is tricky and can easily ruin the boat.
Different woods and different widths of planks, different frame spacing, different requirements for fiberglass, and many other factors come into play as you change from one method to the other. The reason I asked what your maximum plank widths were was because you are using chestnut and the wider you go, the more problematic the result as the boat ages.

[Ilan Voyager]

Troy. Apex gave you the answer. Composite wood epoxy has nothing to do with classical boat building, and visibly you have not experience of it. I worked on my first epoxy wood boat on 1971...

Alan. Words of wisdom...never mix building systems it's a disaster. But it's too late for Teoman, he has to use glass. Improper method, improper wood.

Apex. Many thanks for your enlightening posts. And your knowledge of the local conditions is invaluable.
Germany having one of the best chemical industries of the world, no doubt you get excellent products for the boats...and with post cured resin, no problem of heat by the sun! I agree totally with your last post.

Teoman. The hull is done, not in the proper way, and the simplest way to achieve this boat is to encapsulate it inside with 3 coats of resin (and a fourth coat in the bilges), and outside with 2 layers of glass cloth at 45 degrees (so all the fibers will be used to "support" the glue lines and the wood fiber) with at least 3 to 4 four coats of resin over the cloth. And a good paint. It's the lone system that insures a minimal transfer of water (and water vapor) in the wood.
I insist heavily that the resin must have an elongation of 5 % for this application. A more rigid resin (like 2 or 3 % elongation) probably will be too brittle for this particular application and will have micro-fissuration or delamination if the boat is a bit flexible.
A very hard work, but maybe worth to do, it to divide the width of the outer planking so the stresses will be lower. A small fast circular saw, like those used for cutting tiles, with a small wood cutting disk , a good ruler, and lot of "elbow oil" (ie work) are needed. You cut just through the first plank, about 80 % of its thickness, in strips of about 2.5 cm. After the cuts are filled with epoxy and filler. Finishing as said above with glass and epoxy. A big delicate job...
The chine is a very important place because of the angle change with the induced concentration of stresses. 4 layers of cloth (made by the over lapping) are mandatory. The chine must be rounded so the cloth layers do not "break" over the angle or you'll have surely bubbles and probably a crack line later. The overlap must be at least of 20 cm each side after the glue line of the chine. A lot of fairing is expected...
Try to contact SICOMIN. They have good products and the prices were good compared to the imported American brands in France. The technical service was excellent. My data is a bit old as I live in Mexico now.

[apex1]

I beg to differ Alan.
He is not building with wooden veneers! (cold moulding)

Glass IS mandatory to strengthen the layers of resin on the outside and apply some abrasion resistance. He otherwise would soon have water intrusion into the wood.

The building method choosen is (unfortunately) very common in Turkey. The people do not really understand the advantages of the classical building methods and try to "improve" them. Usually the result is sufficient to last for some 10 - 12 years.
Due to the fact that the planks are already glued together with EP he MUST encapsulate the entire structure in EP too.
And thats where his original question derives from, it is done so every day in Turkey.
Of course that is not a proper method. Strip planking would be better, cold moulding like my boats, far better.

The species of chestnut you find in North America are not what is used here I think. "Castanea Sativa"

Regards
Richard

Ilan you type too fast for me mate.................


teoman

have a look here how we do it:
http://www.boatdesign.net/gallery/showphoto.php/photo/14467/ppuser/11121

and more important, look how they do it in Tuzla!

[alan white]

I beg to differ Alan.
He is not building with wooden veneers! (cold moulding)

Glass IS mandatory to strengthen the layers of resin on the outside and apply some abrasion resistance. He otherwise would soon have water intrusion into the wood.

The building method choosen is (unfortunately) very common in Turkey. The people do not really understand the advantages of the classical building methods and try to "improve" them. Usually the result is sufficient to last for some 10 - 12 years.
Due to the fact that the planks are already glued together with EP he MUST encapsulate the entire structure in EP too.
And thats where his original question derives from, it is done so every day in Turkey.
Of course that is not a proper method. Strip planking would be better, cold moulding like my boats, far better.

The species of chestnut you find in North America are not what is used here I think. "Castanea Sativa"

Regards
Richard

I didn't say he was building cold-mold. I only commented that the putting together of two layers was a "method" that included an aspect of cold-molding (that being epoxy between layers and between edges) IN COMBINATION with several other methods.
Question: Did the builder also encapsulate the frames and back-coat the inner planks, ends, floors, etc.? Did he narrow up his planks in anticipation of adding cloth?
Cold molding or strip alone would be, I think, the better way to go (leaving behind remnants of traditional plank on frame). Cold molding (with thin veneers) is probably best with hard-chine designs as it would self-fair.
If strip-built in the old way, 1" thick strips could be edge-nailed, and in addition, if carefully stripped, without any adhesive or in fact anything between strips (use fasteners that won't corrode, obviating the worry of acidity causing damage). A lot of ways to go, but now it appears that glassing and heavy encapsulation is the only thing to do at this point.

[apex1]

Alan,

my comment was a bit sloppy formulated. I did not understand you said he was cold moulding. I did contradict on the "glass is not required" part!

Due to the fact that he is not cold moulding he needs to glass the outside. That was what I wanted to say.

Sorry for confusing.

Regards
Richard

[Ilan Voyager]

Alan. Look at the pics and you will see immediately that the frame is identical to the chine frames of the post WW2 war chine plywood boats. Massive wood and some plywood pads. No EP coated at the moment of the pic, no laminated beams.

A such method building uses normally resorcinol glues, that withstand the stresses of a swelling wood. A lot of a long lasting plywood boats (some have 50 years now) have been done like that in the 50's and 60's. But these boats were made with excellent African hard wood plywoods, mahogany structures and silicon bronze screws.

The double plank variant used oiled calicot, or white lead compound, or lead minium compound between the planks (I imagine the face of a sanitary inspector if you were using now such poisons...) and tons of copper rivets, bronze screws, or double dipped nails. The English luxury yachts used for finishing the Cascover system (a nylon cloth glued with resorcinol).

As Teoman's boat is already made, all he can do is to coat the inside with three coats of EP, and to keep a close eye on that in the futur.

A little trick is to make fillets of glass bubbles - only glass bubbles no other filler- everywhere a beam, rib or other cross the planking. Recipe; glass bubbles, a pinch of colloidal silica (cabosil or other brand) and EP with a little too much hardener (for example if the normal ratio is 2 parts of resin/1 of hardener, he uses a ratio 2/1.05 to 1.1) to obtain a consistence of peanut butter or nutella. That gives a slightly soft, rather elastic, and totally compatible EP whitish compound. It will absorb most of the movements between the planking (and deck) and the structure. It's finished with 3 coats of resin. The lines of possible fracture are suppressed - I hope so-.

All the "outside" corners must be rounded; it's impossible to get a good EP coat on a sharp right angle.

All this work is labor intensive...and not 100% guaranteed.

[apex1]

All the "outside" corners must be rounded; it's impossible to get a good EP coat on a sharp right angle.

All this work is labor intensive...and not 100% guaranteed.

Yeah it is not too easy, but nothing is impossible!

http://www.boatdesign.net/gallery/data/500/medium/P1000847.jpg

there are two more guys involved to get rid of the entrapped air btw.

Regards
Richard

[alan white]

Alan,

my comment was a bit sloppy formulated. I did not understand you said he was cold moulding. I did contradict on the "glass is not required" part!

Due to the fact that he is not cold moulding he needs to glass the outside. That was what I wanted to say.

Sorry for confusing.

Regards
Richard

I completely agree, did before and do now.

[alan white]

Alan. Look at the pics and you will see immediately that the frame is identical to the chine frames of the post WW2 war chine plywood boats. Massive wood and some plywood pads. No EP coated at the moment of the pic, no laminated beams.

A such method building uses normally resorcinol glues, that withstand the stresses of a swelling wood. A lot of a long lasting plywood boats (some have 50 years now) have been done like that in the 50's and 60's. But these boats were made with excellent African hard wood plywoods, mahogany structures and silicon bronze screws.

The double plank variant used oiled calicot, or white lead compound, or lead minium compound between the planks (I imagine the face of a sanitary inspector if you were using now such poisons...) and tons of copper rivets, bronze screws, or double dipped nails. The English luxury yachts used for finishing the Cascover system (a nylon cloth glued with resorcinol).

As Teoman's boat is already made, all he can do is to coat the inside with three coats of EP, and to keep a close eye on that in the futur.

A little trick is to make fillets of glass bubbles - only glass bubbles no other filler- everywhere a beam, rib or other cross the planking. Recipe; glass bubbles, a pinch of colloidal silica (cabosil or other brand) and EP with a little too much hardener (for example if the normal ratio is 2 parts of resin/1 of hardener, he uses a ratio 2/1.05 to 1.1) to obtain a consistence of peanut butter or nutella. That gives a slightly soft, rather elastic, and totally compatible EP whitish compound. It will absorb most of the movements between the planking (and deck) and the structure. It's finished with 3 coats of resin. The lines of possible fracture are suppressed - I hope so-.

All the "outside" corners must be rounded; it's impossible to get a good EP coat on a sharp right angle.

All this work is labor intensive...and not 100% guaranteed.

Right. A lotta work.

[magwas]

It is said that for wood hulls it is better to use polyester cloth than glass:
it is more abrasion resistant
it moves better with the wood

see http://www.woodenboat.com/forum/showthread.php?t=6640

[Ilan Voyager]

It is said that for wood hulls it is better to use polyester cloth than glass:
it is more abrasion resistant
it moves better with the wood

see http://www.woodenboat.com/forum/showthread.php?t=6640

I do not think that Xynole would be found in Turkey. So the following post is an "aparte" from the thread's subject. It's better for Teoman to stick with a well known and "cheap" material. Plus the added diagonal strength of 2 layers of glass will be a welcome plus for his boat, which has too much longitudinal wood fiber for an EP wood construction.

The French Navy had tried a lot of sheating materials for the project of a mine hunter in composite EP wood, with true engineering tests including cyclic fatigue and accelerated aging in salt water. Nothing that a common boat builder or West System can afford. Evidently, the results are not public.
A mine hunter must survive to a lot of factors, specially the close explosion of a mine (this goal has been met with polyester/epoxy/vinylester resins, UD glass, plywood and a lot of different foams)

Polyester "cloth" like Xynole adds nothing to global strength and weights a lot. It's finally like a mat close to the coremat and similar. It resist to abrasion mainly because the result is very thick.

You can get close results with a good cotton or linen cloth. Simple bulk agents for keeping more resin, nothing more. Air bubbles may be problematic with some tight woven clothes.

Nylon or polypropylene cloths are a pain, because of their low density (it floats on the resin), difficulty to sand, and very poor adherence. After all lot of peeling ply cloths are made in nylon and/or polypropylene...Good impact resistance, lot of reparation after a big shock.

Kevlar, Vectra and consorts are more interesting but so expensive. Adhesion is not the best, and using this clothes is a pain. Difficult to cut, impossible to sand. The kevlar fashion in boat building didin't last a lot, and these fibers are used now where they belong: armors, sail clothe, ropes etc.

Carbone is not good as sheathing material, too sensitive to impact. The price also...

So fiberglass cloth is difficult to replace. It has a lot of advantages; price, resistance, excellent adhesion with the proper surface treatments (and it must be kept perfectly dry, as the silane or volane surface treatments are hygroscopic. In humid conditions the fiberglass must be dried in a oven.), easy to wet, and transparent so you see what you're doing. Add it can be sanded very well, and not problem to cut it.

A note about the thread in Wooden Boat you mention; the Xynole seems to have better peeling strength than fiberglass. It's simply because the fibers are too weak to break the EP. Cotton is also impossible to peel. Or you put enough fiber and EP to break the wood substrate.
Fiberglass is stronger than the EP, so the glass can fracture the EP when peeled. Mesh steel wire do the same...

[apex1]

There is Poly cloth in Turkey, (and every sort of peelply too).

But in this application, as Ilan said, it has no advantage. A well done pattern of glass cloth is the way to go for Teoman.

[Ilan Voyager]

All we can do now is to wish to Teoman good luck...he has a lot of work to do, but with care an acceptable result can be obtained.

This thread illustrates that a any boat is an engineered project, which requires a perfect knowledge of boat building by the designer. No mix of systems (hybrids accumulate often the disadvantages, none of the advantages)...

[teoman]

Good afternoon,
I apologize for the late reply to all your posts, I was on a long flight away from Istanbul.
It was a great pleasure to read through what you all said and I thank you for that.
First of all I researched the adhesion of epoxy to chestnut. A university in the Black see made a research and thee results were more than acceptable. No problem was sighted.
I will still do the test on my own as you suggested. thanks for that.

Concering the epoxy to be used, I checked West epoxy specs, and elongation is reported to be 9-10 % . This sounds good I believe.
West products is a little more expensive than others here, but I think it will be worth it. What you think about the 9 % ??

Finally I will go with 2 coats of resin on the inner, and probably a 4th on the bilge, and 2 coats of fiber on the outside at 45 degrees each, and 2 final layer of resin only on top of that.

Thanks for your time guys . Hope to send you the finished picture someday :)

[alan white]

Layers of resin can be applied thick or thin, like paint. If in doubt, go thicker. The surface inside and out should be uniformly smooth without dry-looking areas.
Three coats inside would probably be best if in doubt, and two outside over glass will probably work fine. Look for that solid semi-gloss appearance.
West is good stuff, very easy to use and forgiving. I recommend it for the beginner. Later, when more experienced, other cheaper resins can be used.

[Boston]

Fantastically informative thread folks points to one and all. The parts about not mixing methods was most helpful as were the bits about wood species and moisture induced stress

cheers
and best of luck
B

[teoman]

So when I start with the epoxy layers, would you guys recommend that I wait until each layer (resin layer only) is fully cured then sand it prior to next layer, or can I go ahead and apply the next layer before it drys and cures ??

[alan white]

If you apply coatings wet on wet, or before the previous coat has completely hardened, no sanding is needed. You'll be achieving a chemical bond rather than a mechanical bond.
Most of the fairing should be done before glass is applied, so it shouldn't be necessary to do more than scuff between coats to take down, and fair lightly just before the last coat, using microlight or simlar fairing compound.

[apex1]

So when I start with the epoxy layers, would you guys recommend that I wait until each layer (resin layer only) is fully cured then sand it prior to next layer, or can I go ahead and apply the next layer before it drys and cures ??

Well,

what Alan wanted to say (I assume) was something like my recommendation:

Get ALL your friends out of the bush and do the entire epoxy work in one single go !!!!!!!!!!!!!!!!!!!!:!: :!: :!: :!:

You will feel the need to spend some Raki later, but that is no expense compared with the labour and cost of sanding.

And more important, you get a homogenous layup which never will delaminate!

Sorry for my late reply, I am sailing at present.

Regards
Richard


Boston

could´nt find the points again, you do that hidden...............

[alan white]

Yes. And cool temperature is on your side, and so is tropical hardener. In some cases, you could draw the wet-on-wet job for weeks. Then you'd have some real control. when finished, put the heat to 'er.

[apex1]

Yes. And cool temperature is on your side, and so is tropical hardener. In some cases, you could draw the wet-on-wet job for weeks. Then you'd have some real control. when finished, put the heat to 'er.

Quite important point! thanks




dunno why, sometimes have the impression we like to agree....

[teoman]

Ok I think I get the point. Thanks...

Richard there is one epoxy on the Turkish market called "Teknomarin" ERA 4000. Did you heard about that one ??
any idea, would you recommend it ??

[apex1]

Ok I think I get the point. Thanks...

Richard there is one epoxy on the Turkish market called "Teknomarin" ERA 4000. Did you heard about that one ??
any idea, would you recommend it ??

Forget you heard about it...............


basically it is not a bad formulation, but unstable. (I mean it does not provide the same properties in each supply)

R
R

[teoman]

ok thanks, I never Heard of it ...

hehe

[CatBuilder]

The original poster must *definitely* do as Ilan Voyager says a couple posts back. If you have used epoxy as a fastener anywhere, but leave the wood open to the elements, the wood will breathe (ie: expand and contract with varying moisture and temperature). As the wood changes shape and size, it will break free of the epoxy, if left untreated.

You can sheath the outside with glass/epoxy for durability, but you MUST put 3 coats of epoxy on the inside of the hull, absolutely encapsulating all wood so that you can be sure it doesn't breathe and go to work loosening the existing epoxy joints you show in the photos.

[teoman]

Would you guys rercommend I mix anything such as West Microfiber to the resin when applying the inner side of the boat ??

[CatBuilder]

I wouldn't suggest you mix anything with the epoxy. Just roller it on, 3 layers of it. You aren't applying it for strength in there, just to keep the moisture level of the wood stable. That's its only purpose.

[wolnym]

Abrasion ??? From whom ?? :) When you expoy both sides the wood bewteen epoxy start faster rot. In stripe planking method stripes inside the both you must paint using breathable varnish, 5-6 layers.

[alan white]

What comment are you referring to about abrasion, wolnym, and haven't you heard that epoxy inside and out is exactly how normal modern strip-builds are done? Varnish is a very high maintainance coating compared to epoxy.
You may be more familiar with the older type of edge-fastened strip construction.

[wolnym]

Alan,
modern and wooden for me it's not the same. Maybe I'm not perfect in English but epoxy for me means using cold molded method on polished wood. Put the epoxy resin with mat glass on both sides of the boat it's not a good idea.
p.s.
If I something missunderstood, I'm sorry. :)

[alan white]

No problem. I think you may misunderstand, but not speaking English well, it's still good to see you posting. I am not sure what you read that you don't agree with. Which post?

[apex1]

Put the epoxy resin with mat glass on both sides of the boat it's not a good idea.


Well it is in fact a very good idea when the design was done accordingly.

Regards
Richard