RTM VS. Hand lay-up

[Kovaceski]

Hello group, can anyone tell me some link where I can compare the costs and the threats bedween RTM and Hand lay-up?
Thanks.

[apprentice]

RTM please explain

[Kovaceski]

RTM (Resin Transfer Mould)

[apprentice]

cool thanks couldent rember for the life of me what RTM stood for.

i think you should go with hand layup method i just believe you have greater controll of the finished product than resin transfer. i work fro haines signiture and we still use hand layup quite often. but thats just my spin on it

[Kovaceski]

I can't stay on Hand lay-up. If I do that, I will lose my client. My plant is located in a small city and it's very hard to find qualified workers. On the other side, I have to diliver 70 to 80 boats per year to my client. He is already preapering a new model for the next year and therefore I have to do something to speed up the production. I hope you understand my problem.

[apprentice]

do you have moulds for your boats because if u do you could use pre preg or wet preg to lay up your boats with

[Kovaceski]

yes, I have molds (for open molding). But, what is "pre preg" ; "wet preg".

[apprentice]

pre preg is a form of chopped strand but it is pre inpregnated with hardner and resin what you do is lay it in the mould apply heat and it cures the disadvantage is that u dont have a long shelf life with the roll of reinforcement unless u have the ability to refrigdeate it

wet preg is another form that is used on large boats down here it is a roll of reinforcement (any type) and it sits on a roller the motorised roller then pases the reinforcement through two other rollers that pass through a tray of resin this enables you to do large areas at a time u only need two people to guide the wet reinforcement on to the mould and another two to roll it out

[Kovaceski]

ok. I have visited some links (conected to wet preg and pre preg) on the net. I have to say that it is still dirty work but, it is better than hand lay-up. I will read more about it and I will consider the possibility on applying it.
I just want to ask one more question.
Do you have any experience with RTM technology? Because, (to be honest) it seems to me that there are some "hiden" problems or extra costs behind all those presentations.

[Pericles]

Hello Kovaceski,

http://www.proboat-digital.com/proboat/200610/ has to be the first place you look.

Yesterday, I received 2 samples of a E-glass fabric called ParaGlass 22 3D. http://www.parabeam.nl/Product/Index%20product.htm

One sample had been infused with resin and the other in its natural state. It is a fabric woven out of a 100% E-glass yarn and consists of two decklayers bonded together by vertical piles. These piles are woven into the decklayers thus forming an integral sandwich structure.

The fabric is infused with a thermoset resin, the fabric absorbs the resin and due to the capillary forces of the piles, the fabric rises to the preset height. In this one-step process a lightweight and strong sandwich laminate is formed that offers excellent mechanical properties. Parabeam® can be used for many applications in the composites industry and offers multiple advantages against traditional sandwich materials or solid laminates.

The process is only really suitable for hand layups because vacuum bagging would prevent the fabric expanding, but the boat created would be lighter and stronger than other core materials. The nearest supplier to you is in Slovenia,
but it was Sandra Coulthurst http://www.univar.co.uk/downloads/Parabeam_for_yachts.pdf who sent me the samples. Contact her sandra.coulthurst@univareurope.com

You will discover the ParaGlass is a material that should allow you to continue building boats without RTM. There are a number of thicknesses up to 22mm. My cured sample is 150 mm x 100mm x 22mm. I weigh 120Kgs and I stood on the sample with all my weight on one foot. No change to the structure. :D I plan to build my boat with ParaGlass, marine ply and epoxy.

Good luck,

Pericles


Slovenia supplier:
SPS d.o.o. Mr. S. Podbevsek
Neveljska pot 23
1240 Kamnik
Slovenija
Phone: +386-(0)1-8397384
Fax: +386-(0)1-8397385
E-mail: mailto:podbevsek.sps@siol.net

[MarshallT]

Kovaceski
I think what you are looking for is Vaccum infusion instead of RTM. With RTM you need 2 molds (male and female). This is good if you want to have a part with 2 good surfaces (inside surface and outside). RTM can be used for larger production runs since the tooling costs are high. There is another version RTM Light which uses composite tooling instead of metal tooling but you still use 2 molds.

For Vacuum Infusion you can use standard female molds as long as they can hold a vacuum. It is very clean and consistent as long as you pay attention to details and do not cut corners. With a bit of practice you should be able to easily do 80 boats a year. What size is the boat? I don't think it wil speed up your production. It may make it easier for you to get better workers since it is a clean process.

As for the Paraglass this material was developed for double wall tanks and is not meant to be used for boat hulls. It will not be a good laminate since the tranverse fibres keeping the 2 layers seperated will not be able to handle the shear stress.

FYI: If you vacuum infuse the Paraglass until you get the resin to wet out the fibres then you can release the vacuum. It will have the correct amount of resin and will spring up the same as in hand layup. This is a good technique to make heated molds (you flow hot water between the 2 layers)

[MarshallT]

Kovaceski
I guess I didn't really answer your original question. I will try to give some info assuming what you are looking for is Vacuum Infusion (VIP)

In general the cost is the same for VIP versus hand layup. Of course this is a general statement but from what you are saying if you need to switch then I doubt cost will be a barrier. In the begining the cost may be higher but that is woul happen any time you make changes. With VIP you will use less resin so you will save there but on the other hand you need a vacuum bag so that is an additional cost.

There is a learning curve but there are now a lot of people and companies who have a lot of information. Unless you have a very difficult project or circumstances you should be able to get there easily.

I feel the biggest advantage is in consistency. With hand layup you need to rely on the person applying the resin (too much or too little??). If you have a core did they wet it out enough and is it well bonded?? With VIP you will know if there was a failure. With a proper procedures hopefully you will not have failures. Some companies are doing 100ft and longer hulls by VIP so you can be sure they cannot have failed attempts very often. There are some good examples in Professional Boat Builder magazine which is availalble on line.

If work force is a problem you can look into precut laminates. The complete laminate will arrive in boxes labeled and ready to apply. You can also get the vacuum bag made for the size of your hulls. You will have check to see if either is availalbe in your area.

If you want to email me more details of your boat I can try to give you a better answer.

[fiberglass jack]

go with rtm lite , and use a silacone bag , if u are going to be building 70 to 80 boats the silacone bag will save you time and money in the long run. i see your problem with workers hard to train them for this system, the oldtimers love hand lay up and are hard to teach, read as much as u can on resin infusion its very simple

[Kovaceski]

Dear MarshallT & fiberglass jack

Is the resin influsion same as VIP method? I call that vacuum bagging.
If I use those methods, will I have good quality of the surface without spending so much hours of laminating and “decorating” the surface?

fiberglass jack
You mean to use silacone bag as female mold? That will be more vacuum bagging than RTM Light. Am I right?

If I use vacuum bagging, can I produce deck part as well? Because If I can’t, I still have to laminate by hand lay-up and I will still have same problems (mainly with the surface).

The model of the boat I’m producing is 4.20 meter long. But, that’s not the only product we are producing (we produce tanks, insulation panels, public equipments and some other products as well).

In the normal terms, production of 70-80 boats shouldn’t be some problem. But, with my 15 workers (only 5 of them can laminate) that is my maximum. On the other side, my plant is 4.500 m2; we are using 1/3 of the space and we work only one shift. And that is the shame. Therefore I’m looking for new method where I can seed up the production with minimum qualified workers. After that, I can easily find workers for the assembling.

One thing fears me with vacuum bagging. On JEC Show in Paris, I was on a presentation of vacuum bagging method. After the presentation, many people came to speak with the presenter about their problems with this method. I was just listener there, but I’ve understand that dry areas and leaks are real threats with this method. That was the main reasons for me, to start thinking about RTM or RTM Light. There, after you invest in the mold, you don’t have problems. Or, it only looks like that?!

[Richard Hillsid]

Yesterday, I received 2 samples of a E-glass fabric called ParaGlass 22 3D. http://www.parabeam.nl/Product/Index%20product.htm



I tried the Parabeam a few years ago, it has nice potetial above waterline and in decks, or building double waled tanks, when using normal polyester i noticed i had to use a UV light and some ventalation, something to do with styrine gases geting traped, but a exelent product in the right place.

[Pericles]

MarshallT and Kovaceski,

The ParaGlass website give the technical data in SI units and good old Imperial. This link gives SI units. http://www.parabeam.nl/Technical/Technical%20Data%20Sheet%20Metric.pdf

You will see the shear strength figures for both ranges and thicknesses of the fabrics. Certainly, the ParaTank fabrics were developed for the manufacturing above and below ground double wall storage tanks. Univar sent me the manufacturing manual for using both male and female moulds in tank construction and Paratank is available in 3, 4.5, and 6 mm, for this use. One of the primary functions is to provide a leak monitoring interstice as well as the sandwich properties.

ParaGlass, on the other hand, has been developed with boat building in mind, so the thicknesses range from 3 mm to 22mm. I have in front of me the Parabeam Industry brochure sent by Univar. I shall quote from it.

"Parabeam has been tested by many independent institutes around the world and is pending certification of Lloyds and DNV for appointed applications. Many reputed boat builders have already been using Parabeam in their production. A reference list is available upon request."

The Univar website shows Sunseeker using ParaGlass in the 105. http://www.univar.co.uk/downloads/Parabeam_for_yachts.pdf
I picked up on this product from the pages of the latest edition of Professional BoatBuilder. I am inclined to believe ParaGlass is very suitable for boat building, replacing PVC foam, Coremat, balsa and solid laminates.

MarshallT, by what authority do you claim that "As for the Paraglass this material was developed for double wall tanks and is not meant to be used for boat hulls. It will not be a good laminate since the tranverse fibres keeping the 2 layers seperated (sic) will not be able to handle the shear stress."?

Do you have the ASTM mechanical properties for the other cores used in boatbuilding? A prominent marine surveyor in Florida, David Pascoe, has written a number of articles about the problems associated with the incorrect uses of laminated cores in boat building, His work is on-line. http://www.yachtsurvey.com/structuralissues.htm

Kovaceski, most new ideas have their detractors. You should get your hands on fabric samples and run your own tests. I gave you a contact in Slovenia and the UK. ParaGlass features include excellent drapeability, ,superior thermal resistance, a one step process, humidity and corrosion resistance. The core and face are one (no delamination of core upon impact) and resin use can be 60% less compared with solid glass laminates.

The final decision will always be yours, but being first will give you advantages and the others are all playing "catch up". ParaGlass would give you a "Unique Selling Proposition", which is never a bad idea. But hey, I'm a salesman. I never say "What will it cost?" I always say "How much money can I earn?"

In the begining, was the Word. And the Word is?


CASH!:D :D :D :D :D

Pericles

[MarshallT]

David Pascoe, has written a number of articles about the problems associated with the incorrect uses of laminated cores in boat building, His work is on-line. http://www.yachtsurvey.com/structuralissues.htm


Pericles
I suggest you lay up a hull with the Paraglass so that David Pascoe will have another article to write :-) Paraglass is a good material and will have many application on boats but the ones I have seen would not be suitable for the hull. Remember the original question was to make hulls.

[Pericles]

Hello Richard,

Styrene vapours are the most dangerous and injurious factors involved with using polyester and vinylester resins. Your personal health and wellbeing is far more important than saving a few Kronar. Epoxy resins are far safer. They may cost more, but you will live longer to enjoy messing about in boats. Dave Carnell wrote this. http://www.angelfire.com/nc3/davecarnell/epoxy.html

That said, you must still take care.


SAM DEVLIN ON SAFETY

The most controversial aspect of epoxy use is the matter of safety. There is no way around it: The improper use of epoxy can be injurious and hazardous to your health. But constant vigilance and continuous care for safe and proper use will minimize the hazard. Boatbuilders using normal precautions and staying safety-minded at all times can use epoxy with the best of results while fully protecting their health. Wear safety glasses, respirators and gloves. Tyvek suits are great protection.

The strongest advice I can give you is to keep epoxy off your skin. Prolonged contact with the resin and hardener can cause an allergic reaction--sensitization--in some people. Once sensitized, the slightest contact with the resin and hardener, their fumes, or even standing dust from epoxy that hasn't fully cured can bring on a reaction.

Keep epoxy off your tools, and always wear gloves that protect wrists as well as hands. I know of three examples where boatbuilders threw caution to the wind and suffered the consequences. Two were first-time builders of boats, but one was a professional who should have known better. The common denominator was failure to use proper gloves. The professional was a reckless fool in all aspects of his life. He refused to use gloves and would plunge his hands into acetone at the end of each job to clean off half-cured resin. While using urethane paints, he would refuse to wear even the simplest dust-filter mask, let alone an organic-vapor respirator or even a fresh-air system. Predictably, he experienced lung damage from the urethane paint and spent several days spitting up blood. In addition, the exposure to the epoxy caused a rash on both wrists and his forehead that resembled a reaction to poison oak. The rash would disappear after five or six days if he stayed clear of epoxy, but as soon as he walked back into the shop, it would reappeared. In the end, he had to give up boatbuilding with epoxy altogether, and the last I heard of him, he was at work in a can factory.
Once you have epoxy on your gloves,
you WILL have an itch on your nose,
your eyes WILL need to be rubbed,
and you WILL begin to sweat
and need to wipe your brow"
-- Devlin's Law

Most gloves available to boat builders are adequate for epoxy but will never stand up to cleanup solvents such as acetone or lacquer thinner. When cleaning up, discard the thin latex gloves you used for epoxying and don heavy, solvent-proof gloves.

And then there's "Devlin's Law", a variant of Murphy's Law. After a goodly amount of experience I have identified three natural temptations that you will experience when you are working with epoxy. Once you have epoxy on your gloves, you WILL have an itch on your nose, your eyes WILL need to be rubbed, and you WILL begin to sweat and need to wipe your brow. I guarantee you'll experience these urges, and just as surely, if you succumb to temptations, you will experience some nose or eye sensitization due to epoxy exposure.

There is simply no alternative to constant vigilance: using safety gear, working as cleanly as possible, and not getting epoxy on your skin. Keeping Devlin's Law in mind, one reason for wearing a canister respirator--apart from the fumes and dust--is to keep yourself from scratching your nose.

After fifteen years of using epoxies almost daily, the only reaction I notice is a slight constriction of the throat during extended use. But when I use a respirator, I never experience the throat irritation.

Of the two epoxy components, the hardener is the most toxic. Keep this in mind, particularly when cleaning the hardener side of your epoxy dispenser. Extreme caution should also be used when sanding partially cured (green) epoxy surfaces, as may happen in the winter in an unheated shop. Always wear a respirator and protective clothing, even if it's only street clothes that are laundered daily and cover all parts of the body likely to come in contact with uncured epoxy. If you insist on keeping your beard, a full-hood, powered-respirator fresh-air system may be the only answer, since regular cartridge-type respirators will not seal properly over a beard.

The bottom line, my macho friends, is to respect these chemicals; just because the hazards are invisible does not mean they are absent.

I have seen a couple instances of almost magical acts of reverse gravity in which epoxy or its resin and hardener components splashed up into boatbuilders eyes. In each instance we had to rush the victim outside to a water hose for a lengthy flushing of his eyes. Then rush him to the emergency room where the doctor repeated the process--not something anyone would do by choice. Wear eye protection at all times. Safety glasses don't work well for me because I find them uncomfortable. And if eyeglasses are uncomfortable, at some point you'll find yourself working without them--and that's when accidents happen. Even if you don't wear eyeglasses for vision, get yourself fitted with a proper expensive set of frames with clear lenses. Spend some money on them so you won't treat them casually and wreck them. Then wear them constantly in the shop so you get used to them.

And even the protection can't be taken for granted. I've also seen a worker develop nasty looking, painful hands as a reaction to latex disposable gloves, which in his case was probably a reaction to the talcum powder in them. He was fine after he switched to non-talc gloves over soft lightweight cotton liner gloves.

Moderation is the best protection. Always shower after a work session; it will help keep your body clean and healthy. Also don't forget to launder your clothing often. Wearing the epoxy-encrusted clothes day after day just continues to expose you to uncured resin or hardener.


http://www.masepoxies.com/safety.htm

Curiously, it is possible to follow expert advice and still be harmed. I just found this. http://www.second-opinions.co.uk/fats_and_cancer.html

It seems that the only fit place to consume corn oil and vegetable oils is in the heart of marine diesels.:cool:

Pericles

[Pericles]

MarshallT.

"but the ones I have seen would not be suitable for the hull. Remember the original question was to make hulls."

Well, I guess that says it all. The ones you have seen. But, NOT used. What fools you must think Sunseeker are.

Sunseeker 105. Core, ParaGlass 18, Skins, chopped strand 450 gr/sq. m., all glass resin laminate.

What un-utterable idiots the Sunseeker personnel are, by your opinion, to have built a $5,000,000 vessel using the incorrect materials. I wonder if they know?

I shall be building the hull of my boat using ParaGlass as part of its construction. Using Epoxy/Marineply/ParaGlass composite construction, the "U B'stard", for such is its name, will be just fine. Diesel electric water jet propulsion by OSSA Powerlite and Hamilton, an 'ybrid of the first water, ------ but that is a subject for another thread.

Pericles

[MarshallT]

Kovaceski
Here is a summary of the terminology that I think is normally used.
-Resin Injection Molding is used to make plastic parts using thermoset resins. The resin is forced into the metal mold under pressure. This is similar to injection molding which is used for thermoplastic resins
-Resin Transfer Molding also uses metal molds (male and female) and pressure is also used to inject the resin into the mold cavity. In this case however fibres are present in the mold.
-RTM Light is a less expensive method which uses fiberglass molds instead of steel. Because of the strength of the molds you cannot simply apply pressure to the resin to inject it into the mold cavity. Vacuum is used to reduce the extra pressure needed to get the resin in the mold. You can also use only vacuum.
-Vacuum Infusion (VIP) uses only one mold (normally the female mold) and uses a vacuum bag (either a throw away plastic or reusable silacone bag). It is called vacuum infusion instead of vacuum bagging because the fibres are place in the mold dry (without resin) then the vacuum is applied which will draw the resin in the mold.
-vacuum bagging usually means a bag is applied after the fibres have been hand layed with the resin. This is usually to remove air within the laminate or to apply uniform pressure on the core for bonding.

With VIP you can easily make flat panels or deck parts. If you are making a lot of different parts you have to keep in mind the extra cost of the molds for RTM light. From the sounds of it you only want to use RTM Light because you think you ar less likely to have problems. I don't have experience with RTM Light but I doubt that is the case. I think either works well when done correctly.

Leaks are only a problem with VIP if you start to infuse without making sure there are no leaks (or if you let workers play with sharp objects during the infusion :-) ) In the beginning you may spend more time looking for leaks but as the workers get better at vacuum bagging there should be fewer leaks to find. With well layed out flow channels you should not get dry spots but if you do there are techniques to fix it. The only really big problem is sudden loss of vacuum during the infusion. If that happens the part is lost. That is why you keep the knives or scissors well away from the vacuum bag. This method takes more planning than hand lay up but it is very possible to make the switch. Start with small parts and work your way up to the larger parts.

[MarshallT]

Pericles
I am sure Sunseeker did a good job but from the article you sent it does not show any application where it was used to replace a cored laminate for the hull.

Also if you are so confident that it can be used to replace a cored laminate for boat hulls then you should remove the Marinply (i.e.core) from laminate schedule on your "to be built" boat.

If I remember correctly you have recently received (maybe 3 days ago)samples from Parabeam. So perhaps you can explain to me how this makes you an expert on its use??? Oh the magic of the internet.

Brings to mind the saying "Fools Rush In........"

[Richard Hillsid]

Hi Pericles

I have used the said 3D glass, a few rolls of it in my time and have some thoughts on it. I think the first time was in 2001 or 2002

It is a excellent idea, and when it manages to cure right with polyesters its pretty stiff.
I have used it in open moulds, 2 part moulds spaced just for it and as a stiffener added to ready laminates, made boxes out of it etc.

The stuff is not so easy to work with one might imagine and I do recommend doing many test peaces before you plan to use it in production, as I said the concept to use it in a boat is very interesting but before it is used as a structural hull part one must really test it out there are problems as water condensation into it, how to drain that etc. plus how much reinforsing it neads as it collapses when bent.

For panels its great, have used aluminium and thin ply as face. If I remember right it is used in some helicopter as a non structural wall panel.

As to Epoxy versus Polyester, the choice is not always mine to make, the customer and designer have a say too.

PS: been around all the resins since the 60’ and my hairline is not reseeding too bad so I guess I have taken care with all the fumes and dust I have swallowed and breathed.

Wearing the epoxy-encrusted clothes day after day just continues to expose you to uncured resin or hardener.
At diaper age all new comers get messy so diaper need changing, using techniques of today we put on white overalls to protect the built part being contaminated by the worker of for PR photos. :)

[Pericles]

Hello Richard,

I am using the ParaGlass as the core between layers of 6mm marine ply. The first shaped hull bottom sheets are held in position in a cradle and bonded together with epoxy and bias tape. The ParaGlass is cut to fit, epoxy resin is applied to the marine ply and the fabric draped in position inside the hull.

More epoxy is applied and the 3D fabric rises as it is infused. After the resin has cured for the correct time, the next precut panels of ply are bonded in place. All raw or exposed edges are completely sealed with tape and epoxy. In this way I can build an incredibly tough, yet lightweight, monocoque hull and superstructure without vacuum bagging. Whether I use Kevlar or bias fabric over the interior of the hull remains to be seen. The exterior will be laminated with glass cloth and epoxy in the time honoured manner.

Water condensation is not a problem as we need dry air temperatures around 22 centigrade for the epoxy. I am glad to learn your lungs are still ok. I have been working with Hydrofluoric Acid HF for 10 years now and 4 years ago there was one small incident when I inhaled the fumes.

Now I take no chances and wear face masks for every procedure. There are no second chances with HF and epoxy dust can trigger breathing spasms now. No more diving for me any more.

Pericles

[Richard Hillsid]

Water condensation is not a problem as we need dry air temperatures around 22 centigrade for the epoxy.


This is not quite what i ment, but if you but your boat on the scale yearly you might figure it out.

[ClarkT]

FYI: If you vacuum infuse the Paraglass until you get the resin to wet out the fibres then you can release the vacuum. It will have the correct amount of resin and will spring up the same as in hand layup. This is a good technique to make heated molds (you flow hot water between the 2 layers)

Man that is a great idea! Have you had much success with that method? Do you need to take care in how the air is re-introduced to the laminate? Seems like a great way to do low temp pre-preg molds.