West system VS. everything else

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

macosxuser

Well-Known Member
Joined
Jan 20, 2007
Messages
52
Ok, I'm an A&P Mechanic and RV builder. I've done a little composite work throughout the course of my job and for the RV, almost exclusively using West System.

It has come to my attention that this may not be the BEST epoxy to use fore structural fiberglass work, so I was wondering what is? I have a Rutan 'practice' kit with a little EZpoxy, and I was going to try my hand at using that. I know Vinyl ester is superior for higher temps, but am hesitant because of the fumes.

For epoxies, is it there a better solutions than West for strength/weight? I've only got a gallon of it right now, so it wouldn't cost me that much to change except for the learning curve. I've used West both proportioned by weight (at school) and by Volume (with the pumps, at my hanger).

The applications vary from fairings and cowling repair, to complete aircraft structures (basically, I want to get very familer with one system that I can use all the time).
 

orion

Well-Known Member
Joined
Mar 2, 2003
Messages
5,800
Location
Western Washington
This is probably one of those subjects where you'll get as many recommendations as the number of people that answer. It's also one of those subjects where the answer is really dependent on what you're trying to do. The basics to consider are whether you're looking for a resin system for lamination, secondary bonding, high temperature application, odor sensitivity, or any other criteria that you might come up with.

You're right, the best resin system for high temperature application is Vinylester. It's also good for secondary bonding of Vinylester based parts, although that's generally true only for parts less than about a month or two out of the mold. Older parts will not have as many free molecular chains to link with and as such, more part prep work is required to get a bond of sufficient strength.

The smell of Vinylester is as that with Polyester - it's Styrene. Today's resins though have a much lower concentration of this stuff (five to ten percent, some even less than that) than about fifteen years ago where some systems had over 20%. If the smell bothers you then yes, you really have little choice but to look at epoxies - just keep in mind you are not going to get the temperature and chemical resistance that you would've with the Vinylester.

For secondary bonding of laminate structures my favorite are the Hysol products. EA9430 is the old standard and still delivers some of the best bond properties possible, regardless of substrate. But as good as it is, it can be a pain to work with since on a cool day the resin has the consistency of taffy. Part B is however more like water so when you mix the two you end up with a nice working consistency. I usually heat up Part A before using it - it makes it easier to get out of the can and it really does not shorten the working time all that much.

EA9412 is the same base as EA9430 but it is much thinner. It too could be used for secondary bonds, especially where secondary laminations are required. I have used it for wetting out larger parts but generally I don't recommend that since it is still a relatively thick system and if one is not careful it is easy to get areas of too much resin, resulting in a bit of fabric float.

Hysol of course makes a whole line of products so choosing the right one is really a mater of finding a local distributor and picking what you need. These resin systems were formulated for most industries, including aerospace, so some can be a bit pricey but given the properties, I generally can justify the slightly higher price.

Over the years I've worked with numerous laminating systems including several from Shell (yes, the oil company), Jeffco, and West System, among others. I really don't have a favorite among those since the choice really depends on application. Secondary bonding is critical and as such, there I do tend to migrate toward the Hysols more so than anything else.

For laminating, the interesting thing is that for optimum structural (strength and stiffness)properties the laminate is not all that sensitive to the epoxy you use. Most of the properties are more a function of the type of fiber and weave you use rather than the resin, and whether you vacuum bag or not. As such, the resin choice will most likely be a function of your own personal preferences.

The only word of caution I would have is not to use a too thin a resin system (unless you're doing a vacuum infusion), especially if you're laminating a deep part and/or one with steep walls. If the resin system is too thin it will tend to flow off the walls and pool at the bottom of your part, leaving the wall laminate on the dry side.
 

Waiter

Well-Known Member
Joined
Mar 17, 2005
Messages
156
Location
Northwestern Ohio
I'm the owner/builder of a LongEZ;

I would use the recommended epoxy for structural components, especially on a new build. Several of the epozies (i.e. EZ-Pozy, SAFE-T-Poxy) were formulated to have a couple unique features, one of the features was to temporarly "soften/melt" the sytrofoam to enhance epoxy bonding to the foam.

HOWEVER: West system has been approved for Cozy Builds. I use West System for structural repaires on my LongEZ, and occationally when building none structural components, I like the use of the fast (105?) hardner.

I recently completed a new cowl for my EZ using West systems.

http://www.iflyez.com/LongEZ_Retrofit_DEC_06.shtml

Waiter
 
Last edited:

wsimpso1

Super Moderator
Staff member
Log Member
Joined
Oct 18, 2003
Messages
6,531
Location
Saline Michigan
I use Geogeon Proset made by the same folks as West System.

West is just about magic for wood. Proset is intended for composites. There are several resin viscosities and several hardener speeds, so you can use what suits. they even have a line of adhesives that are just terrific.

I use 135 resin for plain wet layups and 125 resin for vacuum bagged parts because the excess comes out of the nagged layup more readily. I generally use 226 Hardener on small jobs, and 229 Hardener on the big ones to give adequate working time and excess epoxy removal. My test coupons exceeded book values for epoxy laminations.

The only drawback is that it is a bit pricey...

Billski
 

macosxuser

Well-Known Member
Joined
Jan 20, 2007
Messages
52
Ok, I do a fair bit of laminations and less of the secondary repairs. The repairs I do are usually on non-structural parts, such as wheel fairings. If I ever get into structural composite repair, I can revisit that. I currently have both fast and slow hardeners for West, because here in Socal when the temps get >90° the fast hardener has a very short working life, usually less than 20 min.

I don't currently have a vacuum bag setup, but I'll be looking to get one in the next few months. I've done a couple of one-off parts from male molds, but nothing too big yet. From what I'm gathering West system is OK, but the ez-poxy might be stronger?

I also work on a Whitman Tailwind, so the wood properties of the west system aren't to be overlooked. I might build a new set of wingtips for that in the future, so I'll have a use for the west system.

I think i'll try out the ez-poxy I have, to see how it works. If I like it, I may stick with that, if not maybe try the Proset. I don't think I do enough secondary bonding to justify the Hysol. I personally don't mind the fumes of vinyl ester, but the people I work with do...

Any more recommendations are welcome. I'll read them all :D
 

DaveK

Well-Known Member
Joined
Apr 21, 2007
Messages
347
Location
Northern California
I thought I read that West System was explicitly not to be used for structural parts. An excerpt from a Cozy newsletter

"The West System is an epoxy system developed by the Gougeon Bros. for boat builders. It is a softer epoxy and recommended for contouring (mixing with micro and spreading over finished layups), because it has excellent adhesion and is much easier to sand. It is not suitable for making glass layups! We were very distressed to hear that one builder was using it for all of his fiberglas layups. It is not approved for Iayups!"
 

orion

Well-Known Member
Joined
Mar 2, 2003
Messages
5,800
Location
Western Washington
........because the excess comes out of the nagged layup more readily.
Can you explain this process in more detail - does this mean that if I stand over the part for a time during the cure and complain about the slow cure and other things it may be responsible for, now or several years ago, that it will develop better properties?
 

Dust

Well-Known Member
Joined
Feb 9, 2004
Messages
302
Location
Troy, Michigan
I thought I read that West System was explicitly not to be used for structural parts. An excerpt from a Cozy newsletter

"The West System is an epoxy system developed by the Gougeon Bros. for boat builders. It is a softer epoxy and recommended for contouring (mixing with micro and spreading over finished layups), because it has excellent adhesion and is much easier to sand. It is not suitable for making glass layups! We were very distressed to hear that one builder was using it for all of his fiberglas layups. It is not approved for Iayups!"
The west system with the EXTRA SLOW hardener is approved by burt and nat, but as it only has a TG of 129 F, i prefer mgs, also approved
 
L

LongEz360

Guest
Do not use the standard commercial West System resin system in structural layups for Rutan or derivative canards. Personally I would not use it for so much as a repair on a fairing - It has extremely poor laminating characteristics, and poor structural performance. Spend that little extra money and use a good room temp cure resin system - e.g. MGS L285/H285.

There's too much bad information out there on EZ forums (and others) from people who are not engineers, or assume that level of knoweldge having built an aircraft or part thereof. Many base their recommendations to others are not substantiated. They do not seem to understand how primitive the construction methods are in these aircraft, the quality requirements or impacts of deviations from plans requirements. Our best work is barely acceptable.

Wayne
Long EZ, VH-WEZ (N360WZ) builder & pilot
Boeing M&P Engineer
A&P (AME)
Melbourne Australia
 

bmcj

Well-Known Member
HBA Supporter
Joined
Apr 10, 2007
Messages
13,309
Location
Fresno, California
You're right, the best resin system for high temperature application is Vinylester. It's also good for secondary bonding of Vinylester based parts, although that's generally true only for parts less than about a month or two out of the mold. Older parts will not have as many free molecular chains to link with and as such, more part prep work is required to get a bond of sufficient strength.

The smell of Vinylester is as that with Polyester - it's Styrene. Today's resins though have a much lower concentration of this stuff (five to ten percent, some even less than that) than about fifteen years ago where some systems had over 20%. If the smell bothers you then yes, you really have little choice but to look at epoxies - just keep in mind you are not going to get the temperature and chemical resistance that you would've with the Vinylester.
Hi Orion,

Besides the fumes, sensitivity, and poor secondary bonding of aged parts, do you consider Vinylester (or Polyester) a superior system for structural layups. What other negatives does Vinylester have?

Bruce :)
 

orion

Well-Known Member
Joined
Mar 2, 2003
Messages
5,800
Location
Western Washington
I wouldn't necessarily say that the Vinylester secondary bonds are poor - let's face it, there are a lot of Glasairs and Express aircraft (among others) that have been flying for many years with no problems. But in the same breath, I have seen a couple of secondary bond failures that occurred either due to poorly considered application or poor surface prep. So personally, I do prefer high strength epoxies but will not necessarily rule out the VE.

As far as laminating is concerned, yes, I think the resin is ideal. Personally I like the DOW systems because they are very predictable and modifiable. the latter is very important as the temperatures turn from Winter to Summer. The DOW has very flexible promotion schedules and can achieve a full cure with quite a range of catalyst percentages.

I've had horrible luck with the Reichold resins so I don't recommend them for our application.

The only negative I see with the VE is the cure sensitivity to temperature changes. But this is an issue for most resins, VE and epoxy alike so take that as just a general comment.

The only other negative I've come across with VE is that it cures with a bit of a "rubbery" surface. This is not an issue of structure and can be minimized with peel-ply, but it is a pain if you have to sand something.
 

Corsair82pilot

Well-Known Member
Joined
Jun 18, 2006
Messages
83
Location
MD
VE is the only way to go in my book. Easier to work with, less expensive, better tollerence to heat. Stinks, but no allergic reactions. Full cure is a little slower, unless you post cure, but strength wise, more than sufficient. And you can paint your aircraft any color you please.

TP
 

mstull

Well-Known Member
Joined
Jun 23, 2005
Messages
1,263
Location
West Texas
I prefer Jeffco epoxy laminating resin for a few reasons. First off, it is unusually non-toxic and low odor. It's not even hazmat, which can save on shipping.

Second, it is extremely temperature forgiving. The warmer the conditions, the faster it cures, and the cooler, the slower... but it will always cure to a nice crisp layup. Some resins won't cure at all in cooler temps. You'll still want to do the layup in 80 to 85 degree F conditions if possible. And you do want to post-cure it.

Third, it is fast curing. Even their medium is fast. So doing vertical surfaces is possible, even though the resin is low viscosity. If you like to work fast, you can lay up a huge amount of fabric in a day with Jeffco. And it has a decent shelf life. Their fast is extremely fast.

Fourth, its low viscosity wets out the cloth effortlessly. The cloth soaks it up so well, you don't have to spend extra time making sure it is perfectly wet out. I've even wet out more than one ply at a time in warm temperatures. It's great for those thick (large tow) unidirectional tapes. It's even low enough viscosity to lay up Kevlar.

Fifth, it cures into a very crisp/hard/stiff substance. For my ultralights, I'm usually trying to make a stiff part out of a minimum of plies and thickness to save weight. Jeffco is ideal for that. Some other resins make for a more flexible/rubbery part, even after post cure. So they take more plies to make a self-supporting, stiff part.

It may not be the strongest, but I've never had a delamination. And it is sensitive to humidity during cure, like many resins are. All in all, it's the most user friendly, room temperature, laminating resin I've found. And it's always been consistent year after year.
 

Big Steve

Member
Joined
Jul 31, 2008
Messages
5
Location
Filer Idaho
I will stick my .02 in here. I have used saftey poxy (now deaceased) and ez 84 epoxy, The replacement for saftey poxy. It is less exspensive than some of the other epoxies, Its cure rate gives me plenty of time to work it. I do have to use a hot air gun to get it to flow well even on a hot day. It cures rock hard within 24 hours and gets even harder for quite a while afterwards. I have thought of using some of the thinner epoxies that wet out much easier but they cost almost twice as much and I would have to change my pump. I have no exsperience with Vinel Ester but I hear it make really good gas tanks. I Have used the west system as a finish over the ez poxy with micro balloons it works great but I think it is to soft to make structural parts with. I have never tried the Jeffco epoxy but have heard good things about it. It is an approved epoxy for the Cozy I would like to learn new systems but would never use a resin system not approved by the designer. Steve Build on
 

gschuld

Well-Known Member
Joined
May 9, 2007
Messages
422
Location
Toms River, New Jersey
This subject is very interesting to me as I intend to start on a wood/composite plane fairly shortly. Plane building will be new to me, but I spent 10 years(most of which as the head guy) building custom wooden boats, mostly race boats. I have spent a bunch of time laminating, general wood to wood bonding, vacuum bagging wood and foam/Carbon structures, fiberglassing with carbon , zynol, dynell, etc. and I have used two epoxy systems. West System and Interlux epoxy systems. I have used the Interlux epoxy more for cloth layups in colder weather as it is a bit thinner and wets out faster. I have used West for everything else. There are different hardeners and fillers available to handle just about everything. I have never in all those years experienced a joint or lamination failure on anything that was bonded correctly in th efirst place. I am quite confident that the epoxy products mentioned in earlier posts in this thread are very proven, quality products. As I am coming into this airplane building project with a very good level comfort, confidence, and experience with these two products, I am fairly reluctant to go elsewhere as I will be trusting the epoxy with my life(plus I can get West System and Interlux products for 30-40% off retail. a BIG help;)). I am always open to learn and adapt to new processes and products so I am prepared to be convinced otherwise.

Thanks for all the info so far...

George
 
Top