West Systems tips and techniques needed

Had some miserable experiences with BSI today. Not blaming it, definitely me and my technique (or lack thereof more specifically.) But if I need to learn some skills, I'd rather learn them with something that transfers forward.

I don't laminate anything. So my construction is wood to paper, wood to QT, G10 to paper, G10 to QT.

West Marine is down the street, so West Systems seems like an obvious choice. Price vs shipping.

I understand that 105 resin gets mixed with 205 fast hardener or 206 slow hardener at a 5:1 ratio by weight or volume. It's the thickeners/additives I dont get exactly.

I'd like to get some formulas by additive and weight ratio if possible.

1. Straight bonding.

2. Interior fillets - like centering rings to motor mounts, fins to motor mounts or fins to interior body tube.

3. Exterior fillets - fins to body tube.

I've read from the West Systems site about ketchup, mayo and peanut butter. What ratios are needed to achieve the different states? I'd prefer not burning through $45 in resin for a learning curve if possible

Thanks!

OC_Rocket_Man said:

Had some miserable experiences with BSI today. Not blaming it, definitely me and my technique (or lack thereof more specifically.) But if I need to learn some skills, I'd rather learn them with something that transfers forward.

I don't laminate anything. So my construction is wood to paper, wood to QT, G10 to paper, G10 to QT.

West Marine is down the street, so West Systems seems like an obvious choice. Price vs shipping.

I understand that 105 resin gets mixed with 205 fast hardener or 206 slow hardener at a 5:1 ratio by weight or volume. It's the thickeners/additives I dont get exactly.

I'd like to get some formulas by additive and weight ratio if possible.

1. Straight bonding.

2. Interior fillets - like centering rings to motor mounts, fins to motor mounts or fins to interior body tube.

3. Exterior fillets - fins to body tube.

I've read from the West Systems site about ketchup, mayo and peanut butter. What ratios are needed to achieve the different states? I'd prefer not burning through $45 in resin for a learning curve if possible

Thanks!

Click to expand...

I don’t think anyone would will be able to tell you exactly. The difference between the three thicknesses you listed is slight. Just add a little at a time to unmixed resin and hardener until you think it’s the right consistency.

Steve Shannon said:

I don’t think anyone would will be able to tell you exactly. The difference between the three thicknesses you listed is slight. Just add a little at a time to unmixed resin and hardener until you think it’s the right consistency.

Click to expand...

So in our rocketry world, which fillers are used where? I've read tons of TRF threads and the West Systems site.

For instance, I've read on TRF that the 406 Collodial Silica is very strong and impossible to sand. So does that mean its the best filler for all internal adhesion?

West says the 403 Microfibres is best for wood. Does that mean not to use it for G10 to phenolic or G10 to QT?

I have only used colloidal silica for external fillets and nothing else. It is just a thickener & it does sand, not sure where you read it doesn't??

Also, West System sells pumps. Get them. No more measuring.

As far as thickening, you just keep adding little at a time and keep mixing until you get the consistency you want - don't think there is any formula that will suit your needs!

I use West System almost exclusively. My filler of choice is 404. When starting out, I used the pumps to measure the ratios, and they work fine. However, that wasted a lot of epoxy, as they compelled me to use more than needed at a time. A small electronic scale was a worthy investment. I still use the pumps for dispensing, but use the scale for determining the right mix.

Why 404 filler? You don't hear about it here. Looking at this selection guide, I went for bonding strength between dissimilar materials and in fillets rather than the lowest weight.

When mixing, you can pretty much tell when you have the right consistency. If injecting fillets, you want it to flow. For fillets, 'peanut butter' works well. You'll know pretty quickly what you like.

Definitely get the pumps, if i'm doing something small or large i'll find something else to epoxy or laminate to reduce wasted epoxy.

There really isn't much of a learning curve with the West systems fillers. If you know what you want it's pretty easy to mix a little at a time until you get it just right, you have a long pot life so take your time. If you accidentally add too much filler, it's easy to add 5 more drops of part A and 1 of part B to loosen it up a bit.
The only time I messed up any batches was when learning how very little chopped carbon it takes to make a hair ball.

When using 406 filler you will find that using 4-6 times the amount of filler gets you external fillet "peanut butter"

That is... if using standard 30ml mixing cups and you have 20ml of mixed epoxy... it will take adding 3-4 cups of filler [90-120 ml] 406 and stir the crap out of it. Mushing the lumps out on side of cup.

I mix about 2-3 minutes after adding each cup......mix now...sand easier later! [less lumps in fillet]

Simply pull your stick out of epoxy...when the "spike" stays put without losing shape, you have enough filler.

406 sands well. 404 sands like concrete.

Cj........ I wrote the book on this stuff.....Lol

Book:
https://www.rocketryforum.com/showt...eme-DarkStar-4-Build-75mm&p=113388#post113388

Mixing cup there is much larger than standard 30ml...it was automotive paint cup. so don't judge filler amounts by pics. I use 3x or more than the amount of mixed epoxy....always!
You will find hotter the ambient temp....more filler needed to get same thickness as less used in colder temp.
Start there for fillets, internal & external. read the whole thing to learn how to build a fiberglass rocket.:wink:

PS:
for mixing smaller amounts of epoxy I use syringe West 105 mixes at 5 resin to 1 hardener. So just use 5ml or cc [they are the same] to 1 ml. I keep 2 syringes .....1 for resin & one for hardener on hand all the time.
They give them to you free at Walmart phamarcy.....just ask for type used to give kids medicine.

ericm541 said:

Definitely get the pumps, if i'm doing something small or large i'll find something else to epoxy or laminate to reduce wasted epoxy.

Click to expand...

IMHO, yes and no. I transfer the resin into an empty pour style Tide bottle and weigh the epoxy with the electronic scale Worsaer mentioned. Much more accurate.

To answer the OP, I either use 405 filleting blend or (non-West) Cabosil for fillets, leave that rough, then follow up with microlight for the easy sanding finishing touch. For all mixes, the thick peanut butter is the reference. If it doesn't stand up the stick there isn't enough, but if it has large clumps then there's too much. You want to feel just a bit of resistance when you stir it.

I appreciate everyone's input. I know there's lots of ways to skin a cat and now I have some better ideas.

I going to buy a quart of 105 resin, some 205 fast hardener, some 206 slow hardener, some 404 filler, some 406 filler. I found a $15 off $100 coupon for West Marine and a 5 miles/$ gig through British Airways Mall to ease the sting. I'll use a scale for the resin/hardener mixes and then learn by failure for the fillers. West Systems even talks about combining fillers just to make things more confusing for the novice.

Jim Hendricksen I read through your build threads and epoxy guides...lots of great info and tips. Thanks!

Forgot to mention... and it probably need not be mentioned... but always remember to tare your scale for your mixing cup. (!)

Buy and share with a buddy!
Scales, for small batches.
Squeezy bottles to help dispense the small amounts I need into the cup on to the [tared] scale.
405 thickener for fillets, and mixed quite well.

Popsicle sticks with the round cut off (usually cut square, but at a slant for easy mixing & applying)
Hotel room keys for spreading, flaring, and filelting

Just a few thoughts ...

I use mostly 404, 406 and some sort of fiber (usually, milled glass). I also have some 410 and the graphite powder (I have lots of black rockets).

The 404 is for general thickening. I think it makes the "neat" epoxy less brittle.

If I'm making a thicker epoxy, then I will usually use some of the 404 and some of the 406. The combination uses less total filler. However, the primary value of the 406 is to produce a thixotropic mixture. When you are applying shear to the mixture, such as when forming a fillet, the mixture will flow and form a smooth surface. However, when you remove the shear, the mixture stays put. This is of great value when forming a rounded fillet, such as with a dowel. You can form the curved shape and then that curve will be retained and not sag into the valley of the fillet. When West says that 406 is good for filleting, what they mean is that you apply it and it stays put.

One thing about 406 is that it is tough to mix. The little clumps are difficult to distribute. I use a popcycle stick and shear the epoxy against the side of the cup. Eventually, the filler gets mixed in.

404 and 406 will increase strength, but if you really want the epoxy itself to be strong, you need a fiber. On fillets, I use 10% by weight milled glass (hate the stuff).

Often, when I'm using epoxy with a lot of additives, I will first paint the part to be bonded with neat epoxy. Then, I will wipe it off and then apply the epoxy mixture. The reason for this is to make sure that some epoxy gets into all of the little scratches. With a thick mixture, this may not happen.

I use 410, in combination with 406, to make sandable epoxy structure (a transition cone is an example). It makes a wood-like material that is easy to work and to sand.

Jim

I ended up ordering 105, 205, 206, 404, 406 and the pump set from Discount Marine Supplies. Discount Marine was $106 including shipping. West Marine was going to be $145 plus tax if I ordered through them.

I ordered Monday at 1pm and UPS dropped it off at my doorstep today Wednesday at 9:45am. So price and service were both excellent.

I need a scale that measures 0.1g. I just realized my kitchen scale's lowest resolution is 1g.

I was given about 1/10th a can of resin and some hardener and it lasted me about 3 years (measured with a spoon since the pump was trashed). If it takes a whole can to figure it out, you're mixing too much at a time!

RE: BSI, recently tried the Slow-Cure and it's definitely better ... unless you're in a hurry of course, but still a lot faster than WEST/206.

BTW, if you do a test with short chopped fiber added to epoxy, you might find it doesn't make much difference. Mix some up, lay down a ribbon on some wax paper and let cure. Do the same without the fiber. Bend once cured for a week... The odds of a fiber being aligned adequately to support the applied load with random fiber orientation in a 3D volume is rather small. Most of the fibers end up being worthless for any given applied load direction, so the few which are aligned reasonably can't take much load and break (or break their bonds if the fiber length is too short and the bond not good enough), followed by the matrix breaking. Getting high fiber volume ratio is also difficult with random fibers. With unidirectional and fabric layup one should get 60% as a ballpark average for a good layup. Not so with random fibers. To even get close without having large air inclusion would require vacuum or ultrasonic techniques.

https://www.azom.com/images/Article_Images/ImageForArticle_13608(1).jpg
https://image.slidesharecdn.com/com.../composite-materials-10-638.jpg?cb=1459333364
https://www.researchgate.net/figure...omposites-as-a-function-of-CNC_fig3_269710665 - Not what I was looking for, but should give you the idea.

Gerald

G_T said:

BTW, if you do a test with short chopped fiber added to epoxy, you might find it doesn't make much difference.
Gerald

Click to expand...

I'll bite ...

Jim

Let us know what you find! I did that test years ago. I'll still use chopped fiber, but I no longer expect it to make much difference. Longer fibers, 2D vs 3D (as in get it in a layer thinner than the fiber length or otherwise orient the fibers to the load) makes more difference.

Gerald

Once you've got your fillet (using Colloidal Silica) in place, lay a piece of waxpaper over it, taking care not to trap any air bubbles. Remove the waxpaper about midway through the cure. Put on a latex glove and dip your finger in denatured alcohol then shape the fillet. Very little sanding will be necessary

If alcohol diffuses into the fillet, which it will, then you've cut the ultimate strength of the epoxy matrix perhaps in half. Even a little epoxy of any common variety severely negatively affects the epoxy strength. Isobutyl alcohol would work without costing nearly the strength, but it is not common!

https://epoxyworks.com/wp-content/uploads/2014/08/thinning4.jpg

Gerald

The chart you posted shows a 5% alcohol solution is needed to "cut the ultimate strength of the epoxy matrix perhaps in half". A tiny bit of alcohol from a dipped tool/finger may transfer to the surface of the partially cured fillet but it evaporates within seconds.