SailNet Community banner
1 - 20 of 21 Posts

·
Registered
Joined
·
4,181 Posts
Discussion Starter · #1 ·
Fiberglass resin fillers/thickeners - what do you use and why?
I have used glass micro-beads, phenolic micro beads, wood flour from my own tools - all for relatively small repair or coating jobs. Heard about people using regular flour.
At this point I'm not sure what the differences really are - all this stuff seems to work fine for the intended purpose of thickening the resin and not allowing it to run.
What are your experiences?
 

·
Registered
Joined
·
4,217 Posts
It depends on what you are doing. If you are bonding, or even more so, filling a hole you will re-drill, colloidal silica (Cabosil M5) is much stronger. It is also much more abrasion resistant, and in fact, darn difficult to sand. Which is why you use a lighter and weaker filler for fairing. For example, when I extended my transoms I used Cabosil for all of the structural work and microballons for visible finish work.

I use Cabosil a lot more often than lighter fillers. I only use light fillers when fairing a large area or where sanding will be difficult (inside corners).

Do a couple of test things with scraps and see.
 

·
Registered
Joined
·
4,181 Posts
Discussion Starter · #4 ·
PDQ - thanks for the info - you obviously have the experience. What is your take on using wood flour as a filler?
 

·
One of None
Hunter 34
Joined
·
8,647 Posts
Kriss, wood flour works with glass but it's gosh darn ugly against usually white FG. it's the epoxy that bonds so very very well to everything except polyethylene and some other plastics
 
  • Like
Reactions: krisscross

·
Registered
Joined
·
4,217 Posts
PDQ - thanks for the info - you obviously have the experience. What is your take on using wood flour as a filler?
No resent experience with wood flour. My recollection is that it kept absorbing epoxy and thus was less economical and heavier than you would think. Although I still use it occasionally on a cosmetic project to match color (add a little silica to lighten the color), I didn't like it as well as other things. I'm also sure it varies with fineness and the type of wood. Another thing is that most of us tend to stay with just a few products, because we hate surprises!

My suggestion is to read the ling Rich posted, and then to play with each of the products.
 

·
Registered
Joined
·
8,473 Posts
I use West system fillers, partly because I use West System resins and hardeners, and I know I won't have any compatibility issues, partly the convenience of being able to get supplies at every chandler in the area (they are all West dealers), which comes in handy, partly quality control- I know and like West products and know they aren't coming from some guy in a garage with vats of stuff he bought from the lowest bidder, and lastly, I appreciate what the Gougeon brothers have done for boatbuilding and boat design, and their eagerness to share their knowledge- I support those who support us.
 

·
Registered
Joined
·
196 Posts
It depends on what you are doing. If you are bonding, or even more so, filling a hole you will re-drill, colloidal silica (Cabosil M5) is much stronger. It is also much more abrasion resistant, and in fact, darn difficult to sand. Which is why you use a lighter and weaker filler for fairing. For example, when I extended my transoms I used Cabosil for all of the structural work and microballons for visible finish work.

I use Cabosil a lot more often than lighter fillers. I only use light fillers when fairing a large area or where sanding will be difficult (inside corners).

Do a couple of test things with scraps and see.
Im going to call you out on this one if your using Cabosil for Structual work you should have done your homework. Cabosil is used as a thickener for fairing or bonding like wood to fiberglass for non structurl uses. Cabosil has zero structural components to it and should never been used for structure. if you want to add some structure to your resin especially for filling holes that need to be redrilled to support bolts for winches or anything that may go under strain you have to use milled fiber if its a larger surface like that prop picture i would mix chopped fiber and milled only then if its a little runny for your liking add a very small dash of cabosil like one to two TSP.
 

·
Registered
Joined
·
765 Posts
I've built several boats and have used some strange things such as wood flour, real wheat flour, sevin dust, Bronze dust, silver dust, phenolic micro-balloons, milled glass fiber, milled poly fiber, graphite dust and stuff I forget.
Wood flour is generally used for "fillets" where one wants to turn an inside corner and you dont want the glass to make a sharp bend.
Micro-balloons and Cabosil is a fairing material filler. Use milled fibers for structural work. Graphite dust makes a nice coat for the bottom of a boat and is supposed to be tough but it seems no tougher than anything else to me. Bronze dust produces a really cool looking surface but I doubt it'd have any anti-fouling properties.
I've heard of using aluminum flour but am not sure what for.
BTW, real wood flour is much much finer than the wood flour from your saw.
 

·
Registered
Joined
·
4,217 Posts
Im going to call you out on this one if your using Cabosil for Structual work you should have done your homework. Cabosil is used as a thickener for fairing or bonding like wood to fiberglass for non structurl uses. Cabosil has zero structural components to it and should never been used for structure. if you want to add some structure to your resin especially for filling holes that need to be redrilled to support bolts for winches or anything that may go under strain you have to use milled fiber if its a larger surface like that prop picture i would mix chopped fiber and milled only then if its a little runny for your liking add a very small dash of cabosil like one to two TSP.
406 is a very strong filler that creates a smooth mixture, ideal for general bonding and filleting.

403 Microfibers, a fine fiber blend, is used as a thickening additive with resin/hardener to create a multi-purpose adhesive, especially for bonding wood.

WEST SYSTEM | Filler Selection Guide

We'll need to disagree until you post data. Could you have your product names confused, perhaps? Cabosil is colloidal silica.

Calling me out is rude language.
 

·
Registered
Joined
·
196 Posts
I do composite repairs for a living except it's on multi-million dollar aircraft . I also composite work at home as a hobby on my boat what you posted isn't even data

Sent from my HTC One using Tapatalk
 

·
Registered
Joined
·
196 Posts
Even frogwatch posted the same response. I use some pretty crazy fillers at work like aluminum resin mix made by henkle 9394 if you can get that and add 10percent milled fibers that makes for some very strong bonds

Sent from my HTC One using Tapatalk
 

·
Senior Moment Member
Joined
·
13,300 Posts
For non-structural and fairing filler I use talc thickened epoxy. I was told about it by an old German boatyard owner. It makes by far the nicest sanding filler I have ever used and it even leaves your skin feeling nice & soft. :D

Many people are afraid of it because talc is hygroscopic but I have found that the resin in the mix and the topcoats preclude any absorption.

It's also dirt cheap - I got a cement sack of it for $20.

For structural filler I like mill fiber - also in epoxy. I never use polyester resin anymore.
 

·
Registered
Joined
·
196 Posts
I use epoxy for small structural work but if I'm making large objects I use vinyl esters resin have very similar properties to epoxy but is the same type of system as poly but you don't get bubbles like you do with poly it's the happy cheaper medium works extremely well and is solid you can get a painters pail size for $60

Sent from my HTC One using Tapatalk
 

·
Senior Moment Member
Joined
·
13,300 Posts
I use epoxy for small structural work but if I'm making large objects I use vinyl esters resin have very similar properties to epoxy but is the same type of system as poly but you don't get bubbles like you do with poly it's the happy cheaper medium works extremely well and is solid you can get a painters pail size for $60

Sent from my HTC One using Tapatalk
I don't believe that Vinyl resins have the same quality of secondary bonding characteristics as epoxy. Since all my jobs are "after" or secondary bonds, I stick to epoxy.

For making parts - locker lids, hatch garages etc. poly or vinyl work just fine.
 
  • Like
Reactions: smj

·
Registered
Joined
·
4,217 Posts
I do composite repairs for a living except it's on multi-million dollar aircraft . I also composite work at home as a hobby on my boat what you posted isn't even data

Sent from my HTC One using Tapatalk
a. Neat.

b. Obviously. Only the manufacture recommendation.

So, present data. It would help the discussion. I'm sure the nature of the fiber matters, and we we were discussing wood flour at the time, which I'll bet adds little. If the fibers were of a high strength material with good bonding properties (fiber-filled polymers are effective--I've speced them for industrial projects numerous times) they certainly can help. But specifics are needed. It could well be the West System fibers in question are not high strength and rather are selected for there anti-sag characteristics and ease of sanding--this too is common. So we just don't know without specifics.

I've built FRP gasoline tanks for boats, using resins not generally available. It does me little good to suggest products they cannot buy.
 
1 - 20 of 21 Posts
Top