"Help!" for: Fiberglassing, Resin, & Bondo

RobotChicken · Jul 8, 2013

2560 posts in fiberglassing, resin, & bondo. That's a lot of reading (currently up to #801) of the same repeated questions over and over, so I instead did a few searches (at the top level to include all forums) which returned zero results. I could search Google, but that wouldn't necessarily give the opinions of the experienced builders here (who do excellent work, by the way). My question is, what tools do you prefer (and why) for scribing lines into dried-but-not-cured filler? The pep doesn't include all the scribed armor lines (nor is it practical for it to), and I'd like to add them into the filler. I attribute more value to the opinions of people who have successfully added scribed lines to their armor for what works well and what doesn't. Thanks, and now back to more reading....

Carpathia · Jul 8, 2013

RobotChicken said:
2560 posts in fiberglassing, resin, & bondo. That's a lot of reading (currently up to #801) of the same repeated questions over and over, so I instead did a few searches (at the top level to include all forums) which returned zero results. I could search Google, but that wouldn't necessarily give the opinions of the experienced builders here (who do excellent work, by the way). My question is, what tools do you prefer (and why) for scribing lines into dried-but-not-cured filler? The pep doesn't include all the scribed armor lines (nor is it practical for it to), and I'd like to add them into the filler. I attribute more value to the opinions of people who have successfully added scribed lines to their armor for what works well and what doesn't. Thanks, and now back to more reading....

Ha! Yeah, trying to read through this thread to find a particular question is a task in futility, which is why the same questions are asked over and over. An FAQ section is one of the many ideas the admin staff are considering.

To answer your question, I can offer what I did with my Mk VI torso...

carpathiavh99 said:
Updated time!

Over the course of yesterday and today, I managed to get the shoulder area of the back plate bondoed and detailed. Here's how it started out...

My mouse sander decided to crap out on me today, and started throwing sanding disks, so I had to file/sand everything by hand tonight. But, I managed. To get the detail added in, you guessed it, I went to 1/16" mat board...

Now, I've never been particularly good at scribing trenches, so I took a bit of a different route (not a new one, just a bit different). I cut some strips of mat board the same width as the gap between the two detail parts shown above, and tacked it to the side of the armor with a bit of hot glue...

Then, I bonoded over top of the mat board strips, and sanded the bondo down, level with the top of the strips...

Then, I simply peeled away the strips...

...leaving behind very nice trenches...

Then, I added in the last bit of detail...

...and covered everything...

So, I messed around with my mouse sander for a bit tonight, and I really hope that I got it fixed. Otherwise, I'll be forced to sand the rest of the torso using only my dremel, files and sand paper (at least until I can get to my inlaws' and get my orbital sander).

I estimate that I could be finished with the bondo stage for the torso by Friday (if everything goes well) and have it painted on Tuesday (since I need to buy some paint, but have to wait until payday) and FINISHED by next Wednesday, including the full paint job, weathering and strapping. If I manage to get my battle rifle finished with enough time to spare, I'll go back and install the electronics as well. It would be nice to have them for the film shooting and the launch, but they're not completely necessary for either. I've also got to find some time to finish up my other knee and get both of those finished. I'm thinking about taking the thigh mounting points off the undersuit and attaching the straps to a belt that will be worn under the undersuit. That way, the thighs won't be pulling down on the undersuit, but they will be held up so they don't fall down over my knees while I walk (although the knee pads should aid in that as well).

So, there it is. Getting close!

You can use a variety of thicknesses for whatever width you want your detail lines to be.

RobotChicken · Jul 9, 2013

That's an interesting approach I hadn't thought of, thanks! I think I'll modify it slightly to cut down on weight by sanding the resin smooth where the mat board will be and apply the mat strips directly to the resin. No need for two layers of bondo when the inside is primed with rondo and then glassed. I plan to start a WIP thread soon to document my build (after reading the PhotoBucket tut and a few other threads I have bookmarked). Thanks for the idea - now I don't need to look for any special scribing tools when I'm at Harbor Freight on the weekend.

kdbar · Jul 9, 2013

Hi again!

So far I have most of my pieces glassed and hardened! I have two questions regarding the next step.

What grit sandpaper should I get for the bondo stage?

Should I invest in a mouse sander or can I do without it and just get a sanding block + my dremel for sanding?

Thank you! I will update my thread when I get the extra fiberglass trimmed off the ends

Gokussj5okazu · Jul 9, 2013

You should use either 80 grit, or 60 grit preferably for your first shaping pass. Then go up from there. Personally, I go 60, then straight to 120 and shoot primer right over that. Then the primer can be smoothed a bit more later.

I prefer just using a good rubber sanding block for flat and slightly curved faces, then free handing the rest. A mouse sander will take a bit less elbow grease, but honestly may take a bit longer.

Carpathia · Jul 9, 2013

I would also recommend looking in to using a rasp and files, like Cereal Killl3r does. This method works wonders (the torso in my post above was smoothed almost completely with files).

A mouse sander is a nice tool to have as well, but for final sanding, I always hand-sand with 120 grit.

BiGHARYSCOTSMiN · Jul 9, 2013

carpathiavh99 said:
I would also recommend looking in to using a rasp and files, like Cereal Killl3r does. This method works wonders (the torso in my post above was smoothed almost completely with files).

A mouse sander is a nice tool to have as well, but for final sanding, I always hand-sand with 120 grit.

After seeing his work and hearing about files I've been using them all the time and yes they are extremely useful for hard to reach corners and for making grooves.

About the sander though... Whenever I sand anything with resin and/or filler the material clumps on my sandpaper "clogging" the sandieness turning it into paper. I have 6 clogged up pieces of sand paper now and I know for a fact the thing I'm trying to sand dried. I put a good amount of hardener both liquid and cream in my Rondo and after a week of drying it's as hard as plastic.

My question is... how can I prevent sandpaper clogging? Can I save the old paper from their impending doom into the black bin? If I can get the stuff off the paper I'm SURE I can use it again. I just think it's a shame they have to go into the trash only being used for an hour or so.

I tried everything to make things better, and turns out the mouse sander gets screwed up the quickest. I found that hand sanding and palm sanders used with a hand-sanding (back and forth) motion don't get clogged as quickly. Also, heat does something as well. When the paper got too hot the dust particles clumped onto the paper but at least that stuff can be picked off.

I am simply looking for a better way to sand. Detailing for me takes what seems like forever. One side of the top of a helmet can take a whole day, like it did with my Recon helmet the curvy faces are supposed to be easy right? Is it really supposed to take that long...? I'm thinking about a belt sander to do the job in the future I can only hope the belt sandpaper doesn't get packed though.

I know this question theoretically should go in the Sanding/Detail section but it deals with Rondo... and there is a mini discussion about sanding above me so this may serve as an add on. besides, I haven't seen this question before so it might not be a wide-spread problem... but I'll move if I have to.

Thanks, any advice will surely help. It's mostly a confidence problem you see. It's unsettling seeing a heap of what-could-be good sandpaper.

Carpathia · Jul 9, 2013

BiGHARYSCOTSMiN said:
After seeing his work and hearing about files I've been using them all the time and yes they are extremely useful for hard to reach corners and for making grooves.

About the sander though... Whenever I sand anything with resin and/or filler the material clumps on my sandpaper "clogging" the sandieness turning it into paper. I have 6 clogged up pieces of sand paper now and I know for a fact the thing I'm trying to sand dried. I put a good amount of hardener both liquid and cream in my Rondo and after a week of drying it's as hard as plastic.

My question is... how can I prevent sandpaper clogging? Can I save the old paper from their impending doom into the black bin? If I can get the stuff off the paper I'm SURE I can use it again. I just think it's a shame they have to go into the trash only being used for an hour or so.

I haven't had that problem with my own sander. The sand paper does clog up over time, but not after only an hour. I typically use a single sheet of sand paper on my mouse sander for multiple pieces over the course of a few days. Though, I don't start with the mouse sander, and never have. I used to start with a dremel, knocking down the high spots, then switch over to my mouse with a rough grit paper, then finish with a fine grit paper. Now, though, I start with the rasp, then move to a finer file, then to the mouse sander with a finer grit if necessary. I find that the surface of a layer of filler, even if it's cured properly, is gummier than what's underneath. So, if you remove the surface first, the remainder should sand nicely.

BiGHARYSCOTSMiN said:
I tried everything to make things better, and turns out the mouse sander gets screwed up the quickest. I found that hand sanding and palm sanders used with a hand-sanding (back and forth) motion don't get clogged as quickly. Also, heat does something as well. When the paper got too hot the dust particles clumped onto the paper but at least that stuff can be picked off.

I am simply looking for a better way to sand. Detailing for me takes what seems like forever. One side of the top of a helmet can take a whole day, like it did with my Recon helmet the curvy faces are supposed to be easy right? Is it really supposed to take that long...? I'm thinking about a belt sander to do the job in the future I can only hope the belt sandpaper doesn't get packed though.

I know this question theoretically should go in the Sanding/Detail section but it deals with Rondo... and there is a mini discussion about sanding above me so this may serve as an add on. besides, I haven't seen this question before so it might not be a wide-spread problem... but I'll move if I have to.

Thanks, any advice will surely help. It's mostly a confidence problem you see. It's unsettling seeing a heap of what-could-be good sandpaper.

As far as how long a piece takes to sand, it, again, depends on the technique. I find that I can knock down the rougher filler quicker with a rasp than I can with any powered sander. In doing this, I also form the general shape, making subsequent detailing easier. I can't say how long it would take me to sand a helmet with this technique, as I started doing it like this well after I finished my Mk VI helmet. The technique I used for my helmet (described above) took a few days; I think it even pushed a week to get it to where I was happy with it.

BiGHARYSCOTSMiN · Jul 9, 2013

carpathiavh99 said:
The technique I used for my helmet (described above) took a few days; I think it even pushed a week to get it to where I was happy with it.

Oh ok good to know I'm not the only one sitting there for hours and hours trying to smooth one area down.

I guess I'm not good with mouse sanders or something. I haven't used mine in a while because I started using my palm sander and vanilla 80 grit and files for detailing. It's too weak for large surfaces yet too big for detailing. It simply didn't fit into my POU (philosophy of use).

the mack · Jul 9, 2013

noob here. Getting ready to begin my first build and have a question about the building up and strengthening the outside or the armor. i've searched high and low on the forums for this and havent found an answer to this exact question (sorry if i over looked it) so figured i would ask

what amounts of bondo to resin mix should i use on the exterior of armor? (i.e. 1 part bondo to 1 part resin etc) im looking for a mixture that can coat the exterior well but will also not be so thick that it starts filling in detailed ares.
i know the answer is probably based mostly on personal preference but trying to get a general idea of mixture amounts.

Any advice will be much appreciated.

thanks to everyone in the 405th for having me!!!!
,Ozone

BiGHARYSCOTSMiN · Jul 9, 2013

the mack said:
what amounts of bondo to resin mix should i use on the exterior of armor?
,Ozone

Hey Ozone, it's a joy to see new people eager to learn.

Well normally instructions should come on the package of whatever you buy, so you can trust those. Most people refer to amounts of filler when they say inches, like use 3 inches worth of filler with 1 inch of hardener.

With that said, I'll say the best (for me and my California weather) ratio is 2 inches of filler with 1 inch of hardener. It might not say that on your filler package, and I just came up with my own thing.

Remember to use small amounts at a time because you don't want the stuff to harden before you've used it all. Since my hardener ratio makes filler oxidize super quickly I use about two-three water bottle caps' worth at a time.

I'll be looking out for your project, be sure to share it with us!

the mack · Jul 9, 2013

sorry forgot to specify that i'm making "rondo". That was my fault (what i get for playin with my son and trying to post a question)
i was wondering about how much Bondo to mix with fiberglass resin to get a good consistency to hold on to the details in armor but also coat it decently.

but that actually answered a question a had for mixing my bondo for filling in imperfections.

i'm looking forward to posting some pics VERY soon of my project. I cant wait.

thanx bighary!!!

RobotChicken · Jul 10, 2013

This question has probably been answered in as many different ways as it's been previously asked, and it's because of the ratio discrepancies (personal preferences, I guess) that I'd like to find out from the "pros" what ratio for mixing rondo is appropriate for the scenario below so the pieces aren't uncomfortably weighty. I've read 50/50, 3:1, and a few other ratios.

1. Layer of rondo on inside for smoothing out angles, getting the hard-to-reach areas, and providing an "etch-stop" when sanding the outside. (50/50 mix?)
2. Fiberglass mat (with resin, of course) over the rondo. (two layers..?)
3. Second layer of rondo over the fiberglass for a smooth interior surface. (ratio for this?)

Thanks!

BiGHARYSCOTSMiN · Jul 10, 2013

Well for Rondo, it really doesn't matter how it's mixed, because as long as hardener is added into the equation before you apply it to your work it should give you the structure you desire, because theoretically you can go straight up resin with hardener and it wouldn't be different.

So why do we mix filler with resin? Well the solution turns out a nice chalky plastic feeling instead of the cheap ABS plastic-feeling if you go resin only.

Whenever I mix up a batch of Rondo I just roughly pour out a 50/50 ratio like you guys said, and that should work fine. Also I discovered one time that you need both types of hardener liquid and cream (if you use 3M) because for some reason resin reacts with liquid only and so forth. I used to put in only liquid hardener until one day my Rondo stopped hardening and I would get clumps of just hardened resin and un-hardened filler pooled around it.

You can mix virtually anything into it, for my "specialty Rondo" I put Resin and Filler as a 3:1 ratio, ground up paper, ash from barbecues and the fireplace, and water so I can still work with the Rondo consistency. It's not like the extra ingredients do anything special like turn it into kevlar hardness, but it's just my take on recycling materials since Resin and Filler's cost can add up.

My advice and answer to Mack and RobotChicken's questions are: Don't worry about all this, you WILL make mistakes and will learn from them... hopefully. There isn't a universally correct way of making armor IMO because everybody has a different situation and everybody wants their armor to turn out and be used in a specific way. For example, me who uses recycled Rondo and very little fiberglass may differ from somebody who lives in a cold climate and uses... plasti-dip or something.

EXPERIMENT GUIZE! I strongly suggest finding out yourself.

the mack · Jul 10, 2013

Thank bigotry! I'll have to try that recycling materials mixed in. Thanks for the advice. This noon appreciates it

BiGHARYSCOTSMiN · Jul 10, 2013

the mack said:
Thank bigotry! I'll have to try that recycling materials mixed in. Thanks for the advice. This noon appreciates it

Just remember if you add in something that readily binds to fiberglass (like paper lol) it clumps and turns to paste. I just realized that clumpy stuff might be easier to apply as a body filler alternative... but anyways you might want to use a tiny but of water. The first time I tried water it didn't dry for half a day so I attacked it with a hair dryer and let it settle outside in the sun for almost a week.

Tell me what you mix! I've been thinking about fabric scraps and building a massive blender for mincing old plastic toys and such as well...

the mack · Jul 10, 2013

I actually thot about using some scrap fabric to mix in to help strengthen and hold it all together almost like fiberglass mat but without having to pay lol

Katsu · Jul 10, 2013

RobotChicken said:
This question has probably been answered in as many different ways as it's been previously asked, and it's because of the ratio discrepancies (personal preferences, I guess) that I'd like to find out from the "pros" what ratio for mixing rondo is appropriate for the scenario below so the pieces aren't uncomfortably weighty. I've read 50/50, 3:1, and a few other ratios.

1. Layer of rondo on inside for smoothing out angles, getting the hard-to-reach areas, and providing an "etch-stop" when sanding the outside. (50/50 mix?)
2. Fiberglass mat (with resin, of course) over the rondo. (two layers..?)
3. Second layer of rondo over the fiberglass for a smooth interior surface. (ratio for this?)

Thanks!

The ratio is variable and depends on your needs. There's never "one answer" for any question, especially related to resins. Also, never feel badly about asking a question on the HELP threads, I don't think anyone is expecting you to leaf through 260 pages of Q/A.

How I usually do my rondo mixes depends on the need. 1:1 is really watery and good for getting a thin coverage over a large area, as it flows more quickly and evenly. If you want to bulk up the piece to get a good buffer zone for cutting, you may have to do 2-4 layers of this ratio, but it'll get pretty good coverage, beware pooling though as excess will sit at the bottom of the piece.

3:1 is good for bulking up a smaller area, as it doesn't flow as much, so you can pile it up more easily. If you have a section that needs to be filled, or has some really sharp edges (like usually the ear cups tend to be pretty steep geography) this will do that in fewer layers. It has a higher bondo ratio, so it'll also sand a bit nicer but not be as strong, but realistically you shouldn't be relying on rondo AT ALL for strength.

so..
1. I'd do 3:1 if you have the time, especially as an etching layer and smoothing angles.
2. 2 layers of fiberglass is the minimum. Some people will do rondo -> 1 fiberglass -> thin rondo -> 1 fiberglass -> thin rondo -> 1 fiberglass -> thin rondo. For a very strong helmet. But 2 layers of fiberglass over the first rondo layer will be good enough for wearing.
3. I'd do 1:1 to cover the fiberglass. You want to smooth it out but there's no use for bulking that "inner" layer since it shouldn't ever see the blade of a dremel.

RobotChicken · Jul 10, 2013

(Sorry, I don't know how to quote yet.) I realize the ratio depends on the application (i.e. hardening for casting will be different than hardening for wearability). However, I don't believe the ratio "doesn't matter". It's not like the filler evaporates - it will remain on the piece, so the higher filler to resin ratio, the higher the viscosity and heavier (weight) the piece. Too thin and there's no buffer when filing/sanding (so why bother then). Too thick and you've got a great buffer but then also reduced interior area and increased weight. I'm not using the Rondo for strength - that's what the fiberglass will be for. This is for a child's costume, so it doesn't need to withstand multiple conventions, etc. However, being for a child, it does require some durability. You're right, I could experiment. But an experiment gone bad could mean re-pepping a piece (which would not be cool). So I was hoping to learn the results from people who have already done the experimenting.

BiGHARYSCOTSMiN · Jul 10, 2013

RobotChicken said:
This is for a child's costume, so it doesn't need to withstand multiple conventions, etc. .

I sense a Halloween project incoming... or maybe not.

If so, however, I suggest getting a move-on. two months is a hell of a window for a new person, I thought I could get my ODST done in a month... and I ended up finishing it three months AFTER Halloween... :C

Also, to quote somebody you have to click the "reply with quote" part... on the bottom right corner of each reply. You should see one right..............................................................< under here >

"Help!" for: Fiberglassing, Resin, & Bondo

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