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

[kingair983]

Asked this question about a week ago, but would anyone know if it is possible to apply heat (say, through a hair dryer or so) to a rondo'd piece that has been warped to bend it back into position? I have a chest piece where it's caving in a little bit in one spot, and I was wondering if I could just heat it up and push it out, so I wouldn't have to use up as much bondo building it back up.

Honestly, if at all possible, it would be better to simply cut out the 'bad' area of rondo and patch it. I've been in the exact same situation with another chest piece, Rondo doesn't reheat like resin (remember it actually heats as you aply it in order to cure). On my chest piece i tried using a space heater in the middle of a Florida summer, and when i tried to reshape it the entire piece cracked. But, I had a very thick layer of rondo too, if your area is thinner I'd say go ahead and try and let us know how it goes. Good luck!

 

[misfitjh]

If the chest is caved in a little, then you can fix it with bondo on the outside. No need to waste time trying to reshape with heat.

 

[TheMagicNumber]

Thinning resin with acetone...

..as the title suggests, has anyone had any experience with trying this?
I'm doing a HD MK VI build and a lot of the parts are very small detail, UK resin is quite high viscosity (when I look at US builders work after resining it looks like you guys have painted on a coat of water - UK resin is like honey) and I'm worried about losing detail (or giving myself a shed-load of extra work) so after getting the resin to a warmer temp I'm going to try to thin it with Acetone - starting at about 5%.

Just wondering if anyone has tried this and what was the outcome.
Of course if I was building a boat I wouldn't do this due to molecular mismatch, air pockets blah blah, but I figure I'd get away with it on armour?

Thanks

 

[Drewhinkle09]

..as the title suggests, has anyone had any experience with trying this?
I'm doing a HD MK VI build and a lot of the parts are very small detail, UK resin is quite high viscosity (when I look at US builders work after resining it looks like you guys have painted on a coat of water - UK resin is like honey) and I'm worried about losing detail (or giving myself a shed-load of extra work) so after getting the resin to a warmer temp I'm going to try to thin it with Acetone - starting at about 5%.

Just wondering if anyone has tried this and what was the outcome.
Of course if I was building a boat I wouldn't do this due to molecular mismatch, air pockets blah blah, but I figure I'd get away with it on armour?

Thanks

Acetone is basically the paint stripper for resin. I doubt it will cure at all with acetone in it. Same goes with water, they're cure inhibitors. Haven't tried it but I know that when you have a bad resin job you use acetone to take it off. For the record though, my resin is pretty high viscosity too, it's very sensitive to temperature, so maybe it's just thicker because its cold, depending on the temp there. Just make sure it's at room temp and it'll be as thin as you need it to be. You just have to brush on small amounts at a time. Try not to slap it on and you should have a pretty detailed outer layer. If its still too thick for you, you could try smoothcast, it's very thin. That can cause it's own issues though, it's easy to get runs with that stuff.

Anyway, best of luck and cheers!
Drew

 

[TheMagicNumber]

Acetone is basically the paint stripper for resin. I doubt it will cure at all with acetone in it. Same goes with water, they're cure inhibitors. Haven't tried it but I know that when you have a bad resin job you use acetone to take it off. For the record though, my resin is pretty high viscosity too, it's very sensitive to temperature, so maybe it's just thicker because its cold, depending on the temp there. Just make sure it's at room temp and it'll be as thin as you need it to be. You just have to brush on small amounts at a time. Try not to slap it on and you should have a pretty detailed outer layer. If its still too thick for you, you could try smoothcast, it's very thin. That can cause it's own issues though, it's easy to get runs with that stuff.

Anyway, best of luck and cheers!
Drew

OK, thanks for the feedback Drew....Can you actually remove cured resin with acetone? I thought it could only remove uncured, not hardened resin?

 

[Drewhinkle09]

OK, thanks for the feedback Drew....Can you actually remove cured resin with acetone? I thought it could only remove uncured, not hardened resin?

Ya know, I'm not actually sure lol. I'm just going off what I've seen in other sources. I had read some things about polyester resin so that's where I'm drawing this from lol. I haven't actually had to use acetone, so hopefully some more experienced guys can jump in an say from their experience. Polyester resin is pretty sensitive to cure inhibitors though so I'm thinking that since it can be removed with acetone it won't cure when mixed with it.

Hope someone can shed more light on it though. Love your build btw! Making good progress!

Drew

 

[Katsu]

This is a sticky subject indeed!

From what I've heard, you can add a tiny amount of acetone and get away with not hurting the strength too much, but the more added, the weaker the resin, assuming it works. I've heard you should add it before mixing hardener, and I've heard you should add it after mixing hardener, so it's really a crap-shoot. If you want to try using acetone, practice on a scrap piece of cardstock and see what the different results do. I've also heard anywhere from "no more than 5%" to "no more than 10%" so the amount of resin you can mix is low.

But my personal opinion is that it won't work. Acetone is such a strong solvent, and specifically wrecks wet resin, but I've never had the inclination to try thinning down resin so it very well may work! Try it out and let us know!

Also there is always UK Resin Thinner:
http://www.mbfg.co.uk/additives/styrene-resin-thinner.html

Seems designed for the job.

 

[TheMagicNumber]

This is a sticky subject indeed!

From what I've heard, you can add a tiny amount of acetone and get away with not hurting the strength too much, but the more added, the weaker the resin, assuming it works. I've heard you should add it before mixing hardener, and I've heard you should add it after mixing hardener, so it's really a crap-shoot. If you want to try using acetone, practice on a scrap piece of cardstock and see what the different results do. I've also heard anywhere from "no more than 5%" to "no more than 10%" so the amount of resin you can mix is low.

But my personal opinion is that it won't work. Acetone is such a strong solvent, and specifically wrecks wet resin, but I've never had the inclination to try thinning down resin so it very well may work! Try it out and let us know!

Also there is always UK Resin Thinner:
http://www.mbfg.co.uk/additives/styrene-resin-thinner.html

Seems designed for the job.

Katsu - Thanks very much, that seems to be much more suitable, never heard of it before and as I was going by a train of thought and not research I hadn't actually thought of searching for a specific substance. Nice one and thanks again.

And thanks for the build comment Drew

 

[Redshirt]

Actually, thinning the resin with acetone does work. By resin. I specifically mean polyester resin. A small amount added before or after catalyzing will help you paint it into details without filling them. More importantly, it helps the resin penetrate and bind with the fibers in heavy card stock. Add the right amount of catalyst for the volume of resin, not the volume of resin and acetone. With the acetone added, the resin cures in two stages, just like auto paint. First there's flash time, when the acetone evaporates off, leaving the resin behind. Then, then the resin catalyzes. You will have a longer curing time. Now the caveat: The more liquid-saturated your card stock gets, the weaker it becomes while you are waiting for it to cure. That means it will really want to warp and sag more than with resin alone. You have to do small areas at a time and support the areas that are curing. If you look at the pepakura pages of my Spartan Laser build, you'll see that I used thinned resin on that model (and learned all the advice I just gave you--the hard way). Good luck.

Redshirt

 

[VashtheStmpde00]

Hello all, total noob to all of this modeling process. I'm planning on making a gears of war armor build and maybe some weapons. Currently I'm starting on the hammer of dawn gun cause its the first pep file I found and looks easy enough for a beginner. But I'm wondering about strengthening it. Would I just use the resin or do I bondo it too? Also would I do anything to the inside to help it also? I apologize if this has been asked and answered, 239 pages on a phone during a lunch break is a loot to go through. In the future ill check before asking. Thanks.

 

[Katsu]

No problem asking questions in the help threads!

You do need to take measures to strengthen the inside of weapons, and it's not as easy as strengthening armor.

Once you build the cardstock model, you cover the outside in a thin layer of resin to help strengthen it a little bit further, but this isn't enough to use it!

Next, you cut a small (quarter sized to golf ball sized) hole in a flat part of the model, mix some rondo (50-70% bondo, 50-30% resin) inside. Cover the hole with painter's tape securely, and then rotate the model to slush the rondo around the inside. This will do an okay job of reinforcing it, but I wouldn't drop it! You can further reinforce it by adding expanding foam to the inside after the rondo hardens.

 

[Jake D]

...
Next, you cut a small (quarter sized to golf ball sized) hole in a flat part of the model, mix some rondo (50-70% bondo, 50-30% resin) inside. Cover the hole with painter's tape securely, and then rotate the model to slush the rondo around the inside. This will do an okay job of reinforcing it, but I wouldn't drop it! You can further reinforce it by adding expanding foam to the inside after the rondo hardens.

Be careful that you don't tape it back up too securely! If it's completely sealed when the Rondo starts to cure it'll heat up causing the air to expand and distort your model outwards. I had that happen with an Assault Rifle I did, the stock swelled about 1/4 inch on each side.

 

[Katsu]

I would imagine the most likely case is that the rondo is getting hot enough to de-cure the resin layer, weakening the piece and making it more susceptible to the weight of the rondo, as hotly mixed rondo can get... VERY hot, much hotter than hotly mixed resin.

Can always tone down the ratio of rondo to catalyst for that, but most people want a shorter working time so it can be hardened faster.

But if you are super worried, the best bet is to slush the bottom and sides of the piece with the hole fully exposed, and then slush the top side with the hole sealed as a second stage.

I usually try and do it in two or three slushes anyways, because the rondo pools meaning the topmost side will always have the least amount of rondo on it, so might as well pool the bottom and then the top.

 

[Jake D]

The resin was fine, It's just the expansion generated by the heat proved to be a bit much. I know because the expansion was uniform, and when I punched a hole in my pour gap, it was pressurized. I experimented on the magazine, and the same thing happened.

I just tape it up tight, slush it around, and then remove the tape covering the pour hole. Just make sure the hole is uphill-- having a piece rondo'd to the ground isn't too fun.

 

[TheSlammerss]

This is more about sanding bondo. whats a good way to get a nice defined angle? i have a couple of rasps but im trying to make the curved part of a recon helm that's on the top on top have a more pronounced and defined looking line. thanks

 

[Jason 078]

My way of sanding bondo into an edge is two-fold. First, you need a flexible metal ruler. Hold it over the edge and sand one side. Then told it on the other side of the edge and sand the other.

Or, you can carefully do it with a sanding block.

 

[Halex]

Hey guys, I'm working on a foam-core board DMR (link in sig) and was wondering what would be best to seal it with. I need to be able to apply bondo to it and add the finer details that are harder with less flexible mediums. Was planning on using the standard fiberglass resin in thin coats over the paper sides and heavier on the foam, but wasn't sure if anyone had a better suggestion.

Thanks in advance!

 

[Toxic R4ptor]

I have a few questions on bondo, and I'm very sorry if these are stupid or annoying, but what is the purpose of covering the outside of the desired piece with bondo? After resin-ing the piece and fiberglassing it, wouldn't you just be able to skip the bondo? I'm sorry if these questions are stupid, I'm just not the brightest in this project and i just started.
Thanks for any help and all responses!

 

[Corweena]

Bondo is used on the outside of the helmet to give it a smooth, round, realistic look. If you were to just paint the helmet after resining and fiberglassing, then the outside will retain its angular look from the 3D model. By applying a layer of bondo over the angles, you can sand the helmet into the round shape it should be.

 

[spartansonny]

exactly like Corweena said. Bondo is almost like the holy grail to all the fine detail work and smoothing in a project. It lets you make your round edges, uprised details, fill gaps, fix a mistake. it has endless possibilities. I have even seen people use bondo like clay and sculpt it to awesome figures on modded video game consoles that come out great.