Some questions on Rondo

[Benton188]

Hey everyone,
I have a few quick questions about the rondo mixture. This will be my first time attempting to use rondo for the inside of a helmet and I want to make sure that I'm doing everything correctly. The only information I know so far is that it is a 1:1 ratio mixture of fiberglass resin and bondo...resin....gel....stuff lol. So here are my questions:

1. How many cups do you mix when you want to coat the inside of a helmet?
2. Which hardener do you prefer to use, the fiberglass or bondo?
3. Do you add any additional material before or during the application (i.e. Fiberglass matting, Fiberglass mesh, chicken wire)?
4. How thick should the rondo mixture be on the inside when done (i.e. 1/8", 1/4")
5. After it is all cured do you sand down through the resin layers and even through the cardstock itself?

Thank you for taking the time to look at my post, and I hope to hear from some of you shortly. Thank you =)

 

[Chernobyl]

1. How many cups do you mix when you want to coat the inside of a helmet?

As many as you need.

No, I'm serious - that's a tough question to answer. How large are these cups? How large is your helmet? How large are your batches? How thick do you want the inner coat to be? The best I can suggest is to simply work in medium-sized batches (100ml-200ml or so) and coat the inner surface evenly until you've got a thickness of about 5mm - a larger helmet will take more batches to mix up. It's always better to mix up smaller batches to work with rather than slamming a larger batch in at once, having it cure on you, and then panicking because you either can't use it all up in time, or it's threatening to harden into a blob in one area rather than spread evenly. Sure, it'll take a little longer, but what's a little more time when you're focusing on a good, clean end product?

2. Which hardener do you prefer to use, the fiberglass or bondo?

I would recommend trying to find a brand of resin that shares the same type of hardener as your bondo product (Bondo-branded products should use the same hardener), but if that's not feasible, I'd suggest the resin hardener.

3. Do you add any additional material before or during the application (i.e. Fiberglass matting, Fiberglass mesh, chicken wire)?

I wouldn't say so. Too many layers of other strengtheners will add excess weight to your helmet and before you know it you'll be wearing something that weighs an unpleasant amount. Plus, bear in mind that if you're using the rondo process to aid with smoothing down later (see question 5) then you're defeating the point by having a 'rough' internal layer (wire/fibreglass) between the cardstock and the rondo.

4. How thick should the rondo mixture be on the inside when done (i.e. 1/8", 1/4")

See above - no more than maybe 5mm at the most 1/8th of an inch. You could go slightly thicker, sure, but as above - more rondo = more weight, and I highly doubt that you'll be sanding so intensively that you'll abrade through more than maybe 1/2mm of the rondo layer, if you even breach the cardstock layer at all.

5. After it is all cured do you sand down through the resin layers and even through the cardstock itself?

You can, sure, but generally speaking, if a model has edges sharp enough to require that amount of sanding down to get them smooth, it's probably a bad model to be working with. Most of the time you're going to want to build your model to make your smoothing process as easy as possible - this is why 'smoothed' model unfolds have become so popular. However, sometimes it's unavoidable, and yes, it's entirely possible that you're going to be able to sand through the cardstock and into the rondo internal coating - but I generally wouldn't recommend it unless it's absolutely unavoidable.

 

[hacxor]

I guess you are talking about fiberglass and resin. To mix the resin and hardener follow the directions. My bondo brand resin is 1oz to 10drops of hardener.
You have a very short working time and depending on how hot it is outside it could be shorter.
I pour it in disposable plastic cups. I make about 5 different cups with 1oz of resin in each. Then I only add the hardener to the cup I am working on.
I use this type of fiberglass sheets and cut them up into multiple different sizes to use.

You can add as many layers of fiberglass as you see fit. You may need only 1 and you might want 4 to make it really strong. You can add a new layer as soon as the first layer hardens.
Hope this helps


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[Chernobyl]

I guess you are talking about fiberglass and resin.

He's not. 'Rondo' is a 50-50 mix of resin and bondo - the aim is to create a 'liquid bondo' that you can roll and spread around on the inside of your helmet instead of using fibreglass - it's sort of a sandable 'inner layer' that can act as a buffer if you ever need to sand 'deep'. It's also useful if you're trying to build up detailed areas on your build quickly.

Cereal Kill3r has a few videos on his Youtube channel which might go some way to explaining the concept (specifically 'Rondo Coating And Cutting In Half).

 

[hacxor]

He's not. 'Rondo' is a 50-50 mix of resin and bondo - the aim is to create a 'liquid bondo' that you can roll and spread around on the inside of your helmet instead of using fibreglass - it's sort of a sandable 'inner layer' that can act as a buffer if you ever need to sand 'deep'. It's also useful if you're trying to build up detailed areas on your build quickly.

Cereal Kill3r has a few videos on his Youtube channel which might go some way to explaining the concept (specifically 'Rondo Coating And Cutting In Half).

Oh wow I never knew about doing that! That is cool.
When would be a good time to use that over fiberglass and resin?


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[Chernobyl]

Oh wow I never knew about doing that! That is cool.
When would be a good time to use that over fiberglass and resin?

Any time you wanted to, I guess - like I said, the aim is to make a runnier, more viscous bondo solution that you'd be able to pour as opposed to spread - otherwise, the properties are reasonably similar to regular bondo. As far as I'm aware, bondo is basically a polyester resin plus some form of powder to thicken the mixture up, and adding more resin works to dilute the powder mixture down and return the bondo to more resin-like state. It's still meant to be easier to sand, as opposed to fibreglass which really isn't, but you could certainly coat fibreglass with a rondo mixture if you really wanted to. Since the general process is that you layer your cardstock with resin, then add a fibreglass layer inside of that for structural support, adding a further internal layer of rondo serves no real benefit on top of the internal fibreglass layer.

If you're using rondo, I'd suggest using it as an alternative to fibreglass as opposed to a supplement - again, rondo's main feature is that it's essentially a much more runny version of bondo, while still retaining all the product qualities of bondo (ease of sanding, etc). Using it in tandem with fibreglass would only really serve to add unnecessary weight to your build, and it would defeat the purpose of having an 'inner layer' of bondo to cushion against 'breaches' caused through excessive sanding.

 

[hacxor]

Any time you wanted to, I guess - like I said, the aim is to make a runnier, more viscous bondo solution that you'd be able to pour as opposed to spread - otherwise, the properties are reasonably similar to regular bondo. As far as I'm aware, bondo is basically a polyester resin plus some form of powder to thicken the mixture up, and adding more resin works to dilute the powder mixture down and return the bondo to more resin-like state. It's still meant to be easier to sand, as opposed to fibreglass which really isn't, but you could certainly coat fibreglass with a rondo mixture if you really wanted to. Since the general process is that you layer your cardstock with resin, then add a fibreglass layer inside of that for structural support, adding a further internal layer of rondo serves no real benefit on top of the internal fibreglass layer.

If you're using rondo, I'd suggest using it as an alternative to fibreglass as opposed to a supplement - again, rondo's main feature is that it's essentially a much more runny version of bondo, while still retaining all the product qualities of bondo (ease of sanding, etc). Using it in tandem with fibreglass would only really serve to add unnecessary weight to your build, and it would defeat the purpose of having an 'inner layer' of bondo to cushion against 'breaches' caused through excessive sanding.

I watched that movie(link didnt work but I found the exact video). I saw him pouring the rondo and looked interesting but it seems like it would be more flex able and less structurally sound. Seems like it would be smarter to use resin fiberglass for what he was doing, but I guess adding rondo on top of one layer of fiberglass would be easier and may have some benefits. Not really sure. I do understand the sanding benefit which could be good if excess sculpting needed to take place to get your peping correct.
Sorry to hijack this thread.
Thank you for all the excellent info. I learn something new every day!


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[Benton188]

Thanks Chernobyl! By cups I actually did mean cups in the unit of measurement. I've heard from somewhere else that it usually takes about 2 cups of each resin to fill a helmet with a 2mm-3mm thickness, but I wasn't sure how much to mix at one time. I think I'll start with half cups to get a feel for if it's too much or too little. One other question I did think of was this: Do you pour it in and roll it around or do you apply it with a brush? I've made the mixture before and tried sloshing it about, but it almost seems to goopy for it to slosh properly. What's your take on that?

 

[Chernobyl]

I saw him pouring the rondo and looked interesting but it seems like it would be more flex able and less structurally sound.

I'll agree with it being less structurally sound, but bondo isn't generally known for being incredibly flexible. It tends to just crack and shatter.

Campion608Seems like it would be smarter to use resin fiberglass for what he was doing[/quote]

Bondo/rondo is a lot easier to sand and smooth over than resin fibreglass - and, as I may have mentioned in another thread elsewhere, pouring fibreglass resin into a lump tends to make it crack. Believe me, I've had this problem a few times.

Campion608but I guess adding rondo on top of one layer of fiberglass would be easier and may have some benefits.[/QUOTE]

It has none whatsoever - you may as well just use resin rather than wasting bondo on a mix you can't sand smooth. There is literally zero point in using bondo or rondo in direct conjunction with fibreglass - it offers no enhanced structural integrity over simple resin and fibreglass, you can't sand it smooth decently, and it adds more weight to a product.

Take this as the bottom line for your concerns:

- Assemble Pepakura project
- Apply external resin coat
- Apply internal resin coat
- Repeat steps 2-3 if required
- Apply rondo mix INTERNALLY if required
- Forget entirely about fibreglass if you're using rondo

One other question I did think of was this: Do you pour it in and roll it around or do you apply it with a brush? I've made the mixture before and tried sloshing it about, but it almost seems to goopy for it to slosh properly. What's your take on that?

Rondo can be applied by a brush if needed, but I'd suggest using some form of spatula if you're going to be spreading it around at all - you'll ruin your brushes and no amount of acetone will clean the mixture off. A spatula can be made out of something as simple as a piece of stiff cardboard or a popsicle stick/medical tongue depressor.

If you're concerned that your mixture isn't runny enough, I'd advise experimenting with your ratios - most people will advise a 50/50 mix, but you could go for a mix of 2/3rds resin, 1/3rd bondo, or even further - it's all a matter of dilution. Remember - your bondo product contains resin itself (that's why you need to apply a resin catalyst to make it set solid), all you're doing is increasing the ratio of resin against the concentration of powder (which, surprisingly enough, is simple talcum powder - yes, you can actually make bondo at home without needing to buy it from the stores).

 

[hacxor]

Take this as the bottom line for your concerns:

- Assemble Pepakura project
- Apply external resin coat
- Apply internal resin coat
- Repeat steps 2-3 if required
- Apply rondo mix INTERNALLY if required
- Forget entirely about fibreglass if you're using rondo

Do most pro/advanced builders choose this route instead of using fiberglass? Is this what Adam would use? WWAD?(what would Adam do)


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[Itachi]

Hey everyone,
i was think about make Jun's or Carter armor and wanted to now what would be the best way to do this project, this will be my first one also
Thank you

 

[hacxor]

Hey everyone,
i was think about make Jun's or Carter armor and wanted to now what would be the best way to do this project, this will be my first one also
Thank you

Are you asking how you go about it?
These links can help
http://www.405th.com/showthread.php?t=10744

http://www.405th.com/showthread.php?t=26849
Or are you asking about rondo?


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[Benton188]

Once again, thank you for all the help and advice. Went out there today and learned a little through trial and error. Seems the best size batch to make is about 1/4 cup at a time if you want to brush it on. Anything larger will solidify too quickly and be unusable.