Rondo: What am I doing wrong?

[glib71]

Hi all,

I was hoping for a little help from this wonderful community on a problem I've been running into. I've looked through a bunch of old threads, but nobody seems to have had the issue I'm having. Any help would be much appreciated.

I'm using Rondo in place of fiberglass. I've tried this on foam (using docholiday's method of sealing with PVA glue then 1:1 rondo mixture over top) and on cardstock (sealing with straight resin first), but the problem is always the same: my Rondo cures with huge drips and brush marks and uneven spots. Normally this wouldn't be a problem, right? Except that for some reason my mixture is IMPOSSIBLE to sand. I worked for hours with the grittiest sandpaper and the imperfections weren't going anywhere. On my next project, I went to town with an oscillating tool, which roughed out the drips, but the end product was far from smooth.

All the Rondo posts I see on here are of perfectly sanded, perfectly smooth pieces, and my stuff isn't even in the same ballpark. Is it a problem with my Rondo? Is there some magical sanding technique I don't know about?

My next project is a Dredd helmet, and I want it to be as perfect as I can get it (open to either foam or paper). Should I even bother with Rondo or is fiberglassing really the only way to go? Thanks in advance, I've already learned a ton from everyone here.

 

[The Schlitzie]

I've only used rondo for strengthening the inside of cardstock projects, and I had to do insides of helmets in sections so as to avoid big sharp drips. Maybe you're going with too thick of coats? I use a dremel and a palm sander, I couldn't imagine sanding anything substantial by hand.

Anything i've done has taken at least a half dozen thin coats of bondo and sanding on the outside to get smooth.

 

[wiIIiam]

You really need to build it up in thin layers, sanding each one as you go or you will run into this problem. If you keep sanding, it will get smooth eventually but could take a really long time.

 

[glib71]

Thanks a ton, this is why I love the RPF. Quick follow up question on thinner coats: do you guys use foam brushes or bristled paintbrushes? I've been using regular paintbrushes, but I'm thinking foam might be better. Opinions? Thanks again!

 

[Xexonix]

You want to paint on the Rondo???

Mmmm that is a new idea, I have never thought about using Rondo on the outside of Pepwork, usually I use straight Bondo with an old expired credit card to smear it in thin layers and then to sand down...

 

[The Schlitzie]

Hehe, that's new one. What do you do when you run out of expired ones?

You want to paint on the Rondo???

Mmmm that is a new idea, I have never thought about using Rondo on the outside of Pepwork, usually I use straight Bondo with an old expired credit card to smear it in thin layers and then to sand down...

 

[Xexonix]

Ha ha ha ha ha, then I use the cards that shops keep sending me in the hopes I will actually use the credit... Ooooorrrrr you go to a mall, and purchase a few "gift cards" put on about R50 each, then go spend said money and keep the card as a scraper....

That being said, I tend to sand down my card each time I finish using it so the Bondo/Rondo doesn't stick....

 

[Tildane]

Are you sanding with a block of wood? Sounds like a stupid question but if you're sanding just using your hand and paper you'll never get rid if the dips and bumps. Wrap the paper around a flat block of wood and sand with broad strokes in all directions.

 

[Uridium]

Ok, I am currently painting a Dredd helm. Here is my method. (BTW this is my first proper build of this type)

1. Pep with 200gsm cardstock.
2. Resin the outside. (could give the inside a little resin too)
3. Fiberglass cloth + Resin on the inside.
4. I then used RONDO inside (to make it smooth, add strength/thickness and to cover the sharpness of the fiberglass)
5. BONDO outside, Use thin layers and sand smooth.

Please note (and this is not meant to be condescending), there is a difference between Rondo and Bondo.

Also, buy a 'Mouse Sander', seriously! If I had to do all that sanding by hand, I would have thrown that helm away long ago!

 

[wiIIiam]

Hang on, what is the difference between rondo and bondo? I was thinking about the generic polyester filler you use to repair dings in car bodywork, which indecently, i spread on with a spatula.

 

[Knowone251]

Hang on, what is the difference between rondo and bondo? I was thinking about the generic polyester filler you use to repair dings in car bodywork, which indecently, i spread on with a spatula.

Rondo is a slang term for a Resin and Bondo mix. I have also heard it called mud

 

[wiIIiam]

Rondo is a slang term for a Resin and Bondo mix. I have also heard it called mud

Ah, thanks Knowone, I've used 'rondo' in fiberglass molds before, nice to put a name to things.

If it's helpful to glib, I gave up on using bondo on paper or foam after a project a few years ago (a Gondoran helmet) because it is such a hassle to work with. If I make a master of a costume piece now, I just use plasticine. It smooths out much quicker, and best of all there's no dust. You can also add fine detail to plasticine which you would really struggle to get with hard bondo.

[edit]

I thought I'd post these pictures to give you hope for sanding your project, and because the first one made me laugh:





You can get it smooth eventually, although I seem to remember using a big power sander usually used to remove the varnish from table tops

 

[glib71]

Thanks to everyone for the responses, I'm learning a lot.

I like the idea of Rondo for strength on the insides of pieces, then straight Bondo on the outside, applied in very thin coats (I think that has been my problem in the past). I'm wondering aloud whether this would work on foam as well as cardstock?

For the record, I usually sand with one of those rectangular sanding blocks, though it's sounding like I should probably spring for something of a slightly higher quality.

 

[Xexonix]

Ah, thanks Knowone, I've used 'rondo' in fiberglass molds before, nice to put a name to things.

If it's helpful to glib, I gave up on using bondo on paper or foam after a project a few years ago (a Gondoran helmet) because it is such a hassle to work with. If I make a master of a costume piece now, I just use plasticine. It smooths out much quicker, and best of all there's no dust. You can also add fine detail to plasticine which you would really struggle to get with hard bondo.

[edit]

I thought I'd post these pictures to give you hope for sanding your project, and because the first one made me laugh:

View attachment 273327

View attachment 273328View attachment 273328

You can get it smooth eventually, although I seem to remember using a big power sander usually used to remove the varnish from table tops

Except one problem, how are you hardening the plasticine??? We use Bondo or Rondo on armor that we wear for cosplay or halloween etc.... I am not sure plasticine would help in this regards, although if you have found a way to super harden it, it would be great for detailing....

Except one problem, how are y

 

[wiIIiam]

of course sorry, I make silicone moulds and cast in resin. I concede that this would be very expensive if you were making large pieces such as Armour.

 

[Starkilla]

Why do you use rondo and not just straight bondo obviously its harder but if you have fibre glassed the inside could you not just smooth it out with bondo

 

[Matchbox]

I dont know why you would use Rhondo on the outside to be honest, its a bit runny! I find the best application of rhondo is on the inside of a pepakura model then you can soak off the paper and have a really tidy final piece as the paper creates the flat surface you want as the 'visible' part of the armour

OR (heres one I like to do) Mudglass haha you pour the rhondo on the inside and do the usual sloshing about and while its still wet lay in strips of fibreglass that soak into the rhondo to add the extra strength, it really is the nuts!

I wish I rhondo'd the inside of my HEV suit Torso but hey live and learn XD

 

[afdanw]

You want to paint on the Rondo???

Mmmm that is a new idea, I have never thought about using Rondo on the outside of Pepwork, usually I use straight Bondo with an old expired credit card to smear it in thin layers and then to sand down...

this is right. Resin is harder to sand than bondo. just spread on thin layers of bondo and sand that. I would not use an old credit card. spend the $5 and buy a bondo paddle set. many people are talking about using rondo, but if you talk to any real fiberglass fabricator, or auto body man, they will tell you using rondo in general is a joke. just use bondo and sand that. even on the inside were some people say to use rondo, i still dont. i do many layers of resin. resin is stronger than bondo, so by weakening the resin with bondo, to add strength to the inside, is a bit self defeating. Someone also mentioned a mouse sander. that is a good option for small detailed areas, but for large areas, go with a randomizing orbital sander, it is better, but just a bit too big to do details with.

This was done with 0 rondo, and nothing but an orbital sander. I am going to resand it and pull off all the paint because i am not happy with the colors, but u get the idea.