Lightweight alternative to bondo?

[Weslicon]

Hey guys! I was scratch-building a helmet from cardboard for the first time and I was wondering if there's something I could use to smooth it out besides bondo. Bondo is great and all, but it would just be way to much for an entire helmet. I remember seeing some type of material used in posts before that's applied right to the paper. (or resined paper) it had a white-ish, yellow-ish color to it and seemed to have similar properties to bondo. If anyone knows what this is or has any recommendations, please let me know. Thanks!

 

[Zat German]

Durham's Rock Hard Water Putty has an ivory to yellowish color to it, depending how much water you add. The more water you add, the more towards white it looks. It also takes longer to completely dry with more water though. However, from my tests with it, it seems to have about the same weight as bondo.

The only other thing I can think of that you may be thinking of is Smooth Cast 320 but that is used to harden stuff, not so much smooth it out.

 

[Weslicon]

Cool! So are either of those easier to sand than bondo, or would bondo be the best choice?

 

[Zat German]

You can work Durham's Water Putty before it is completely hardened. From the website:

Let set about 20 minutes. The putty will be like hard soap. Shave off the excess with a putty knife, leaving very little sanding to be done. This method gives a firm, smooth texture – perfect for shaving, cutting, and carving!

About 40 minutes later, DURHAM’S will become very hard and have great strength. Let set about 8 hours, however, before sanding if an especially smooth, light ivory surface is desired. For craft items, or repair jobs in which large quantities have been used, let DURHAM’S dry even longer.

Also, keep in mind that Durham's is a filler. It is not going to work that great as a skin over an already relatively smooth surface because it may just fall off. Just do some tests first, the stuff is super cheap.

Smooth Cast is a plastic so I am not sure how well it is going to take sanding. You could hunt around for some other threads that have used it. As far as I recall, most people use it to harden the paper and then cover it in bondo and sand that except for a bit of sanding to round out corners before the bondo.

 

[Fudz073]

Smooth Cast is a plastic so I am not sure how well it is going to take sanding. You could hunt around for some other threads that have used it. As far as I recall, most people use it to harden the paper and then cover it in bondo and sand that except for a bit of sanding to round out corners before the bondo.

Smooth Cast is some seriously awesome stuff. However, it's more of an alternative to fiber glassing than smoothing. I poured smooth cast into my pepakura helmet to reinforce it. I does sand really well. I then used bondo to fill into the gaps. So it's not really for smoothing, but more for structure. Hope this helps!

 

[Pappa Midnight]

"Wall board compound" / "wall joint compound" I don't know why everyone ignores my posts about this awesome amazing product. its a fraction of the price of Bondo, it is ultra lightweight, It's water based so it dries pretty quick ( not as fast as bondo), and It's EXTREMLY sandable (be careful not to dig/gouge). Now it's best to use this if you are going to be making a mold of the helmet and you would seal it before hand. it gets hard enough to hold walls together but it isnt as hard as bondo. So, if you want to wear it as is I would say; make sure It is dry (this is a must), then sand and detail, after that just coat it with a couple of THIN coats of resin ("after you have sanded and detailed it").

to give you an idea of prices, Bondo: 1Qt = $10-$11 & 1gal = $18-$20 Joint compound: 1gal = $5 & 5gals = $12-$15.

look for yourself here's a link to Lowes website: http://www.lowes.com/pl_Drywall+Joint+Compound_4294858286_4294937087_?storeId=10151&N=0&langId=-1&catalogId=10051&UserSearch=joint+compound