Bondo for seams and spirals? Or only cars...

Forgive me for asking about such a basic idea and product, but I'm looking for a little advice from people who have used the product.

A number of people have suggested that they use some form of filler or Bondo to fill and remove any evidence of kraft tube spirals for their low-power rockets. While this seems a little excessive/compulsive to me, I thought I might explore this before I condemn or ignore it completely.

How hard is it to work this material and product? Does it remain soft and pliable like peanut butter during application? Or is it more stiff like clay?

(My late father once bought a can when I was in high school and worked some up to repair rust on a fender of a used "beater" car that he was driving around town for a couple of years. He also used a small home-made air-compressor to spray the fender and eventually matched the car paint reasonably well, so that your eye was not drawn to the repair for the rest of the years that we owned the car...(another 4-5 years, as I recall.)

Now, I'm thinking of buying a can, but I'm not sure if this is the material that I want. What say you?
Also, I thought I might use the excess to attempt to pour a resin or plastic numeral (8" tall) to number our house for the postman. Is this a reasonable product to use with a sand-mold, similar to Plaster of Paris mold or something?

Advice please.

Bondo Body filler you have to work quickly with as it sets up fairly quickly, the more you have the faster it sets (its polyester resin after all, and heat is the enemy when time is on the line).

Bondo Spot and Glazing putty on the other hand also sets up fairly quickly however its a lacquer based product so no mixing required.

Both start out about creamy peanut butter consistency but quickly change, Bondo Body Filler weighs more than the Glazing putty, however for filling spirals the difference is fairly negligible, Glazing putty seems easier to sand.

Glazing putty is best applied over a primer coat, while Body filler can be applied over or under.

Neither is pourable, and anything you put it into short of a silicone mold it will want to stick too unless release agent is used.

3M spot putty, red in colour goes on easily with a spreader, dries fairly quickly so the trick to applying it is to apply it and leave it. If you drag your spreader through it when it starts to dry out you will leave marks. I would also use it in a well ventilated area as well as use a respirator, as it does have fairly strong fumes. You should also prime first, then spot putty, sand then prime again look for areas that need to be touched up, spot again, sand/prime again, and keep going until you get it where you want it. Normally that is about 3 prime coats with the Dupli-color filler primer, which is a mastic primer and fairly thick. Sand with 120-150.

Your gonna get a lot of answers and suggestions so be prepared ! That said, I almost strictly use glazing putty. It works best applied over primer and is for all intents and purposes simply a thick primer. If you have large voids or dents to cover do not try it in one coat. it dries from the outside -in so it not only takes longer than several thin coats but will shrink and crack. The stuff sands great , just sand down and feather the edges and prime. Easy as that.

This is what I use. It starts out pretty thin but dries quickly. I usually apply a dab, spread it with my finger then start another dab. I wear nitrile gloves as it is pretty strong stuff. It sands pretty easy and works well for me straight on clean plastic or paper tubes.

OK, so perhaps I'm looking at the wrong product for pouring a resin or plastic numeral for the house.

Assuming that I fashion some sort of mold out of wet sand, possibly set in the freezer to freeze it in place.... what product would you recommend that I could "pour" into the mold? I'm looking at something that would result in about an inch square volume and about 8 inches tall. That is, if it were the number 1, all elements could be constructed out of a 1x1 stick of wood...except I'm trying to pour it out of resin or similar plastic material that might flow or cure into something durable in the weather. Paintable is a plus.

Understand that I'm just puttering here.... If I wanted a professional job, I could go to a sign maker, or hardware store and order something up.

Thanks.

Kirk- checkout www.alumilite.com for casting stuff-easily done. Has all the mold and casting materials you could ever need. As far as filling spirals- I use Elmer's carpenter's Wood Filler in a tub slightly watered down. Just did a full length 3" blue tube yesterday-dries fast-sands easy and stays put. 220 grit knocks it down and it doesn't load the paper. 400 smooths it and then it's on to primer.

fyrwrxz said:

Kirk- checkout www.alumilite.com for casting stuff-easily done. Has all the mold and casting materials you could ever need. As far as filling spirals- I use Elmer's carpenter's Wood Filler in a tub slightly watered down. Just did a full length 3" blue tube yesterday-dries fast-sands easy and stays put. 220 grit knocks it down and it doesn't load the paper. 400 smooths it and then it's on to primer.

Click to expand...

CWF is also nice and light, and I use it on anything without a fiberglass skin/tube.

On the alumilite, the RTV silicone mold stuff is great to work with, I used to copy some of my wargaming miniatures with it, place the part in a box made out of Lego sealed by a bead of glue (good ole Elmers Glue-All) around the inside edge of the box, place the part on the bottom of the box, if the part is light weight glue it to a piece of styrene or plexiglass sheet used for the bottom of the box (once again with Elmers Glue-all). Then pour the RTV silicone mold over it, the RTV will reproduce a fingerprint if its there, mix a two part urethane resin and pour. Caveat is it would most likely be cheaper to buy the part you wanted to cast, unless its in some way un-obtanium from another source, the first part would probably cost about $50.00 (NVM, just looked up the cost of materials these days, ouch a 2lb kit of the Plat 25 RTV silicone mold material is $48.00 by itself, good stuff though)

Sorry, I guess this should have been a thread over in techniques instead. Please excuse the mis-categorizing.