Help for a Newbie on helmet build??

[IcedJemz]

Hello to all. Im new to the forums and would like some advice regarding using filler on a pepakura model - if this is in the wrong section I apologise! Wasn't sure if this was the appropriate place!

I am currently trying to start my first helmet build. I have been playing around with pepakura for a couple of months but I decided to take this one to the next level - fibreglass, resin, filler, sanding - u know the routine!

Anyway I have resined the helmet and applied fibreglass on the inside. Its solid enough to start applying filler. As its my first time working with filler (using P-38 isopol which I believe is similar to bondo) I'm not sure what the best way to tackle the helmet is. Do I apply the filler all over and then sand? or do I do parts at a time?

As im spreading the filler obviously its creating divets as im not a master at spreading a smooth layer yet. Do I allow this to dry, apply some more filler ontop, then sand to make it level? or sand first and then fill in the gaps/dips with filler or something like spot putty? On one side I have tried to apply a little air drying clay to raise the dips as the pepakura model caves in a little where I stuck pieces together. On the other side I slapped on a higher level of filler to raise the dip - im seeing which method makes a better result but advice would be welcome!

Help a newbie out please?? Any advice appreciated.

P.S i'm in awe of peoples costumes/props! (and maybe a little jealous ) I have a green ranger helmet mould on its way to me so I need some practice in advance so I don't destroy it!

 

[IcedJemz]

anyone wanna help a girl out? if no one has time I shall continue to attempt on my own and see how it goes

 

[DaveG]

Well I'd be happy to help you out with a bit of advice! It's looks like Isopon P38 is a polyester based filler like bondo. so it should handle similarly. First of all, safety! Polyester resins have some nasty chemicals in them but they're perfectly safe if used correctly. Work in a space with adequate ventilation, outdoors is best. Where a respirator, not just a particle mask, but a respirator designed for organic vapors. You should find one at any shop that sells autobody supplies and most home centers. Wear gloves, disposable ones are good since they are pretty thin and you still have good dexterity when using them. When sanding or grinding cured resin wear goggles.

The trick to working with Bondo (i'm just going to use that name) is to mix up small batches of resin at a time. If you mix up too much it's likely to kick off before you've spread it all out. I like to mix bondo on small pieces of scrap cardboard from boxes, then I can through the scrap out after the resin has set. There's no point in using mixing cups. You shouldn't be mixing up that much at a time anyway and it's easier to mix on a flat surface like cardboard. Squirt out a little (less than you'd think!) of the hardening cream and stir until it's thoroughly blended. Usually the cream is a color like red or blue which makes it easy to see when it's mixed in. I use a tongue depressor to mix the material so again, I can just toss it with each batch rather than clean. Don't tried to mix the resin/hardener by weight. You'll get the hang of how much to use after a few batches. It's not rocket science and the ratio doesn't need to be precise. More hardener will kick faster, less, slower. If it's a hot day it'll kick faster too.

I like to use flexible plastic spreader when applying bond to curved surfaces like a helmet. You can get them at auto body shops and many home centers. They are very flexible plastic in a variety of widths with a thicker base and thinner edge. Cured resin doesn't stick so they can be reused. By using a wide spreader, 3 to 4 inches, you smooth out the resin and fill in shallow areas like you've described. Apply the mixed up resin in small thin payers. As the resin kicks of it'll stop spreading thin and get rough. Stop then, don't try to keep working it as it cures.

Usually it's a good idea to rough sand down the high spots of a cured spread of resin before applying the next coat. One trick is to slice of thicker areas of resin with a single edge razor blade of sure form tool after is started to cure and is kind of rubbery. Easier then sanding it later when it's rock hard.

You can apply a new spread of resin over one that hasn't fully cured yet like I said, it's often better to trim down and sand each layer before applying the next. Be patient. Work in small thin batched.

To sand the cured resin I like to use Sure-Form tools to first plane down the high spots. Then sand using a very coarse sandpaper, 80 or 100 grit. Don't worry it the surface looks really rough, you're going to get to a smooth finish with several coats. Sanding resin will clog sandpaper quickly so change to fresh sheets often. Work to progressively fine paper as you go. Resins sand better using wet-n-dry sandpaper, the black stuff, and water. Keeps the paper from clogging and give a nicer finish.

Once you've go a pretty smooth surface you can fill small pin holes and scratches with a paste filler that work by evaporation, not a hardener. This is only to fill very small holes.

Finally you'll want to use a spray primer, sanding smooth between coast with wet-n-dry paper and water, 220, 320, 400 grit, etc.

Good luck!

 

[IcedJemz]

wow thank you for the detailed advice!!

fortunately I have done a bit of research into resin and filler before attempting anything so I have been using gloves, respirator and goggles during the couple of parts ive tried. And also been doing it outside. So top marks there then!

The first time I mixed the filler I used too much and learnt I needed to be a bit quicker. second time didn't use a lot of hardener so took longer to cure but I liked that. Allowed me to work it in a bit more. Been using some 3-4 inch plastic spreaders. May have to buy some smaller widths online or ask at a shop.

Its mainly the applying and sanding I need the practice with. I guess you learn by doing im not too bothered if I do mess it up as its a first attempt. Im gonna see how to clay plays out as well as I did find that a lot easier to build up the dips with it. I'll know tomorrow!

So would it be better to coat the whole thing in filler (not in one go!) and then sand it down, then reapply all over (again, not in one go), then sand, and repeat?

or just work on small area's at a time until that particular part is finished?

 

[DaveG]

Kudos on using safety gear, So many people forego it and regret it later!

I'd apply a small area, let it cure, sand it, then apply another small area and repeat. As you get more comfortable with the process you can increase the size of the areas you're working on. Takes a bit longer but there is nothing worse that having too much bondo kick off on you and having to sand a bunch down.

BTW, you can buy more hardener separately from the resin. Everyone ends up running out!

 

[IcedJemz]

Oh i cant deal with crap in my lungs! As a nurse, we know better lol

Tbh i dont mind the sanding that much. I quite like making a mess with it! Will take me a while anyway cause im working around looking after my 6 month old!

And fortunately my dad has a couple of spare tubes of hardener laying around - same brand as ive got. Does hardener ever go bad? Not sure how long hes had them.

What would you recommend as a paste filler? Not sure what id put in to search for some. Keep getting ones with hardener included.

 

[DaveG]

As far as I know the hardener doesn't go bad, try a test batch out to check. the brand shouldn't matter. Polyester hardener is polyester hardener. It's all basically MEKP (Methyl Ethyl Ketone Peroxide) in crème form. In fact liquid MEKP catalyst for fiberglass resin can be used as well but it tend to kick off pretty fast.

Try looking for Automotive Spot Putty. Not sure what brands you'll have in the UK. Here we have Bondo brand spot putty, 3M and others. Any autoparts store or auto body supplier will know what you're looking for.

 

[IcedJemz]

Will do. Thanks alot for your help! i will post an update when i do some more work on it

 

[IcedJemz]

Ok so I put some filler on on two sides to experiment with sanding.

This is the side with some clay on as I wanted to see how that worked at building gaps - incase anyone was wondering, this is a Dragon Knight helm from the game Dota 2

and this is the side ive just put filler alone on

need to do a lot more sanding...

but my question is, with dips like this:

is it better to sand the high bits down to one level, then do a second coat?? or apply more filler to raise the low bits up first, then sand?

 

[DaveG]

Looking good, and exactly what you would expect at this point. Usually better to sand down the high spots, then do a second coat to fill in the low spots.

 

[IcedJemz]

How many coats on average does it take to get a smooth surface? I guess it depends on how well the filler is spread and sanded too.

And whats the best way to get the sanding dust out of the dips? Ive blown most of it out but some sticks. Dig it out? Wet it out? I presume the dips wont fill properly with another coat if theres dust cogging it up

 

[DaveG]

There's really no average, too many variables. But you should have something pretty good after 3 to 4.

Try brushing the dust out with an old tooth brush.