Question about the necessity of fiberglass cloth?

Hey i've been looking around this forum and just getting into pepakura. I have my first salem mask done and ready to be resin'd. I was just wondering if it is necessary to use the cloth or if i can just resin it and then put bondo body filler on top of that and paint it. Would that look alright and be sturdy enough or is the cloth really necessary. Thanks in advance and i love the community so far for this kind of stuff.

You need the fiberglass, or Rondo or what ever you are going to use on the inside to harden the part. The bondo on the outside is not strong enough on it's own. You can use other products to like smooth-on 320 on the inside if you are not keen on fiberglass. Rondo is just bondo thinned out with resin and you'd slush cast that. But you def need some thing on the inside to harden it.

can i just resin the inside and outside without cloth? would that be hard enough?

From my usage of resin in the past, not for armor making, it tends to be pretty brittle and can be prone to cracking when thin. The fiberglass cloth/mat acts like a matrix strengthening and keeping the cracking down to a minimum and allows you to use less resin to achieve your desired strength.

alright thanks, i guess i'll just have to pick up some of that cloth. So just so i have this right 1. Resin the outside. 2. Resin the inside 3. Fiberglass/resin the inside ontop of the resin layer. 3. bondo the outside to desired shape. 4 Prime and paint?

nick.d said:

alright thanks, i guess i'll just have to pick up some of that cloth. So just so i have this right 1. Resin the outside. 2. Resin the inside 3. Fiberglass/resin the inside ontop of the resin layer. 3. bondo the outside to desired shape. 4 Prime and paint?

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You will probably need more than one coat of resin (depends on the cardstock you used), but you don't have to put them on both sides. If you're uncomfortable with fibreglass cloth, you can also mix the resin with chopped fibres or you can go without fibres altogether. All these methods have different advantages, but just painting two layers on and being done is definitely out of the question.

Also, please do read the tutorials on the forums, they answer questions like this. Here's a list to get you started: http://www.405th.com/showthread.php/30542-NOOB-reading-list

thank you so much for the help!

In my experience, resin by itself won't cut it :/ I missed a spot fiberglass-wise on my helmet and it's actually chipping there. (The chin for the record) If you can get the money for the supplies it's definitely worth it and you're protecting your investment.
Keep up with the reading list!

nick.d said:

alright thanks, i guess i'll just have to pick up some of that cloth. So just so i have this right 1. Resin the outside. 2. Resin the inside 3. Fiberglass/resin the inside ontop of the resin layer. 3. bondo the outside to desired shape. 4 Prime and paint?

Click to expand...

As already mentioned, slush casting works great. I highly recommend it and if you want extra strength, you can buy fiberglass MAT, which is different from cloth as cloth is woven and mat looks like osb board. For slush casting, to add more strength I like to destroy a fiberglass mat before I mess with the rondo mix, and throw in the fibers into the rondo mix for that extra strength. But that should only be used for 1 or 2 coats. If you slushcast, you should have at least 1 later of fiberglass. If you don't slushcast; you should have at least 2 layers of fiberglass.
For your actual fiber-glassing phase; I highly recommend you use fiberglass CLOTH. As I stated earlier, the fiberglass cloth is woven and is less messy to deal with and is actually stronger. (See links at bottom of post for comparison between fiberglass mat and fiberglass cloth.)
Your actual steps after pepping should go as follows:
Without Slushcasting (rondo):
1. VERY LIGHTLY COAT the outside then inside of your pep with resin to strengthen the paper to take the weight of fiberglassing. LET IT COOL for 4 hours MINIMUM.
2. Apply resin to an area on the INSIDE of the resined model and then apply your fiberglass cloth before it dries. Make sure you seat the cloth firmly in the resin so that it soaks up the resin. Then apply a thin layer of resin over the top of the cloth to ensure that the cloth soaks up enough resin or it won't harden properly. (Resining both sides of fiberglass cloth or mat is a MUST if you want it to be sturdy and not be crappy quality.)
3. Finish one layer of the entire piece bit by bit until you have 1 complete layer of fiberglass.
4. Lightly scuff the fiberglass layer you just layed down. (This should only take you 2-3 minutes per piece, even the chest, as you don't want to remove layers of fiberglass, just rough it up for better fiberglass adherence on your second layer)
5. Repeat steps 3+4 until you have the desired strength.
6. Bondo or rondo the exterior to desired shape.
7. SAND or dremel your exterior to get all the details in and make sure your edges are squared where needed and smooth where needed. Then lightly sand so your primer sticks.
8. Prime and paint.

With Slushcasting (rondo)
Same as above, just rondo before step 4 and step 5 can be skipped


Fiberglass Mat:
http://compositeenvisions.com/images/fiberglass chopped mat.jpg
Fiberglass Cloth:
http://carbonsales.com/images/T/HEXCEL7532PLAIN-01.jpg

Wow you guys are great! Thanks for all the help and i'll be sure to keep searching and researching info before i ask questions that have probably already been answered. Thanks again!