Quote from Hangar45 Admin on December 7, 2017, 9:34 am

(Original thread started on 09-09-15 by Justin Fletcher)

Quick question for those of you who have fiberglassed your shells. Did you cover each half of the shell in one layer of fiberglass before moving on to subsequent layers? I'm thinking about doing the 3-4 layers of fiberglass on the upper half while the shell is sitting upright on the base. Then splitting the halves and laying them down and doing the 3-4 layers on the bottom half. I've read this portion of the SAM 100 times already and I'm thinking this is going to be my plan of attack. Does this seem logical?

 

(Posted by Ron Rollo on 09-09-15)

I think I did one layer of fiberglass over the whole shell, then came back with a second layer over the whole shell. If I had to do it again I would add a third layer.

 

I see your question. I think it would be okay to do it that way. If you were making a boat or an airplane that has to be seaworthy or airworthy, I would say no. The reason being is that you want to overlap the fiberglass mesh to create a stronger structure/shell. Strength is important with the shell but the three layers of fiberglass will be more than enough to give you the strength you need.

 

Just a side thought: Your orbital sander is going to be your best friend! I love the way it finds the high sports in the fiberglass and levels everything out.

 

(Posted by Steve Cooke on 09-09-15)

Like Ron said I went with 4 layers. 3 layers of mesh and the top layer was the cloth like material. The cloth material made it easier to sand and fill in any low spots with Bondo. I would recommend sanding after each layer to keep the high spots to a minimum. Just a few things I learned between doing the two sides. If you want to see some pictures you can check out my thread LJ45-011. I have a link in there.

 

(Posted by Shane Barnes on 09-10-15)

I did the upper half then split it. My first layer I left a little exposed and moved the second layer back a bit and moved the third layer back a bit. This allowed me to attach my first layer from the top into my first layer at the bottom and then the second and then the third. Just remember to rough up the area where the layers will connect to one another for a good bond.

 

(Posted by Jeff Peters on 09-08-16)

Newbie wannabee fiberglasser...er questions.

Okay, so I am at the stage of fiberglassing. I have looked through the SAM, online, and talked to some people but I would like some opinions.

 

Is the cured "Great Stuff" foam (tm) impervious to whatever resin I go with? I would hate to see the foam melt as I apply resin.

 

What weight of cloth would you experienced "glassers" use. (Not planning motion but want a good strength)

 

Did you do a seal coat first or do I even need one?

 

When you cut the strips of fiber mat as pictured in the SAM did you overlap each strip?

 

Thanks for any answers, opinions, or just comments. This is going to be so much fun I can't wait!

 

(Posted by Ron Rollo on 09-08-16)

Hey Jeff, I will help answer some of your questions. Shane, Justin or Maciej can add to this as well.

 

Do you have a Wal Mart near by? The Bondo resin that they sell there in the automotive section is the kind you will want to use. It will not eat the foam.

 

https://www.walmart.com/ip/Bondo-Fiberglass-Resin/17130349

 

You will need three or four gallons to get you started. Depending on how many layers of mat you put on which I have said I wish I did four instead of three.

 

Again, what they sell at Wal Mart is perfect. But the quantity will cost you which is why you need to go on line to find the great deal. Somewhere around here we have the source for that, it might even be in the SAM.

 

The weight means that the mat (actual fiberglass) will hold more resin. So if you were to use a really thick mat, you might be able to get away with only two layers of mat. The kind I used needed a minimum of three and four would have been better. The extra weight of one more layer would would be around 10 to 15 pounds I would guess for the shell.

 

I did not seal anything. You can start right on top of the foam.

 

You should overlap about an inch so that the mat bonds. The extra high areas will need to be knocked down with an orbital sander which is a must have in this project. The orbital sander is the key to a nice looking shell.

 

Plan on making a mess and making mistakes. But the cool thing about fiberglass is all your mistakes can be fixed by either adding more and sanding them away.

 

You are on the right path, asking good questions and getting prepared. But at some point, you will have to dive in. And that is when the lessons in fiberglassing begins.

 

By the way, adding the activator to the resin is a little tricky. In either case it is not a big deal. If you add too much activator, your resin will get really hot and set faster than you can finish applying it which will leave you with a bunch of wasted resin. If you do not add enough activator you will be waiting a long time for it to set. And this can be bad because your resin will want to run down to the lowest parts or even off the shell all together. So you will be stuck there with your brush pulling the resin back up to the higher areas slowly watching it run back down. Again, this is part of the learning curve and after one or two mixes you will get the hang of it. Worse case, you grind away the high points or mix more resin.

 

One last tip, use blue painters tape along all the edges of the shell to help make and control your edges.  If you have any other questions before you get started just ask!

 

(Posted by Eric Tomlin on 09-08-16)

To add a little bit about fiberglassing. Try to follow the instructions on your ratio of activator to resin to get a good idea of how long your setup time is. Once you get a good feel for that (working in large quantities of material at a time) then add just a little bit more of the activator to make it a tad "hot". Once you get the hang of it, you will be able to work a little faster in this part of the process. As Ron said, don't go overboard, because then you get resin that gels way too fast.

 

(Posted by Justin Flether on 09-09-16)

I was like you, a rookie at fiber glassing until I started this project. This is excellent practice, and like Ron said, you can always fix your mistakes. Here is my two cents:

 

Since your are still at the foam stage, be very picky about the "smoothness" of the foam. Any imperfections (bumps, large holes) will be amplified by the fiberglass. I had to repair a small section of foam while I was glassing and it set me back a few days waiting on the foam to cure.

 

Buy several, I mean 20-25 of those cheap throw away paint brushes. The resin will harden making the paint brush useless. I got a new brush every time I mixed up a new batch of resin.

 

I put down a thick tarp, Visqueen, or some other plastic sheeting to protect my garage and it worked great. I thought the hot resin would melt the plastic and get on my garage floor but it was thick enough that it just cured right to the tarp. Just think about protecting your work space because it is really messy.

 

Also, Definitely make sure you follow the SAM and tape around the windscreen templates. That's a time consuming step but it is worth it in the end. The blue tape makes it easy to separate the template from the fuselage after the resin has set up. There were a couple areas I had to break out the Dremel to cut away the resin but, it was really minor. Have fun with it! You are learning a new skill!

 

(Posted by Maciej on 09-09-16)

Hi Jeff, nice to see another member getting on this part of the project!  With this project, PREPARATION is a key to success.

 

Below on the picture is what you can call "fiberglass survivor kit":

 

Few things are missing there such as resin, fiberglass mat, "breaking bad" suit, wooden sticks to mix your resin (the one they have to stir paint - you will need a handful of it).

 

Random thoughts from my project:

* Get 50+ of 2" wide brushes to apply resin - you will throw away each after 20+ minutes. Wall Mart stocks them and they are cheap.

 

* Get 25+ plastic mixing cups - you will throw away them after 2-3 batches if you can empty the cup by the time resin starts setting.

 

* Mix small amount or resin (I never mixed more than 6 - 9oz at the time). Temperature will affect setting time. Warmer it gets, less time you have to empty your cup and move resin to fiberglass. If it starts turning into gel, throw it away and mix new batch.

 

* Resin will heat up during mixing. Mix it well with wooden stick. For some reason resin likes to set at the bottom of the cup first.

 

* Get box of vinyl (or other type) gloves (biggest size you can get). Dressed up in suit plus gloves, you will heat up as effectively as resin. Use baby powder on your hands to help quickly remove and put new set of gloves when you need it.

 

* Extra resin hardener is advised to have handy. In theory 1ml should produce 20 drops... In this case it doesn't (it most likely has different density than water). You will run out of it sooner or later. My way of adding resin hardener was through little hole that I drilled in hardener tube.

 

* If you add as many drops as resin manual says, it is going to be too much and you won't have enough time to finish each batch. I think I was doing 7- 9 drops per each ounce of liquid resin. Please adjust amount of hardener to your needs.

 

* Respirator with organic cartridges is a must. Get some extra cartridges to get you through without being exposed to harmful fumes.

 

* Cut fiberglass mat first. All of it. All layers. Mark them with permanent marker with numbers or letters so you know which one goes where since all of them will have unique shape and size. Using permanent marker put a dot in left upper corner (or any other corner) of each piece to let you figure out quickly the orientation of the piece you gonna be working on.

 

*Wet surface fist with layer resin then apply mat. It will help to stick fiberglass mat to surface and not to brush while you dabbing resin on.

 

I didn't cut the mat to overlap each other. when soaked with resin it will stretch giving you enough to overlap if you choose to.

 

(Posted by Jeff Peters on 09-10-16)

Excellent advise guys. I have printed it out and will call it my fiber bible and its got me thinking about some stuff. I'm guessing the reason we cut all of our mat into strips is on account of the compound curves. I have ran down what looks to be the answer here. This mat says there is no need for cutting as it will conform to compound curves. Obviously at some point there would be a limit it cannot conform to but it looks promising. What do you think?

 

http://plasticworld.ca/store/index.php?main_page=product_info&cPath=11&products_id=160.

 

I like what you said Ron, thicker mat = more resin, which would mean = less layers = flying sooner. I don't know how well it will perform but I am thinking of going with a high weight (8-10 oz), Triaxial, conforming fabric, in no more than two overlapped layers and see how that does. If it feels really strong after two, move to paint. I can almost smell the resin now.

 

(Posted by Ron Rollo on 09-10-16)

Don't use weaved fiberglass, it will show a pattern thru your paint. Mesh is the way to go because it can be manipulated better to conform to what you need. And if I recall, Shane says that the weave pattern will show through to your paint no matter how well you sand it and prime it.

 

(Posted by Maciej on 09-11-16)

Part of your job with fiberglass is going be a proper thickness build up especially around window templates dictated by thickness of the material you use (1/8" Masonite in my case). I'm not sure if 2 layers of heavy type will equal 3 layers of medium weight mat.

 

After each cured layer (or approx. 1 hour), I sanded everything to remove bumps and high spots and brought it to as flat as I could so that gave me 3 chances instead of 2. This same applies to air bubbles....3 chances vs. 2 to find them and remove.

 

Heavy mat will take in more resin and time plays key role. You may not have enough time to finish each section with the amount of resin you need. Either you will be forced to reduce the size of each cut fiberglass section or not being able to finish it before resin starts to set. I found size 1 square by 3 squares with medium weight mat big enough to finish it before resin start setting.

 

Make sure you soak mat with resin really well. Don't get stingy while you apply it.

 

Pay close attention to the edge around window templates to avoid any air bubbles there. I had few of them that needed some work. I had an air bubble that collapsed when exposed to paint after all sanding and body filler part was done!

 

It's better to be lower in between "ribs" than too high. Sanding through fiberglass too deep will compromise the strength of the spot so before you say "I'm done here" check each square to make sure its middle part is not too high (or too low). If you need to go back and add layer or two here and there because it is too low, please do it now. Trying to fill it up with body filler will take much more effort and time than with fiberglass.

 

I got total of 9 rolls of FIB-942 fiberglass mat 1.5oz 38" wide and 3 yards long. I might have gone away with 8... not 100% sure.

 

(Posted by Jeff Peters on 09-11-16)

Great tips and valuable advise from you guys. There is no excuse for not getting this right after all the above!