First attempt at making fiberglass cowl need advice (Full Version)

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winglift -> First attempt at making fiberglass cowl need advice (5/4/2008 7:58:37 PM)

I am building an Utter Chaos and decided that this would be an opportunity to try my hand at making a fiberglass cowl if anything just to learn. There is very little room in the 3/4 balsa cowl and the nose gear arm, located below the engine is very tight. I could make it work, but it would be better if I had a fiberglass cowl.

I am thinking of making a one shot, lost foam, cowl using floral foam on the top to accomidate the engine, the recreate the already make balsa cowl with floral foam. Not sure if to lay the glass on top of that using epoxy or polyester resin? It was suggested that I use 2 and 6 oz fiberglass, but found out that there are several types biaxial, triaxial, satin, twill, hexcel, crowfoot, and more types of weaves available. Which type should I use?

Photos of Utter Chaos.




John Sohm -> RE: First attempt at making fiberglass cowl need advice (5/5/2008 1:55:05 AM)

The twill will probably drape better and conform to any curves. Don't use polyester on the floral foam. Use epoxy, that should be safer and not eat into the form. Make sure the epoxy is a finishing resin type and not 15 minute or 30 minute. You want it to have time to wet out well. When laying additional layers of glass and epoxy, make sure you give it a light sanding and wipe it down with denatured alcohol to get any oils or waxes off between coats. Don't use acetone because again, if any gets on the foam, so good bye foam. A few layers of 6 oz cloth should do the trick.



Campy -> RE: First attempt at making fiberglass cowl need advice (5/5/2008 4:06:11 PM)

I also suggest covering the foam plug with a LOW TEMP film such as Econocote. This protects the foam from the resin AND makes the inside of the cowl smoother. When I do "one of" cowls I use 2 oz fiberglass cloth cut into strips 2" wide x 8" - 10" long. I typically use 2 - 3 layers of cloth (I find it easier to get everything wetted out using multiple layers of thinner cloth). Use a flux brush for applying the resin. If you see a white spot/area on the cloth it means the resin has not completely wetted the area. You may need to "poke" the area with the bristles of the brush to get the rein all the way through the cloth.

After the resin has dried, DO NOT REMOVE THE PLUG. Do all your sanding with the plug still in the cowl. If there are any low spots, holes, etc., use spot putty (comes in a tube, is usually red and can be found in the auto section of Wal-Mart) to take care of these areas. To remove the plug (do this outside ), cut an "X" in the back of the covering and pour a little gasoline on the foam (2 - 4 oz is plenty for a 40 - 60 size cowl) and wait about 20 minutes. Then just pull the covering and the sludge from inside the cowl. Wash the cowl THOROUGHLY with soap and water.

The cowl is going to be soft and pliable at this point. Do any final shaping needed and set the cowl aside for a couple of days to harden up.

As John said, the twill will most likely "lay" better. Fiberglass cloth is coated and the coating is designed for polyester, epoxy or both types of resin. I suggest getting the type for both types of resin.

FWIW - I suggest thinning the resin with denatured alcohol (NOT ISOPROPYL ALCOHOL [rubbing alcohol]) or acetone about 5% BY VOLUME. IN NO EVENT EXCEED 10% !! This will thin the resin enough to ensure proper wetting out. 5% will not weaken the resin by any noticeable amount, however, it will lengthen the drying/curing time.



winglift -> RE: First attempt at making fiberglass cowl need advice (5/10/2008 8:41:46 PM)

quote:

The twill will probably drape better and conform to any curves. Don't use polyester on the floral foam. Use epoxy, that should be safer and not eat into the form. Make sure the epoxy is a finishing resin type and not 15 minute or 30 minute. You want it to have time to wet out well. When laying additional layers of glass and epoxy, make sure you give it a light sanding and wipe it down with denatured alcohol to get any oils or waxes off between coats. Don't use acetone because again, if any gets on the foam, so good bye foam. A few layers of 6 oz cloth should do the trick.


Thanks John. Sorry for the slow response. I did not know that. Do you happen to know if floral foam is a version of styrofoam? Michaels also had a foam, that was not called 'floral foam', but it was of a different consistency and stated that it was styrofoam?

quote:

I also suggest covering the foam plug with a LOW TEMP film such as Econocote. This protects the foam from the resin AND makes the inside of the cowl smoother. When I do "one of" cowls I use 2 oz fiberglass cloth cut into strips 2" wide x 8" - 10" long. I typically use 2 - 3 layers of cloth (I find it easier to get everything wetted out using multiple layers of thinner cloth). Use a flux brush for applying the resin. If you see a white spot/area on the cloth it means the resin has not completely wetted the area. You may need to "poke" the area with the bristles of the brush to get the rein all the way through the cloth.

After the resin has dried, DO NOT REMOVE THE PLUG. Do all your sanding with the plug still in the cowl. If there are any low spots, holes, etc., use spot putty (comes in a tube, is usually red and can be found in the auto section of Wal-Mart) to take care of these areas. To remove the plug (do this outside ), cut an "X" in the back of the covering and pour a little gasoline on the foam (2 - 4 oz is plenty for a 40 - 60 size cowl) and wait about 20 minutes. Then just pull the covering and the sludge from inside the cowl. Wash the cowl THOROUGHLY with soap and water.

The cowl is going to be soft and pliable at this point. Do any final shaping needed and set the cowl aside for a couple of days to harden up.

As John said, the twill will most likely "lay" better. Fiberglass cloth is coated and the coating is designed for polyester, epoxy or both types of resin. I suggest getting the type for both types of resin.

FWIW - I suggest thinning the resin with denatured alcohol (NOT ISOPROPYL ALCOHOL [rubbing alcohol]) or acetone about 5% BY VOLUME. IN NO EVENT EXCEED 10% !! This will thin the resin enough to ensure proper wetting out. 5% will not weaken the resin by any noticeable amount, however, it will lengthen the drying/curing time.


I would not have thought of using a film to cover it, but doesn't the heat affect the foam even though its low temp? These are great suggestions! Thanks for the help.



bkdavy -> RE: First attempt at making fiberglass cowl need advice (5/11/2008 8:04:12 PM)

I wanted to do a one off cowl for my first attempt as well. The process I followed was basically:

Shaped green floral foam to desired shape using knives, sandpaper.

Covered the green foam plug with finishing resin to stabilize the shape.

Sanded the resin and used light drywall compound to fill any low spots.

Covered the plug with Sig Aerokot Lite.

Gave the plug about 4 layers of Johnsons paste wax.

Sprayed the plug with mold release compound.

Used a cardboard dam and modeling clay (non-drying) and then made a two piece mold with .5 oz cloth (from the LHS) and the heavier cloth from Home Depot. Used Finishing resin for the layup.

After 24 hours, broke out the plug from the mold. Gave the mold about 5 days to cure.

While the mold was apart, waxed the mold with Johnsons Paste wax (5 coats) and sprayed with Mold release compound.

Put the mold back together, filled the visible seam with modeling clay.

Used an initial layer of .5 oz cloth and then two layers of the heavier cloth.

After 24 hours, broke out the finished cowl. After a few weeks, I sanded the cowl, gave a final coat of finishing resin, and painted.

Bottom line, while there are more expensive, higher quality systems out there, if you're in it for one or two pieces, finishing resin, readily available light and heavy cloth from the LHS and Home Depot, Johnsons Pastewax, and mold release spray (from a local craft shop) should be all you really need to make it happen.

Brad



Campy -> RE: First attempt at making fiberglass cowl need advice (5/12/2008 3:42:46 AM)

Provided you keep the temperature within the range stated for the low temp film AND do not leave the iron too long on one spot you will not have any problems covering the foam. I keep the scraps of my low temp film from other covering jobs, and this is what I use to cover the foam plug with (some of the end result color schemes get pretty wild[:D] )



winglift -> RE: First attempt at making fiberglass cowl need advice (5/12/2008 5:21:02 PM)


quote:

ORIGINAL: Campy

Provided you keep the temperature within the range stated for the low temp film AND do not leave the iron too long on one spot you will not have any problems covering the foam. I keep the scraps of my low temp film from other covering jobs, and this is what I use to cover the foam plug with (some of the end result color schemes get pretty wild[:D] )


Sounds good. I ran into a snag though. I don't have a photo, but after rough shaping I soon discovered that there were places too thin to hold its shape, in fact some places just fell off and left a hole. The foam is very soft and I am not sure if I could use it. I am not sure what to use, but perhaps a harder type foam or even balsa. I did notice at Michaels harder foam that I might be able to use, it was a styrofoam product, but much finer. Any ideas welcome.



bkdavy -> RE: First attempt at making fiberglass cowl need advice (5/12/2008 5:37:10 PM)

Its not beyond the realm of reason to shape your cowl with balsa and then use that for the plug. In some cases, it can be easier to achieve the desired finish on balsa than on the floral foam.

Brad



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