FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: jayb on April 07, 2016, 12:14:31 AM
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One of the things I wanted to do to my race car this year is try to lighten it up a little bit. I've been trying to come up with various small projects to take about 100 pounds total out of the car. One of the first thoughts was to swap out the bumpers for fiberglass copies. The front bumper on my car is not available commercially in fiberglass, so I decided to build one in fiberglass. This is a lot of work for a fairly minimal weight savings, probably only 20 pounds between the bumper and brackets, but that weight is hanging way out in the front of the car, and my car is relatively nose heavy, so I thought it would be a worthwhile project. Back in my model airplane days I did a lot of work with fiberglass on very large models using multi-piece molds, so this wasn't a particularly difficult project in comparison.
The first thing you have to do is mount the piece you want to duplicate on a parting board. This is just a flat surface that the part mounts on and seals to, so that the fiberglassing chemicals don't leak all over the place when you lay up the part. The picture below shows the original bumper, some 2X12s I cut up for support, and a couple of pieces of masonite to form the flat surface:
(http://fepower.net/Photos/Posts/fglassform1.jpg)
Here's the parting board put together. The holes in the board are for the brackets that are welded to the bumper.
(http://fepower.net/Photos/Posts/fglassform2.jpg)
The bumper is placed on the parting board and bolted in place to some of the wood framework underneath, with the factory brackets:
(http://fepower.net/Photos/Posts/fglassform3.jpg)
In this case one side of the bumper fit up nicely with the parting board, but the other side had a pretty big gap, as shown in the photo below:
(http://fepower.net/Photos/Posts/fglassform4.jpg)
The way to handle this is to build up some masonite on the parting board wherever there are gaps, to minimize any gaps between the bumper and the parting board, as shown in the photo below:
(http://fepower.net/Photos/Posts/fglassform5.jpg)
Finally, to get ready to make the mold, you use clay to fill in any remaining gaps between bumper and the parting board, and also between the pieces of masonite:
(http://fepower.net/Photos/Posts/fglassform6.jpg)
Now that the part you want to duplicate is in the parting board, you have to apply mold release. This is a two step process. First, using a wax called Partall #2, you wax the part and the parting board. You apply the wax just like you are waxing a car; apply, let dry for a few minutes, and then buff. Three coats are required, with about one hour drying time between each coat. After the last coat is dry, you spray on a chemical called PVA (Poly Vinyl Alcohol). This is a water soluble chemical that forms a skin on top of the wax. You don't put on too much, just mist it on in a couple of light coats, and let it dry.
After the PVA is dry, maybe an hour later, you can start the layup. First part of the layup is spraying on the gelcoat. This is a fairly thick polyester product that puts a hard skin on the surface of the mold. I use tooling gelcoat, which is designed to handle the rigors of pulling many parts from the mold, even though I planned to just make one or two bumpers. I have a special gun for spraying gelcoat, because it is so thick, but a cheap pressure pot style gun will also work; I used one of those for several years. The gelcoat has to go on to a thickness of around 20 mils; I have a cheap thickness gauge that you can put into the wet gelcoat that measures its thickness. If you go too thin, it doesn't want to cure, and if you go too thick, it will tend to wrinkle, so you have to be careful at this point. The gelcoat is a polyester product and is catalyzed with a chemical called MEKP, which is the same thing used to catalyze polyester resin. After you catalyzed the gelcoat you have to spray it within 15 or 20 minutes, otherwise it will start to set up in the mixing cup. The photo below shows the bumper and parting board sprayed with the gelcoat:
(http://fepower.net/Photos/Posts/fglasstgel.jpg)
Usually within an hour or so the gelcoat will start to set up after spraying. When you can touch the gelcoat with your finger and no gelcoat transfers to your finger, you are ready to start laying up the fiberglass. For molds I use fiberglass matte, and cut it into pieces that can be laid up against the part. Fiberglass matte is basically random fiberglass fibers, rather than cloth, held together with a binder that dissolves in polyester resin. You mix up a pint or so of polyester resin and MEKP, and using a disposable paintbrush start laying the matte on the part and soaking it with resin. As the binder breaks down the fiberglass fibers start to stick to the part and parting board. You cover the whole works with one layer, and then do it again. I put a total of four layers on this mold, to make it fairly rigid. Here's a picture of the layup at this point:
(http://fepower.net/Photos/Posts/fglassmlayout.jpg)
Next is a part where timing is somewhat critical; this is trimming the excess matte from the mold. When the polyester resin starts to set up, it can be easily cut with a utility knife. However, if you wait too long, no way a knife will cut it, and you will have to use a cutoff wheel to trim the mold outline, which is a pain and will put fiberglass dust all over the shop. I tend to check the layup every five minutes or so, and just hang around until it will cut easily without tearing. Here's a picture of the trimmed mold layup:
(http://fepower.net/Photos/Posts/fglassmtrim.jpg)
After letting the mold dry for 24 hours, you can pull it off the part. This is the hardest and most nerve wracking part of the whole process. The mold will separate from the parting board pretty easily because it is flat, but pulling it off the bumper is a challenge. I have a bunch of plastic wedges I use to put pressure on the mold, and after half an hour of screwing around it finally released with a loud crack. I'm always worried about breaking the gelcoat during this step, but usually it comes out OK. However, if your layup does not have sufficient draft, you may have to break the mold to get it off the part. Fortunately, this bumper had plent of draft, so the mold came off looking just fine:
(http://fepower.net/Photos/Posts/fglassmold.jpg)
I like to let a mold like this fully cure for a few weeks before trying to pull a part from it, so that's what I did with this one. After that time had elapsed, I used soap and water to thoroughly clean the mold and prepare it for making a part. Then, the whole process basically is repeated. The mold is waxed three times, then sprayed with PVA. After the PVA is dry, the gelcoat can be sprayed into the mold. I used regular part gelcoat for the part, which is white. I also masked off the parts of the mold that weren't going to be the bumper. Here's a pic of the mold with the gelcoat sprayed:
(http://fepower.net/Photos/Posts/fglassgelcoat.jpg)
In order to keep the bumper strong yet lightweight, you use fiberglass cloth to lay up the part, not fiberglass matte. Pound for pound cloth is a lot stronger. However, cloth is woven together and not attached with a chemical binder, so it doesn't conform into tight corners as well as matte does. So, in order to take the sharpness out of the corners, you use a dry powder called Cabosil, and mix it with some polyester resin to form a paste. I use a tongue depressor to fillet all the sharp corners in the mold with this Cabosil paste, to make it easier to lay up the cloth into the mold. You don't want gelcoat in the mold that is not backed up with some solid material, so the Cabosil addresses this issue. Here's a picture of the mold after the masking paper has been removed and some of the Cabosil paste has been put into the corners of the mold:
(http://fepower.net/Photos/Posts/fglasscab.jpg)
Next you mix up some more polyester resin and MEKP, and after cutting the fiberglass cloth into strips, start laying it up into the mold. I started with two layers of four ounce cloth, and then finished with two more layers of six ounce cloth. Its a good idea for strength to put the cloth layers in at different angles, rather than all lined up together, so I laid the first section of cloth in at 45 degrees from the length of the bumper, and the next section along the length, then repeated this with the six ounce cloth. Here's the layup at this point:
(http://fepower.net/Photos/Posts/fglasslayup.jpg)
Once again I checked the layup every few minutes to see when it became easy to cut with a knife. Took about an hour this time before it was ready, then I trimmed the excess fiberglass cloth at the edges of the mold. I left some cloth at the ends, so I had something to pull on to help get the bumper out of the mold:
(http://fepower.net/Photos/Posts/fglasstrim.jpg)
After 24 hours I got to work removing the bumper from the mold. I used my plastic wedges to work between the mold and the part, to help break it loose, and finally after 20 minutes or so I got one of the ends pulled up, and then the rest of the bumper came out without any trouble. Here's a picture; the purple residue you see on some parts of the bumper is PVA that is still attached:
(http://fepower.net/Photos/Posts/fglassbmpr.jpg)
From here I have to sand the bumper's edges nice and smooth, clean it up and spray it with some primer, and then figure out how I'm going to mount it to the fiberglass bumper brackets that I got from Crites. When I've got it successfully mounted on the car, I'm going to pull it off and try one of those spray-chrome products to see if I can make it look as much like chrome as possible. I also purchased a rear fiberglass bumper from a fiberglass place, so I will try to chrome that one at the same time. I will report back on my results with the chrome stuff when I have them - Jay
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Great write up and pictures! Thanks Jay.
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Looks good, Professor of FEology! Where did you get the tongue depressor? :P
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I know where you're going with that, you devious trunk monkey! You think my wife stole those tongue depressors from the hospital LOL! Truth is that the stores that sell supplies for fiberglass work offer all that kind of stuff for sale, including tongue depressor and popsicle sticks, mixing cups, rubber gloves, disposable brushes, etc. etc. I get all my stuff from a local outfit called Express Composites.
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Very cool Jay! Yes, you must have done lots of large scale plane work to know not only how-to but also get the best materials. Lots of work though as you said for small gains.
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I know where you're going with that, you devious trunk monkey! You think my wife stole those tongue depressors from the hospital LOL! Truth is that the stores that sell supplies for fiberglass work offer all that kind of stuff for sale, including tongue depressor and popsicle sticks, mixing cups, rubber gloves, disposable brushes, etc. etc. I get all my stuff from a local outfit called Express Composites.
Why would I think something like that?
(http://i34.photobucket.com/albums/d137/HemiJoel/td_zps3nioomlv.jpg)
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that looks good Jay but messy as we all know. and not to bust your bubble but Crites makes that bumper. for 155 bucks
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Crites does not make a fiberglass bumper for a 69 Shelby, they make one for a stock 69 Mustang. The bumpers are significantly different.
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That takes me back a few years.
When I was a kid I worked for Cole boats in Chatsworth, Ca.
I did the hardware installations but was always being called to the fiberglass shop to help with molds and laying up hulls.
We used to use compressed air and rubber hammers as our release agents.
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Very interesting Jay, nice write up and pictures like always. I have wanted a fiberglass bumper for my Cougar for some time now. A while back somebody said they were going to make them but never did. I am not sure I am up to the task but I am tempted. I did get some aluminum to make the support brackets and mounts, was going to "Swiss cheese" the existing frame to lighten up the front. There is probably more to be had in weight reduction on my grills and maybe next winter I will do all of it.
Keep us posted on the spray-chrome materials and process, quality and results etc. Should be interesting for sure. I almost think it would be easier to use vinyl wrap, but not sure about the end result on that. Did you ever look into that?
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Jay, I also appreciate the tutorial on making fiberglass parts! I've done some repair work (like on my Fairlane AC / heat plenum) but never made entire molds and parts from scratch before. Just to be clear on the Cabosil paste; is it used to fill in and give strength to the sharp corners where the glass cloth won't conform?
Thanks,
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Yes, a wrap is a good idea as some I've seen are hard to tell from real chrome.
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your right I forgot about the Shelby. as opposed to the mustang. my bad. ill keep my big trap shut :-X
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HCMC...almost lost it ;D
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Jay, I also appreciate the tutorial on making fiberglass parts! I've done some repair work (like on my Fairlane AC / heat plenum) but never made entire molds and parts from scratch before. Just to be clear on the Cabosil paste; is it used to fill in and give strength to the sharp corners where the glass cloth won't conform?
Thanks,
Yes, basically if you have a real sharp corner where the fiberglass cloth won't conform, you will have an air bubble in the finished part between the gelcoat and the glass. In the sun, the air pocket will get hot and expand, and the gelcoat will blister or break in that area.
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Regarding the chrome wrap, I have read some bad reports on that stuff, so I'm a little reluctant to try it...
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Jay can you please elaborate what you heard about chrome wrap shortcomings?
They sure seem to completely chrome wrap a lot of super-cars on the web... despite what they say it scares me silly thinking the wrap can be removed w/o harming the paint...
"chrome wrapping" a Lambo
https://www.youtube.com/watch?v=ypLUq6h718o&nohtml5=False
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Its been a while since I read about it BB, but I think it was on yellow bullet where several people said the chrome wrap didn't conform to the shape of the bumper without a bunch of joints, and then turned yellow pretty quickly after installation. I have no personal experience with the stuff, so I'm just repeating what I've read...
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Very interesting Jay, nice write up and pictures like always. I have wanted a fiberglass bumper for my Cougar for some time now. A while back somebody said they were going to make them but never did. I am not sure I am up to the task but I am tempted.
I want a fiberglass Cougar bumper, too. That's two orders already Jay!
Interesting write-up and pic's.
paulie
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most chrome vinyl is usually made of mylar & has no stretching ability like regular vinyl, so you have to piece it. It also has a very short outdoor life. however, Avery has what they call Conform Chrome that is supposed to be able to stretch & bend. They wrap whole cars with the stuff, so it may work well & has a 3 year life, bubble free, & removable. I never had a customer looking for it yet so I have no experience with it. It only comes on a 48" wide role & probably costs more than a real bumper. Maybe I'll chrome my whole 62. Get out the sun glasses... ...Nope, my trunk monkey says no.
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A guy here had a cromed plastic TP holder ???
with the manufacturers name in it. He contacted
them and they cromed his bumpers for free
but like all others they have moved to China
But if you have a company making cromed
plastic things close to you that may be an
alternativ
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I can't resist after seeing all that work about the FoMoCo weight reduction program. Jay how much weight comes off utilizing the Ford magnesium SOHC valve covers vs the cast aluminum's your running?..................I'm thinking about that weight savings of a Shelby Mustang Bumper Assembly vs your Glass assembly? It ain't the front of the car but it's not that far back and it's high.
Decades ago I got a refund from Holman Moody for the few bucks I paid for their clearance sale catalog after the one thing I tried to buy was SOLD OUT,,,,, You guessed it SOHC VCs
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I have never measured the weight difference between the aluminum and magnesium SOHC valve covers; that's an interesting question, BB, and I will check it out this weekend and post what I find - Jay
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A stock 69/70 Mustang bumper assembly weighs 24-25 lbs. This includes the brackets, supports, small tabs and turn signal lights. The range is because I get two weights depending on which scale I use.
Bare bumper 11 lbs
Bare arm 3 lbs 14 oz
Outer support rod 2 lbs 1 oz
One turn signal assembly ~ 1 lb
Some aftermarket bumpers are cheesier and probably weigh less
The Bud Moore Trans Am cars used the stock bumper arms with large holes cut out in the center and lighter gauge bumpers.
http://www.ebay.com/itm/69-70-Mustang-Boss-302-Bud-Moore-Shelby-Trans-AM-lightweight-parts-drops-100-s-/222071089526?hash=item33b477e976:g:twEAAOSwvUlWrRfn&vxp=mtr
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The Bud Moore Trans Am cars used the stock bumper arms with large holes cut out in the center and lighter gauge bumpers.
http://www.ebay.com/itm/69-70-Mustang-Boss-302-Bud-Moore-Shelby-Trans-AM-lightweight-parts-drops-100-s-/222071089526?hash=item33b477e976:g:twEAAOSwvUlWrRfn&vxp=mtr
[/quote]
Hey, thanks for posting that very interesting link babybolt. I knew those cars had some lightweight parts but never saw pics of them before. Interesting they were all front end parts with the likely goal of getting closer to a 50/50 weight distrbution, although I had read they stalled at about 52/48.
I liked especially the 'glass front fender extensions as the stock ones weight a ton! When I did my Mach 1, I dumped the OEM Mach grille and fog lamps for the regular Mustang grille (plastic/no lights) for significant weight savings. A non-ram steel air hood, less all the underhood plumbing saved a lot as well.
But one of the best savings was dumping the OEM disc brakes system (heavy!) and adding Baer Racing's discs w/bolt-on racing type aluminum hubs and lighweight, vented steel discs plus aluminum calipers. These easily saved 60+ lbs off the front! I'd like to dump the cast iron brake reservoir (hard to find a direct replacement) and add a carbon hood (frightfully expensive) but who knows what I'll get myself for Chrtistmas!
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I'd have to look back in my notes for some more 69/70 weights but the fiberglass hoods are a good weight savings. The aftermarket race hoods with no underneath trim and no hood hinge provisions aren't street friendly. The Trans Am cars used a steel hood with the underneath cut out and a stiffening rod welded to the perimeter (at least the privateer car hood I looked at closely and weighted) which remarkably weighted just about the same as an aftermarket fiberglass hood with the underside details.
Not familiar with the Baier parts, but a know a guy who works on the Trans Am stuff for the road race guys and they had some trouble with some aluminum hubs and wound up making steel hubs with bearing spacers for the large side loads from the track. Wilwood makes some lightweight front brake stuff that is more oriented to straight line racing. I saw a serious 69 Mustang drag car using this setup.
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Whew that is one rare and fascinating collection of T/A parts. I recall way back when there were Boss 302 2x4V Dominator Intakes routinely on ebay... Crazy to imagine two Dominators on a BOSS 302 but Bud and others ran them successfully
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Wow 25lbs for the bumper assembly.
I haven't weighted it, but I swear my 63 Galaxie's bumper is 75lbs or more. Of course those cars are an exercise in overkill.
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I was just lazy I guess, ofcourse a race car with a bunch of fiberglass parts already isn't as critical. I just used the inside of my bumpers as the mold. Made front and rear bumpers for my 69 and Ofcourse there scaled down a bit but for a race car such as mine they look just fine . just a short cut . on a car like Nays or anything show quality, then the way they have been done here is most definitely preferred.. Good job..
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Wow 25lbs for the bumper assembly.
I haven't weighted it, but I swear my 63 Galaxie's bumper is 75lbs or more. Of course those cars are an exercise in overkill.
On my 64 Galaxie each bumper and bracket assembly weighed 55 pounds. Took 100 pounds out of the car when I switched to fiberglass.
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"I'd like to dump the cast iron brake reservoir (hard to find a direct replacement) "
The mid-80's Ranger pickup had an aluminum master cylinder that looked very similar to the late 60's to early 70's Mustang unit, and the lines even exited the drivers side. I don't know what the bore sizes were on the Ranger. At the end of the 80's Ranger they switched to the type of master cylinder with the plastic reservoir. If you order a replacement master cylinder for the Ranger now they would probably come with the plastic reservoir, but if you could look through old stock or hit a junkyard an aluminum unit might show up.
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We use this master cylinder for ours. Fits the Fairlane and even clears pentroof valve covers, steel and finned aluminum.
DORMAN M39568
{#E6TZ2140B}
Manual brakes; Bore: 15/16 In. Got it from Rockauto.com
Jay, I would also like to know how the chroming process works out for you and as always, excellent work!
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This kinda stuff is why I think Jay is the ultimate gear head. The guy does EVERYTHING himself. 1000hp SOHC? No problem. Body work and paint? No problem. Wiring and programming electronics? No problem. Dyno Tune? No problem. Mig/Tig..Etc Etc Etc. But the best part is that you share all this knowledge with everybody. I really appreciate it. I sure am glad your an FE guy!! Got any pics of some of those r/c planes that you built?
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"I'd like to dump the cast iron brake reservoir (hard to find a direct replacement) "
The mid-80's Ranger pickup had an aluminum master cylinder that looked very similar to the late 60's to early 70's Mustang unit, and the lines even exited the drivers side. I don't know what the bore sizes were on the Ranger. At the end of the 80's Ranger they switched to the type of master cylinder with the plastic reservoir. If you order a replacement master cylinder for the Ranger now they would probably come with the plastic reservoir, but if you could look through old stock or hit a junkyard an aluminum unit might show up.
Great and thanks! I will look into that.
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Looks great Jay! I can appreciate all of the thought that went into that process. Look forward to seeing a finished bumper on the car :)
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85 and older Ranger had the aluminum master cylinder that looks like the earlier Mustang units. Rockauto sells new replacements made of aluminum with a 15/16" bore. I think the castings on the original aluminum Ranger cylinders was a little different. Some of the master cylinders sold at Rockauto for this application are iron castings so you have to read the fine print.
http://www.rockauto.com/en/moreinfo.php?pk=309668&cc=1137350&jsn=991
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Next, he'll be going on the Atkins diet to lose another 30 lbs. Stay tuned... 8)
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85 and older Ranger had the aluminum master cylinder that looks like the earlier Mustang units. Rockauto sells new replacements made of aluminum with a 15/16" bore. I think the castings on the original aluminum Ranger cylinders was a little different. Some of the master cylinders sold at Rockauto for this application are iron castings so you have to read the fine print.
http://www.rockauto.com/en/moreinfo.php?pk=309668&cc=1137350&jsn=991
Great! I'll look into this one as well. Thanks to all!
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Howdy Jay,
Nice work there sir! Have you considered swapping out the fiberglass for kevlar? Its half the density but about the same strength. Since you have the molds, it might be worth it if you're trying to cut as much weight as you can. Just be sure to purchase ceramic scissors...kevlar is tough stuff but those scissors cut through the stuff really easily.
Joe
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Don't know a lot about FE engines but I do about fiberglass. Jay instead of using Cabosil you could use fiberglass tissue. It will conform to your sharp curves and weigh less. If you have sharp corners get some fiberglass woven roving's that is sprayed in a chopper gun (fiberglass rope) and lay that into your sharp corners first then lay your glass matt over that. Less chance of air bubbles. Also fiberglass is like concrete it takes about 20+ days to cure correctly so leave your molds to cure for longer periods before removing them from any pattern. Nice work on your mold by the way.
Cheers
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Thanks for the tip, I've never heard of fiberglass tissue. I will have to look into that stuff...
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Yes it's about 1/2 an ounce and works great in tight spots.
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I have a new aluminum master but lines come out the wrong side .. It needs a new home