At this age sometimes it just stops working...

Here's a brief side note in our hood repairing saga.  I've been going on and on about how you have to do things right when fixing fiberglass.  It's not hard to do, but it is easy to mess up little things and have problems down the road.  This is one of those little things.  It's not uncommon to see Gen I and II Vipers with bubbles in the paint, even on cars that have never been wrecked or repainted.  They look just like rust bubbles would on a steel car.  My car is no exception, two places on the hood had these bubbles.  They're easy to see when you're looking at the car, but very hard to photograph in 2D.  To make the bubble stand out, I lightly sanded over it so you can see it clearly.

Then I started sanding down into it with my DA.  Even though my hood has been repainted several times, it wasn't re-work that caused this bubble.  It goes all the way down to the fiberglass.  The original factory primer lost adhesion to the fiberglass.  A large chunk of it was no longer stuck down, and that's what caused the bubble.  It's also why some cars have bubbles when the body is hot but they seem to disappear again when the body cools down, the loose paint gets hot and expands more than the fiberglass beneath it.

It just goes to show that even the experts can sometimes have trouble getting everything to work right with fiberglass.

Next!

Just a little update because I'm so far behind on my posting.  Continuing my theme of smallest to biggest, I fixed some more cracks on the Vipers hood.  Same process as the last ones and like all the others they looked like tiny imperfections until I started grinding into them.  Same location too, the corners of the hood scoop hole create stress points where cracks will start if flexed enough.  You can so see that I've got a tarp laid out under the hood.  It's there to keep most of the dust out of the engine compartment, and catch any drips of fiberglass resin or Bondo.  For the time being, I'm also not worried about fiberglassing over the paint.  Normally that's a huge no-no, but the whole area will be sanded down to bare fiberglass before the bodywork is completed, and none of the paint overlapped areas will still be there once that's done.

Gotta start somewhere

Time to actually start fixing the top of the Viper's hood.  I started with the crack in the upper passenger's corner of the hood scoop.  As you can see in the pic, after it was "fixed" it continued to crack.  You can also see towards the bottom of the pic another crack that never got addressed at all:

Grinding into the crack revealed another problem.  Just like the area further down the hood, some of the fiberglass has delaminated.  There are some fibers that have broken loose from the rest of the panel.  You can see too that though the main crack had some new fiberglass over it, it was still very much there.

When you start grinding onto these things, it's actually fairly easy to see the cracks and delamination.  As you're grinding, you just keep following the cracks until you get back into solid fiberglass.  If you're not ready for it, it can start to look pretty grim as you keep grinding, and grinding, and you're still chasing the crack.  With this crack for example, I ended up having to grind out a sizable chunk of hood to get rid of all the damage.  Much of it goes all the way down to the inner panel.

The rest of the repair is the same as any of the other repairs I've showed.  I do have another bit of how-to to add though.  As you're laying up fiberglass, you are going to get bubbles in the resin.  Bubbles can cause problems down the road, particularly if they're close to the surface.  You can, to some extent, use a bondo spreader to work the bubbles out, but it doesn't always work for small bubbles.  Fortunately, there's a tool for that.  For around $15, you can buy a fiberglass roller.  It's made specifically for rolling out fiberglass, and works great for working out bubbles.

The only down side to a fiberglass roller is that you have to use it and get it clean before the resin starts to set.  If the resin sets before it's clean, you may as well throw it away.  Dunking it in a tub of acetone will help dissolve the resin, as well as slow down the reaction giving you a few more minutes to get it clean.

That's just not right, Pt 2.

With the hood back on the car, I could finally get started on the important part, the top side(although really since the top is just for decoration while the bottom actually provides the structure, it should be the other way around).  The "repairs" on the top of the hood are another exercise in how not to do things.  Instead of diving right in with my grinder, I used my DA to sand the paint off, exposing the "repairs" in all their "glory."

The first thing I noticed was that this hood has been painted FIVE TIMES.  I don't mean there were five coats of paint on it, there were five distinct base/clear layers.  I know the bumper skin was repainted because it's flaking in places.  I had no idea that the hood it's self had been repainted, much less five times.  All the damage I found was from the crash that wrecked it just before I got it, so I don't know why the hood was painted so many time.  Anyway, lets look at a picture, because you're all really here for the pictures, right?

One pic, lots of trouble...
1.  There is a crack here repaired with fiberglass.  As you can see, the fiberglass is laid OVER the paint.   Paint is not a suitable substrate for fiberglass.  It wasn't properly ground down, and will have adhesion issues.   The whole repair could literally pop off the part because the only thing holding it on is paint.
2.  Cracks filled with bondo.  They didn't even bother to grind out the crack on the right(that's the one we took an in depth look at a few posts back).  It's no wonder it recracked, there is no structure holding the crack together.
3.  Loose/delaminated fiberglass.  We'll take a closer look at this area later on
4.  In a one-two punch, here we have more fiberglass on top of paint, and more crackes just skimmed with bondo.
5.  A crack that was ground a bit, but not completely gone so the crack continued to spread.
6.  Fiberglass laid in without a proper bevel.  These are major cracks and in several areas the only thing the new 'glass is holding onto is the vertical edge of the old 'glass.  In time, these crack would reappear.

Here's a closer look at area 2, where the crack reappeared.  You can see there is nothing holding the cracks together but a bondo bandaid. It's a wonder that it lasted as long as it did before recracking.

Here's an up close look at area 3.  The impact from the crash caused some of the fiberglass to delaminate.  You can see the ragged dark edges towards the center of the pic where some fibers of the top layer of fiberglass broke loose from the rest of the sheet.  They were just skimmed with bondo.  This sort of damage may or may not ever develop into a full crack, but it will definitely cause paint adhesion problems as the broken layer of fiberglass can move independently of the rest of the sheet.  You can also see a myriad of still existing cracks under the fiberglass repair on the left side of the picture.

One more picture, because everyone likes pictures.  Area 4 is basically all the other problem areas combined in one area.  There is just so much wrong in this picture...

SEMtastic!

It's still too cold to do any actual work on the Viper, so I'll do more posting instead.  It's time to finish the bottom of the Viper's hood.  Unlike the paint on the outside of the car, the paint on the bottom of a Viper's hood is not catalyzed.  If you wipe it with a strong solvent like lacquer thinner, it comes right off.  Because of that, I don't feel bad using non-catalyzed products to refinish it.  I'm also going to cheat just a little bit because I know my work isn't exactly as it was originally anyway.  I'm going to use a pair of SEM products.  As a company, SEM doesn't make any bad products.  Their Color Coat plastic/leather/vinyl/cloth paint beats Duratec as my #1 favorite product.  Here, I'm using a pair of products I've had good results with in the past.  The first is #39853 Texture Coat, the second is #39143 Trim Black. 

Texture Coat is just that, it's meant to give some texture to an otherwise smooth surface.  The Texture Coat is made to match OEM textured surfaces like you find on bumpers and some interior plastic parts.  You can also vary the texture by changing your spraying distance and how heavy you put it on(and as a benefit in my case, it will also hide sand scratches).  Here you can see the texture I ended up with on the Viper's hood. 

Trim Black is a satin black that very closely matches a lot of OEM finishes like you sometimes find under hoods, in fenderwells, and misc exterior trim. It's very close to the original black under the Viper's hood.  It's a good, durable, air dry paint that stick well to most surfaces.  It looks a bit shiny and uneven here, but it's still wet.  Once dry, it's a bit more satin, and very even.

The only thing left is to reinstall the hood pad and put the hood back on.  I expected the bottom of the hood to be a weekend project, but it was a month and a half before I actually got it done.  It was far more damaged, and the repair done much more poorly than I expected.  Even though it was off the car for a month and a half, because of the other demands on my time, I really probably only have 35-40 hours in it.  An actual professional bodyman probably could have had it done in 20-25 hours.

Just a little sprocketing

I mentioned some time ago that my Dad is rebuilding a Suzuki RE5.  The frame is set up to use later Suzuki Katana wheels.  Things like this are rarely a direct swap.  In this case, aside from basic wheel fitment issues, the Katana is made to use a 520 size chain, while the RE5 uses a 530 chain.  Swapping the RE5 to a 520 chain is pretty straight forward, but you need to buy a matching front sprocket and a chain.  It was decided that it would be easier to just adapt the RE5 rear sprocket to the Katana hub. 

The first thing I did was drill the new bolt holes.  In stead of doing the math to figure out where to put the new holes, I just drew up the bolt patterns in Solidworks.  From that, it was very easy to measure how far from center in X and Y the new holes had to be.  After center finding the hub hole, I drilled all the new holes.

Here you can see the new holes.  One new hole overlaps one of the old holes.  With a 5 hole pattern(RE5) and a 6 hole pattern(Katana) so close in diameter, you will always have an overlapping hole somewhere in the pattern.  On something like this, it doesn't make much difference.  Even a modern high power 2L sportbike doesn't have anywhere near enough torque to shear off the bolts. 

Then I set about enlarging the hub hole, it needed to be opened up by about 1/4".  The easiest way to do this on a manual mill is with a boring bar.  I had a whole long explanation of how these things work and how to use them, but it was just boring...

That's really all there is to it.  I don't have a pic of the RE5 sprocket on the Katana hub, but it fit like a glove. 

Back to the grind

Try as hard as I might, I couldn't get all the bodywork done on the Viper.  Every time I got going on it, other people would start making demands on my time.  Now, it's too cold out for fiberglass and bondo to cure properly, so I figured I might as well catch up on my blog.  When we last left the Viper, I'd just finished laying in all the new fiberglass on the bottom side of the hood.  Since the fiberglass is what makes up the structure, we could just leave it as it with some minor trimming.  But, it's the bottom side of a hood in an engine compartment that a whole lot of people ask to see so it has to look pretty too.

Before we can really start grinding, we need to know where to stop.  In a few areas where there was original undamaged fiberglass, I left some spots of the original black paint.  I know that paint is where it should be, so I know that that is where the surface should be when I'm done.  None of it is super critical on the front of the hood, but you still want to make sure the latch hooks are close enough to their original position that it will latch properly(even then, the latch has a lot of adjustability in it).  The round circle is one of the hood scoop nut recesses, the odd shaped black splotch is original paint telling me where the surface should be once we're done.

I started again with my trusty Harbor Freight grinders, first the 7" to knock down and level the big flat areas, then my 4.5" to hit the smaller areas, and finally a 2" pneumatic grinder for the tight spots.  Grinding it down serves two purposes, first to knock down any high spots, and second to roughen up the surface for additional filler work.  Here it is all ground up.  You can see the shape is roughed in pretty well.

You'll notice that three of the four the hood latch hook holes have been completely fiberglassed over.  Before I put any filler on, I want to be sure I know where they are.  Here is where Mineral Spirits works some more of it's magic.  Wiping the ground fiberglass with mineral spirits turns it transparent enough that you can see through it.  here you can see one of the hood latch hook holes under the fiberglass.  It shows up as the dark circle about in the middle of the picture.  All the holes will get drilled out before I add any filler.

Here's the part that I don't generally recommend, but am going to break my own rule and do anyway.  I've mentioned filler a few times.  Standard body fillers work good for a lot of things, but they don't have much strength.  Fiberglass is strong, but is hard to work with(and sands like concrete.).  There is a product that lands directly between the two, fiberglass reinforced body filler(often called Kitty Hair or Tiger Hair).  It's essentially bondo with chopped up fiberglass in it, and has the added benefit of being waterproof like fiberglass(and unlike standard bondo).

I don't generally recommend it for two reasons.  First, because it's fiberglass reinforced and stronger than standard fillers, a lot of people use it instead of doing proper repairs.  This hood had several areas that were just filled with kitty hair instead of being repaired properly with fiberglass.  Far too often I see kitty hair band-aids on things that need actual repair, both on fiberglass and metal cars.  Second is the bubbles...

Because of the fiberglass strands in it, kitty hair doesn't mix or spread as well as bondo(especially the long strand variety).  As a result, you often end up with large bubbles or voids in the filler that might cause problems down the road.  I decided that for the bottom side of the hood, I wanted the extra strength of the reinforced filler and would just deal with the bubbles.  You can see here the kinds of voids and bubbles you typically get in kitty hair:

You can't just fill the voids because filler won't stick to the (relatively) shiny surface of the bubble. The only way to deal with them is to grind them out first, then fill them.  Using a carbide burr in my die grinder, I ground out all the bubbles I could find.  In addition to the big obvious ones, there were also a whole lot of pinholes that needed to be filled.

Once the bubbles were ground out, I filled them with regular body filler and sanded it all smooth:

Unlike the outside of a car, the bottom side of the hood has lots of odd shapes and small contours, so it took a variety of sanding tools to work everything smooth.  For all the filler work, I used 80 grit sandpaper.  I bought a big roll of sticky back 80 grit, it's the most economical way to buy it.  From top to bottom I have my rigid 6" block, a flexible 6" block, a rigid 3" block, half a tongue depressor wrapped in sandpaper, a whole tongue depressor wrapped with sand paper, and my trusty 8" Durablock.  For this kind of work, improvised sanding blocks are often necessary too. Find something that fits where you need it to fit, and wrap it in sandpaper.

Even though most of the surface is covered in filler, it's not very thick.  Just like laying the fiberglass down, I worked a section at a time until I had the shape I wanted.

Once the filler was sanded down, I renewed my love affair with Duratec primer-surfacer.  It's just such a wonderful product, and it's made specifically for fiberglass to boot.  The repaired areas of the hood got a healthy dose, followed by sanding with 220 grit paper.  Normally, you'd want to sand much finer than that for paint or you'll get sand scratches showing through, but I'm going to do something a little bit different and don't need a super fine finish.  For now, just enjoy the Duratec'd goodness...

H1 , Chapter 6.

The next chapter of my H1 build has lots of nifty stuff in it.  At this point, I'd gotten most of my engine back together, and have most of the shiny bits bolted back on. While I was at it, I put some stiffer clutch springs in. Fortunately, it seems as though the clutch it's self was replaced not to many miles before I bought the bike, so it didn't need to worry about that.

With most of the bike it's self down to painting and bolting stuff on, the rear fender is the last big "fabrication required" project. A plain smooth fender like I've got is fine for a race bike, but this one will be street ridden. That means it's going to need blinkers and a tail/brake light. I started planning them as soon as I started planning the fender. I didn't want them to look like tacked on afterthoughts like you see on so many customs, and even a lot of factory bikes. I explored lots of options. What I decided on is very custom, very visible, and most importantly don't stick out like sore thumbs.

The blinkers are made out of 1/2" Lexan. I cut 1/2" off the bottom of the fender, 'glassed on some tabs, bolted the Lexan down and sanded to shape. I then ground out the back sides for some LED strips. I've got 21 LED's shining out through the Lexan. More on the blinkers later, but here's a rough pic so you get the general idea:

Next up is the tail/brake light. This one took some finesse to get looking how I wanted. It's a straight forward process, but involves a lot of fitting. Like the blinkers, this lens is going to sit flush with the fender so it doesn't interrupt the lines.

I'm using the oven method of plexiglass forming. I'd like to use Lexan, but it's not as forgiving as plexiglass when baking it in the oven. First thing I did was make a plaster cast of the back of the fender. I just used some modeling clay to make the walls after I'd figured out what size and where I wanted the lens.  Mixing in some plain white Elmers glue will greatly increase the strength of the plaster.  You don't need much, around 5%-10% of the water added to the plaster mix works well.

I let the plaster cure/dry out for about a week. It can take awhile for all the water to finally evaporate out of the plaster.  warming it in teh oven can help too, as long as you don't heat it up too fast(or it could crack).  Then I cut a piece of plexiglass, set it and the plaster mold in the oven and baked it at 300*F for 10 mins or so. It gets soft enough that, with some gloves on, you can smoosh the plexiglass into the plaster buck. It took a few re-heats to get the shape just right. Also, you can see the pencil on the plaster, that's about where the lens is on the fender. I found that if you draw it straight on the fender, the pencil line will transfer nicely to the plaster.

With some rough trimming, you can see how well it conforms to the fender.

The next part take a lot of grind, check, grind. Took me about a day of messing around to get it perfect. Once the hole is cut in the fender, the lens can be cut, ground, filed, and sanded to fit just right. When you're done, you've got a custom flush fit lens that perfectly matches the contours of the fender.

Then I dyed the lens. It's pretty easy, but it took a few test pieces to get the time & temperature right. Plexiglass can be easily dyed any color you want with Rit fabric dye. The secret is to heat it up. If the dye is to cold it won't take, if it's too hot the plexiglass can get soft and warp. Just under boiling seems to work best. I've had the best results with the dye heated on the stove to about 190*F, and a cook time of around an hour. More or less depending on how dark you want it, and a meat thermometer works great for watching the temp. The same process works for dying the clear fuel line the color of your choice.

If you want to use Lexan(polycarbonate) instead of plexiglass, there are a couple things to note.  First, Lexan absorbs moisture like a sponge.  If you just try to heat it to it's forming temp, you will end up with plastic full of bubbles.  This is caused by steam forming in the plastic and having nowhere to go.  You MUST pre-dry Lexan before forming it.  The general rule of thumb is to bake it at 250°F for one hour per .010" of thickness, so 1/8" Lexan should be baked for 12.5 hours.  Second, Lexan forms at a much higher temp than plexiglass.  It needs to be heated to around 375°F to be moldable.  Third, You cannot dye Lexan, it just won't work.  If you want some color other than clear, you either need to start with that color plastic, or use one of the few paints on the market that will stick to polycarbonate(regular spray paint won't stick well).  The paints made for RC car bodies(NOT standard model paint) are made for polycarbonate and are available in translucent colors.





Now, back to the blinkers.  The first thing I did was get one of THESE $10(shipped!!!) 40 LED 3rd brake lights(and if you don't shop DealExtreme, you should. They have all kinds of nifty stuff at dirt cheap prices. Shipping is sloooooow, but it's free.  The price you see is the price you actually pay, no extra shipping or handling. Stuff is so cheap, you can't afford not to buy it :D  http://www.dx.com/p/40-led-third-brake-tail-light-for-vehicles-12v-10524#.Vf97V5cqvXw

Then I opened it up, and cut the circuit board in half, giving me two 20 LED strips. I got out the Dremel and ground a slot in the back of the Lexan for the LED strips to sit in. Unfortunately, Lexan(polycarbonate) doesn't dye like Plexiglass does. The dye just doesn't take. I tried some other things, but couldn't get consistent results. That means I had to paint it. I used white, then black on the top(the white base coat helps reflect any stray light). I used SEM Color Coat, which sticks to Lexan fantastically.  The edge and bottom are painted with Duplicolor's Metalcast red. It's basically a red tinted clear in a spray can, made to give chrome an anodized look.  It also sticks to the Lexan like a champ.
http://www.duplicolor.com/products/metalCast/

Here's how it looks. It's just taped together for now, the final pieces will be siliconed together to weatherproof the circuit board. It lights up nice and bright, and reasonably evenly. The dark strip is one of the bolt holes through the Lexan. You can't really tell in the pic, but unlit, the lens is a nice deep red.  Off:

On:

Just for kicks, here's what the blinkers look like lit up when they're installed.

That's all for this chapter.  The end is approaching... :)

Some things you just have to do right.

I've spent most of my posts explaining how to do things.  I'm going to take a minute now to explain a why.  Since I started fixing the Viper's body, one of the big things I've been harping on is the need to do things right to prevent future cracking.  I've also mentioned repeatedly how the previous "repairs" on the car weren't done properly.  You'll notice that I always put repairs in quotes.  With cracked fiberglass, you CAN'T just band-aid it, it must be done properly or it WILL crack again.  As with many other things on this project, the hood has again provided me a perfect example to demonstrate why.

 

Lets take a closer look at this crack here.  As I mentioned a few posts back, this crack appeared after the car had been "repaired."  That much is obvious because it's cracked through the primer that covers the "repair."  The question is why did this "repaired" crack come back?

Without the paint covering it up, the reason was very apparent on the bottom of the hood.  Here's where the crack is on the bottom side of the hood.  The white is the original panel.  All the 'glass on the bottom is stuff I added during my repairs(and before I repaired the front lip).  The stuff in the middle is just kitty hair(fiberglass reinforced filler) from the previous "repair."  You can see that not only is the crack still very much there, there are voids in the kitty hair and much of it isn't actually bonded to anything.  The crack is basically just bondo'd over.  While it might have looked smooth from the outside the structure is cracked and has no strength.

Grinding into the back side of the crack further shows how poorly this crack was "repaired."  Not only was the crack only glossed over on the top side, just below the surface on the back side there is no more filler.  There is just a large void under the crack.  So, we're left with a still cracked panel that has no reinforcement behind it. 

It's no wonder that this crack reappeared.  There's almost nothing holding the shattered fiberglass together.  The top side just has a skim coat of filler covering the crack.  The back side has a little filler just kind of holding the pieces together.  This, right here, is why so many repaired fiberglass panels crack again.  Covering up a crack doesn't address the problem, it just makes it look nice temporarily.  You can't actually repair a crack in fiberglass, you must completely remove the crack and replace it with new fiberglass.  If you just cover a crack with bondo or even a layer of fiberglass, it's not a matter of if the crack will reappear, but when.

ODing on crack

Working from the back forward, I got all the minor cracks in the Viper's hood fixed.  All that I had left was the front end.  I decided to do the repair in four stages, the two corners, the center section, and the front lip.  The previous owner of this car slid the passenger front corner of the nose under something.  When that happened, that corner of the hood was shattered.  I started with the most crunched area, the passenger front corner.  I assumed from the beginning that I would have to redo all of the previous work, but I didn't know just how bad it was until I started grinding away at it.

Almost the moment I started grinding, I started finding poorly laminated "repairs," and layers that weren't really connected to anything.  So I kept grinding.  And grinding.  And grinding.  Even though it had already been "fixed," there were still tons of cracks in the original fiberglass.  Like the previous repairs I've done, I ground out any and all cracks I could find.  I also ground out nearly all of the previous repairs.  Anything of the old repair that I did leave I left strictly as a backing for the new fiberglass I'd be putting in.  You can see just how much of the nose was replaced.  The white is the original panel, the darker color was part of the previous "repair".  Also, there was a block of wood under the "repaired" fiberglass.  Basically, I needed to rebuild the whole corner of the hood.

Ideally, you'd want your new fiberglass to be one big piece.  Because of all the curves and corners on this thing, that is neither practical nor possible.  You will never get a single big sheet of 'glass to go around all those corners and lay down flat.  Trying it will just lead to frustration and more grinding, trust me on this.   The next best thing is overlapping layers of smaller pieces.  Smaller pieces will lay down easier, and go around corners better.  Any time I do fiberglass work, I always plan where and how I'm going to position my pieces before I mix my resin.  I cut and lay my pieces down about where they will be laminated onto the panel, then lift the whole thing off and lay the pieces out on cardboard in the order and approximate location where they will go.  Pre-planning all this before I mix the resin allows for quicker layup, as well as keeps my scissors from getting sticky from cutting 'glass with resin covered gloves.  Here you can see how all the overlapping layers of fiberglass will be placed.

With everything planned out, all I had to do was mix up the resin and lay it up.  The pieces go on one at a time.  Lay a piece of mat on, saturate it with resin, work the bubbles out, and repeat.  Most of the new fiberglass is laminated to 1/4" thick, with many areas being even thicker.  You'll notice the color of the resin is different here.  As I've mentioned before, the Evercoat SMC resin uses standard bondo hardener.  I decided to use blue hardener this time, mostly because I have a big tube of it. 

With that done, I moved onto the other corner.  This corner wasn't nearly as damaged.  It also hadn't actually even been repaired.  Only one crack was "fixed," the rest were left from the accident.  So, like everything else, I ground out all the cracks, and the previous repair material.

Same deal as last time, cut the mat, plan the layers of fiberglass, and add some resin.

The third area I needed to fix was the center section.  This area had a big crack going through it and instead of laying in more actual fiberglass, it was just filled with Kitty Hair(fiberglass reinforced body filler).  Kitty hair in useful for some things, fixing cracks in fiberglass isn't one of them.  So, once again, I ground out the cracks and previous repair material.  This repair also overlaps my previous corner repairs.  Now, fiberglass won't stick very well to shiny surfaces, and cured fiberglass is (relatively) shiny.  Any time you put new 'glass over cured 'glass, you need to grind the shiny off of it.  24 and 36 grit grinding wheels work best.  Even though you don't have interlocking layers, if it's ground back like this the fiberglass should never have delamination issues.  Here you can see the cracks ground out, and my previous repairs ground back so the latest layer of fiberglass will stick.

Same routine, cut, plan, add resin.

The last section to do is the front lip.  I decided to do the front lip as it's own separate section because it has so much damage.  I decided I would just rebuilt the whole front edge.  It's also easier to manage as it's own section, and I wanted to lay it up very thick.  For the new front lip, I decided that the bulk of it would be built from the bottom, and only the outer surface would be rebuilt from the outside.  To do it I ground back all the fiberglass, both old and new, until I just had a very thin edge left to use as a guide/backstop. 

To backfill the lip, I laid in lots of long strips of fiberglass.  All in all, most of the lip ended up being around 1/2" thick.

That's all the fiberglass that needed to be added to the bottom of the hood.  It may not look like much, but to give you a sense of how thick most of the new fiberglass is, I used almost 30 sq/ft of fiberglass mat and 3/4 gallon of resin.