Fairing in prep for paint.

Yes, it has been a while since this blog was updated, but I have been suffering through the hell of fairing the boat and didn't really want to talk about it. Now it's all shiny and the plastic tent is gone and my shop is no longer a dusty pit. I still have to paint the boat, but that seems like less of a chore than fairing.

Many parts of the boat had fairly even gelcoat application and the boat was quite fair to begin with, so it could have been much harder. Areas where gelcoat spraying was difficult, the gelcoat was applied with a brush. When it was removed, it left deep ridges and valleys that needed to be filled and sanded multiple times. The cockpit, both sides of the seat backs and aft crossarm were really a chore to fair. The tan and reddish colors in the photo below are areas filled with microlight or low-density fillers.

The fairing started with some careful selective filling along the waterline and where the gelcoat was left under the wing.  

The light shining under the batten edge shows how thick the gelcoat is.

The copper color in the lower part of the photo is the copper/epoxy bottom that was applied in the mold. The light shining through is where the gelcoat used to be. 

Both of these areas had to be carefully filled before applying a thickened coat of epoxy to the surfaces of the hulls.

The gelcoat was faired in with my long, strait, and sharp edged application tool.

This step was done before filling the uneven edge at the waterline.

The waterline (all 105 or so feet of it) was faired in using a wide putty knife, applying pressure only to the edges of the knife.

A heavy "fill coat" was applied to the lower topsides over the still-tacky waterline filler.


All surfaces that had had the gelcoat stripped were thoroughly sanded and fill coated with epoxy and 410 Microlight filler mixed in at almost 50 percent by volume.
The fill coat was applied with a short (1/4") nap roller.
The nap roller will spread the thick fill coat mix out evenly (with lots of rolling), something that a foam roller can't do.

I used good quality rollers for applying the fill coat. A 9" roller cut in half worked well and was more economical as the rollers soak up a large amount of epoxy.

The fairing process was not pretty and not at all photogenic, I used mostly longboards with 80 and 100 grit for fairing and smaller plywood sanding blocks of varying thickness and stiffness for fairing really curved areas.
The method of rolling on a thick fill coat worked beautifully. The 410 microlight filler combined with WEST 207 hardener made for a fill coat that was both thick and easy to sand. This combination of ingredients seems to somehow flow out fairly smooth, even though it is applied thickly with a nap roller.

When fairing, the low spots remain easily visible as they are semi-glossy (unlike when fairing high-build primer). Low spots were filled and the surfaces sanded again.
I used multiple different knifes for applying thickened epoxy to low areas, from a 12" wide drywall knife to a 3" wide thin putty knife. All knives had sharp & straight edges.

Early on I realized that for me to get the boat sailing, I needed to lower my standards. I skipped steps that really should have been done to make the surfaces more fair or more ready for paint. That being said, what I did was pretty efficient time-wise.

I rolled (and tipped with wide foam brushes) a coat of 105/207 over the entire boat after fairing and this coat will be lightly sanded before paint. No primer will be used.

A gloss coat of epoxy has many advantages over epoxy primer. It "flows out" to make a smoother membrane and because it is glossy, you can see imperfections that may need more work before painting. Most epoxy primers stink for days after application and, while primer is softer for sanding, one is sure to sand through it in places, so there is no solid color advantage to using primer. Primer is also softer that two-part paints, so using epoxy instead of primer may make for a tougher paint job.

Like sanding the fill coat, sanding the glossy epoxy coat is made easier because it is glossy. It's easy to sand just enough for the glossy spots to disappear, without sanding through the gloss coat.
I had some seams in the gloss coat (because I broke the surface into different sections for coating) and even though I tried to thin the coating at these taped edges, the seams were still difficult to sand flat.
I use a thin flexible fiberglass plate sanding block for areas like this, using 220 grit sandpaper, which is appropriate for 2-part paints (photo below).

Most finish sanding is done with  a random-orbit sander. For edges and corners, a hard rubber sanding block and a foam rubber sanding block, all with 220 grit. Remaining glossy spots are hit quickly with a 3-M abrasive pad.

I have finally started painting and it is going well, even with two large exhaust fans pulling dust through my shop. Better some dust in the paint than to absorb nasty fumes.

We are taking painting photos in order to update our book "Rolling perfection", an e-book we sell about using Interlux "Perfection", a two-part LP paint.

I built a honeycomb & fiberglass hatch for the cabin. It's compound curved to fit the cabin and has a gasket notch machined into the edge.

The hatch is made from honeycomb with fiberglass skins so that it can let light into the cabin.
My previous boat had a honeycomb and glass companionway drop board and the light it let in was not only welcome but quite beautiful as well. Hard to show in a photo...

The hinges were made in a long blank from G-10 plate and G-10 tubing that were glued together before bagging carbon over the length of the blank.
I took careful photos of building the hatch and hinges and may do a blog post about it if there's interest.

The molded in rudder gudgeons had carbon reinforcement (this was visible without the gelcoat), but I did some reinforcement and clean-up anyway.
The holes for the pin were a bit sloppy, but it was super easy to remedy that, thanks to aluminum's thermal expansion.
The holes were drilled out to a larger diameter and opened up a bit at the upper ends to allow epoxy to enter. 3/8" hardware store aluminum tubing was waxed and inserted. Vacuum bagging mastic was used to seal the lower ends of the holes as shown before heating both upper and lower gudgeons with drop lights.  Epoxy was syringed in and because of the temperature, quickly flowed in to fill the void around the tube.
The drop lights were kept aimed at the gudgeons until the epoxy had fully cured. After cooling, the aluminum tubes pulled out easily by hand.

Gelcoat Chippin'

The gelcoat is finally off and was hauled to the dump today as a matter of fact. We didn't remove the gelcoat from the underwing (last photo), but it's off all other areas except for the forward beam, where it seems to be stuck quite well.
Was it a good idea to strip the gelcoat? It seemed like a good idea at the time. It was coming off easily in areas and I couldn't see patching in areas with epoxy only to have it start coming off somewhere else. The reality is that the gelcoat was adhered reasonably well in most areas and very well in others. Of course, there were some areas where it just fell off, but the final tally was only 70 lbs of gelcoat removed. Considering the work involved, 70 pounds doesn't seem like much. When I say work involved, I'm only halfway there, as the the boat still needs to be faired and painted.

Gelcoat removal never would have happened without a little help from my friends. Alex Spear got it all started just by stopping by for an hour or so every few days.

We quickly learned that warming the area with a heat gun set on low really helped. I bought 3 heat guns.

There may be a miracle method for removing gelcoat, but I don't know what it is. We used sharp chisels and heat. All of the chisels got noticeably shorter from sharpening, even my high grade Japanese chisels.

I think this means ours is the 9th G-32, even though the sail number is 10.

I have a gimpy wrist, so I added a very long handle to my favorite chisel so I could use both hands.

The heat gun is strapped to my forearm with an elastic bandage.
There's a foam pad in there to angle the gun up and just the right number of wraps this way and that to aim it in the right direction.
Most of the large areas came off with this goofy set-up.

The gelcoat stuck well to the copper/epoxy near the waterline.
I chipped from above to get down to the waterline. Pushing back and forth on the handle gave a slow controlled pace until the chisel stopped at the copper/epoxy edge.

Chuck Hosmer just chipped off the very last piece of gelcoat, that's why he looks so happy.

Chuck bought this G-32 new in 1992 and has taken good care of it until I bought it last year.
















This is what 70 pounds of gelcoat chips looks like. Did we catch all of it? No, this stuff really flies when it chips off. All of the shop shelves have gelcoat chips on them, even using plastic curtains. I'm sure that some of the kits we have shipped had a chip or two in them.
At least we didn't have to grind the stuff off. No Dust is good dust.

The remaining gelcoat can be seen below. It's an area about 12 feet long x 7 feet wide. It isn't stuck particularly well there, it's just hard to get at because my ceiling is so low.

The dolly I have been using to move the boat around the shop can be seen here. The cross-pieces are made from very strong Fir 2x10's with 600 pound casters set inboard of the hulls so that the flexing of the 2x10 make up for the uneven floor (to keep from wracking the boat).

The long fore & aft blocks spread out the load on the hulls and are placed where the watertight bulkheads are located. When jacking the boat up or down, the whole assembly is tied to the hulls to keep it from moving (see next photo).

I have been lifting the boat up and down with a screw jack from my truck (that's what the yellow cordless drill is attached to).  Lifting on center means that the boat can be blocked up relaxed (not twisted), but the underwing at the fwd end is not supported, so I use a long padded 2x10 to spread the load.

Straighter and stronger stems

 The bows on my G-32 had two issues that I wanted to remedy; they were misaligned and they were delicate.
The misalignment wouldn't bother anyone but me, but the rest of the boat is so beautifully fair and I didn't want to look at crooked stems.

The delicate part probably wouldn't bother anyone not sailing in the North West where floating logs are a menace, but I do sail here and this boat has plumb stems, so there's little chance of riding over a log.

In the G-32, the core stops about 2' back from the stems and it's solid laminate foreword of that, which is all good, but in my boat the laminating must have been done on a friday, because it was very thin in some areas and not thin in others.
In the builder's defense, it would have been very difficult working in the stem areas of these molds.

So, I wanted the stems to be stronger and I wanted them straighter and I got both with the help of wood, carbon, glass & epoxy.

 From a cardboard template I cut hard mahogany caps and glued them to the front edge of the stems

A long and stiff sanding block (with 40 grit paper at one end only) was used to bevel the stem caps to the plane of the hull surfaces.
This step was where the straightening of the stems happened. Compare to the photo above.









The new stem is obviously thicker than the old, so thickened epoxy was applied to fair the thicker stem into the rest of the hull.
Yes, this added weight, (I used over a quart of epoxy for fairing), but the filler had a benefit:  A layer of glass cloth was applied over the whole area as a final step  and that, with the filler acting as a core, made these areas of the hull very stiff.


Because the areas being faired were still flexible, the filler had to be applied carefully. Sanding a flexible area with a longboard doesn't really work. The flexible parts  yield and the firm part's don't, so only the firm areas would be abraded and unfairness would result.






Lot's of thickened epoxy was applied and then was carefully tooled or "swept" with a very stiff and sharp edged tool.








The tool in this case is a strip of cored panel that had one edge cut to 45 degrees on the table saw.
A straight and sharp edge is necessary and when using a strip of cored panel, one of the skins becomes the sharp edge.

I swept all areas a second time. The second pass is easier as there's less volume and the epoxy can be mixed thinner.
I did both on the same day for a good bond.

I did a bit of sanding and shaping, then scribed a centerline on the front edge of the stem cap.



























The stems were 5 sided and then rounded as shown using a block plane and both stiff and flexible sanding blocks.

 I wanted these stems to be strong. Did I say that?
A good whack of carbon seemed like a good idea.

The problem with laminating a bunch of fiber around the stems is thickness buildup, which means applying more filler to the sides.
To get lots of fiber without lots of thickness we had to vacuum bag the carbon.

The carbon shown is 9 oz (300 gsm) biaxial, which was quite conformable. We applied one layer as shown and another 4" wide strip that can be seen in photos below.

The bleed stack (that's what it's called) consists of a layer of peel ply, a layer of perforated film, and two layers of breather (fuzzy blanket material).

These layers were lightly glued together with spray adhesive in a big sheet and the parts shown were pre-cut from cardboard templates and placed on the wet carbon.
















The Vacuum bags were large rectangles with mastic applied to all 4 edges and pre-applied to the boat on one edge only. When the time came, I folded the bag around the stem, attached the other edge and then did the top and bottom edges. The corners of the bag were folded back as shown to allow working out potential wrinkles.

As you can see, nothing but the bag went over the sharp edges of the stem.This allowed visual inspection for wrinkles, where wrinkles would form. As vacuum Pressure was building, I pushed back hard on the bag as shown to move the laminate away and tighten the laminate around the corner.

The laminate looked fine when the bags came off. No wrinkles and little thickness buildup.

The thickness buildup can be seen here and the
remedy (another pass with the sharp-edged stiff & straight tool) can be seen below.

Thickness of vacuum bagged laminate can be figured quite easily if you speak metric.
Fot every 100 gsm (grams per square meter) of fabric, there is .1 millimeter of thickness.
I used 2 layers of 300 gsm fabric and had .6 of one millimeter of thickness buildup (not very much).

5.7 ounce (200 gsm) is the most commonly used carbon cloth. It takes 5 layers to make 1 millimeter of thickness.





     








































The reason the carbon laminate extends so far onto the upper part of the hulls is that we wanted to replace the stainless U-bolts that were in this location with fiberglass tubes that run right through the hull. The holes were cut with a hole saw and the tubes were carefully bonded in with epoxy.

After a bit more sanding, the foreward  26" of the hulls are glassed with 8.9 oz  "Rutan" cloth. We did this one side at a time, (the opposite side done the following day) wrapping the glass around the stems each time.

The glass cloth pieces were rolled onto a length of cardboard tube when flat on the bench, which allowed rolling them onto the wet (with epoxy) vertical hull sides in a controlled, wrinkle-free way.









 The excess cloth was trimmed with scissors to allow just enough cloth to wrap around the sharp edges.
This cloth was wet out around the edges (with the roller) and then held in place with small squares of light peel ply as shown below.

For this to work, a light film of epoxy was rolled onto the opposite side near the edges for the peel ply to stick into and the peel ply pieces are stretched around the corners, making the glass behave like it wouldn't otherwise and making sanding the edges later a breeze.

I also added strips of peel ply to the aft edges to smooth the cloth into the the hull.















Yes, I had to sweep the whole thing one more time with the long straight thing.
I was able to do this the same day, so this was like the fill coat and fairing all in one. I always like for things to be fair without too much sanding... Don't know why.

The G-32 has a copper/epoxy bottom that was applied in the molds. Under the wing deck where there's no sun exposure, this copper bottom is still shiny and smooth. Everywhere else it is oxidized  and green, but a light sanding and polishing makes it look like a shiny penny again.

We had to re apply copper/epoxy to the bow areas, which was easy, just mix the copper powder into the epoxy (lots of it) and roll it on. I warmed the areas with a heat gun while I was rolling and then tipped with a wide foam brush.

I don't know where to buy this stuff, but I asked Tom Pawlak, my favorite tech advisor at Gougeon and he sent me a small can that had been gathering dust on his shelf for decades.


The "Rutan" cloth we mentioned above  is a type we use a lot of and sell with our kits.
Hexcel 7725 is a glass cloth developed with the help of Burt Rutan for his composite aircraft. The fibers are very fine and lay relatively flat (2x2 twill weave).
While it is a bit different to work with than regular cloth, this stuff is very strong for it's weight and thickness and takes less epoxy than comparable weights of cloth.

There is a unidirectional version as well (7715) and both are available in cut lengths from Aircraft Spruce & specialty.

Forward crossarm / Headstay attachment

The forward cross beam area got a bit of a critical look the first time I ever saw the boat. It seemed like the lower edge of the trampoline could attach to the underwing to clean up the aerodynamics and I also wanted to make the structural part of the headstay attachment point really strong.

I'm doing many things to this boat (while it is in the shop and stripped of gelcoat) that may or may not be necessary, but I'm doing what seems right to me with the view that this boat may have some hard sailing in it's future.

This photo shows the original trampoline and the stock aluminum strap bobstay.

As can be seen, I went a bit nuts in this area from a structural point of view, but I figure that if this had not been a production boat, a lot of these areas would have been tied together in a similar fashion to what I have done.
In this boat, the headstay loads are taken in an unusual way for a catamaran.  it is more like a monohull with a bowsprit, where the headstay loads are transferred to the bobstay and the bowsprit is in compression.
This photo shows that the "bobstay" is now a carbon tube and the "bowsprit" part has been tied into the cabin front and hulls with carbon tapes.
The front crossarm is now tied to the hulls with carbon (was mechanically fastened before), and yes, there is now a carbon chainplate for the headstay.

Notice anything different between the two photos? The gelcoat chippers have been busy.

I cut away the flange that joins the upper and lower halves of the boat at the cabin front. I did this with a sawzall and what's left of that flange can be seen on the right.
I wouldn't do this again most likely, but the idea was to reduce obstacles for the trampoline (and air and water) to pass by in this area where lots of air and water will be passing by.
Biaxial carbon tapes on both the inside and outside will more than make up for cutting away the flange, but the work involved was significant.

 A relatively simple job was carbon taping the forward crossarm to the hulls.
The gelcoat seems to be well bonded to the crossarm, but I removed enough for the taping with chisels, a scraper, and a sander.


I applied filled epoxy to the upper & lower edges of the flange (straight parts) before filleting around the beam ends to make it possible for carbon to wrap around the sharp fwd & aft edges.

 

After a thorough sanding, two layers of light woven carbon were applied to the upper and lower edges of the crossarm ends.


These were cut to a length that did not extend past the fwd and aft ends of the beam to make it possible for the next step.

A large patch of heavier twill weave carbon was added to the forward and aft ends as shown. These pieces were able to conform around the complex shapes before applying peel-ply to all but the really complex curved areas.
These areas will take some carefully applied filler and some careful sanding before painting.












The carbon chainplate and carbon-tube bobstay were a bit over the top, but I have never related to metal all that well and like to get rid of metal parts whenever possible.

I have made lots of carbon chainplates, but this one is most unusual, being attached to the front of a crossarm and then tied to a carbon tube "bobstay".

I won't try to explain everything I did here, hoping that you won't fall asleep.  The pictures will provide the general idea.

I toyed with many ideas, including suspending a stainless thimble in just the right place and winding carbon strands over it and down onto the carbon tube, but the eventual method was to make a chainplate that tied around the forward edge of the crossarm and in a second step, tie the chainplate to the carbon tube.

These two photos show what the chainplate was formed around.
The aluminum shaft was used as a mandril to make a light fiberglass tube.
The fiberglass tube has a wedge of epoxy with low-density fillers bonded to it as shown. That step was easy, I just laid the tube on a flat waxed surface and applied epoxy with a wide putty knife and block sanded later.

The laminates for the chainplate were cut from 9 oz (300 gsm) unidirectional (uni) carbon and 5.7 oz (200 gsm) woven carbon cut on the bias so that the fibers ran at 45 degrees to the uni pieces.









THE NEXT SIX PHOTOS SHOW ONE "WET LAYUP.

The laminates were fully wet out with epoxy on a piece of plastic taped to the bench.

The unidirectional layers were wet out before applying and wetting the woven pieces to them.
A putty knife was used to lift a corner of these pieces off the table for application.

The longer piece in this photo was not used because we ended up with more thickness than expected.









The resin-rich layers of uni (with bias -cut woven layers underneath) were applied to the tube-with-the-wedge-thingie one by one and pressed firmly onto it by hand from top to bottom, layer by layer.
The thingie had thickened epoxy applied to it first.

Thickened epoxy was applied to the front of the beam. A bit too much down low...

Note the hot-melt-glued together and clamped-on rod-holders....

The wet laminate-on-the-thingie were brought to their new home and applied as shown.

Heavy roller pressure were used to both pull the laminate downward and to force it firmly onto the beam.



This was allowed to cure and was sanded and shaped a bit with a random-orbit sander.

                                                       

THE NEXT 7 PHOTOS SHOW ANOTHER "WET" LAYUP, THIS ONE VACUUM BAGGED.

The laminate above could have easily had some extra long layers that would tie the chainplate to the carbon tube (bobstay), but no, I wanted to vacuum bag those layers in a separate step to compact the strips of uni onto the tube.

The photos make this chainplate look massive and it is a bit large for the loads involved, but it does get trimmed, notched, and drilled.

These strips of uni were mostly applied on a slight diagonal so that they would wrap around the tube with lots of contact to the tube and the strips were narrow so that they could pass the beam/tube intersection without wrinkles or puckers.




Most of the layers came up over the top of the chainplate and onto the crossarm. They were left "bridging" as shown and then pushed into the corner when vacuum bagging to help tighten the laminate and keep wrinkles from forming at the top of the chainplate.

The uni's were covered with bias-cut woven carbon.
I had ground the flange away to laminate the chainplate, so carbon was applied there as well to tie the beam back together.

Vacuum bagging laminates requires many layers of stuff that all go in the trash afterwards (consumables they call them) and since there are many layers, there will be many photos.

The entire wet area is covered with peel ply and then perforated film.
Most of these pieces were cut before hand, so applying them was easy.

The peel ply sticks into the wet epoxy, but all the perforated film parts are lightly sprayed with spray adhesive while laid out on a scrap of cardboard and then applied as shown.
Overlaps and wrinkles are placed in areas where bridging could occur in both the peel ply and the perforated film to allow those non-stretchy
materials to push into the low spots

and inside corners.




Layers of breather (fuzzy blanket material) are taped in place....











Vacuum bagging an area like this requires a bit of planning and a bag that is cut much bigger than seems necessary.

 This piece of bag film had just the tips of it's corners taped to the bench, stretching the bag tight before applying the mastic to the edges all the way around.
The mastic should be as close to the edge as possible to avoid the edges of the bag folding over into the mastic.


This bag was applied by draping the bag over the area with half of it hanging off the front of the beam. The backing was peeled off of the mastic just where needed to attach the bag to the top of the "bowsprit" before folding the hanging part of the bag back to wrap around the tube, joining the bag on the way up to the underside of the bowsprit, then splitting off to meet up with the top half of the bag.

The breather can be seen absorbing epoxy through the holes in the perforated film and the vacuum hose can be seen on the upper right of the photo.
Patches of breather were placed over the end of the hose.

The lower end of the carbon tube was also "bagged". Long, narrow strips of uni run from the tube well out onto the underwing. These strips were run a bit off-axis, so that the strips crossed the tip of the tube on center, but the upper end of the strips wrap halfway around the tube and the lower ends of the strips fan out onto the underwing.

One of the risks of vacuum bagging laminate is having wrinkles develop and we got some here. I filled over these areas with thickened epoxy before sanding.












It looks a bit more aerodynamic after a bit of trimming with a hacksaw and sanding blocks.

Grinding the flange away was necessary, but I could have just removed the flange just where the chainplate went.
After the paint goes on I want to forget that I was a hack, so the hollows either side of the chainplate must be filled.

Since it's so hard to shape areas like this by sanding, I did it as shown and it didn't take long.

The skinny clamped-on stick had a strip of plastic tape stuck to the aft edge and was clamped with it's lower edge parallel to the flanges.

The blue tape was placed carefully and stuck down well before lightly thickened epoxy was poured from the top to fill the void.

After popping off the stick, the top edge had to be filed down the the thickness of the flange. A small fillet was applied to the top edge to make the final radius from flange to beam.







The holes are for another time, though I can tell you that the lower one has something to do with the bowsprit attachment.

The new trampoline was patterned before all the above was even a twinkle in my eye...
Compare this photo with the one at the top of this post.