This is going to be some continuing documentation on the refit of my new-to-me 2010 Goodall C2 F18 cat.
My intention is to eventually race this cat, so a few goals are to make the platform as rigid as possible, the hulls and foils as fair and smooth as feasible, along with good sails and easy-to-use (fast) rigging.
The first major order is ensuring that the beam-to-hull connections are strong and rigid enough. One of Texastuma's recent posts indicated that he had inserted Time-Sert threaded inserts in his P18-2 hulls.
Brett Goodall responded to my query in facebook F18 group. He added a PDF showing the chainplate anchor assembly, which he indicates is the same as the beam bolt anchor assemblies.
Looking at the 'nut' in the pdf graphics, it might be problematic drilling it out to a large enough ID for a Helicoil insert or a Time-Sert.
After cleaning the aluminum nut threads, they don't appear to be too eroded. I'm quite hesitant about boring into the hull to replace those aluminum nuts. Hopefully they're still enough thread material to allow the prescribed 20Nm bolt torque (with grease) to hold and not strip.
So I thought that this pdf might be useful to someone else, too.
I'll resume my hull long-boarding/fairing after this very cold weather snap is concluded. I will need to repair some cracks that emanate from both LE and TE of the starboard bottom daggerboard well. I'm not yet sure if the laminate is also cracked, or merely the gelcoat.
I've been in the process of repairing a few faux-pas on the ol' C2 F18 in between the cold, wet weather days.
The port hull's bottom surface at the dagger well leading and trailing edges had cracks in the gelcoat. The port daggerboard also had a transverse gelcoat crack (parallel with the deck) approximately 12" down from the top of the board.
Hmmm. Perhaps a past sailor attempted to right the cat by jumping up and down on the daggerboard like a diving-board at the public swimming pool?
Anyway, I ground down the dagger's gelcoat at the crack with a DA sander using 80 grit paper disks. I didn't find any cracks in the underlying plain-weave carbon fiber. But there was a few little divots. So I vacuum-bagged a layer of 12-oz uni-directional CF onto the board over the small divots to provide a base material for leveling the surface better for an additional uni-layer of CF.
This pix shows the vac-bagging of the first layer of uni-CF.
Above shows the cured CF after the peel-ply and absorbent/breather layer was removed
Below is after sanding the new CF flush with the existing plain-weave CF.
Next task on this dagger is to vac-bag larger pieces of uni-CF over the full area of the existing exposed CF... just to ensure no more cracks show up. Then add new gelcoat to the whole board... actually gelcoat both boards.
It appears that a previous owner (1st owner?) had coated both boards with a graphite/epoxy coating and sanded it with a DA sander, leaving the tell-tail sanding swirls. Then, perhaps the 2nd owner applied white gelcoat over the 1st coating, with no real fairing involved, much like some portions of the hulls that he 'touched up.'
Above is a board after being faired with long-boards of 4"x24" and 4"x36", each of 120 grit sanding belts.
Today I dived into the exploration of the port hull dagger-well cracks on the bottom of the hull.
Being quite careful with a flapper wheel on a grinder, I ground-off the gelcoat over the thin cracks. With the aid of a magnifying glass, it appeared that the cracks from the LE and TE of the dagger well were not merely in the gelcoat, but also into the fiberglass laminates. After some penetrating dye testing, the cracks were more apparent.
So off came all the gelcoat surrounding the dagger well. The big belt-sander helped a bit, but I did most of the removal with 60 grit DA sander.
After grinding on the well's TE and LE, the dye was still visible. The cracks were not just skin deep.
Above, cracks emanating from the LE (leading edge) of the well are visible.
Same with the TE of the well.... crack still visible.
Dang.
Ok... let's grind DEEPER!
Here (above) I ground down into what appears to be 'bog' filler (bits of chopped strand mat (CSM) as a resin-filler) which was used to adhere the dagger well onto the bottom laminated surface. The red dye in two cracks is barely visible... likely cracks within the vertical parts of the well.
Above is the TE of the well, with the red dye visible in a crack, also within some bog.
Yeah, I ground down pretty deep.
Next I will likely grind down into the bog with a dremel and fill with high-density epoxy and ensure that the well liner at the bottom is water-tight.
Then, make a wood plug to insert into the dagger well, temporarily-seal that air-tight so that I can then Vac-bag some uni-fiberglass transversely into the low areas that I ground down.
After that is cured, I'll level-off (by sanding) the new laminates so that more vac-bagged laminates will lay fair.
Then fill and fair all the other little faux-pas on each hull and apply a few coats of gelcoat, then sand with the long-boards again.
She'll be like new!
@cat-scratch I am loving this so far, all the detail will help C2 owners thinking about a repair.
Please keep reporting as you go.
In the spirit of Easter Sunday and Resurrection, and the sad fact that there hasn't been any posts on this forum for at least six days, I'm gonna tell a story of some of the refit processes that I've been doing on the C2 F18.
So where was I the last time we looked at the C2.... Ah yes, I had ground down the trailing edge (TE) and leading edge (LE) dagger well areas on the bottom of the port hull in search of solid fiberglass (without cracks).
In order to vacuum-bag any laminates into the dished-out areas (LE,TE), I had to fill in the dagger well slot in the bottom hull surface with acrylic caulk for an air-tight substrate. Then, laminated a bunch of layers of alternating types of 'glass composing of style 477 fiberglass (4-oz, 4-harness weave) and a 6-oz unidirectional transversely-oriented fiberglass, all saturated in epoxy. These laminates were wetted-out on a piece of 6mil plastic sheeting, one by one, then another sheet placed over them, and some of the excess epoxy resin then squeegeed out.
This stack of laminates were placed on the carved-out TE area of the hull, minus the sheeting, vac-bagging materials placed over them, and vacuum applied for a few hours.
Same with the LE new laminations. Judicious use of the grinder (with 40-grit flap-wheel), DA sander, and a longboard with 120 grit, leveled those patches to the original hull bottom laminates.
But then…. I found evidence of water intrusion into the core material forward of the LE patch.
I drilled 1/16” holes into the existing top laminate into the core. Water. Dang!
I removed more and more gelcoat along the centerline toward the bow so that I could verify where the core appeared to be dry.
I even tried to evaporate the moisture within the core via vacuum bagging. After five hours of deep vacuum, the core was still saturated.
Decision time!
Gotta open her up and commit to major surgery.
Ouch!
Above shows the ‘cleaned-up’ inner hull laminate with a couple boo-boos in the core extraction process. Actually, I had to carve a bit more forward before I found dry core.
In order for vacuum bagging to work, I had to patch those inner laminate holes with some style 477 glass/epoxy, then apply a tight skim-layer of epoxy/colloidal silica to ensure an air-tight condition of that laminate.
Notice the bulkhead mortice/tenons?
This tenon (marked arrow) must be the locator for the dagger well bulkhead. There’s another tenon at the shroud chainplate bulkhead. They are situate directly on one side of the centerline seam.
Why mortice/tenons in this construction?!
So, why so much water intrusion into the core?
My guess is that it wasn’t solely from the dagger LE cracks, but from water intruding in from the bulkhead tenons while the boat was sitting idle, catching rain water, then freezing in the winters of the DC area of Virginia.
The freezing water separating the lower bulkhead adhesives, then the thaw allowed water to seep into the core.
However, it was not easy to separate the outer and inter laminates from the wet pvc core material…. So did I REALLY need to do this surgery? Would the patient be strong enough without it? Maybe. Maybe not. It likely would have been fine.
Oh well… too far along for second guessing.
Let's go!
Above: Vacuum-bagging a style 1708 laminate (17oz. +45/-45 unidirectional + CSM) onto the existing inner laminate. The existing inner laminate was very flimsy-feeling.
Above: New inner laminate completed. Nice, tight new laminate with perfect fiber/resin ratio. I love vac-bagging! No worries of improper, incomplete secondary bonding.
Now to trim and level the edges of the new laminate to the existing exterior laminates. Then…. Lay in some new pvc core (Divinycell).
Pix above: Previously-epoxied-in and vac-bagged 0.25” thick pvc core (green strips), sanded down to appropriate contours for the next exterior laminates about to be vac-bagged here.
I applied a skim-coat of epoxy/colloidal silica to ensure all crevices were full and the transitions were smooth. Not shown here, I laid down two layers of the 1708 cloth saturated with epoxy.
Peel-ply and breather cloth is laying in wait on the left side, with the vac-bag partially in place below the bagging site before laying down the epoxy-saturated laminates that were readied on the workbench.
And BAM! Exterior laminates in place after the bagging, with a little careful, delicate trimming with the grinder (sounds kinda oxymoronic, eh?). The grinder makes quick work of removing the excess laminate edges... but ya gotta FOCUS, or you'll be sorry.
Next, I will be adding another laminate of 6 oz unidirectional ‘glass transversely-oriented over the dagger well areas just to ensure adequate strength.
Then, a little faring compound, then gelcoat!
Is this fun or what?!?!
More to come…..
Happy Easter!
I haven't posted updates of the F18 in a while.
So here goes....
I guess I forgot to take pix of the last layers of uni-directional 'glass/epoxy that I vac-bagged over the whole repaired area. Too bad. Two layers, 6 oz crows foot (4H) over 10 oz uni. Came out perfect as usual. Sanded the edges to match existing laminates.
Then applied some West Systems 105 epoxy mixed with Microlight filler (reasonably easy to sand to fair compared to other fillers) with a notched plastic bondo spreader that I re-cut on the table saw.... 1/4" indexing to make 1/8" notches in the spreader, about 1/8" deep.
This makes longboard fairing much easier as you're having to cut through only half of the surface area and material volume. Plus, it creates only a 1/8" consistent fill depth.
I also filled in the divots left by the dual rear rollers of the trailer, as well as some other low spots on the hull bottom. I used one of the ancient 36"-long longboards that I had made 25 years ago or so, adhered a new 80 grit belt sander belt onto it and faired the those ridges down. Taking opportunities to verify fairness with a 48" long aluminum straight-edge, rolled fore and aft along different paths, ensuring a smooth 'roll.' Low and high spots show up immediately by the straight edge 'thumping' over lows and becoming 'high centered' over highs.
The only problem with the notched fairing method is that it requires at least three coats altogether to become extremely close to perfectly fair. Epoxy filler shrinks a bit, so to fully fill in the faired notched surface, two more coats are required.
Second coat. Nice.
Below: Some more fairing near the port bow. The internal bulkhead at the bridle chainplate didn't shrink as much as the hull skin did over the years.... high spot!... gotta try to fair in that high spot by filling in the adjacent lower areas.
So I got tired of balancing on the trailer while doing fairing work.... let's fix that!
Continued....
Yes. In previous posts I've described making PVC hull cradles... but never shown the methods.
Let's begin...
Start by cutting your 6" diameter cored PVC pipe. For these cradles, I cut four of them 10.5" long. Why 10.5"? Eleven inches just doesn't fit in my shop's toaster oven. DON'T USE YOUR KITCHEN OVEN! It might stink up your kitchen. Anyway, a miter saw works well, a hand-saw works well too.
Ok, now saw each segment down it's length. ONCE!
Let the saw blade protrude over the deck just enough to cut through the thickness of the pipe. Use the fence as a guide, obviously.
You could do this with a hand saw as well, or a jig saw, or being very very careful you might be able to use a circular saw ('skil-saw'), but be aware that there WILL be kickback from the spring-action of the pvc attempting to close.
The outside perimeter of these 6" PVC pipes is roughly 20". So mark the center of the pipes from the longitudinal cut (10"). You will pat yourself on the back later on for making these marks on both sides of each pipe.
Ok.... let's shake and bake!
Pre-heat the oven to 350 deg. F. I found it best to locate the longitudinal cut on the bottom. Also, use a cooking sheet on the bottom rack so that you don't scorch the pvc.
The pvc will get squirrelly, so best to watch it....
lest you scorch it on the top burners.
Reposition the two 'sheets' something like above. USE GLOVES! MIG welding gloves work well. Regular heavy leather work gloves will work if you don't mind the heat.
I reposition the pvc sheets and turn down the oven temp to about 300 F while I prep the hull (mold).
Yeah, I had the straps pre-positioned, brought the two hot pvc sheets and slapped them on the widest part of the hull, then strapped them down tight. Perfect. Be sure to align the center marks on the pvc with the hull's keel-line.
Be aware. The first time I did this the other day (not the very first time though) I molded both pvc layers at the same time.... the hull surface became a bit warm. If you're going to do it this way, I'd recommend putting a heavy towel or something to help insulate the hull a bit from the heated pvc. The second set I molded I molded the first layer, let both the pvc and hull cool, then added the second pvc layer to the first. That kept the hull a bit cooler. Not a big deal with vinylester hulls, but polyester hulls might revolt from the heat. I don't know.
Anyway, I take the pvc out of the oven when it is 275-285 deg F., or when it is pliable enough. Cored PVC becomes pliable at a lower temp compared to 40 schedule pvc.
I release the molding straps when the pvc's surface temps are around 140-150 deg F. They're stable enough at that temp range.
Now for the adhesion of the two pvc layers.
Abrade well the mating surfaces. I used a grinder with a 40-grit flapper wheel, then on the second set, I used a DA sander with 80 grit paper. Both worked ok and rapidly.
Next, wipe mating surfaces with acetone.
Slobber on your favorite polyurethane adhesive. I like PL-2000 in the caulk-gun size. I draw a thick bead of adhesive all around, near the perimeter and in the middle. Be aware that the goop in the middle areas will take longer to cure due to less moisture and air, so don't go nuts with mucho adhesivo.
Clamp the two pvc moldings together. And wait. 24 hrs?! Er, yeah.
After that, trim up the sides on the table saw, or whatever, and round the corners with that flapper wheel, or whatever.
Add some carpet or foam, and make a base to attach the cradle to whatever (trailer, dolly, um.....)
Ok.... there we have it! A nice hull dolly. Positions the hull at a perfect working height.
Yay.
Yup, Finnagan likes it too.