The first half of the mold is done; the other side of the plug has been waxed and will be gelcoated tomorrow. There'll be a second coat of gelcoat on Thursday and fiberglass will be added Friday evening. If all goes well the mold will be ready for use by Monday.
In 22 years of mold-making I never have - I'll drill at least 10 holes for bolts through the keel flanges before removing the mold from the plug. When bolted together the mold alignment should be fine. In this case there are several shallow defects in the gelcoat of the keel flange that will act as keys. I'm a little concerned about the gelcoat defects on the flange; there might be some on the mold surface that will need filling and sanding and delay hull production. This is a rare occurrence and puzzling because the catalyst to resin mix was carefully measured and well stirred. It's possible that I applied the second coat of gelcoat too soon (after 12 hours) though the first coat was hard. This time I'm going to wait 24 hrs before more gelcoat is added. I always use a lot of gelcoat in case there are defects in the mold surface to sand out.
I've just had my first mold failure in 22 years. The old MEK catalyst I used must have been defective (I didn't think it had a shelf life and was using it up before starting on a new bottle.) It was carefully measured at 1.5% and well mixed but the port side had areas of resin that didn't get completely catalyzed and ate through the gelcoat and the Zinsser paint on the plug. The port mold surface is severely damaged and may not be repairable with bondo. There's quite minor damage on the starboard side, though more than I've ever had before on a mold. I can make another port side if it can't be fixed with bondo but the plug is damaged and will take ~2 weeks to fix because I'm back to work full time. This means I may not have a usable mold before the weather gets too cold for hull production. Bolt holes drilled before removing the mold from the plug. Photos of extensive port side damage due to incompletely catalyzed resin. Damaged port side of the plug - not as bad as the mold and repairable within 2 weeks if necessary. The relatively limited damage on the starboard side - easily repaired with bondo.
All is not lost! I realized all of the mold defects were voids so could be filled. After 2 1/2 hours work with bondo and sandpaper this evening the relatively undamaged starboard side is patched and ready for fine sanding and about 1/3 of the major port side defects have been filled and sanded smooth; the bulge surface is shaping up nicely. I found more voids under the port side gelcoat after sanding the first application of bondo; those will be filled and sanded tomorrow. I expect to finish repairing the mold by Monday evening so the mold defects will have delayed hull production by only 2-3 days.
The mold repairs are almost finished. I thought I'd be done yesterday but sanding of the bondo along the bulge thinned the gelcoat enough that small cracks appeared over new previously unseen voids. The voids were all small so I opened them and used Tamiya model putty as filler - it's softer than bondo so can be sanded with finer sandpaper and not remove as much gelcoat. The mold will be waxed tonight and the first hull should be done by Saturday - a week later than planned. Evening: The repairs are finished and I'm waxing the mold - photos tomorrow. It was impossible to get the surface of the repaired bulge perfectly smooth but all of the defects on the hull will be high and the vast majority are very small. Thicker gelcoat will be applied over the repaired areas so the high defects can be sanded smooth, but depending on window location there might be no visible imperfections when the hull is cut out. I'm a little concerned about the durability of the mold because there are probably more undetected voids. I hope to get at least 3 hulls out of it in the next 3 weeks. I plan to repair the plug over the winter and make a new port side of the mold in the spring.
Mold photos: Close up of extensive port side repairs of crazed gelcoat and underlying voids, using Bondo and Tamiya putty. Nearly all of the imperfections will be removed when the windows are cut out. A new port side of the mold will be made in the spring but this one will give me a hull to build as a heavy cruiser (Hawkins) or faster light cruiser (Effingham) during the winter. Waxed and ready for use. The forecast has changed so I can apply gelcoat tomorrow, fiberglass on Thursday and potentially have the first hull out of the mold Friday evening.
Ralph Coles just had problem with a defective batch of gelcoat from the same supplier and had to strip it out of a mold; sometimes things go awry even if the procedure is done correctly.
Success and Failure: Success: The first Hawkins Class hull turned out well. The port bulge sanded completely smooth, which I didn't expect to happen. However, this is what came out of the mold ~90 minutes earlier (port side): Despite the mold having been heavily waxed and buffed (5 times) much of the bondo used to repair the mold stuck to the hull, as did a small amount of the Tamiya putty. Apparently mold wax doesn't work on those fillers. Luckily they hadn't bonded chemically to the hull so a small wallpaper scraper and wet #320 sandpaper removed all of the gunk and left a smooth hull surface. The Failure: The mold is unusable unless repaired again, this time with gelcoat. The molding process revealed even more port side voids (as seen below). I could repair the port side of the plug and make a new port half of the mold, but doubt that can be done before the temperature gets too cold for molding hulls. That means there will probably be no more Hawkins hulls made until March or April. To think that all of this was probably due to using an old bottle of MEK catalyst when I had just bought a new one! This is my first mold failure in 22 years of making 1/144 scale hull molds.
I started to repair the plug this evening and discovered the Zinsser paint had dried in a stretchy film, had not adhered well to the spackle, and lifted off the spackle in many, many places during the mold making process. Looks like dozens of shallow blisters. I'd always used dry wall compound in the past and the Zinsser bonded to it well. Even worse, there's no way to hold the starboard side of the mold tightly enough against the plug to make a new port half. I would have to repair the entire plug, peeling off the Zinsser and respackling, and make a completely new mold. Now that I'm back at work full time that could take months. So, back to the port half of the mold. I'm removing as much bondo as possible, breaking open all the voids I can find, and will fill all the defects gradually with small amounts of gelcoat. This will be slow but a lot faster than resurfacing the entire plug and making another mold.
I've marked the hull windows for removal and wondered where to put the bulge stringer. On the Canarias and Cumberland I ran it along the top of the bulge where it met the hull side but that made part of the 1/4" waterline strip impenetrable ('legal' though). I moved the bulge stringer further down on the Hawkins hull so it'll provide support to the balsa where it bends the most, help prevent ram damage and hopefully block some below the waterline hits. Thanks to the hull angle aft there's not much penetrable area near the stern between the 45 degree point on the curve and the waterline. (Same as with the Canarias/Kent Class hull.) Repairs of the hull mold have started: most of the bondo was removed and 2 applications of gelcoat made to the recessed defects and voids in the mold surface. Wet sanding later today, then more applications of gelcoat, more sanding etc. It might be usable in 3 weeks, which would give me time to make 2-3 more hulls.
Well, the mold may have problems, but that first hull looks beautiful. I'd still move the stringer back up to the crease at the top of the bulge, that's the real weak spot.
Thanks Commodore. I'm pleased with the hull - that's the 'bad' (port) side in the photos. I'll move the stringer as you recommend - it's more likely to stop BBs there than 1/2" below the waterline. There might be more hulls sooner than I expected. I spent most of yesterday and this evening repairing the port side of the mold and have nearly finished restoring the bulge surface. The big defects at the bow and stern are filled and sanded. There are about 40 minor low spots left after sanding. A few more light applications of gelcoat will fill them. It'll take 2-3 days to restore parts of the edge where the upper bulge meets the hull side and a couple more to repair voids along the edge of the mold where it meets the flange. Repair of the starboard side will take 1-2 days. The repairs could be finished in a week. A warmer than normal fall is predicted so there should be time to make 2-3 more hulls.
I took a break from sanding mold repairs today - I've been wearing off my right fingerprints! Back at the mold tomorrow evening - all defects have been filled and sanded and the port bulge shape has been restored; fine sanding tomorrow evening, then waxing. If the mold holds up I'll be able to make a few more hulls by mid-October. Fiberglass decks for HMS Hawkins have to be made and installed asap - cold weather is coming.
Hull #2 has been laid up. I have to make another HMS/HMAS Albatross hull tomorrow, then Hawkins hull #3 on the weekend if the mold is OK after #2 is removed. I don't have any more Hawkins Class hull orders so will make a fiberglass deck for my model and cut out the hull windows next week.
Hull #2 turned out fine but very small sections of the mold surface detached, mostly flakes of the final layer of gelcoat used to repair the surface after the first pull. Two more voids were revealed but can be repaired easily. I'm inclined to not repair the small areas that lost chips of gelcoat because what came off was mostly less than 0.25mm thick. All the resulting defects on a hull will be high, thin and easily sanded off in a few minutes. Colder weather has arrived earlier than expected so by the time the mold is repaired (next week) it might be too cold to make a third hull.
Unusually cold and wet (rain and snow flurries) fall weather has shut down Hawkins hull production for this year. The plan was to make a 3rd hull after a quick mold repair last week but one of my Scotties became seriously ill and after a few days of treatment had to be put down, so the mold repairs didn't get done. I'll be working on my model of HMS Effingham over the winter and will be able to resume hull production in late March or early April. Work on the Java and Tre Kronor hull plugs will start in early November.
