We've reached the most time consuming stage of hull plug construction. The basic shape is quite good but there are small defects to fill and sand, and fill and sand, again and again until one accepts the plug will never be absolutely perfect. I brought the plug home tonight and will take a break from the IJN Ibuki build to finish shaping it. Hopefully it will be done this weekend. When finished the upper and lower hull sections will be separated, mounted on bases for molding and given several coats of Zinsser sealer/shellac before waxing and the addition of molding flanges. The plug I made several years ago for my first I-400's hangar is shown atop the hull plug. It's a good match to the new plans so only requires some minor repairs before a new mold can be taken from it. The first mold was damaged when I made the hangar for my I-400. The conning tower mold is undamaged and can be used for our new subs. Bob
I'm still skim coating and fine sanding the I-400 plug. Some low areas between ribs are nearly corrected - another couple of skim coats should do it. Unfortunately we used balsa for the box keel and it's been damaged during plastering and sanding so its sides are now 'wavy'. This is going to be a major pain to fix because when the keel's sides are sanded the hull bottom next to it gets abraded too. The work is going slowly because I can't sand much inside (the dust goes everywhere and we just finished cleaning the entire house after having some walls replastered). The weather is crappy, with heavy snow today and rain for the next 4-5 days, which limits sanding time outdoors. The mold completion date is likely to be pushed back to late April/early May. The plug's shape is pretty good now but I want it to be better before molding. Bob
Most of the lower hull has been sanded smooth and given several coats of Zinsser sealer/shellac. There are a few areas that still need more filling and sanding including one cross-section near the bow that was too wide on the plan and needs to be filed down and replastered. The lower hull will be ready to have the molding flange attached by the end of the long Easter weekend. The upper half needs some reshaping at the stern and installation of the floatplane catapult before it can be sealed, so it should be done within a week. Bob
After several coats of shellac and some fine sanding the sides of the I-400 hull plug are smooth. The stern is OK but the ribs are still noticable along the entire bottom and the bow is a bit asymmetrical. I'm going to put some more skim coats of plaster on the bottom, file down one side of the bow and skim coat it again. Still on track to finish the plug over Easter weekend. Bob
Hangar plug with upper hull section behind it, with a fresh coat of drywall compound on the deck. Today I started repairing a wooden plug made years ago for I-400's hangar mold. The conning tower mold is in excelllent condition but the hangar mold's gelcoat was badly damaged in removing the first hangar. We need a hangar mold for our new I-400 hull, so the old plug has to be fixed. The damage was to the plastic wood used to mold contours between the 'planked' basswood hangar deck and the main piece of the hangar plug that was carved from pine. Chunks of plastic wood came off when the mold was removed from the plug. The final coat of plastic wood has been applied and will be filed and sanded to shape, after which the plug will get several coats of Zinser sealer/shellac before waxing. With Kim away for 2 weeks I've taken over the kitchen table, where the lighting is far better than in the basement. Here you can see the nearly complete lower hull plug and the far from complete upper hull plug, with the wooden hangar plug to the left.. Upper and lower hull sections separated without difficulty. The lower hull section has received multiple coats of Zinser sealer/shellac over the last 5 days, each of which was sanded smooth. I used the paint on type first to fill minor depressions in the surface, and am finishing up with the spray, which is gradually filling the remaining minor defects in the surface. Each layer has to dry before being sanded. I started Thursday evening and been at it over the 4 day Easter long weekend. As a result nothing was done on the Ibuki, which can be seen in the background. The plug posed some major and unexpected difficulties in shaping because we didn't get the frames cut out and glued to the keel accurately enough. As a result the bow was quite asymmetrical port to starboard and there were humps and dips between amidship frames. In fixing the bow I had to recontour the port side, which was too bulbous. The type of expanding foam used was softer than the brand I normally use, so as I sanded areas of plastered foam would collapse inward. I had to dig those areas out, fill the holes with plaster, sand and shellac, only to have adjacent areas collapse. I ended up rebuilding quite a bit of the port bow. I think any remaining minor hull defects can be sanded out of the mold, so extra thick layers of gelcoat will be applied when the mold is made. Here's the nearly complete lower hull plug and the upper hull plug, which has also been a major pain to work with. The hangar plug is at top right showing its complex shape. The upper hull plug had areas of asymmetry along the sides due to the framing being a little off, but most have been corrected. The main problem is the deck. The deck had been sanded but wasn't completey level, being lower to port in some areas and to starboard in others, and rarely flat all the way across. I tried to sand it flat but the skim coat of plaster was thin and the foam was exposed. I bought pre-mixed drywall compound this morning and gave the deck a thick coat. In 24 hours it'll be dry enough to sand. I hope one or two coats will be enough to get a completely flat/level deck, after which it'll be sealed and shellacked, then returned to Steve Hill to have the catapult made and installed at the bow. At that point it'll be ready to mold. Bob
Hey Bob, When you remove the plug from the mold, is the plug destroyed with the drywall compound flaking off?
If the plug has been sealed with Zinsser shellac and waxed thoroughly it'll come out intact. The last 2 molds I made were for HMS Vanguard and HMS Duke of Edinburgh - those plugs came out of the mold without a scratch. One of my first molds was a different story. I waxed the unsealed plaster surface of the Espana plug at least 10 times but it still stuck to the mold's gelcoat and had to be chipped out of the mold. The mold was OK after much sanding but the plug was completely destroyed. The problem with my original I-400 hangar mold (made in 2002) was that I didn't seal the wood and plastic wood plug with Zinsser, so the gelcoat stuck to the plastic wood despite the plug being waxed. Bob
I see the last set of photos appeared twice. I edited the first post to fix some typos and now there are 2 copies. Maybe Justin can remove th 12:22 post. Bob
I sanded the skim coat on the uneven deck this evening and it turned out almost perfect. The entire upper hull plug got another skim coat tonight so with careful sanding tomorrow it should be finished and ready for the Zinsser sealer/shellac. Then it can go to Steve to have the deck catapult installed at the bow. That'll leave me with the hangar plug to finish while the other guys make the molding flanges for the upper and lower hull sections. Bob
This morning's (April 16, '09) photos of the I-400 plugs: Above are the completed lower I-400 hull plug and the repaired and shellacked 2002 hangar plug on the upper hull plug. As received, the upper hull plug had been sanded to the wrong shape at the stern, having a flush deck all the way back. You can see it's being corrected to match the plan. Here's a closer view of the stern. In reshaping it to match the plan I again broke through to the expanding foam which had to be removed and the resulting voids filled with drywall compound. I used a coarse square file and then a fine Swiss file to shape the pointed end of the casing deck. It was too low because too much material was removed by preliminary sanding, so it's been built up with more drywall compound, this being the final skim coat. For some reason there appear to be diagonal lines across the top of the hangar plug, although they aren't really there. View of the wooden hangar plug with it's very complex shape. You can see the area to port that matches the outline of the port half of the conning tower. This thing was a real pain to make in 2002 so I'm very glad the repairs worked and I didn't have to do it all over again. Once again we see non-existent diagonal lines on the hangar's top deck. The 'planking' on the basswood hangar deck is visible. Port quarter view of the hangar plug. You can see a little bit of plaster requiring final sanding on the port deck edge. I'd planned to finish reshaping the stern tonight but was too tired after 2 hours of fencing practice. It should be finished and sealed/shellaced tomorrow PM. All 3 plugs will be on display at the Maritime Museum of the Atlantic model ship show this weekend, along with my I-400 built from a modified Battlers hull. Bob
Thank you for sharing this detail. It's very interesting to see all the hard work and meticulousness you put into the plug.
I'm not sure. Steve Hill had two types at home. One was for sealing around newly installed windows and was low expansion. It was softer and I think that's what I was dealing with at bow and stern. Steve wasn't happy with it and removed most of it from the plugs. I think the next type he used was by Dap which expands much further and is harder when cured. Bob
if you're in Canada you can buy it at Canadian Tire, Home Depot, Kent Building Supplies and similar stores. I don't know where it's available in the US. Bob
The three I-400 plugs have been mounted on their baseboards and will have midline molding flanges attached this week, after which the 2-part molds can be made. Waxing of the lower hull and hangar plugs has started but the upper hull still needs to have its bow aircraft catapult made and installed. If all goes well the molds will be started this weekend and should be ready for use in two weeks. Bob
