Step 51 : Taping / Masking hull details
Time to complete : 16 hours.
Total time to date : 270 hours.
Since I knew I was going to need my hole punches for this step, I decided to repair (not fix) those first from the damage they sustained from punching the heavy guage paper of my plans. If I ever build another hole punch, I will make it out of steel. The brass is just too soft to hold up to a good shot with the hammer. I thought I would go into some detail as to how I built these, since I would be basically redoing the process.
A piece of brass (steel next time) tube is used that is the right size. If you need a punch for a round hole, you're basically done and can move right onto the sharpening phase. If you need an oval hole, a little more work is required. Using a hammer, I pounded it into "roughly" the right oval shape. You will never get a nice semmetrical shape by just doing this, I tried. Pound the shape a little "thinner" than the oval that you need. Put a piece of brass rod (not tube) in your vice with about 1/4" sticking out. This piece of brass rod had to be the same diameter as the rounded ends you require of your oval hole punch. Pry your "slightly thinner" piece of brass tube open just enough to allow the brass rod to slip in. Place the end of the tube to be shaped over the brass rod. Pound....no, TAP...with your hammer until the end takes the nice round shape of the brass rod. Do this for both ends. The reason that you make it a little skinnier at first is that the process of rounding the two corners kind of pulls the sides the right shape and quite straight. Once you do the corners, just some fine tuning is needed by tapping with your hammer here and there. When you have the shape down, clean out the inside edges with a round and flat file, then sharpen the end with a grinder so that it cuts the mask easily. No rocket science involved, just some "blacksmith" work.
See, not very difficult at all. Now onto the taping / masking part.
I used 1/8" mask to do the outer hull brace lines (the heavier lines on the outer hull) and 1/16" mask to do the weld lines. I just masked right on top of the lines that I had drawn on earlier. The mask had to be applied 3 times in order to build up enough tape to make a nicely raised ridge. There is 280' of masking tape on this plug. ....I know....I couldn't believe it either. The 1/16" stuff worked great, but it's not cheap. I have about $60 invested in masking tape.
The purpose of masking the details like this is that once another coat of primer is applied, the mask will essentially be raised lines, representing the details of the hull, most notably, the weld lines. This raised detail on the plug will be transferred to the female mould, which in turn will be transferred to the casted hull piece. In short, putting these details on the plug at this point saves having to do all this detailing on every casted part. Hopefully, this proceedure will become more clear to those unfamiliar when I get to the step where I'm casting the parts.
Time to mask the flood holes. The moment of truth as to whether these hole punches are worth the effort. I put 3" masking tape down on a self healing mat and then just started punching away with the hole punches to punch out the "holes" out of the masking tape. The reason this is done is a little different than the weld lines. The flood holes are masked off on the plug at this point. When the following coat of primer is applied, the mask will then be removed from the plug, leaving a very slight indentation in the primer in the shape of the mask, which is the going to be the shape of the flood hole. This indentation, like the weld lines, will be transferred to the female mould and then onto the casted part. These lines on the casted part will indicate where the flood hole is, with the modeller using the lines as a guide to drill and file the holes from the casted part. Once I had the weight I needed to use with the hammer figured out, these punches worked excellently. Hit too hard, you damage the punch, not hard enough, you don't cut the masking tape all the way. I was able to punch out masking "holes" from the 3" mask very quickly and easily. Punching them out like this ensures that each "hole" is identical and accurate. Once the holes were punched, I just peeled the masking tape back. The "holes" remained stuck to the mat. I then picked each "hole" off with a hobby knife and placed it on the hull, using the previously painted on markings as a guide. I was very happy with how smoothly this process was going. If there is a better/faster/more accurate way to mask off flood holes, I don't know what it can be. Quite simply, if you are doing a build that requires the masking of flood holes, build these punches. Having said that, if I do it again, I will build these punches out of steel and not brass. The brass is just too soft to really give 'er. You have to be careful, it doesn't take too much of a hit with the hammer to distort the cutting edge of the punch. All in all, very happy with the punch idea. Thanks again Steve Neil for the idea.
The plug was now lined and masked, which gave an indicator of the kind of detail that the final boat was going to have. I was only becoming more motivated to keep working at this project the farther along I get.
More to come
"I don't have anything else planned for this afternoon." - Lt. Col J.O.E. Vandeleur
A Bridge Too Far (1977)