Wednesday, January 11, 2017
Loft without a loft
I want to preface this whole thing with the fact that this is what is required for THIS design and may be different on another design. The reason being is that I already have CAD (computer aided design) renderings of my design and lofting is not really necessary. CAD verifies all the dimensions to within a 1/32" and provides frame bevels, dimensions and angles.
However with that said, partially lofting the boat is still recommended by Mr. Buehler as the lofting will provide an easier way to lay out your rabbet line and patterns. Additionally, I have found it has given me a some scale to the project to understand how I'm actually going to build this thing. The loft gave me a full size pattern of the keel which allows me to understand how it will fit in my boat shed and an understanding of the necessary placement of tools and equipment.
My biggest problem to start was the fact that I could not find a large room with a wooden floor that I could drive nails into. In George's book he recommends a school gymnasium, but I think my local school may have an issue with me driving nails into their floor regardless of how high my taxes are. Equally intolerant would be my lovely bride if I started banging nails into our hard wood floors.
So the only thing I could think of was to create a temporary loft floor in the boat shed. I added additional 6x6's to my building cradle every four feet. I then laid down the OSB I purchased for my framing table lengthwise and screwed it down. I rolled out my red rosin paper (bought a 100' by 36" roll at home depot for $13) and used masking tape to hold it in place.
Obviously this platform is much to small to loft the whole boat, and even the entire keel would not fit. However I was able to put all the stations on and was able to mark the rabbet at every station except the first and last one. The other trick was the fact that I did not have a baseline to work off of. I moved my baseline up to the bottom of the OSB and made my measurements from that point. This required a little math but I kept it simple and used 12" as the number to subtract from the stated measurements. The only downside to this is that the very aft end of the keel was less than 12" so it could not be drawn in its entirety. I chose 12 inches based on the dimensions stated in the design and I go into more depth on that subject on the building video on my YouTube channel .
I then used my 300' surveyor's tape measure, 25' tape measure, 48" drywall T-square, chalk line and various colored markers to lay down the points indicated in the plan. It was not difficult provided you are careful with your measurements. Having the CAD file allowed me to take my own measurements in the program for dimensions that were not specifically indicated which made the process much easier. CAD also allows you to take exact measurements of the angles of intersecting parts of the design, very helpful.
My first step was to use my chalk line to snap a line for the bottom of the keel. I then drove some 8 penny finish nails at each station on the rabbet measurement. I later learned that you should actually drive those nails the thickness of your batten material above the rabbet measurement. I then used some 1/8" plywood as a batten to draw in the rabbet line. On some stations I had to secure the batten in between 2 nails in order to get it to remain firmly against the designated point and maintain the fair curve. The batten was 8' long so I would draw in about 6' worth of the rabbet line at a time and then slide the batten down another 8 feet to the next station nail and repeat the process.
It's difficult to see the rabbet line in the pictures but if you click on them you get a large view which makes the lines visible.
I then plotted the points for the top of the keel at each station. Once again the availability of the CAD format made it much easier to accurately draw in a true representation of the top of the keel. The top of this keel was not a smooth fair curve as there were a few ups and downs for the various keel lamination's and the shaft log.
My overall impressions of the process for the beginner was very good. It's much more difficult to read about it then to actually do it. At least for me anyway. Additionally, since this was just a partial loft I was not drawing in diagonals or buttocks or anything that difficult. I had no need for a traditional loft as well as the fact I will essentially be lofting each frame at the framing table when I get to the frame construction. So while it seems lofting can be intimidating, George's design's at least, are relatively easy to do.
My goal for the loft of the keel was to have something to make full size patterns from for the keel. I will use some more of the 1/8" plywood as pattern material to mark each station and it's rabbet. Once I get my keel lamination built up it will be easy to lay the pattern on it to mark the various transitions and rabbet points for the entire keel. More on the pattern process next time.
I was able to get all the lofting done in about 6 hours and I found it to be quite enjoyable. Once I'm done with this loft, i plan to modify by loft floor so I can loft the transom and bow. Those sections require the OSB to be turned 90 degrees so I can get an 8' long by 12' high loft floor. I think it'll be more clear when I have some pictures.
That's all for now, thanks for reading. Please become a follower on this blog and be sure to check out our YouTube channel where we are documenting the build with a video series. You can click on the link below to check it out. Please subscribe to our channel as well.
Happy new Year!