BUILDING JIGS TO ASSEMBLE THE RIBS
==========
SASKNELLIE: "For the sake of those of us who are novices, could you post a picture of the jig you used to make the arches?"
==========
There are two "classic" profiles for the gothic arch shape. One uses the full width of the floor as the radius to draw the arc (this makes a taller, narrower-looking shape). The other uses 2/3 of the floor width as the radius (this makes a shorter, wider-looking shape). For ease of reference, I call them "full-width arch" or "2/3-width arch." The 2/3 width arch (in the pictures) has five 3' facets on each side and they all join each other to form a 15 degree angle. This shape is 16' wide and about 10' high. The only exception is at the ridge which is a 45 degree angle. At the ridge, you remove 22-1/2 degrees of wood from the top end of the two pieces which meet each other at the ridge. The lower ends and ALL the other pieces have 7-1/2 degrees of wood removed from BOTH ends. An arch shape can be drawn (and built) using any combination of height and width. This particular one makes a good first choice because the angles are whole numbers and it's a reasonable size for a first effort.
==========
The simplest way to make a jig is to carefully cut and assemble four rib components together with the plywood plates on one side only. Lay 2-1/2 sheets of plywood down to form a shape 8'
wide and 10' tall and fasten them edge to edge with hinges or blocks of wood. In the lower right-hand corner, draw a rectangle 5-1/2" wide and 1-1/2" high -- this will represent your sill plate that the ribs will set on. Position the lower end of your mostly assembled rib on the line -
- just as it will be on top of the 2x6 sill and put a nail or screw (in a pre-drilled hole) close to that lower end so the rib assembly can pivot on that fastener. (This allows you to move
the top end of the rib while the bottom end stays in place.) Next take your fifth rib component (7-1/2 degree on the lower end; 22-1/2 degree on the upper end) and position it so it is touching the top end of the assembled four components AND is flush with the center line extending
down from the ridge (the left edge of your sheets of plywood). Then it's a simple matter of making sure nothing moves and carefully tracing both sides of your rib all the way from the
ridge to the sill plate. Then you can install 2x4 blocks -- two on one side, one on the other of EACH facet and presto -- your jig is done. When assembling the ribs, I start at the ridge and put a screw into that top piece to make sure it holds at the centerline, no matter what. Install all four plates (even the ridge plate can be installed just leaving half of it sticking out in mid-air) and then carefully remove the rib from the jig, flip it over (no jig required for this step) and immediately install the remaining four plates (but NO ridge plate on the second side -- that plate will be attached to the rib coming up from the other side). It's easier to leave the
ribs UNattached at the ridge until immediately prior to standing them up into final
position.
==========
SASKNELLIE: "In my case, not having a chop saw, I would probably make a jig for the cutting as well."
==========
That can work just fine -- use a sharp blade and keep your RPMs up -- go slow and let the saw do the work. Much of your FREE pallet wood will end up with nails embedded in it. I use
chisel-tip blades (go slow to not damage the blades) and swap 'em out as soon as they start
to get dull. It's cheaper to have them re-sharpened than it is to replace good quality blades.
==========
SASKNELLIE: "What angle are you cutting for the full sized version?"
==========
The full-width version has SEVEN 3' facets on each side and is 20' wide and about 17' 6" tall. On this larger model, the ridge angle is 50 degrees so you remove 25 degrees of wood from each
of the two pieces where they meet each other at the ridge. At the other end of those two pieces and BOTH ends of all other pieces, only 5 degrees of wood is removed from BOTH ends. This allows them to join each other and form the necessary 10 degree angles.
==========
SASKNELLIE: "Another question, what will the span be at the level of your loft? I would like to build this in the spring as a garage with lumber storage in the loft area. I'm wondering how much weight this can support before you have to use posts to support from below."
==========
I don't have the drawing in front of me (it's at work) but the span on the loft is considerable -- 14' or so -- too wide to support much of anything without support below it. Were you planning on the solid T&G (Tongue & Groove) 2x6 deck or something more like "collar beams" to store lumber on top of? As a cabin, one would want a wall under the loft to separate the kitchen area from the bath/utility area so making that span manageable with a wall underneath it (splitting the span in half or keeping it at 10' or less) is no problem. Depending on what you want to do, we'll have to get Laren involved to help calculate the anticipated load and what will be required to safely support it. We can only hang so much weight down from the arch ribs. The rest must be supported underneath the loft with either a wall or posts and a beam. So the big question at this point is: solid T&G loft or open framing -- like collar beams? And how long will your loft be -- assuming the width will be "fixed" by the 20' wide gothic arch?
==========
sail4free
==========

BUILDING MODELS
==========
I like building models of ideas which are more or less to scale. My favorite scale for shelters is 1/4 scale (right?) where 1" in full dimension is only 1/4" for the model. I got a weird start with my pallet gothic arch model and it ended up 36-1/2" wide (representing 16') but it should have been 48" wide and now I kinda' wish it was. My rigid arch facets (representing 3') are only 6" long but would have been 8" long using the 1/4 scale.
==========
These are sizeable models but I'm able to use 1/8" wood paneling scraps for the glue plates where 1/2" plywood is used in real life and I can actually attach the miniature plates with glue and a 1/4" crown air-powered stapler = four staples per plate. I attach my girts and purlins with an 18 gauge air-powered brad nailer (5/8" leg length) and a spot of exterior grade wood glue. If I'm making 1x4s for the model, I rip 1/4" thick strips from a standard 3/4" thick board (2x4s are 1/2" thick). A truer scale would have a 2x4 being 3/8" thick by 7/8" but 1/2" gives a little more "meat" to work with and the standard 3/4" dimension is easier to come by. This scale allows a standard 2x2 (actually 1-1/2" x 1-1/2") to represent a 6x6 post (common for pole barns) and a 3/4" x 3/4" (aka "1x1") to represent a 4x4 post.
==========
Building models allows one to really see what they're getting themselves into and as you're actually cutting and assembling the individual pieces (much as you'll do building the full-sized one), it's great practice and you'll find a few things will be "worked out" in the model MUCH easier than they would be on the actual building. It's also a great way to show the rest of the world what this thing is that YOU can see so clearly in your head BUT may have a hard time communicating to others -- now you can just show 'em. One of my coworkers was clearly impressed that all my rigid arches lined up so well. He said, "You put all those together on a jig, didn't you?" Well, of course! Only a jig allows things to be consistently "off" and still look good 'cause all the frames are "off" the same -- as long as you never switch 'em end for end, right? Very few things are perfectly symmetrical -- or perfectly plumb and square for that matter -- in the REAL world. It's important to label your frames so you'll always know which side had the glue plates installed first and then just make sure all those "first" sides face the same way. To minimize the variables, I always face my "first" sides towards the front end of the building.
==========
Actually, with the pallet gothic arch I'm recommending the rigid arches be assembled as "ribs" only = NOT joined together at the peak until just prior to standing the rigid arches up into their final position. The ribs can be easily hauled in a pickup with the tailgate down and are much easier to handle this way. As the angle at the peak is different from all the others, the ribs end up lining up whether one labels the "first" side or not -- the right half of the rigid arches will all face the same way and the left half will all face the OTHER way = no worries -- it all works out with no labels necessary.
==========
sail4free
==========

FLOOR OPTIONS -- DIRT/PLASTIC/CARPET
==========
Dirt inside can be kept 4 to 6 inches above grade and converted into a floor of some sort. One of my favorites uses redwood 2x4s buried on edge around a room's perimeter. Using these to define "level" the dirt is leveled and compacted in place. A layer of black plastic is put down (stapled to the 2x4s) and then a layer of carpet (preferably used) is stretched over the plastic = instant floor and noone will ever know they're walking on dirt IF you don't tell them. (Thanks to Mike Oehler of "$50 and Up Underground House" for this idea.)
==========
Another advanatge of the carpet-plastic-dirt floor is it's easy to run new wiring circuits or new plumbing lines -- pull the carpet and plastic back and start digging! When done, backfill and tamp smooth and REinstall the plastic and carpet = no damage, no waste. One can even get "direct-bury" Romex (gray outer sheath) that can be laid all by itself and buried. If rodents are a problem in your area, though, better to fish it inside of plastic pipe to protect it from sharp vermin teeth. Small trees and plants can be planted right IN the floor -- how's THAT for "alternative?"
==========
sail4free
==========