Cutting the dome ring lap joints.

I must say that I don't much like the Rawlink spring clamps. The jaws are as long as the slippery handles and this makes the required hand pressure uncomfortably high. The green, self-aligning jaws keep falling out to compound the irritating hand pressure to obtain a wide enough gape. That said they were cheaper than chips at 20 Kr. or about £2 each from memory. Luckily I only bought 6 small and two of the larger.

I shall definitely look elsewhere for another make since I could do with many more for the coming work. They do have a firm enough grip, at the jaws, to be useful and are far quicker and lighter to use than G-cramps. Particularly for thinner jobs like gluing or holding plywood.

But why bother to put green, entirely decorative panels on the handles if they aren't sticky enough to grip firmly with the major fingers and thumb? Even a drooling idiot can easily see that the shape of the handles makes the hand automatically slide down to the point of minimum leverage at the pivot/fulcrum! Leaving the reserve digits and pinky to apply any further leverage. Brain dead dullards could do better! Why can't the manufacturers?   

I went over and started marking out the half lap joints on the arcs. Then I realised that one can't just put a try square on a circle. Certainly not on the convex outside. So I used my newly acquired "speed square" and reversed it each time on the concave curve. Following on with a bisection line by eye. A quick check with a 6" protractor showed that I was spot on. So far so good. The odd thing is that my circle laid on the ground seemed to have far larger overlaps than these measly 3" joints. Perhaps I just didn't have them lined up well enough with each other? I'll have to lay them out to the new markings and see what happens.

My maths is worse than I thought! I carefully laid out the ring arcs on blocks to the pencil marks and clamped them together after close alignment. The overlaps at each end were 16cm or over 6". Exactly twice my calculated overlap. No problem though since it gives me more leeway.

The image above shows my measuring pole at half way and the 1/4 circle marked with another pole. I mark the poles with tape and this saves hours of fiddling with 10' of extended and floppy tape measure. I can quickly go around the circle checking the diameters are all equal without being in two places at the same time.

I brought out the table saw to do the half lap joints. Then couldn't summon the nerve to shove a 5' tall arc of wavy plywood through the blade set to full 3" cutting height! So I brought out the router instead and cut the material away with a 1/2" bit across all seven arcs laid out at the same time. A crude fence stopped it taking chunks out of the shoulders. I cleaned up with a block plane and checked the depth by reversing a pair of joints. I had already set the router's last cut with a vernier caliper on the plywood. Now I just have to do the reverse laps on the other ends. I just hope I remember to do them all the right way around!

The lap joints worked okay but the arcs were slightly too long. So I re-marked them all and used the miter saw to slot the joint surfaces prior to removing the waste material. The ring is now close to the correct size with the arcs well aligned.

After some reorganization of the parking area I was able to make room for the ring further away. This avoided problems with the car reversing into the previous outdoor work site. I shall have to build a work shelter as the weather becomes much more changeable. It would not be possible to "put away" a partially constructed dome every time there was a shower. Even throwing a tarpaulin over such a large object is not without difficulties. The cheap, lightweight tarpaulins really are absolute garbage and quickly become as waterproof as a fishing net. Even four layers of brand new, lightweight tarps has failed to keep my timber stock dry!

Talking of rubbish: I went in local search of better quality spring/glue clamps for the coming build. I found some small Bahco clamps at three times the price of the Rawlink but identical in shape. Unfortunately I did not have "Arnie" with me in full Terminator guise. So my feeble, human hand strength could not open the damned jaws without considerable strain and pain! Somebody actually designed and released these to an unprepared public? And they actually kept their job? Good grief!!

Lest thee think me a wimp: I regularly carry heavy, multi-stretch ladders and 18' lengths of 2x8s and 4x4s about, without effort, working alone. I moved over 20 tons of sand and gravel, 50 yards, by shovel and wheelbarrow alone, in only a couple of days. So get over yourselves!

I have now ordered a selection of Bessey Clippix XC spring clamps without having physically touched them. The handles just look as if they were designed for real human hands. Unlike the Rawlink and Bahco [half-baked?] spring clamps. Another pair of companies where such "alien technology" as basic human ergonomics has, quite obviously, completely escaped their attention.

Even the Ancient Egyptians knew about levers and moments. Why can't the Chinese plastic factories read the hieroglyphics? Has common sense completely evaded all of them before they stick 'Western" labels on their wares?  Has it got anything to do with being "cowboys?" [A derogatory British term for poor builders.]

Click on any image for an enlargement.

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