I am hoping for some suggestions. I want to create a template of an existing paipo board and measure thickness every two inches. All the calipers had arms I have seen were too short as I want to measure off the stringer. I tried to make a plywood set, however the centre is thinner than the rails so I can’t remove the caliper to see the thickness. The board is quite curved which also makes it complex.
I need something that will measure along the stringer (about 10-11") . I have seen digital calipers however (which have the advantage of consistency/accuracy and mot having to be removed to take the measurement), they only have very short arms that do not reach very far.
Measure with calipers at the high points along the rail crown. Measure depth of concave from a straight edge placed across the deck from rail to rail.
Some calipers (Pleskunas) have a gauge on the handle that gives a read-out of distance between the tips. You might be able to score some reference marks on the pivot points while measuring tip distance on the one you have.
I marked the board every 2" top and bottom. Measured the bottom concave as John said above.
Then placed one straight edge horizontally (2by4) underneath the board and one on top. Measured the distance between straight edges on both sides so they matched. Then subtracted the concave.
That worked ok, but I am going to make some large callipers.
measurement T 0" T 1" T 3" T 6" T 12" T 18" T 24" mid point N 24" N 18" N 12" N 6" N 3" N 1" N 0"
You can make really cheap calipers. I have a history of making things with cardboard. I just took some scrap cardboard, cut two arcs, and then bolted them together. It looks cheesy but it works. If you want to step it up you could use wood instead.
Bigshow - I couldn’t see what you used to join the two arcs. I tried a bolt and locknut on some thin artificial board but am not confident that the callipers didn’t move when I withdrew them for measuring the gap.
Next weekend I will experiment with some of the above ideas. The task is complicated by the bottom having a central channel as below (the board is a paipo board) and the deck is concave - 3" deep at the deepest point.
I built a wood rectangle frame with some threaded bar to hold the board still. I put the board in the frame with the stringer (centerline) just off the edge of the wood, clamp it up and use calipers to measure up from the wood to the bottom deck, and down from the wood to the top deck. I tacked a cheap tape measure to the wood so I could easily get my location every 2" or so.
A bit of subtraction gives you the thickness.
You also get the top and bottom rockers, which is useful, and can work at 90 degrees to the frame to measure top and bottom contours.
A low-tech way is to just put the board through a sash window and measure the gap between sill and window.
I tried to make a plywood set, however the centre is thinner than the rails so I can’t remove the caliper to see the thickness. The board is quite curved which also makes it complex.
A good pair of homemade calipers.
I used construction paper to refine the design before cutting these out, …you can too!
Even if the center is thinner than the rails you should be able to slide the calipers from nose to center or from tail to center
Call Fiberglass Hawaii and order the calipers that Stan Pleskunas designed. They are the best commercially available ones. Simple to use, with a scale built in. Their website is under construction and doesn’t get you to a pic, but they are the best. I think they cost about $65.