Basic woodworking question

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beguinebuilder
Posts: 1
Joined: Mon Aug 17, 2020 12:38 pm

Basic woodworking question

Post by beguinebuilder »

Hello,

I’ve got a couple basic questions about how to cut and glue the best way possible for this project. I’ve done some simple woodworking—just knocking stuff together around the garage, simple work tables, projects around the yard, nothing that needs to fly. Cut to fit, add glue, screw/nail it.

For airplane parts, if you cut a piece perfect and it fits together with everything else, just glue it. But if it needs tweaking, can you sand it to fit? I’ve heard that can make the joint weak. Should you not sand at all and just get new material and do better next cut? Or if you have to sand a joint to fit are there steps to take to clean it before you glue it?

When you use the plywood for gussets, I’ve heard you should sand the sheen off. Is that literally all the more it needs, just a little bit to dull the surface? Doesn’t that fill the plywood with dust? Do you clean out the grooves before you glue it?

When you make a joint like a rib intersection, and some of the pieces are maybe a tiny little bit different thickness than the others, do you sand the area where the gusset goes so it will lay down flat? Like above, if you do, do you clean it afterward, before you glue the gusset?

Last thing...I’ll probably go old school and use nails like back in the day. Is it hard to nail the gussets without them sliding around on you?

Maybe this stuff should be a no-brainer, still have the questions though. Thanks, Will
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taildrags
Posts: 436
Joined: Tue Mar 07, 2017 10:39 pm

Re: Basic woodworking question

Post by taildrags »

Will; I'm very surprised that no one has stepped up to address your questions yet. I'm no expert when it comes to woodworking, but your questions don't require deep knowledge of woodworking to address, especially when it comes to building an Air Camper. I may take a swing at it if no one else does in a day or two.

Oscar Zuniga
Medford, OR
Air Camper NX41CC, A75 power
tom kreiner
Posts: 62
Joined: Sat Feb 25, 2017 9:49 am

Re: Basic woodworking question

Post by tom kreiner »

Will,

Lets do some simple math...

In the case of a simple joint - perfectly fitted, the bond area of the two pieces would be the area of the end of a truss piece as it fits against the cap strip.

For the Piet, both capstrip and truss piece are .25 x .50 inches, giving us a bond area of .125 sq. inches. That would work until such time as a rather high load were imposed at which time the bond would break.

When the same joint is loosely made - that is with imperfect fitting i.e. a gap - the gusset, which, let's say measures 2 in. x 1 in. rectangular, will have a bond line of 2 x .25 + 1 x .25 equal to 3 x .25 which is .75 square inches.

If my math is right, this is 6 times or 600% larger than the perfectly fitted pieces. Because we have gussets on both sides, we double that giving the joint 1200% greater bond area. So, the REAL strength of a gusseted joint is in the total glue line area.

Fitting the joint with up to a .020 disparity in thickness should not be a problem, although when prepping the materials, a saw can be set to cut all of the capstrips at one time, thereby giving them the same dimensions +/- maybe 8 to 15 thousands of an inch, depending on skill and setup.

If the goal is to make each step of the construction of the airplane perfect, you'll NEVER complete it. Remember, Perfection is the ENEMY of Completion.

As far as staples and nails are concerned, the job gets pretty messy when you do this, but many have tried and succeeded. Some guys have developed very nice jigs which are equipped with hold downs, etc., to affix the gussets during cure of the epoxy.

Sanding the plywood and cleaning up certainly won't hurt, and some have recommended it. Personally, I don't think sanding improved significantly, but it won't hurt, either. BTW - a little sawdust won't hurt the joint.

Take a look at West Coast Piet to see how some other builders have made their ribs, it's well worth the time reviewing what we have all learned.
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