Centersection fabric - preparation

Good morning from a snowy(!) Slovenia,
During the past week I managed to get in some concentrated effort on the centersection. By working way afterhours for four days I am very happy to report that the center section is now fabric covered.
Proof:

This image shows the state of the work on Thursday evening. Friday was spent  doing the details.

So, to show you the process, I will probably post two blog entries. This one is about the preparation work involved before laying the fabric. Often overlooked and definitly not much talked about, the prep work is the basis of a masterclass fabric work.

First, we had some details to finish off. Like this big circular wood piece, you see in the center of the image. A fuel tee with a drain valve sits on it. It looks benign, but required some forethought.

The laminated wood block in the center with the through hole.

One of the challanges involved was blindly locating the three nutplates through the skin of the center section. A trick often used in sheet metal was used:

The other holes you see are drain holes.

Then we finally had the piece ready for fabric. One of the most important aspects in composite construction is the minimum bend radius. Depending on the specific weight of the fabric, there is always a certain radius that the fabric can follow. If the radius is smaller then this, you have problem in laying up the composite.

The same thing is actually true for fabric covering aircraft. Most of the prep work involved in preparing the piece for fabric is sanding it, to get off all the grime, dirt and oils, to enable the glue to set up a stronger chemical bond to the wood AND establishing a minimum bend radius on all the edges that the fabric will wrap around. This is actually a massive amount of work.

Most of the time these bend radiuses are made by sanding off the sharp edges, but sometimes filler is needed.

Like here.

No manual (that I am aware off) really states the minumum bend radius for fabric, but I estimate it to be about 2-3 mm for the normal grade aircraft fabric (cca 100g/sq.m). So the filler is then sanded accordingly.

Again, this is very simple, but requires a good amount of work (about 10 hours for the centersection) and is a step that will not only make laying up the fabric much easier, but also the quality improves drastically.
Do a good job on the fabric and you safeguard the structure (if you happen to remember to put drain holes in it!)

Next post is about actually doing the fabric. Before I sign off, I would like to put some faces to the names.
When in the blog I say ''we'' did something, that most probably means that one of the guys in the picture below did something.

On the left is Janez C., right is Igor M.

Remember that Janez is a partner in aereform and does all the wood. Igor is a hilarious kid that is excellent with the spray gun and quite good with the wrenches. While reading through the blog the other day he said, that: ''you know those are my blisters that you are posting to the internet!''. So, yes, it is about time to put some faces and names to our company and into worldwide fame and fortune.

Will post the rest of the fabric process in about a week. Go and build a snowman or something.