What turned me to composite construction came a bit unexpectedly.
After finishing my 2010 EAA sheet metal workshop, I was more convinced than ever about building my dream airplane, the RV-8A (which I still love). Problem was, money was tight as always (two kids in college), and I was finding it difficult to gather enough of it to buy the tools and the tail kit, without having a major impact on our cash flow.
While saving money for the RV, I decided to order the composite practice kit from Aircraft Spruce. I figured I had never really given composites a fair shake, and I would be learning techniques I could later use on the RV trim.
What I had not planned on was enjoying the composite construction as much as I did; but what really sold me on it, turned out to be its incredible strength (more on that later).
 |
| Composites practice kit from Aircraft Spruce. |
 |
| Kit content |
With all the things I needed on hand, including my awesome assisting daughter, we embarked on our first construction project, a flat six-plies layup.
 |
| Trendy glasses
In this layup you only make use of bidirectional fiberglass (BID), with the fibers oriented along, and across, the length of the piece.
|
 |
Actual construction manual drawing |
 |
| It helps that she's a Chemical Engineer. |
The whole point of this exercise is to learn to meter the amount of epoxy used. After trimming the cured piece to a 10” x 16” rectangle, its weight should fall between 10.5 and 12.5 oz. Anything heavier means too much epoxy, anything lighter, not enough of it. |
 |
| Cured piece after a rough trim |
 |
| 10.06 ounces |
As you can see my piece appears to be slightly on the dry side, but it turned out that I cut it slightly smaller, so I believe it still has the proper fiberglass/epoxy ratio, although on the low side of the spectrum (good thing).
So, now what?
Well, I thought it would be fun to destroy my very flexible test piece, by loading it to failure.
How does the biggest hammer in the shop sound?
That’s what I thought!
 |
| This is the heaviest hammer I have |
Well, that was underwhelming!
Let me find another one...
Wow, that didn’t make much of a difference, did it.
Wait, I’ve got one more...
 |
| That's all the hammers I have |
Damn! I’m all out of hammers.
Let’s find something bigger.
Ok, no more Mr. Nice Guy. How about a 25 lb grinder?
Nada!
Ok, this time we are going massive.
A 75 lb, 3 ton floor jack.
 |
| This thing is killing my back! |
Die little fiberglass panel, die!
 |
| I had to screw the two pieces of lumber to the bottom board |
Holy crap!
I suppose when it’s not your time, it just isn’t.
 |
| My "better half" approves |
By the way, after removing the weight, the piece went right back to its original shape.
How does sheet aluminum sound now?!
Good confidence building exercise for the family ;)
ReplyDeleteYou got that right! You really need to get the whole family on board before starting this type of project. I'm lucky to have a very understanding family, though it did take some convincing.
Delete