Chapter 14 Center Section Spar

Sunday January 15, 2012

With 2012 upon us this July will be the 10 year mark for working on this airplane with some breaks due to school and life's typical events. I'm starting to worry whether this will get done in my life time, I'll just keep working on it until it's done.

In this chapter we build the center section of the wing spar. It will be bonded to the aft end of the fuselage and is about eleven feet long. It provides attachment points for the wings. The shape is basically a box that is swept back and up. To get the correct shape a jig is built from particle board with very exact measurements which is difficult to do with particle board. Also everything needs to be straight and perpendicular, again hard to do with particle board, mine kept wanting to curl up like a potatoe chip with changes in the weather. So the spar is basically a foam box with fiberglass layed up on the inside and outside with wing attach points. It will also have thick fiberglass spar caps similar to the canard to provide the main strength of the structure.

Here the three sides of the spar have been microed together and the inside fiberglassed with one ply of BID and local hardpoint areas built up with another ply of BID and four staggered plies of UNI. The hardpoints on the inside of the spar are 1/8 inch thick pieces of aluminum that have been floxed in place (the alodine creates the strange patterns on the aluminum) with another ply of BID over that overlapping an inch all around. Also three bulkheads have been installed with one ply of BID on each side. Near the outer bulkheads another hard point is floxed inplace with the same buildup of BID and UNI. Getting the fiberglass to lay down with out bubbles in all those corners at the bulkheads and end caps made for a difficult layup and took Lynn and I ten and a half hours to complete which had to be done all in one session.


The holes cut into the bulkheads are to allow for electrical wires to run through.



Here the top of the box is microed in place which is actually the forward face of the spar. The plans say it's not necessary to tape the inside corners of this forward face mainly because it's impossible to get inside.


Here are some pictures of the spar out of the jig with the forward face down.


Sunday February 19, 2012

Made some more progress on the center spar. Made the spar cap templates and had an issue that they didn't quite match my spar, however my spar dimensions did match the plans. Contacted the Cozy Group and they said the templates must be undersized, adjust as necessary and get on with it already; so I did.


The templates are used as a guide to make sure you have the correct depth for the spar caps. The spar cap troughs are sanded by hand and I made a sanding block 3 inches wide with another block glued at 90 degrees as a guide, I'll have to add a picture of that. Here you can see the templates for each BL (butt line) location fitting nicely.


Once the troughs are done it's necessary to route out the foam for the outside wing mount hard points which are floxed in place. Once the hard mounts have cure in place it's time to glass the shear web to the aft face of the spar so the forward portion of the spar is masked off to protect from epoxy drips.


It took quite a bit of preparation for the shear web layup, was hoping to get it done on President's Day but thought it would take some time so I took another day off even though that would mean I would be working solo without Lynn. The shear web is 4 plies of UNI laid up at 45 degrees alternating the direction on each ply. The layup was pretty straight forward however took me from 8:30 am to 6:30 pm with two half hour breaks. Lynn was able to help me the last hour and a half. It took two and a half hours just to micro the foam and about two hours for each layup. The layup wasn't difficult, just large. Here is the finished product.


Sunday February 26, 2012

Did the top spar cap layup with 24 plies of spar cap tape, 12 plies are the full length (plans call for 11, I added an extra to make sure the trough got filled) and then each subsequent ply is shorter by about 8 inches, similar to what was done for the canard just a lot more plies. Needed to build a dam to hold the plies in on the trailing edge which is per plans. Didn't take many pictures of the steps but here is the finished product, took about 5 hours for Lynn and I to do. Easy layup just a lot of plies and a lot of epoxy. I'll try and take more pictures when we do the bottom spar cap.


Sunday March 4, 2012

Here are some pictures of the bottom spar layup. This time I put some flox in the corner of the dam to keep the epoxy from running down.


Now a lot sanding to get everything nice and flat for four more plies of UNI. Cured fiberglass scoffs at 36 grit sandpaper. This picture shows the aft face up.


Sunday April 29, 2012

After much sanding to smooth things out we finally got to do the 4 ply UNI layup, this took about 8 hours. Took about an hour longer than it needed to since I had to recut all the cloth larger, mathematical error.



Sunday May 27, 2012

Getting close to completing the center spar. Did the 4 ply layup over the aluminum wing mounting points, this was 3 plies of uni just straight over the hard points and 1 ply of bid at 45 degrees only on the aft face not overlapping onto the top or bottom.


Also did the last large layup over the forward face of the spar with two plies of uni alternating at 45 degrees. Routed out depressions in the foam for access cutouts. This layup took Lynn and I 3.5 hours.


Sunday August 26, 2012

I've actually already started on Chapter 19 building the wing templates and fixtures. But here are some final pictures of the center spar, I've cut out the center and end access holes. So now it's on to building the wings!


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