Ch 14 CenterSection Spar

Now the plane is upside down I can finally finish off a few things. There are a few missing tapes from the firewall to the spar. They are only 2″ single ply BID and they seal off a few little air leaks too.

What are you looking at? Inside the hellhole here we have no tape from firewall to spar at the back or sides.

I added a little flox in the join and some micro down the sides along with a few tiny gaps around the engine mount extrusions. Here we are all done and peel plied.

The next day, tapes off and on to the next upside down job. This time its the front wheel that will get a little extra care.

A simple job today. Just the outside tapes around the wing to spar join. I did the usual layup on plastic and foil as in Pic 1.

Before applying these I had prepared the glass surfaces with a light sand and clean up and then mixed some flox to fill just a few small gaps from yesterdays joining. It’s still not cured completely of course.

Pic 2 has a tape transferred and in place and pic 3 shows the tapes with the edges peel plied too. I again set up the heat tent and hung around for a few hours. I’ll hit it with some more heat tomorrow which will also help the flox join.

A good day for cleaning up a bit and reading the plans again for installing the canard.

Layup on foil

Corner tapes

Done and peel plied

I was at the hangar for 12 hours today. Michael, who has helped many times dropped in yesterday and pointed out that the trolleys I’m using had rubber wheels. That was making things harder to set up as they would move a little. He had some other helpful ideas too. Today had me on blocks but still chasing my tail.

I though I had it all set by 2pm but there were two more hours of trying to get the waterline correct as well as the incidence. I was happy enough with the sweep. Incidence I could get at zero but the waterlines were more of an art form. In the end I’ve set for correct at both tips and about .4″ lower in both centers. So I have a tiny amount of wings up. I suspect it will all change after gluing things as it moves around depending on how you hold your face. I have done my best here.

The wings are supported inboard of the FC1 blocks so the rest of the tip is just hanging relaxed. I’ve shimmed at the spar and that FC1 so that when the flox sets all will be correct. Well I hope so. The fuselage was zero across the longerons and zero along the tops although what really matters is where the canard goes in relation to the wings. Still, it should look straight when you sit in it.

I floxed in the spar spending a long time working the flox through. I used to fix guitars and its the same skill as a broken neck. Work that glue in one side until it comes out the other. That done I added some peel ply so the flox wouldn’t sag too much. I made a heat tent and got over 27C for six hours into that area. It got down to 4C elsewhere in the hangar. Brrrr Long night.

Incidence correct

Water level madness

Heat tent and my flying Long-EZ, VH-JZE

After opening up the spar box a little I could walk the CS spar in without too much trouble. I needed some give so that adjustments could be made. See pic 1

After all the work I found the incidence off between the wings by about .4 of a degree. I thought about it for longer than most people and realised that I needed to take out that extra washer I’d put in to correct the incidence. I’d built things better than I thought, I was then able to get exactly the same incidence on both wings to 0.00 without any washers.

The whole setup is quite a challenge. Pic 3 shows me checking sweep. Its really from the next day but I had room in this log. I’ve used aluminium angle iron clamped together and just done a check from LE wingtip to the F28 center-line. The wings were .4″ different which over that distance is almost noise. Funny in that I thought the sweep was out 2″ when I first checked on the floor, then it was only 1″ after things were bolted together and now I’m 0.4″. All good.

I also checked the wings length left and right and found they were 0.1″ different. Again I thought it was a touch more but it seems things are working out.

Fitting

Setting it up or ‘herding cats’

Checking sweep

Today was resolving a real challenge. The spar with wings needs to go in and out of the fuselage cavity numerous times. I needed a way to hold the spar, move it tiny amounts up and down but primarily not have it suddenly shift. I was very concerned about the weight possibly snapping off a longeron if it shifted suddenly…or something even worse.

The solution was to support the wings at both ends and inboard and have two tables with jigs that could screw up and down a thread. You can see this in pic 3. I tweaked the jigs I’d made for the spar when it was on the ground. So I have 4 point adjustment on both sides inboard.

With one of these each side and the weight also supported at the tips the spar is very secure and I found I could just walk it into the spar cavity below the top longerons by moving very small amounts at each tip.

What was a surprise is that it is a super exact fit. Far too exact for tweaking or even fitting and flox. I’ll have to remove some material tomorrow so its a loose fit and then try lining things up.

Right wing stand screws up and down

Left wing adjusted with foam blocks

Center jigs, one each side

Now the wings are bolted together I wanted to check sweep while it was still on the floor. I ran a fishing line between two weights and lined it up with the front of the spar box. I used Photoshop to make the line visible in the first pic just for you dear reader and set the photo up with this log in mind.

I measured from the line parallel to the LE of the wing tips. Right side was 38.35″ and left 39.35″ Last time I measured this I was 2″ out now the wings are together its only one inch. It will be a tiny displacement of the spar to get them perfectly equal. I didn’t recheck the waterline for dihederal. It is what it is and I’ll set this up when the spar is in place on the fuselage.

I then checked incidence yet again and found I was a touch out. Disappointing after all the efforts. I noticed that when I used the digital level and it shows 0.2 degrees on both sides and this happens as I turn the level around. So I really have 0.2 up one side and 0.2 down on the other. The level doesn’t show this easily. Hahaha well I’d set it for zero when I drilled out so this doesn’t matter.

Today I noted which side the bubble was on AND the numbers. Don’t you get caught out ok? In the end I added one regular thickness washer, AN960-816, to the right wing inboard lower (or bottom) bolt and now the incidence is exactly the same both sides. Exactly. So thats a good result! I continue to adjust out my errors successfully.

Pic two shows some mounts I made yesterday that have the fuselage sitting securely on the landing bow. Pic 3 shows that I have leveled the fuselage and there are straps holding it down as I don’t want her the rear up on the hind legs right?

The wing is now resting on hard foam and on two benches which have wheels. The fuselage is close but not perfectly built. I have it at 0.00 degrees where the spar goes in and I’ll set the canard incidence to the wings so a slight imperfection along the longerons towards the front will have zero effect on having a straight flying aeroplane.

Checking sweep, note the string line

Wheel jigs

In position for the fit

Today was finishing off the end pieces with hand tools and making a 1″ access hole at each end for wiring. I sealed the hole edges with epoxy. Too small for a flox corner and it is hard foam so I’m happy with it done simply for a change.

The pics show the spar still with all the peel ply on. It is very pretty underneath.

The completed CS Spar came in at 33.5lbs, Mike Melvilles was 29.5lbs. My spar tapes are 1000grams/sq meter Spruces were 746grams/sq meter or 29.5ozs/sq yard vs 22 ozs/sq yard. My tapes were 7.5 ounces denser for the same thickness. On this basis I have a good result.

The caps are 0.26sq yards per length. There were 19 and 14 plys, 33 in total but many were shorter although I added full length plies to top and bottom. CP’s have 30 plies total. Lets call it even overall 8.58 yds X 7.5 density difference = 64 ounces or 4lbs. Talk about rubbery figures!

Overall I am very happy with this part that I will be trusting my life to as the main load bearing section of the aircraft.

Access holes

Hard points

Completed

A few smaller jobs today. It still took all day… of course.

Flox corners for the two spar ends, micro over the large foam area too, but not in that order. Micro first very carefully, then pure epoxy in the trough, then the flox then the BID layed up on foil and I peel plyed the ends.

The other similar job was to cut the 2.25″ diameter access hole. This also got the flox corner treatment and a little piece of BID as you can see in pic two.

You can also see the end sections of the spar caps which look quite nice.

Finally I VERY carefully finished off the baggage cutout and did the edges from 80 grit to 800 grit and then scotch brite so those edges should stand up to a bit of use.

Just have the conduit 1″ end holes to go and a bit of a clean up for this spar. It sounds good when you tap it.

Flox troughs

BID in place

Baggage cutout done

This was an overnight preheat of the room and things ready to go. I have the glue in a hotbox with a timer. I decided to do this one on my own despite offers for help. Its seems a reasonable size to handle and I wanted to see how my skills were going.

I first mixed a really small amount of micro and did the sloped edges of the baggage hole with a small brush. I wanted a good surface to work on and no micro on the edges of the hole. That gets pure epoxy, also applied with a small brush.

Next a big mix and coat the spar face and sides using a roller. I had previously sanded and cleaned the surface and a very light wipe with acetone. The premarked cloth was relatively easy to get placed with straight fibers, the sides needing only an inch glass to glass really fell into place. Once happy with the three pieces of layup one (two large lengths one one really short at the end) I wetted it out in the usual manner with the roller and followed up with the squeegee. Lots of trimming with scissors on the sides too. Once happy the second ply went on.

For both plies I spent a lot of time around the baggage cutout as expected and got it to lay down nicely using my fingers as a stippler and then a brush which did the job. It was reluctant to sit without air bubbles so needed persuasion. A nice warm room helped get the glass sticky too as I’m not working too quickly.

After the two plies were done and trimmed. It looked great. Then time to peel ply the lot which took a good couple of hours. Not a fan of the peel… but needed and using the heat gun helped wet it all out. Once cured,k underneath that stuff is a good layup, no excess epoxy and no air I could see either.

It took about 5 hours, the radio on and just working at my own pace. Oh and I’m calling every log entry 10 hours… its always more than that per entry, in this case lots of prep last night and the clean up and so on. Yes just 10 hours per entry is an understatement.

Nice straight fibers

Looks best before the peel ply

Done and curing

Yes lots of sanding of the top and sides was next. I carefully removed lots of peel ply down to the spar caps on each side and then sanded smooth the edges that the peel ply left as well as the forward face that was to be glassed. This was a good days work.

I also redid the oval opening, finally cutting out the middle. I went over the glass edge with my dremel and a cone abrasive bit and ensured I took out from the inside to the out all the foam left over so I have a real glass to glass edge. This removed my carefully placed final line of course. You can see in pic 1 the different colour here. Its a fine line between all the foam gone and some of the glass gone too! I’m happy to have done a bit extra work here.

Then cutting glass cloth and labeling it as prep. I made sure that there were no joins right in the middle at the baggage cut out. This meant a little piece extra right at the end of the spar so I had 3 pieces per ply. No probs. I had a look at the cutout in my flying plane, VH-JZE and I want an even better job on this new build.

Pic 3 has the glass cut out, labeled, covered in plastic and the spar sanded, inspected and ready for the layup the next day.

Plenty of extra edge

Cutting glass well oversized

Prepped and ready to go

A lot of time was spent laying out the simple hole for the baggage area which is on the forward face of the spar. I have kept rechecking that this hole is going in the right place. It is.

Then I managed to draw a lot more lines than I needed. I really want this neat and tidy. I used the router to get a clean oval and tidied up with permatgrit tools. This all disappears but my idea is that if each step is accurate my odds on a neat job go up.

After the oval was done I did a router trim on the inside edge and then very carefully used hand tools to get a nice graduation around the outer lip. Then sandpaper really carefully. The foam divinycell can damage easily.

Oh yeah did I also mention that I had previously microed this whole forward face and that means lots of sanding to get the shine out.

Layout overkill

Routing with care

A nice oval racetrack

Pic one shows the glass laid in place with the foil still intact. A great technique for positioning rather than doing it wet on the job or trying to handle wet glass otherwise. I do a light coat of pure epoxy before positioning, get it settled then peel off the plastic and foil.

Then smoothing it all down and this was quite a job ensuring no air and straight fibers. Quite a job. Once the first ply seemed happy then ply two… same deal and then the third. I spent some time getting it down as it wanted to curl up a little at the hardpoint edges. Taking a while a letting the epoxy get stickier happened automatically. As I moved on to the other ones, I’d go back a check.

Once they were all down I put the BID top piece on and began the same process. Took a while. Then the dreaded peel ply for all the edges. By the time I was done almost all the hard points were covered with just a few patches bare.

It looked OK and I was done.

Glass foil and plastic in position

Mid hardpoint done

Outer hardpoint done