Thursday, 31 March 2016

Week 242 - Fin/Rudder gap, Horz Stab Gap and mod, Oil door

Hours to date: 2400.25

I'm happy to report that the cowling is done (virtually!)

Onto some other jobs.

Following the manual technique for making an even 2mm gap in the fin to rudder junction works very well. Make sure to use more runny micro than usual - although even mine ended up with some tiny air bubbles here and there.

I finally got to finish the oil door. The hinge has to be as far away as possible from the opening for the door to swing up and clear the edge.

Just some body filling on the flush rivets and a little more primer and the oil door job will be done.

Onto my tailplane securing mod. As well as the pin I am making a fail safe connection using a piece of solid carbon sheet bonded into the tailplane and another into the root end of the fuse. There will be a thread cut into them both and then a dome head allen bolt will be screwed and Loctited into place from below (on the outside).

Also with the pin rather than having it go underneath the elevator pushtube I am running the pin from the front instead - thereby eliminating the possibility of the pin and its nylon sleeve from being worn and failing - as happened on a UK Twister a while back (see my previous post about it from February 2014).

As I plan to keep my Twister permanently rigged then the internal pin is not a hassle for me - it would be if you derigged often as you have to take the rudder off to get to the pin.

The other job I did was fill the gap between the tailplane and fuse - again as per the manual's technique. We will see how that turns out next post...

Leveling top of fin using a sheet of Ali (waxed) and a heavy weight on top with runny micro underneath as a filler. Make sure you level the fin top first will a spirit level.

Cowling all done and with a coat of white primer to see how it looks when it is the same colour as the fuse.

Nice curves don't you think?

Rudder after same treatment as the fin - the runny micro gives a smooth uniform finish.

Even 2mm gap between the rudder and fin now.

Bonding in a solid lump of carbon for the tailplane fail safe connection.

This shows the location. I made it slightly too deep so I can sand it down flush later.

Inside - the pin is now going in from the front rather than the back as before.

Masked off tailplane root with packing tape as a release and then flock on the tailplane in the honeycomb to fill the gap. All pins and exposed stuff that is not bonded is waxed too.

Ditto. Using micro and same technique as the rudder/fin on the elevator gap.

After pushing together (and putting the pin in). Will be sanded back to profile when set.

Oil door finally finished. Just have to fill, sand and then prime the flush rivets and we're done.

Oil door gives good access to the dipstick.

Good gap between the cowl and door when open.

Sunday, 20 March 2016

Week 240 - Cowling Part 15

Hours to date: 2364.25

Edging ever closer to finishing the cowl. 

I put a coat of primer on thinking I had it looking quite smooth with the filler but sure enough all it did was show me just how much more work I had to do!

Oh well it will soon be done, just got to stick at it and make it all tickity boo now and ready for paint.

One job that did go well for me was sorting out the fasteners at the top rear of the cowl. These go inside the fuselage and as it is honeycomb then this was much too thick and the wrong material to rivet the sprung back plate to. 

So I Dremeled out a little section back to the outside layer of glass and bonded in 3 layers of carbon to make it strong enough for riveting. Working in a very confined space here and had to use a mirror for one of them. Anyway it all worked out - see pics below for how I did it. A useful technique which I would recommend to anyone who wants to go for this type of fastener in a sandwich honeycomb construction.

The oil door is proving to be much more tricky to sort out than I initially thought.

It's all down to the hinge which is a hidden type. You can buy them for $40 US but I thought I can just make one. Well, not sure if I got the shape wrong or what but it does not work for me - at least not yet anyway - I will keep trying but I think it may be to do with the position of the hinge.

Hopefully by next week I can post about something other than the cowl! (I appreciate your patience dear readers).

Just showing how close the cowl fits together and how flush it is with these fasteners. I am still working on the spinner to cowl gap - stay tuned for an update on that next week.

Oil door with Camloc fastener in place.

View from the inside. I had to 'shape' the Camloc to fit the curved door.

You can see how much work needed to be done to the cowls due to my shitty layup technique. I think they would still need filler anyway as the fabric weave was showing through in many places.

Inside view of the carbon layup for the sprung cowl fasteners. I wrapped a fastener in packing tape and waxed the screw so it held the carbon in place while it bonded but did not stick to the layup. Worked a treat.

View from the outside with the waxed screw holding it in place while it bonds.

Second attempt at a hidden hinge - still not working so will have to try again! Door is catching on the top of the cowl when opening so I think I will have to move the position of the hinge.

Cowl fastener riveted in place.

After a coat of primer this was the filler needed to fix all the errors - haven't even started on the top half yet! Fun and games...

Sunday, 13 March 2016

Week 239 - Cowling Part 14

Hours to date: 2334.75

Slowly getting there with fitting the cowling.

Another week and it should be all done I hope. Then I can move onto some other jobs.

Hinge pin securing at the rear - will use one of the cowl fasteners as double duty to secure the pin here.

When the pin is pushed right in it is away out of sight.

Masking off the top cowl to make the flange on the lower front half.

Flange all done and Tinnermans in place - all very flush.

Early look at oil door size and positioning.

I made this mock up out of cardboard to see if the hole size was going to be comfortable for my hand to fit through. - I ended up making it slightly bigger than this width wise.

Final alignment of the inlet rings before bonding them in place on the cowl lower.

Bonding in the inlet rings - just a small amount of flock at the front at first.

Also closing up the gap in the front top section here.

Drilling and countersinking the fastener holes for the rear of the cowl.

Oil door just after cutting out. Figuring out the placement of the hinge here.

Bonding in the inlet rings from the back now using a shed load of flock - very secure and strong now!

Laying up the flange for the oil door.

Rear cowl brackets with sprung fastener in place - pretty flush so won't affect the air flow too much.

Sunday, 6 March 2016

Week 238 - Cowling Part 13

Hours to date: 2300.5

Part 13 - but not unlucky for me.

Holy Cowl - we seem to have a cowling now!

Lots of air bubbles to fix up but I knew this was going to be the case when I screwed up the layup somewhat.

Plenty of photos this week, so I'll let them do the talking for me.

Ali piano hinges for the sides of the cowl

Extruded type - rather than folded round metal as usual. You must use this type on a cowl.

Stitching together the two halves of the cowl - one side at a time.

Seat belt extension all done.

Tail plane extra securing mod - more about this in another post.

Remember to cover your seat belt with a plastic bag in the middle before bonding on the fuse lower half or the belt will get stuck in place with the micro.

Six months work to get to this point. Cowl finally out of the mold - blue tinge is from the PVA release film. Lots of air bubbles to fix!

Doesn't look too bad. Now figuring out where to part the cowl using a piece of string here.

More figuring out with string for the parting of the top half of the cowl.

Test piece with a Tinnerman washer system - this is how I will fix the cowl at the front and back.

Another test piece with various rivets and a fixing plate for the Tinnerman washers.

Using the mold to steady it while I cut the parting line. This mold has its benefits ya know!

Pre-drilling the hinge - actually didn't need one hole every inch - every 2 inches is enough.

Using a metre long metal ruler as a straight edge for the cut of the parting line for the hinge.

Hinge clamped into place ready for drilling and riveting.

Using Clecos to hold it in place as we go.

End result is a flush riveted join - will most likely close up the gap a little bit with flock.

Lets try this for size...

Some more trimming and fitting to do at the front here. Metal inlets will be bonded to the cowl.

Looking pretty sleek I'd say.

This shows how much exit volume I have - rather generous. I hope this works!