Monday, 29 October 2012

Week 63 - Oil cooler and ducts

Hours to date: 606.0

Well the oil cooler install is coming along nicely. Lots of work this - I just hope it works as planned when I'm done!

This week I've installed the nut plates and also closed up the gap around the edges of the air scoop (where it sits on the flange).

I filled the gap using slightly runny micro and used our old friend duct tape on the flange to seal it and provide a release while doing that.

Fits spot on now with only a tape width of gap all around. I still plan to tape this gap when the plane is finally finished and painted - same procedure as done on gliders - to make it air tight.

After that I made up some brackets for the oil cooler and bonded them on the safety cell with flock plus 2 layers of glass.

With the brackets I drilled another couple of holes in them where they were to be bonded as Pete showed me some brackets made for composite bonding once and they were just metal brackets with a few holes in them to allow the flock to come through and make the bond air bubble free. (I also put some more brackets on the other side but haven't taken a photo for some reason).

The oil cooler must be rubber mounted as the interior of radiators are delicate things that don't like too much vibration. As a consequence of this install location there will be nothing like the vibration that it would normally be subjected to if attached to the engine. So that's another positive in favour of this location - that and the fact it helps bring the C of G rearwards too. I know Pete struggled with the C of G in his install, and ended up putting some components behind the firewall rather than forward of it.

The safety cell will need a very minor mod around the area of one of the hose connectors as space is too tight there. I've looked at the location on the inside and it is in an area where Pete has installed a 'glove box' type bag. It will be behind that and shouldn't present too much of a problem as my right hand will be on the stick whilst flying and won't be affected by a loss of space in this area. It's a pretty small mod in any case.

So having established the placement of the oil cooler it was time to begin making up the foam plugs for the inlet and outlet ducts.

Again a bit of a mess in the workshop with that green foam but I found that I got  to the right shape much quicker than when I was doing the air scoop. I put that down to a simpler shape and feeling more comfortable working with the foam.

I've also bought some gel coat - in flame orange! - and will be using that on the inside of the ducts so it leaves a perfect smooth finish when the part is released. This is important as we want the air flow to be as smooth and turbulent free as possible.

I've never worked with gel coat before but I think I understand the procedure and if it works it will certainly cut down on the workload of smoothing up and painting the inside of the ducts afterwards - which would be a hassle (if not impossible).

This means quite a bit more work on the plugs to make sure they are perfectly smooth before applying the gel coat as any imperfections will show on the surface of that gel coat.

After finalising the shape in foam I will apply body filler and sand until smooth then spay with a primer paint. After that some more sanding with progressively finer grades and then a polish should produce the right finish. Then the plug will only need PVA release adding and it will be good to go.

Nut plates on flange

Ditto (from the top)

Test fit - pretty good - just got to fix that gap now

Fixing gap with micro.

Gap done - perfect fit now.

Oil cooler installed with brackets bonded to cell

Inlet and outlet ducts roughed out of foam.

Thursday, 25 October 2012

EAA videos

These free videos from the EAA are a great help.

Full of tips and good advice for the budding plane builder

Check them out!

Monday, 22 October 2012

Week 62 - Air scoop and flange

Hours to date: 589.75

Making good progress with the Air scoop and having lots of fun doing it. I think this is the most rewarding part of the kit so far for me (although strictly speaking is NOT part of the kit).

After cutting out the panel I stuck the foam core of the scoop to that panel - using runny micro.

Next up I had to stick stirring sticks using body filler to the underside of the hole so that the panel would sit at the right depth - to allow for 3 layers of glass and some filler. So it had to be at a lower level that the surface of the rest of the fuse panel.

After that I used some more stirring sticks and body filler to hold the panel in place - as it has to be upside down when making the flange.

Flipping the whole thing over I put duct tape on the scoop panel - duct tape does not adhere to the resin so is an excellent mould release.

I also didn't like the gap being left open - and possibly having resin drip in there  and bond everything together - that would have been a disaster. So I filled the gap with some plasticine. This also does not bond to resin.

Next step was cutting out 4 layers of fabric - for which I used a paper template so each piece was accurately cut and the same size.

I decided to strengthen the edges of the flange hole with a layer of carbon - just to put back some stiffness that has been lost in this area. It's the same thing you have to do if you have a retractable version and cut the main gear holes in this area.

As I had read that riveting fiberglass is not a great idea I chose to add little buttons of carbon - two layers on each side of the flange in the areas where the nut plates would go.

The next day I was a little nervous that everything would release properly but it was absolutely fine. I got a stirring stick - sharpened at one end and slide that underneath the flange and gently eased it up. After doing this all round I flipped the whole thing over again and just pulled the scoop off with very little force - result!

Next came the clean up and cutting the flange down to about 15mm width all round except for the carbon areas for the nut plates.

A final test fit to see how the scoop sat on the flange and then it was time to put 3 layers of glass on the outside of the scoop.

Just as well I had Zen music playing - a bit a of a stress to get the fabric to happily sit around all those tight curves. I did it in 2 pieces - one big piece that pretty much covered the whole thing - then a smaller piece that was just the front lower part of the intake.

Next up will be putting body filler on the scoop to get it ready for painting (which I will leave up to whoever paints the rest of the plane). Then drilling the screw holes and installing the nut plates.

Hole cut for panel
Sticks to set panel height

Sticks to hold panel in place for flange

Plasticine to fill gap

Panel taped with Duct tape and gap filled

Cutting fabric with template

Carbon reinforcing

All done - released easily.

Flange cut down and showing postion of nut plates

Test fit - looking good

Getting 3 layers of glass on the scoop - not easy.

Panel update

Thought I'd give a panel update as I bought my first instrument this week.

Nothing exciting - just a compass. One of the 3 compulsory mechanical gauges needed in LAA aircraft in the UK.

I think I'm going to splash out and go for Winter Air Speed Indicator and Altimeter - Winter is a well known brand in the gliding world for their class leading gauges - pretty pricy though.

The other pic below is of the panel update mock-up which I did in Photoshop. I've printed it out at 100% and stuck it to the panel - as you will see I am planning to cut the knee holes out a bit more. After a bit of testing I decided that I wouldn't be able to get out of the cockpit in a hurry with my long legs catching on the panel. Also the back of the panel has a sharp edge so I will be modifying that when I get to it.

I've signed up for a two day course in January with the LAA. Day one is Electrics and day two is Avionics.

Hopefully at the end of this course I will feel confident enough to tackle the panel. Conveniently the panel can be built outside of the airframe and then installed later when everything is sorted.

I just heard through Facebook that Pete has finished wiring up his new Twister - so it looks like he will be taking to the air in that soon.

Magnetic compass

Panel mockup

Monday, 15 October 2012

Week 61 - Lower fuse and Air scoop

Hours to date: 573.5

I was damn busy at work this week so didn't get anything done during the week. But I had a decent couple of sessions on the weekend though and made some good progress.

I put the glass tape reinforcing on the lower fuselage seam - so that is all the fuselage reinforcing done now - save for the lower panel which will happen much later on.

The rest of the time I spent refining the shape on the oil cooler air scoop. It's starting to look good.

I put a layer of micro over it and added some of the fumed silica - which actually I didn't need to do as I have changed my mind about how I am making this scoop. Rather than get rid of the foam I will leave it in place to act as the core of a sandwich of glass. The fumed silica when mixed straight with resin acts as a gel coat - so it made the micro quite hard and so harder to sand. But it has made the scoop much less fragile to handle than when it was just foam.

Things are not so simple on this job as the panel this scoop will go onto is not flat - therefore the base of the foam scoop has to be angled to match the panel - and it is curved as well!

I'm pretty happy with the way it fits now and so I cut out the inside and sanded it smooth. 

I'll most likely just put a layer or two of lightweight fabric on the inside - and maybe 3 layers or so of a medium weight fabric on the outside.

Next step will be to determine what shape I want the removable panel to be that the scoop will get bonded to. This will allow for access to the oil cooler - post installation should I ever need to get in there for any reason.

I'll have to make a flange for that panel to sit on. I will most likely use nut plates underneath the flange and countersunk screws on top to attach it with.

In the rear view you can see the hatched rectangle which is where I plan to have the exit duct - ahead of that in dashed lines is the cowl flap location.

You can see why I need to have the scoop inlet well clear of the boundary layer - with the undercarriage leg fairing disturbing the air in front. Although this gear leg fairing is nicely made so it shouldn't cause too much loss of flow.

Fun and games - as I've never done anything like this before - so it is a bit of a 'moving feast'. Still that's what building a plane is all about - learning new things...

Lower fuse seam reinforce

Scoop in place on lower fuse

Inside carved out


Location of exit duct, cowl flap and scoop

Gear leg fairing

Monday, 8 October 2012

Week 60 - Elevator Hexes and Air Inlet

Hours to date: 562.0

Been a bit lazy last week - doing stuff around the house rather than working on the plane - no good.

Stepped it up again this week though.

Tidied up the root ribs on the tailplanes and put the reinforcing carbon roving around the fiberglass hexes. These hexes will get bonded into the elevators and slide over the metal hexes in the tail - so must be a perfect fit with no play.

I found I had to 'peen' the edges of the rivets on the metal hexes as they stick up a bit. Also found I had to file the edges on a few as they were not perfectly in line with the raised part of the hex.

6 layers of roving are needed, I waxed everything on and around the metal hexes and taped up the area of fuselage that is nearby.

After wrapping the roving round tightly I put a strip of peel ply over that - then used a strip of clear plastic around that and finally a strip of duct tape. This made sure that the roving would stay wrapped securely.

Worked out okay - it's best to take off the hexes after an hour or so and give the metal hexes a twist to make sure that no resin has dripped in there and bonded them in place. Then push the hexes back on to set.

After about 5 hours I took them off again and did a 'knife trim'. Something I have read about but not done up to this point. Basically you just wait until the resin has pretty well set but not completely hard and then it is dead easy to trim off the excess carbon for a neat finish on the edges. Works a treat!

I also did a bit more 'donkey work' with body filler on the tail, fuselage, and the spar tunnel.

I also bonded on a glass reinforcing tape around the canopy surround where the fuselage and safety cell join. Body filled it too - looking good.

Finally because I was getting bored with the smell of the body filler and sanding I decided to start on making a male mould for the oil cooler air inlet.

Using the urethane foam blocks I previously micro-ed together and starting with a template that I had printed out on the computer I was able to rough out the shape with a Stanley Surform. (I think this better known as a rasp?)

After that it was sanding with 80 grit and then 180 grit sandpaper to get the shape I was after.

Lots of fun but very messy stuff this urethane. I had to stop every now and then and vacum up the mess.

Doesn't look too bad - I'm not 100% happy with the shape but will leave it for a bit and see how I feel. 

After I am happy with the shape I will add a slurry layer of micro and some fumed silica which should make a nice hard surface which is still easy to sand. Then just sand that until it is perfectly smooth and put some mould release on it - most likely I will use PVA (different to PVA glue). Then it will be good to use for laying up on - the foam will be carved out from the inside once the part has set - thereby destroying the mould - but I don't think I'll need to make more than one of these so thats less work than making female moulds.

I also received a missing part of the kit from the factory - it is for the integrated tailwheel and will replace the lower tail area - this will then be wide enough to accomodate the tailwheel and it's turning clearance.

Root ribs tidied up

Roving bonded onto fiberglass hexes

Hexes with 6 layers of carbon

Donkey work - filler on spar tunnel

Roughing out shape with Surform rasp

Starting to get there

Looking okay

Angled inlet to get more airflow in the climb

Done for now.

Replacement lower tail from factory

Tuesday, 2 October 2012

Twister attack

Adrian Hatton looks like he's going in for the kill in this shot.