Eye Candy Part 2

Some more pics that others have taken.

At the Sywell Rally in 2018

At Breighton for the Club class aeros comp.

Parked up in Reykjavik Airport, Iceland on my way across the Atlantic.

Parked up next to Johan's Twister at Sanicole for the EFLEVA weekend.

I made FlightRadar's Year in Review with the Spitfire outline drawn over Southern England as my tribute to the RAF100 anniversary.

A more detailed view of the path I flew. The coverage is not perfect hence the jagged lines here and there - the actual SkyDemon path flown was much smoother than this.

Landing at Lee-On-Solent in October 2018.

At Oshkosh in the flypast.

At Oshkosh, and featured on Kitplanes 'Guess what' section of their website.

Over Lake Tahoe as part of the Kitplanes early morning photoshoot.

A 'break' from the photo ship.

The best shot from the Kitplanes photoshoot. I like the reflections off the prop disc.

Close up from the Kitplanes photoshoot.

Landing at Conington during the Aeros comp.

Fuel overflow

When upside down the fuel overflow outlets are in an area of low pressure and so vent out a lot of fuel.

This has been a problem since day one and I've only just got around to a long term workable solution.

My idea was to restrict the size of the outlet hole which as standard is quite excessively large at about 6mm.

For a while I was just using a piece of duct tape over the outlet with a small hole pierced in it but that did not last very long as the fuel soon got to the sticky part of the tape and made it fall off. I needed a more permanent solution to the problem.

So I made up two small discs out of thin ali sheet and drilled them in the middle with the smallest drill bit I had - 1mm.

These were then glued to the outlets using 5 min epoxy.

A recent flight test proved that these to work well - there is still a tiny bit of fuel leaking out during and after inverted maneuvers but it is hardly anything compared to before.

I never fill my tanks till they are overflowing so there is plenty of space in the top for expansion should it sit in the sun - the fuel can still flow out of the outlets at a reasonable rate anyway with the 1mm hole so I don't think expansion is going to be an issue.

Fuel venting out whilst upside down. This is before the fix.

Ali plate restrictor with 1mm hole drilled in it.

Wheel pant mod

With the fixed gear Twister it is impossible to pump up the main gear tyres while the wheel spats are in place. You even have to remove the wheel pants just to check the tyre pressures, which is quite impractical.

So I decided to mod the pants by making a small panel which is easily removable.

This panel allows enough access room to both check pressures and pump up the tyre if necessary.

I used 3 layers of carbon for the flange with small patches to make 4 layers where the riv-nuts were to be located.

The panel is flush and the two small M4 dome head Allen screws don't make much drag.

Size and location of the panel. Tape was left on till I painted the flock (which was used to fill the cut gap).

View of the flange and riv-nuts.

Once finished it is hardly noticeable and adds very little drag.

Cowling outlet experiments

I long had the suspicion that my outlets on the cowling were too big. 

I erred on the side of caution when I was making my cowling and made both the inlets and outlet quite a bit bigger than the calculations in case things did not work as I first thought, it being easier to make them smaller than make them bigger afterwards being my thinking.

Until recently I had not bothered to restrict the outlet to see if it made much difference to temps but finally got around to doing that this Winter.

For the first trial I blocked off approx 50% of the outlet (the lower half) using a piece of foam pipe insulation. This didn't seem to make any difference to the temps at all.

I then tried blocking off approx 80% (some of the side outlet being blocked off this time). This did make a difference - I saw a 10 degree increase in the CHT's with a slight rise in oil temps (as the cylinder heads are oil cooled - when they run hotter the oil does too).

On the second test the hottest CHT in the cruise was 99 degrees or some 60 degrees below Max continuous. It was 115 degrees in the climb. All CHT temps stay within 3 degrees of one another (thanks to my 7 odd iterations of baffles on the front cylinders).

These tests were conducted at 5,000 feet with an OAT of approx 2 degrees.

It goes to show I went a bit overkill on the inlet and outlet sizes when building the cowling and it also shows that the sealed plenums work very well.

It also shows that the lower outlet area doesn't do much - it being in a high pressure region does not encourage flow out of the cowl. However the side outlet area works very well as they are in a low pressure region which means the low pressure air coming out of the cowl is more likely to flow to this region.

The beauty of the foam pipe insulation is that it is very easy to remove when the weather gets warmer.

I've also conducted some True Airspeed Tests to see what the exact cruise is at certain RPM's. I used to guesstimate at 125 knots True when light and 120 knots True when full of fuel and baggage (when touring).

I flew 4 way compass headings then added up these speeds (from the GPS groundspeed) and then divided by 4 to get the average. At 2,800 rpm (max continuous) at 5,500ft this resulted in a speed of 129 knots True.

I then flew the same 4 way test at 2,700 rpm (my usual cruise setting) at 5,500ft and this resulted in an average of 125 knots True.

Flying at 2,800 burns around 17 litres per hour but at 2,700 I burn just 15 litres per hour so that is a better rpm to cruise at for economy (and the engine seems to like it better too).

In hotter weather it will not cruise quite as fast due to reduced power from the higher inlet air temp for the engine and the extra drag from the open cowl flap - which I have found adds about 2 knots to the cruise from fully open to fully closed.

Approx 80% of the outlet blocked off with foam pipe insulation. The first test was without the small additions of foam at the top on the sides.

View of the left hand side. The approx 20% remaining outlets are more than enough in Winter to adequately cool the engine.

Tailchase fuun

https://youtu.be/zjQVbThNSzA

Tail-chasing my mate James in his RV-6. (click on link above to see the video).

Canopy repair - again

In December the Twister had it's annual inspection and after sending off the paperwork I did not get anything back through the post - the LAA normally turnaround a Permit the same day if all is in order.

So after a week I phoned the office and was told - "Oh yeah that's on hold as there is a Repair that has not been approved yet".

This Repair was the one done to the canopy frame and hinges after I got back from the Oshkosh epic in 2017. The Repair paperwork was done to satisfaction (or so I thought) in February of 2018 - so what was the hold up?

Their excuse was that they never received the email I sent which contained all the photos and answers to their questions. Quite frankly I do not believe this story as if the email did not arrive then it would have bounced back to me - which it didn't. It is clear that the LAA don't have any kind of system in place to ensure something is not processed internally. I had assumed all was well as I had not heard back about the Repair.

Anyway on sending the email again it was swiftly approved - except now I had to get an inspector to look at the repair and sign off what I had done - more paperwork!

So I arranged an inspection and he discovered that the reinforcing carbon I had used to thicken up the hinge brackets was cracked at bottom end - not surprising since I had done this repair 'in the field' and so the reinforcing had a weak point which was at the end where it was not really bonded to the existing hinge as it was just butted up to it.

Actually I was happy in a way to have another opportunity to repair the hinges properly this time, so I decided to take the canopy off and repair it at home.

I started off by taking away some of the reinforcing carbon, totally so in the region where it had cracked.

I then made up two small blocks of wood that would sit inside the hinges and allow a clamp to force the carbon up into the corner where it had cracked before - thereby ensuring a complete bond this time round.

The back hinge was not cracked but I decided to do this repair to both hinges anyway to make them right.

The front hinge got a further layup of 3 layers of carbon in a strip which was laid over the entire surface - see pics - to closeout the layup and add even more strength to the hinge. The front hinge is subject to much more flex than the rear one due to it's distance from the retaining wire which supports the rear hinge much better as it is closer to it.

After the carbon work was done I primed and painted the whole area, making a much better job than I did before.

The canopy is now back on and signed off by my inspector - I am now waiting for the Permit to arrive but this has taken more than a week already. In the meantime I have used the time to touch up a few things here and there but hope to get the Permit soon.

If I could start from scratch and build again I would consider reinforcing the inside of the hollow canopy frame with runny flock in the area around the hinges. I would also take away some of the micro in this area and replace it with carbon and also reinforce the hinges as I've done here too.

Canopy off and at home to do the repair - a much better idea than trying to do it 'in the field'.

This shows the crack that developed in the end of the carbon reinforcement - it was just butted up to the end and therefore not really bonded to the round portion of the hinge.

Two blocks of wood, shaped to fit and wrapped in Duct tape to release, enable clamps to force the new carbon reinforcement into the corners of the hinge.

Many layers of carbon were used here - it is easy enough to take away any excess afterwards.

One further step with the front hinge with a layup of more carbon over the entire hinge to close out the reinforcement.

Front hinge with it's new reinforcement. Much stronger now.

Rear hinge. You can see that the carbon has added about double the original thickness of the hinge so now it is 3 times as thick overall.

Time to prime.

Front hinge after paint and back in place on the aircraft.

Outside looking better now - I have since feathered off the edge of the paint too.

I am a donkey

I tried moving around an oil hose recently and that required me to first drain the oil. 

I ended up having to do that twice and each time I did not bother to use a new copper crush washer on the sump plug, also I was not using a torque wrench on the sump plug and have been over tightening it as a result - made much worse by the use of an old washer which provides no 'feel' as to the torque as it does not have any crushing properties once it has been used.

So I ended up stripping out the thread in the sump!

What a donkey...

I discussed the possible fixes with Jonathan the UL Power agent here in the UK and decided that a new sump was the best fix - particularly as it ended up being cheaper than a Helicoil type kit to fix the thread (the best versions of this coil - TimeSert - are very expensive).

So I've had to put a new sump on. In doing so it gave me a chance to see inside the engine. 

I noticed the cam lobes had a bit of wear on them which did not look right to me - the engine has just over 300 hours on it.

I consulted Jonathan about this and he shared it with Patrick in the factory too. This was his response (I also asked about the exhaust valve pic below too).

"Morning Andy

Feedback... 

1. Wear on cams nothing to worry about.  A bit more than normal.. but OK.  (Always check your oil filter mat and magnetic plug for material tho!)

2. Your valve picture... apart from evidence of a tiny leak due to uneven bolting of the exhaust manifold the rule of thumb is 'uniform burnt pizza is good'.

Here is an unofficial  guide to valves..

White deposits from lean  / hot

Black deposits from rich / cool

Brown/reddish burnt pizza is Goldilocks  zone 

With the caveat of 'uniform distribution '

Green is bad. Holes are bad. Uneven is bad.

If your compression/leakdown us good and CHT / EGT good you are a winner! 

Normally all 4 exhaust valves should be similar in appearance.

I wonder if this wear was caused by all the Swarf that was present in the engine, when it was new, after machining? - as evidenced in the first few oil filter changes when checking the filter element (if you remember).

Anyway some lessons learnt. Particularly about always using a new copper crush washer and using the correct torque values - 25nm for the sump plug. All the torque values can be found in the Illustrated parts manual from the UL Power website.

Thread stripped out by Mr Donkey - me.

Old sump coming off - took a few 'love taps' with the rubber mallet to come away.

Oil pickup in the old style iSA engine. The long threads limit movement of the pickup.

A chance to look inside the engine.

This cam lobe wear did not look right to me so I asked.

Another lobe with wear. Strangely the front No.1 Cyl lobe did not appear to have any wear.

Overview of the cam.

Wider view of the above.

No.1 Cyl exhaust valve - even 'burnt pizza' is good. The other 3 looked just like this one.

New sump in place.

Maintenance matters, fuel leaks and TPS (again)

I'm pleased to say that yesterday G-FUUN passed it's annual inspection again, so it's good for another year.

Unfortunately I've also had another series of fuel leaks.

I had originally thought they were only coming from the Ali end plates - specifically the central bolt through the fuel sender that tightens the plate (via an ali tube with a thread inside the tank) but as it turns out that was not the only cause.

I've since replaced the ali end plates with new ones and ditched the fuel senders altogether as I now have solid state fuel sender probes. The rubber seal on the Falcon gauges was changing over time and caused some leaks.

The other thing I've done to improve the end plate sealing is making up some thick rubber washers which have a slightly undersized hole drilled in them. Screwing that onto the thread and then putting a large metal washer in front on the outside helps to seal things better than just relying on Proseal. I also made up a smaller washer for the inside which is squeezed between the plate and ali securing tube.

No leaks from the plates anymore!

However recently I got another fuel leak, very small, just weeping out, but very annoying as it took me some time to find out where it was coming from.

To start with I thought it was further up the tank and fixed that supposed hole from the inside with flock - see pic below.

But that was not the cause.

I then bought a UV dye kit which consists of a UV dye and a UV torch. You mix the dye in with about 10 litres of fuel then pour that into the tank. Wait a while then in the dark shine the UV torch and you are supposed to see only the fuel and find out where the leak is from.

Well this did not really help and I ended up leaving it feeling quite frustrated as it still was not clear where the leak was coming from.

When I came back to the job the dye had actually helped as it is orange and visible in the daylight too so does point to where the fuel has been.

A tell tale orange mark from the underside of the wing near the drain finally pointed me in the right direction. It was the ali plate that is bonded into the tank and lower wing skin that was the problem. So I used runny flock to fill in the cavity around the drain and overflow/breather fitting on the inside. Being runny this found it's way into every nook and cranny of this area and sealed up the leak good.

No more leaks again (for a while anyway - fingers crossed).

I will do another blog post about the fuel senders when that is finally sorted as it too has been a bit of a saga and is hopefully soon to be resolved. The manufacturer has admitted to a faulty set of modules for these and the replacements are finally here but stuck in Customs at the moment. 

Finally the Throttle Position Sensor - it has started to fail on me again. Happening when I took of from a bumpy hard runway the other week at Great Massingham.

I checked when I got home and found that it has failed at almost exactly the same number of hours as the previous one - 123 hours approx.

Ironically the next week UL Power released a Service Bulletin which said they are no longer fitting this type of sensor to any new engines in the future. Which to me says they admit there is a problem! 

They are converting to a Hall Type sensor - which does not have the sensing parts touching so therefore is much more robust to the vibrations of an aircraft engine installation.

They are offering the Hall Type sensor as a mod to us older engine users but at a price! Around £600 which is a bit cheeky considering the Hall Sensor is a £25 part. True a new inlet block is needed and an ECU remap and additional wire but £600 is a bit rich.

G-FUUN with it's clothes off for it's annual inspection. It passed again 'without comment'.

 

New fuel sensor probes - more about those in another blog post.

Fuel tank end plates - now without the Falcon senders and with rubber sealing washers.

Rubber washers I made up to help with the sealing of the fuel tank end plates. These are working well.

Port wing off to fix this fuel leak.

I thought it was coming from this 'hole' part the way up the tank.

Which I fixed with flock but it turned out was not the cause of the leak.

This area around the drain and overflow/breather connections was the cause of the leak and has been fixed with runny flock allowed to run into the area.