Sunday, 29 July 2012

Week 51 - Gear align and setting Dihedral

Hours to date: 452.75

I haven't got much done since the last post. Visitor staying with me and I went to the Olympics yesterday - to watch the Cycling Road Race.

As far as the gear alignment goes I think I am there now. I used a laser level to cross check my previous work with the string and it turns out that the string gives a pretty accurate measurement. 

The error was less than 0.1 of a degree - that was on the starboard side and on the port side it was a little more (I kind of knew this would be the case with the port side as I added a tad too much plywood to that one). So I've taken both the plywood blocks off again and got them to where I think they should be perfect.

The other thing that I've done is drill out the 8mm hole in the gear legs and axles so that they can be attached with the allen bolt and made rigid - there was room for play before. I still have to fit the brakes to the axles but this can be done later.

Another job that needs to be done is making sure that the gear has the right amount of dihedral.

To do this I had to build a little contraption out of wood and a steel tube. See pic below.

I've just tacked the plywood blocks back in place and will do a final-final alignment and dihedral check before they are completely bonded in place.

Axle bolted to gear leg.

Laser level check

Dihedral setting rig

Bar is bent to 60mm above floor to set dihedral

Sunday, 15 July 2012

Week 50 - Gear align and spar tunnel

Hours to date: 438.0

A fairly good day in the workshop today. 

Managed to get the gear legs aligned to 0.25 degrees toe-out. I had to take off 10mm on the Port, and add 8mm to the Starboard gear plywood brackets to get them both the same alignment.

With the plywood brackets removed I was able to finish the spar tunnel to safety cell reinforcing with carbon.

Next thing to do is put the plywood brackets back in place - I will just tack them in place with flock to start with. Then check the gear legs again (getting paranoid here) before fully flocking and glassing the plywood brackets in permanently.

On Friday I went to Farnborough. They now no longer have the trade halls open on the Public days (Sat and Sun), but release some special tickets for the Friday which I was able to get - so I had a good look at all the new tech on offer. Pretty interesting to see the Skylon stand with there prototype Sabre engine - the future of space travel? More about Skylon here:

Some pics that I took on this link:

Final bit of spar tunnel to safety cell reinforcing

Tuesday, 10 July 2012

Week 49 - Main gear alignment

Hours to date: 431.5

I spent most of Saturday checking the main gear alignment.

I started by bolting the gear in place - the aluminium bars that go over the gear and hold it in place need radiator hose (30mm works well) over the parts where they would touch the gear legs. They also have 1mm thick rubber sheet underneath between the gear leg and flock mounting block.

Then I just measured the distance between the wheel hubs, found the centreline a good way back on the fuselage - over 2 metres back - and then measured out from there half way with an old broom handle as a straight edge.

I then used string from the wheel hub face all the way back to the broom handle and kept moving it until it was in a perfect straight line with the hub face.

Turns out the Port gear was indeed Toe out - by 4cm at 210cm distance. I then found an angle calculator tool on the internet which made it a breeze to find out, from the two values I knew, what the angle was. It was 1.07 degrees for the Port gear. So I need to alter that as I am shooting for 0.25 of a degree toe out.

On the Starboard gear it was a different story with that being Toe in. By 0.4 of a degree. So both gear leg brackets will need to be moved.

I'm not sure why the factory flocked them on there in the first place - the manual shows these not being in place as supplied.

As you can see from the final photo the holes in the wooden brackets are in very different places. I still haven't figured out if there is a smart way to know how much to move these brackets by to achieve the desired toe out - hopefully I'll have a brainwave before I do this or just go back to the string method if all else fails.

Also as a result of doing this job I found out that the wheel axles I have been supplied have be made wrong. There is a flange that is welded on the axle and I am certain it is in the wrong place. I've contacted the Silence factory to see what they say.

UPDATE: It turns out the axles are fine - it just that the wheels are the wrong size. So the wheel supplier will be sending me two new wheels soon. Sorted.

On Sunday I had another break from the kit to go to the world's largest military airshow - The Royal International Air Tattoo - at RAF Fairford. A brilliant show as always with lots of aircraft I had not seen before and top class flying by all.

Some pics here:

Gear with rubber hose

Establishing gear alignment

Plywood brackets - holes are in quite different positions to each other

Friday, 6 July 2012

Week 48 - Spar tunnel and Oil cooler

Hours to date: 425.0

It's been a lazy couple of weeks - busy at work and then going to Goodwood for the Festival of Speed.

Pics of Goowood here for the petrol heads amongst us:

Anyway I did manage to get some more of the spar tunnel reinforcing done. Just one area left to do at the front underneath - but I will leave this until I have determined that the wooden main gear brackets put in place by the factory are in exactly the right place.

Taildraggers must have the main gear parallel to each other and in line with the direction of travel. Either that or up to 0.5 of a degree toe-out. If they are at all toe-in then a very squirrelly aircraft is what you will have. I'll be aiming for maybe a 0.25 degree toe-out.

I've also got both seat belt reinforcements covered with carbon now.

Now onto the oil cooler.

Being that my kit is a fixed gear version I discovered that there is a large space in between the safety cell and the wing root that is normally taken up by the main gear. This space will allow for a much more efficient set up of the oil cooler - there is ample room for ducting in there to achieve maximum efficiency with the minimum of drag.

The area under the wing is also an area of high pressure - good for the intake and the exit duct will be a simple slot further back on the wing. I will also add a cowl flap on the exit to give some control over the temps (on the ground and in the climb I see this flap being open - but closed in the cruise - much as a P-51 radiator set up is.)

I will copy the F-1 McLaren’s F-Duct for a ram air inlet - sat a little way up to avoid the boundary layer of stagnent air that is close to any skin surface. McLaren know a thing or two about aerodynamics!

I've contacted the UL Power factory and asked them about the extra long hoses and if they see that as a problem. They responded by saying it shouldn't be a problem but advised to use larger diameter hoses to minimise the pressure drop. They also recommended just a 13 row oil cooler as sufficient for cooling. I know Pete uses a 19 row so I will go for a 16 row - just to be on the safe side.

Because of moving the oil cooler away from under the cowl, the cowling will therefore be able to follow the profile of the sump and should look much prettier than Pete's setup - as well as being much more streamlined.

I'm off to Fairford tomorrow for the Royal International Air Tattoo - the worlds biggest military airshow. Should be good, a few new aircraft and display teams I have not seen before.

McLaren F-duct

Radiator theory - 1/6 opening is all that is needed

Dummy oil cooler made out of foam for position check

Pencil lines indicate oil cooler ducts and position

Seat belt support reinforced with more carbon

More spar tunnel reinforcing