Twisted: 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: http://www.flickr.com//photos/andymac53/sets/72157630401758498/show/

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.