The wheel spats are virtually finished now - lots of hours put into these but the fit is now spot on around the gear leg.
The throttle cover is finished now too - just needs painting. It fits very nicely.
It must be time to start on the cowling!
First things first - I have made up some molds for brackets which will hold the cowling clear of the fuselage at the rear - by 25mm at the bottom and lower sides then gradually blending into the fuselage further up.
This results in quite a large exit volume with little drag penalty - as I hope to not have a lip on the exit. I'm also making use of the low pressure area on the sides of the fuselage to help the air leave the cowl easier. Something the Sea Fury and most other late model air-cooled fighters of WWII did.
If you look at the inlet and exits for the Sea Fury it is hard to believe they were enough to provide good cooling for 2,500 hp - a masterclass in cowling design I'd say. The designers also made use of the high speed flow out of the exhausts to suck the low pressure air from the cowl.
Having taken measurements of Pete's cowling inlets and exits I am happy to report that my inlets will be just over half the size of Pete's. With the outlets I am about two thirds of his volume - and without that drag inducing lip (and louvres) he uses.
Pete's inlets total 42,900mm squared, mine total 22,200mm squared.
Pete's outlets total 65,600mm squared, mine total 49,600mm squared with the oil cooler cowl flap open and 44,875mm squared with it closed.
As always the proof will be in the testing but with my sealed plenum then straight away we are talking about a 50% increase in efficiency. With the oil cooler I hope that there will be a further drag reducing element as well as an increase in efficiency with the ducts and sealing. The front of the cowling should also prove less draggy, particularly in the lower front cowl area (where Pete has his oil cooler).
Another principle of good cowling design is to have as little surface area as possible - and certainly no flat plate area's within 150mm behind the prop. Something my design allows me to do.
To allow for any changes to the design I will make a removable piece around the exhaust area which can be easily changed should my design not prove to work perfectly first time round.
So bear with me dear readers as the next few months will just be about the cowling - I hope it proves an interesting exercise - even though most of you will never need the information (you're much too sensible to build your own cowling!).
First stage is to protect the engine before pouring expanding foam around it, so that's where I'm up to this week.
Hopefully I'll be ready to pour foam next weekend and get carving.
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| Fitting spats to the gear legs - filling gaps with flock. |
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| Making the mold for the throttle cover - wood is to hold the foam against the fuse side. |
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| Spats fitting pretty nicely now. |
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| Throttle cover all done - bar painting. I used 4 layers of glass for this, it weighs just 36 grams. |
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| Covering the engine - putting foam around all the sharp bits first. |
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| Foam is to stop the plastic covering from piercing on any sharp bits. |
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| Making up the cowling brackets - these are 10mm deep for the upper transitioning section |
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| Ditto - these are 25mm - for the rest of the cowl. Using 7 layers of carbon here. |
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| Bye bye engine. See you in a few months. |
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| Hawker Sea Fury cowl. Not much exit volume for 2,500hp. |
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