I find the existing cowl a little ugly (sorry Pete). Plus I think it may not be as efficient as it could be.
See the tuft flow photos below for a comparison between a traditional cowl inlet shape and a Lo Presti style round inlet design.
Not only are the traditional inlets much larger (therefore creating much more cooling drag) they have part of their opening in the turbulent (sometimes even reverse) flow which occurs near the spinner.
The Lo Presti style inlets can be up to 40% smaller as they are positioned further out in the hi pressure airstream away from the influence of the spinner. Also they are positioned further forward, closer to the prop. This makes the most of the hi pressure pulses of air coming off the prop before they become mixed with the free airstream further back.
There is a UL260 in France with this style of cowl and to me it looks a lot prettier.
I will go a different route with the oil cooler too. I plan on having a smaller inlet similar to the one on the Jabiru cowl and then a plenum which will expand and slow down the air before it meets the oil cooler. According to all the theory I have read this should result in better efficiency from the oil cooler plus a reduction in inlet size and thus a further reduction in cooling drag.
I know it is a lot of work to make your own cowl (200 hours is the average) but I think it is worth the effort in this case. We will see if I change my mind closer to when this has to be done!
Hopefully patience and persistence will prevail. (don't try saying this too fast).
 |
| Tuft flow. |
 |
| Existing UL260 cowl design. |
 |
| Lo Presti style cowl for UL260 on DynAero in France |
 |
| How the new cowl could look. |
No comments:
Post a Comment