REFLECTOR: Engine cooling NACA scoops

[Dave Philipsen]

That's interesting.  I know I need more oil cooling too.  Sometimes on a 
hot day in the pattern it will creep up to 220 or so.  If I'm cruising 
up around 8-9K it will settle in right around 190-195 but that's after I 
have leaned aggressively past peak and I'm sure the power is down pretty 
low.

The guy I bought the plane from was obviously not much of a stickler on 
getting it right.  He had bayonet probes on the bottom side of the 
engine which didn't really tell the whole story.  I've done quite a bit 
of work on the baffling and enclosing the cylinders more to keep the air 
around the fins longer and I've tried to plug up every last little 
pinhole.  Your idea about using a light is a good one.  I'm even 
thinking about attaching some silicone strips to the inside of the 
cowling where the baffling seals touch it or perhaps sanding it down and 
using some micro to smooth out that area. The fiberglass is pretty rough 
on the inside and a little air might be getting past there.  Yesterday I 
finished putting a smooth approx 3/16" radius on the leading edge of one 
of the scoops in an attempt to reduce turbulence.  If the temps drop 
down a bit on my next flight maybe I'll do the same to the other side.

Where do you get cooling air for your oil cooler in the back? 


Brent Bourgeois wrote:
> Dave,
> I vote for more oil cooler.
>  These engines with piston nozzles transfer alot of heat to the oil. Check your baffles in the dark with a light under, seal all leaks cracks with silicone. I have done a lot of pressure studies on the inlets, cowl(top/bottom) and oil cooler. I have 2 coolers, the front is for an IO540 with another smaller one with its owns cool air inlet on the back baffle. I am in the process of making my armpit scoops smaller for less drag. I have the same engine you have and run 320 on the under probes and 360 on the top plug probes. Never seen over 425 on the top even under the worst case. I have spent a lot of time on this and might be able to help.
> Where are you?
>
> Call if you need,
> Brent
> N61VB
> Std REG
> IO-360
> 985-785-8299
>
>
> --- On Wed, 7/16/08, Dave Philipsen <velocity at davebiz.com> wrote:
>
>   
>> From: Dave Philipsen <velocity at davebiz.com>
>> Subject: REFLECTOR: Engine cooling NACA scoops
>> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
>> Date: Wednesday, July 16, 2008, 7:16 PM
>> I have been struggling with marginal cooling on my STD FG
>> equipped with 
>> armpit scoops.  The only way I can keep cool enough during
>> cruise is to 
>> fly above 6000 feet and run LOP.  I have been somewhat
>> successful at 
>> bringing the temps down by repairing/reworking the baffling
>> and seals as 
>> well as doing a little rework on the scoops themselves but
>> I'm still not 
>> happy with it.  I'm seriously thinking about
>> retrofitting it with the 
>> overhead NACA  vents and downdraft cooling.  My question
>> is:  Does 
>> anyone have templates that I could borrow/acquire so I
>> don't have to 
>> guess about the size and positioning?  Also, should I
>> expect to see a 
>> small improvement in cruise speed with the NACAs after
>> removing the 
>> armpit scoops?
>>
>> -- 
>> Dave Philipsen
>> Velocity STD-FG
>> IO-360
>> N83DP
>>
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-- 
Dave Philipsen
Velocity STD-FG
N83DP