yep will get photos and actually the Korff has been cut off a fair bit at rear and looks better from side. Wish rain would stop so can go to Gulf and give it heaps of hot weather to really give it a test Macca
On 20 September 2010 11:33, IAN G WILLIAMS <[email protected]> wrote: > Hi Laurie, > > Im really intertested in the air outlet design. The work we did putting > the L2400 in the Grob 109 clearly indicated the cooling issue was a major > one (ref Macca) so we put an airspeed indicator across the engine ... > pressure on top and static below. > We made the baffles as tight as a fishes bum so no leakage except around > the cylinders (ref Limbach tech note) > When we started the flight testing the "engine" airspeed was about 5 kts > SLOWER than the IAS. ( gave us a starting point) We made various flanges > around the exit and came up with a final design which gave an indication > 15Kts FASTER than the IAS. (Low airspeed only) which I thought was real > good. Resulting oil temps around 80 and head temps in the 180 area. > A climb at best climb speed and max continuous power the temps did rise a > little but still well in the range Macca thinks is OK. > I thought the Korff design was a bit ugly. Ours is also a bit ugly but > still retains a nice side profile of the 109. > > Will get my camera charged up and will send you a pic or 2. to see what you > guys think. > > Best regards > > Ian W. > > > > > > > ------------------------------ > *From:* Laurie Hoffman <[email protected]> > *To:* [email protected] > *Sent:* Mon, 20 September, 2010 12:07:36 PM > *Subject:* Re: [DOG mailing list] improving the wheel > > Hi Ian, > Any chance of a pic? > > > *Regards* > > *Laurie Hoffman > 46531233* > > > ------------------------------ > *From:* Ian Mc Phee <[email protected]> > *To:* DOG LIST <[email protected]> > *Sent:* Mon, 20 September, 2010 9:39:06 AM > *Subject:* [DOG mailing list] improving the wheel > > IMPROVING ENGINE COOLING > > THe air out if engine is always important and ideally the out area should > be 1.5 times min the area of in air at the prop (think 1.5 is the figure) > > Original dimona had gills on the underside going in, then later models head > these gills extending outside. Tech Bul 44 says add a lip to kick out air > and suck out more from inside. Then I saw Dave goldsmiths Dimona L2400 with > a big push down panel underside done it Koff and co mod to L2400. I made a > mould of that and several people are using same including Russell White on > his Grob 109A. It was an improvement > > Over last week Allen Rundell convinced this koff and co (L2400 suck out) > outlet was too small and we cut into it with angle grinder and then put a > 3cm big curved lip to suck out the air. Boy did it make a difference and we > may have to install a cowl flap (prob too cold on cruise) and add a bit of > cardboard in front of part of the oil cooler infact try as I might on full > power I could not get oil temp above 72degC in climb and now CHTs are down > by another 10degC. (now just <180deg C +/-2deg and STABLE) This is with our > Sauer S2500 engine (93hp), but our oil cooler is on underside of prop with a > lip to scoop in the air. Previously oil temp would go to 95-100 degC if you > kept the power on full. > > TO explain we did a big curve going in 40% the length of the panel and then > the 3cm lip which sticks down at about 40deg angle to the underside of > panel. Basically the whole underside of muffler is exposed when you lie on > your back.. > > Germans think they know everything but I can tell you they do not!! > > So guess my next design has to be a cowl flap to keep engine warm!!! > > Ian M > > Ian Mcpheeh > > >
