Hatz Biplane Association

Last week I was test flying a new Hatz Classic with an O-320. I flew several flights with a wood prop which produced 2700+ rpm at takeoff power and was sluggish and slow. The old temp would increase to 230 and climbing, so I would land early when it climbed.

We changed the prop to a metal prop , 72 x 58 I think, and the takeoff power was 2400 rpm and the plane was much peppier and faster. The surprise was that the oil temp reduced down to 205 stable.

Would not have thunk a prop would affect oil temp.

Ryan,
If you post your question on BiPlane forum you will get plenty of advice on possible remedies.
Cheers
Fraser

Any suggestions on what I could do to lower my oil temps?

The plane has a fully cowl'ed Lyc O-320 with the oil cooler behind the cylinder in the rear left corner. All baffles appear to be in good condition.

On my trip this weekend the oil temps hovered around 225-230 during normal cruise (225 is the top of the green arc). Adding any power to try and climb further, after cruising for a while, would make the temp build rapidly. It got to redline (245) after only climbing 500-1000' and had to back off to cruise settings to let it go back down.

A google search says check the temp gauge and the vernatherm first. Without a boiling pot of water/oil in the hangar I at least put a thermometer against the oil cooler after a flight. It showed 5-10 deg cooler than the inside gauge, which I am attributing to the inaccuracies of my measurement method. I physically looked that the vernatherm and it looked fine. The oil cooler is hot, so I'm assuming oil is flowing through it. I will continue to try and prove those tests with more accurate methods, but looking to see if any other builders had to add any plenums or anything for their engines?

Ryan