Baffled on Baffling...

[Dan767]

I have a PAU Extra 42% with a DA170 that's about 5 years old in it. I want to maiden the plane next week, one of the few details I have left is whether to baffle or not. I haven't baffled an engine for ages, but thinking this model might need it. I have most of a baffle made up of black foam board from Michael's that needs just a little more work. But, do I remake the baffle from balsa and fiberglass using the foam board as a template? I have seen rectangular extensions, such as those made by ghofffman and others attached to the cowl aimed directly at the cylinders, how well do these work? I have many times repaired the baffling on full scale airplanes, never saw that. How do I measure how far back these types of vents/baffles go?
Tell me/show me what you did and how it works for you.

Thanks,

Dan

 

[Terryscustom]

I say yes, baffle anything with a twin is not really an option. Some of the ready made extensions for other planes are fine but they also let a lot of air escape out over the top of the head since the baffles go straight back. What I typically try to do at a minimum is close off the area between the bottom of the cowl opening and the heads and the side of the cowl opening to the heads angled back to just above the top fin. I have found that many times this is enough unless you find that you have issues or if it is a round cowl airplane.

I have a GP176 in my Extra I can take a pic when I get home tonight of my baffles which has worked well.

 

[Dan767]

Thanks Terry, that would be great.

 

[Phil.Griffin]

I normally use the Creative Foam, (Michaels Craft Store) silicone adhesive, and try to end up with a 4-sided device the that extends all the way back to the fins, and in fact pushes against the fins some. What will happen is the engine heats up the foam, and it will self-form to the fins making for a better fit. The CF is heat resistent enough so that excessive "melting" hasn't been an issue. Having said that, Terry's idea sounds good too.

 

[Bunky.F.Knuckle]

Medium super glue will hold Creative Foam in place, quite well. I did that to a friends EF 104" Extra. Made the baffles just big enough to press against the cooling fins.

 

[Dan767]

I'll wait to see Terry's pictures. I did glue the creative foam with medium CA, so that works great. The cowling isn't straight across the bottom, but is a half circle under the prop shaft. The foam board will bend easily around that opening because the radius is large. Phil, I like your idea of the silicone to hold it in place.

 

[Phil.Griffin]

I'll wait to see Terry's pictures. I did glue the creative foam with medium CA, so that works great. The cowling isn't straight across the bottom, but is a half circle and the foam board will bend easily because the radius is large. Phil, I like your idea of the silicone to hold it in place.

I'm sure the CA is fine, but what I like about the silicone adhesive is it is a flexible product, and seems to soak up vibrations, and also allows the foam to slip past the heads/cooling fins upon installation/removal of the cowling without damage to the baffles.

 

[Ohio AV8TOR]

I have used several things on foam baffling but for all purpose and flexible I like Goop. Grab a handful of stirring sticks at Starbucks the next time you are there as they work great for an applicator.

 

[Terryscustom]

What you use really doesn't matter you can use balsa Lite plywood foam or just about anything that will stay rigid and hold up the temps. I use light plywood that has texalium fabric laid up on it. I make this myself. I tack it in place with medium CA but then go over all the seams and joints with goop in a syringe.

 

[Phil.Griffin]

Very nice. But then again, I'd expect nothing less than "very nice" from the workshop of Mr. Terry.
;-)