Building the RO700

[Aero28]

I started building this plane about 6 years ago. I always thought the Zenair 701 was a good ultralight so I drew my interpretation of it and have started back into it. I had the EA81 in the yellow plane in my member pic but changed that out with a 2000 hour 912 . I had already mounted an old EA81 in this plane so it made sense to bolt the good one in. I'm trying to lighten the 81 as much as I can, lots of lightening holes, a small permanent magnet alternator, i'm thinking of 400mm of steel exhaust from the heads and then into aluminium to the muffler, any thoughts on that?

[Marty_d]

Hi Aero28,

 

That's interesting, I'm building a CH701 down the other end of the state and looks like it's at a similar stage (down to the work light hanging in the cockpit!)

Regarding the exhausts - I'm not sure you'd get that much weight saving, because you have to join stainless to aluminium and back to stainless at the muffler - for a few hundred mm of s/s tube it wouldn't be worth the effort, plus then you worry about whether the aluminium will handle the heat.

Good luck with your build! 

[facthunter]

Don't risk the aluminium tube. I don't think I've ever seen it used.   Nev

[onetrack]

I can't see any worthwhile level of weight saving in using aluminium tubing for exhaust. Steel exhaust tubing isn't that thick. Drilling pulleys is one way of gaining weight reduction, and you may be able to lighten the flywheel.

However, don't just drill holes in the flywheel to lighten it, they need to be machined and balanced properly by experts, to ensure their balance is spot-on.

[facthunter]

Stainless tube is available in thinner wall thickness. It's slightly more likely to crack than MS tube. SS would be my  choice for a U/L.  Nev

[Aero28]

Yeah, good Nev, I'll go and see what the stainless people have, 1.2mm wall would be good

[Aero28]

More pics

[kgwilson]

That is a pretty beefy looking front mounting plate. What does that weigh?

[Aero28]

It's 16mm ally KG, might weigh 3 to 4 kgs

[facthunter]

Less than that I would think.  Nev

[Phillip King]

Hi aero28, I have this Swiss muffler off my 701, it’s 1400mm long 60mm round, made out of thin stainless sheet. My 701 had a Subaru in it when I bought the plane as a part built kit. It had a 4 in 1 exhaust into the muffler under the body, it’s yours if you want it. Cheers Phil

[bushcaddy105]

From experience, if joining pipes from each head at a muffler, make sure that you include a flexible section in one side’s pipe. Otherwise the expansion and contraction with heat cycles will work the flange studs loose in the heads. Been there, done that!

[Aero28]

Thanks for the info Phillip,  I have a muffler like that on my yellow plane, have a look at this video

 

[Aero28]

Time to fit the wings and tail to do a weight and balance to see how its going.