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Permalink Reply by Bob McDonald on November 22, 2011 at 7:41am

John

If you think its critical to spot cracks in the engine mount? 

The integrity of the strut fittings are  a matter of life & death. Paint is simple, cheap and cracks show through as rust. In constructing your aircraft use the "KISS" principal. Follow the plans, keep it light and remember every deviation from the plans not only adds time to length of the build but could affect structure in ways that are dangerous.

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Permalink Reply by John Austin on November 22, 2011 at 11:45am

Hey - this could be as controversial as "Which is better - high wing or low wing?" LOL!

Although I like your KISS philosophy, I think I'll go with powder coat (but to me it seems even "simpler" - you hand the parts to the coater, you pay and pick them up! HAHA!). I wasn't sure about the strut fittings, but I was sure Zenith does  powder coat the steel cabin frame with the powder coat option, and those fittings on the cabin frame that hold the main spars are awfully similiar to the strut fittings! ... and I think everyone would agree they're pretty critical connections!

So, I emailed Caleb this a.m. and asked - he said Zenith powder coats ALL the steel parts on any planes they assemble in the factory - including the engine mount! He maintains that powder coat will crack over steel just like paint.and will be visible if it's a light color.

However, more to the point about hiding stress cracks on critical welds - if you think about it, the lower strut fittings' welds are completely hidden because the latest plan's update calls for the fittings to be pushed up inside the strut 'til the welded tubes are flush with the strut end. Even if a crack was showing through cracked paint or powder coat - you couldn't see it without disassembling the strut! So, fortunately/unfortunately, those lower strut fitting welds are never going to see the light of day again unless disassembled.

So, seems to me that the durability of the powdercoat makes it a little more desireable. The weight difference will be negligible. Since powder coat is Zenith-endorsed, I don't see that as a deviation from plans ... they don't specify the paint finish in the plans, either. But, as you said, paint is simple and cheap and would be fine, too! I've used a mix of powder and paint, mainly paintng parts that won't be exposed to abrasion or scuffing but need corrosion protection. (Ironically, my steel cabin frame is NOT powder coated - I bought a partially-completed kit that didn't get the option. It is however, epoxy-primed, which is pretty tough stuff!) Since the lower strut fittings' flanges are exposed, they might be subject to a little scuffing and would benefit from the powder coat. I'll probably do all the fittings, though, out of convenience.

Regards,

John

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