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Dormoy bathtub spar lay-out

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Flyingboyke

Active Member
Joined
Feb 14, 2011
Messages
31
Location
Belgium
Dear colleagues

About a year ago I gained interested in building a Dormoy bathtub replica. It will be powered by a Citroen visa engine.
I got the plans from Mr. Kimbrel and I started to digitalize them. The cad work for the wing is done so I already started production. All my ribs are manufactured and I want to start with the I spars.
I was wondering if the spar flanges can be constructed of 1 piece. Like the top flange, 1 piece of wood with milled slot. I tried to visualize it on following picture, left is how it is in the plans, right is the change I want to make.
sparlayout.png

It would ensure a perfect alignment between the left and right flanges. According to me it would also ease the the spar manufacturing in general, just slide in the plywood web and glue it together (and nail?). Are these statements correct? I checked ANC18 but I never saw this concept. So I'm wondering what the downside is.

Another question concerns the holes in the spars to reduce weight. In my plans it is just a solid web, but in the 1924 model, there are holes in there, like shown in the picture below. Does someone have data on this? Strength of spars with and without holes.

2019112275.jpg

I made test specimens today with and without holes, and tomorrow I will test them. So I will have some indication how it influences maximum load, but I need opinions on this.

Furthermore you're welcome to visit my website about the tub on : bathtub. You can leave a comment there.

Thank you!
 
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