False Spar Lightening Hols

[Bcone1381]

I am drilling the lightening holes in my all my Spar Blanks. The plans do not have a side view of the false spar, and I assume it has no lightening holes. Although it carries the load of the fuel tank, it seems inconsistent to leave it solid. Is anyone else considered lightening holes in it?

Brooks Cone
Chelsea, MI
Scratch Building Patrol #303

[Chris In Milwaukee]

I haven't seen any builds that have lightening holes in the false spar. I hadn't really thought about it, but I suspect if you watch where the tank straps attach and place the holes as appropriate, I can't imagine you would have any problems with it. There are no appreciable shear forces there to worry about, that I can envision.

[marcusofcotton]

1-2 years ago someone asked Bob and reported back that he said it would be fine to add some. I did.

[geraldmorrissey]

For some reference, I weighed a 5" disc I cut out of my main spar wed. It weighed 1 ounce. There are 14 holes in each Patrol main spar, 2 of which are a little smaller (4" and 4.5 inch) so for one main spar the holes save about 13 ounces. I would be interested in what Bob has to say about it. Might be a little weight savings there.
Gerry
Patrol #30 Wings

[Chewie]

Digging up an old thread: Is it the official consensus that the false spars can have lightening holes once the doubler locations are confirmed? Like others have commented, I can't imagine why they should be left solid, and it provides access to both sides negating the need for nutplates. The Patrol plans and book make no mention of nutplates on the false spar anyway.

[Sir Newton]

Follow the plans until there is a good reason to make modifications to the plan. imho

[N3UW]

Digging up an old thread: Is it the official consensus that the false spars can have lightening holes once the doubler locations are confirmed? Like others have commented, I can't imagine why they should be left solid, and it provides access to both sides negating the need for nutplates. The Patrol plans and book make no mention of nutplates on the false spar anyway.

Hey Mark,
i considered putting lightening holes in the false spar but I did not. I am not sure what my thinking was at the time. Just my 2 cents.

[Chewie]

Talking to Bob this morning, he said lightening holes would be fine in the false spar. He recommended leaving about 1" margin between the holes and the flange (more if flanging the lightening holes which is probably not necessary), and of course keep clear of the doublers. He said he just didn't think of lightening holes here when drafting the plans.

He agreed that regardless of lightening holes, nutplates on the Patrol's false spar are not called out and he didn't use them on his.

Hope this helps!