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Lightening Holes

Rick6a

Rick6a

Well Known Member
Using an accurate postal scale, I compared the VS-808 PP which is common to the RV 7,8,and 9 referenced on DWG 6 with and without the optional lightening holes. Without the holes, this part weighs 1.41 lb. out of the box, with the holes added, the weight is reduced to 1.09 lbs.
vs808pp4zg.jpg

Something to consider given this part is attached in a very aft location.

Rick Galati RV-6A "Darla"
RV-8A empennage
 
lightening holes

your results seem to be about double mine.
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You left some metal on the floor!

BTW, most RV8s run a bit nose heavy, so I didn't drill mine out. I never would have guessed that it saved that much weight. Thanks for the tip (for my next RV).
 
RV7Factory said:
I too weighed my results earlier this week...

050708_010.JPG


More info can be found on my web site... http://www.rv7factory.com/log/050708.html

Rick, what's interesting is when doing the math, your results seem to be about double mine.
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A couple of things to look at. I used a high quality digital postal scale, and differences in the accuracy of different scales may well yield conflicting results. Also, if you look at your waste, you'll notice the bevels represent a good deal of material you did not weigh as it ended up on the floor. Finally, I slightly enlarged 2 of smaller lightening holes from the plans callout.

Rick Galati RV-6A "Darla"
RV-8A empennage
 
Rick6a said:
I used a high quality digital postal scale...
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Rick, don't you know those postal scales always always err on the side of being heavy? It's just another way the PO makes $. :D :D :D
 
Thats interesting to know. I too cut the lightining holes in for my RV-7. My dad is a tool maker so we were able to used a wire cutting machine to do it, very neat and easy.
I would be very interested to know how much weight is saved if you take all the lightning options, anyone know?
 
Probably a dumb observation, but isn't it smarter to weigh the finished part, not the waste, to compare the difference?
 
cobra said:
Probably a dumb observation, but isn't it smarter to weigh the finished part, not the waste, to compare the difference?
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Yup... I guess I am just not that smart. :D

As a point of clarification, I simply posted my original results (with picture) for entertainment/casual discussion value, and I wasn't necessarily comparing my results directly to Rick's. I acknowledged the differences in our methods, and all I said was that the differences in results were "interesting". No direct comparison or challenge (of Rick's results) was intended. Wow, I need to lighten up. Get it, lighten up... lightening holes? Oh, never mind.
 
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Hi

MY VS-808 has an extra #30 hole pre-punched in the middle above the 2 largest lightening holes. It is not on my plans.

It is inline with the "holes drilled in assembly with fuselage" but not found DWG 6 but can be found on DWG 27A View A-A.

What has everyone else been doing with this? Putting another AN470 rivet in here or does it need to be a flush rivet countersunk as it is on the edge of the "flush head on forward side" section?

Thanks
 
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Haydn. On the RV8 (DWG 78) that is a locating hole for when you fit the VS to the aft bulkhead of the fuselage - it locates with F-812B-1 (Angle/Control Stop). I would imagine that applies to the 7 as well.

Bob
www.rv-8.co.uk
 
I've asked this before but never gotten an answer.

Are there any rules or guidelines regarding size, number and/or placement of lightening holes?

Glenn Wilkinson
 
To hole or not to hole...?

Hello,

Structurally-strength speaking.. Does it really make an overall difference drilling the lightening optional holes in the empennage?

I do believe leaving the Spar as it comes from the factory (without drilling) is a little bit heavy on the overall empennage, and drilling the holes will save some weight; but what about its structural strength?

I'm planning on using a 180hp Lycoming and 3-blade CS MT prop on my RV-8, and want it mostly for mild to moderate aerobatics (fair within limits) training and tailwheel transition training (rough landings), and therefore want to know if leaving such part intact will add a little bit more strength to the rudder assembly.

Does anyone know how it will or might/ might not affect?
I'm well willing to sacrifice one or two pounds in exchange for some durability and extra structural safety.

Thanks
 
Lightening holes are placed in locations where the material doesn't contribute significantly to the strength of the structure, which is exactly why you can remove material there to save weight. You can and should cut the lightening holes exactly as shown in the factory drawings, where you can save weight and rest assured that the structural integrity is preserved.

It would be a mistake to believe that your airplane would be "extra strong" if you don't cut the lightening holes. By virtue of where the lightning holes are positioned, the structure would not be significantly stronger without them. Just heavier.

Of course, with or without the lightening holes, you must still always remain within the operating limits of the airframe.
 
You're welcome!

Yes, definitely get a drill press if you don't already have one. You'll find it indispensable throughout the project. And for cutting the big holes in the VS spar, either a hole saw or a fly cutter works great. Just make sure to clamp down the part to the drill press plate (with backing material you can cut into), and use cutting fluid.
 
Bought in Febuary '12, my kit came with the lightening holes already made...

No options for me... :rolleyes:

As you can see here...

PICT3511.jpg
 
mvidalr said:
Hello,

Structurally-strength speaking.. Does it really make an overall difference drilling the lightening optional holes in the empennage?

I do believe leaving the Spar as it comes from the factory (without drilling) is a little bit heavy on the overall empennage, and drilling the holes will save some weight; but what about its structural strength?

I'm planning on using a 180hp Lycoming and 3-blade CS MT prop on my RV-8, and want it mostly for mild to moderate aerobatics (fair within limits) training and tailwheel transition training (rough landings), and therefore want to know if leaving such part intact will add a little bit more strength to the rudder assembly.

Does anyone know how it will or might/ might not affect?
I'm well willing to sacrifice one or two pounds in exchange for some durability and extra structural safety.

Thanks
Click to expand...

roee has already commented on this but I would like to add: One or two pounds here and there may not seem like much but it adds up to a lot of unnecessary weight in the overall aircraft.

What you are trying to achieve is a safer aircraft, but in fact you are doing the opposite. You are carrying unnecessary weight that is putting extra strain on stress members and components.

Bob Dennis
"Down under"
RV9a 893 lb empty weight
 
BSwayze said:
It's been almost 5-1/2 years since I bought my empennage kit, and the lightening holes were already drilled in mine, way back then.

000_0928%20(Small).jpg
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Yup, my empennage was ordered December '07, came with the lightening holes.
 
airguy said:
Yup, my empennage was ordered December '07, came with the lightening holes.
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I'm seriously thinking about ordering the spar and specify Van's to ship a pre-drilled spar only. I hope it doesn't substract any percent of the 51% rule!! :eek:
 
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mvidalr said:
I'm seriously thinking about ordering the spar and specify Van's to ship a pre-drilled spar only. I hope it doesn't substract any percent of the 51% rule!! :eek:
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From a conversation I had with them some time ago, you can get the part blank (no cutting/drilling, only stamped out) or with all the holes/circles cut out - nothing in between. So if you ordered the part "blank" it will come to you without lightening holes and without rivet holes - you'll have to match drill each of the rivet holes yourself in assemble with the other parts, which won't be easy for this piece.
 
airguy said:
From a conversation I had with them some time ago, you can get the part blank (no cutting/drilling, only stamped out) or with all the holes/circles cut out - nothing in between. So if you ordered the part "blank" it will come to you without lightening holes and without rivet holes - you'll have to match drill each of the rivet holes yourself in assemble with the other parts, which won't be easy for this piece.
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Thanks Airguy, I better get myself a bench drill and start measuring som' holes..
 
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