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Building Tips and technical articles. => Building techniques => Topic started by: Paul Wood on March 26, 2013, 07:48:57 AM
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The "Loser" thread recently included a "healthy" discussion regarding lightening holes. Understandably, everyone has their own thoughts on the subject. I personally think lightening holes in sheet balsa is not worth the lost structural integrity. But, in other areas, absolutely. So, I recently cut some holes in the wing ribs shown in the attached photo and weighed the difference to give you some data. The ribs are the wing gear ribs in a "Continental" I'm building from Tom Dixon plans. The plywood is 3/32 x 5 ply aircraft plywood. Not light weight stuff, but very strong. The total weight removed per rib was 3 grams. Not much, but you know how we all feel about weight. Plus it looks really cool!
Paul
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Paul,
It's simple. You take away material and you remove weight. How can that not be understood?
Call it a hole, half ribs, doesn't matter. Weight removal with the building of model airplans, has been going on for ages.
Hollowing out foam wings? Holes in fuselage sides. There's many examples.
I took an incredable amount of weight off The LOSER, A bit more before I planked the fuselage, which, BTW, being egg shapped, added strength.
There's plenty of build sights where the removal of weight, holes or not, is effective in the build.
It all adds up. Or subtracts?
Drope me a note next time your at The LOSER's thread.
Charles
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They're a good idea in sheet metal and plywood. But with something like balsa you're likely to have the grain going the wrong way in what's left of the wood. Rather than a simple round hole, a more-engineered mass reduction is needed.
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Multiply that reduction by the number of ribs in a wing. We learned that every gram saved soon adds up to a bunch of grams.
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Air weighs less than wood so more air is good. But not at the cost of structural integrity. Replace wood with air in areas that don't compromise structure.
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Paul,
It's simple. You take away material and you remove weight. How can that not be understood?
Call it a hole, half ribs, doesn't matter. Weight removal with the building of model airplans, has been going on for ages.
Hollowing out foam wings? Holes in fuselage sides. There's many examples.
I took an incredable amount of weight off The LOSER, A bit more before I planked the fuselage, which, BTW, being egg shapped, added strength.
There's plenty of build sights where the removal of weight, holes or not, is effective in the build.
It all adds up. Or subtracts?
Drope me a note next time your at The LOSER's thread.
Charles
Charles,
Thanks for the info. I guess I never realized any of this. I've only been building these things since 1955. You know I appreciate it.
Paul
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Charles,
Thanks for the info. I guess I never realized any of this. I've only been building these things since 1955. You know I appreciate it.
Paul
Paul,
With all due respect.
I can tell by your cut ribs and gear above that you are an accomplished builder. Very obvious. H^^
I put "Paul" in there just to be polite, my reply wasn't meant for you.
Forgive me. I hope this truthful explanation straightens things out. n~
I do believe however, even in "some" balsa applications, removed material can be a benefit.
Charles
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Holes to remove weight is fine. It's the over use of Polyester resin, fiberglass, epoxy, extra plywood, bad fitting joints and "Doctor Good" that make those holes moot.
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I use "lightning" holes. They're the lightest of all hole types. H^^ Steve
Edit: Tried to fix it so you scanners might catch on. I expect too much, I expect.
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Lightening holes are all well and good, if they're put into wood that needs to be there in the first place and that can stand to be weakened by the hole. Making a flying surface out of oversized pieces of wood, then including useless bits whose only purpose seems to be to have impressive-looking lightening holes cut into them isn't the way to make a light component, though.
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Lightening holes are all well and good, if they're put into wood that needs to be there in the first place and that can stand to be weakened by the hole. Making a flying surface out of oversized pieces of wood, then including useless bits whose only purpose seems to be to have impressive-looking lightening holes cut into them isn't the way to make a light component, though.
Excellent comment and excellent work on the graphic. Unfortunately, it will make absolutely no sense to the one individual who needs most to understand what you are talking about.
Keith
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You people just never quit do you? D>K
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You people just never quit do you? D>K
Glenn,
Sick? LL~ LL~ LL~ LL~
The personal attacts were suppose to stop? H^^
There's nothing wrong with the way that rudder is built, in fact the construction is actually clever. Any acomplished model builder can see that. Especially if they build scale.
Light yet strong. AND it's absolutely 100% scale in construction and appearance once covered, which is the whole idea.
Charles
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Not light weight stuff, but very strong. The total weight removed per rib was 3 grams. Not much, but you know how we all feel about weight.
Paul
3 grams is not much but do that 10 times its over a ounce.
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3 grams is not much but do that 10 times its over a ounce.
Who on earth would have 10 times that many plywood ribs?
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Who on earth would have 10 times that many plywood ribs?
uhhhhmm it maybe possible that someone may use more than 10 ply ribs, there have been planes built before with all ply ribs
Randy
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uhhhhmm it maybe possible that someone may use more than 10 ply ribs, there have been planes built before with all ply ribs
Randy
Yes, and highly doubtful if any concern about how much it weighs.
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3 grams is not much but do that 10 times its over a ounce.
For those who do not understand I was not talking about plywood ribs. I was referring to 3 grams and there are many places you can loose 3 grams in a build. Building is a cumulative process. Lets look at the lighting holes on the rear of a nobler fuse. In the grand scheme of things they mean nothing. If you start out with a 60oz Nobler and take out those sections it wont make a hill of beans. But if your building a plane and counting grams 3 grams here and there is a lot. Do it 10 times its a ounce and in the tail that's a lot.
Many say it don't matter. Weight = Horse power. The less the plane weighs the less horse power it take to pull it, leaving much more reserve. I have had discussions about this Netzban wall. My beam-er project is in line to prove it right or wrong. I would love to have this crossfire in the low 50Ty's. I might monokote the wings just for this experiment. I say you cant build any stunt ship too light. But then again it a personal preference.
I was happy with the Viper at 49oz plus 7 oz fuel so a 55 oz crossfire should be cool.