Intercostals on the DE question

[buzzypeterson]

Hey guys,  I am starting over again on my spar for real this time.  It will be out of aircraft spruce spruce. You should be interested to know the one I built for practice out of Home Depot wood only flexed 2.75 inches when I ran out of weight to hang on it.  I had at least 350 pounds of sand bags and my 200 pounds hanging on it.  It did want to twist but I caged it in with scrap wood. But that's what compression struts are for. It wasn't a very scientific test but it impressed me.

Now to my question,

On the HOme depot spar I used a 7/8 by 3/4 inch intercostle. I'm thinking they probably could be more narrow. I don't see a size  on the plans. What size did you guys use?

[scottiniowa]

Hey guys,  I am starting over again on my spar for real this time.  It will be out of aircraft spruce spruce. You should be interested to know the one I built for practice out of Home Depot wood only flexed 2.75 inches when I ran out of weight to hang on it.  I had at least 350 pounds of sand bags and my 200 pounds hanging on it.  It did want to twist but I caged it in with scrap wood. But that's what compression struts are for. It wasn't a very scientific test but it impressed me.

Now to my question,

On the HOme depot spar I used a 7/8 by 3/4 inch intercostle. I'm thinking they probably could be more narrow. I don't see a size  on the plans. What size did you guys use?

While I am not familiar with your term "intercostle"  the term "intercostal" would mean inbetween, so I would presume your meaning the vertical spar cap separation pieces?  By reading your question, I think your asking if you can use the wood you found for the building of the real rib?

But I don't see you mention, what your weight compared to the spar built of spruce?  (important to the extreme)
And if you feel this is important, I don't see you mention that you built to the same size specs which of course goes back to weight

And for your test, how the DE wing was tested and how you tested yours, borders on unlikely, they were the same kind of test -as you say you had 350# of weight and your 200# but don't say where this weight was applied  or how your wing was supported or held.   (important to the extreme again) 

What I am getting at is simple- if you go down a different build way PATH, you have to compare the Apple to Apple test  or Weight for weight being equal.  Maybe you did, but you didn't mention that this was the case. Simply said, anyone could build a stronger spar, using heavier material or even different material (steel or alum or composite)  and then make a arbitrary test to prove to themselves they have a stronger spar, but if you don't go back to the weight for weight, strength for strength based test, you don't have much other than a one sided experiment.

Just my thoughts.

[buzzypeterson]

Test was just for fun. I did weigh it and without lightening holes it was 22 lbs.  very heavy if you ask me.  We supported both ends hanging from the rafters. We put boards on each side where the compression pieces would be.

[buzzypeterson]

Test was just for fun. I did weigh it and without lightening holes it was 22 lbs.  very heavy if you ask me.  We supported both ends hanging from the rafters. We put boards butted up on each side where the compression pieces would be to keep it from warping.   I'm now starting over with aircraft spruce. I wouldn't fly with Home Depot junk wood. I'm not a wood expert so it was just to get a little experience. 

My question is on the verticals on the spar.  What size did you use? I see nothing in the plans.

[scottiniowa]

Test was just for fun. I did weigh it and without lightening holes it was 22 lbs.  very heavy if you ask me.  We supported both ends hanging from the rafters. We put boards butted up on each side where the compression pieces would be to keep it from warping.   I'm now starting over with aircraft spruce. I wouldn't fly with Home Depot junk wood. I'm not a wood expert so it was just to get a little experience.

My question is on the verticals on the spar.  What size did you use? I see nothing in the plans.

Ok, I didn't know you was just playing around, as other than the word "practice"  I couldn't tell.  And yep for 22 # of spar material, you could hold a tank, supported on both ends. 

Can't answer your DE vertical question, but am guessing because of his very similar plans drawing (from one model to the next) he has this covered on the page of spar measurements. He has it called out twice (two different pages) on the XL model

[buzzypeterson]

Would you happen to know what size they use on an XL?

[scottiniowa]

page 33 & 34 show 1/4 x 3/4 by required height. But what shows on the XL doesn't matter much, if your building the DE as you said. I would suggest you find out what the DE plans call out. Might be the same, might not be.

[Richfroh]

On the DE, the front and rear spars are different thickness. The pieces you are asking about are 1/4" thick. They are 7/8" wide for the front spar and 3/4" wide on the rear spar. They are the same width as the spar caps. The length is the same as your inside dimensions from upper spar cap to lower spar cap.