Panel strength and size

[ekisbey]

Originally posted by John Slade

I might redo the panel and put it in front of me, but for now it goes in the middle

Referring to the thread " Canard Community Forum > Tech Shop > Electrical > Affordable moving map? "

 

 

 

This reminds me of a question and puzzling response during a conversation with Nat last year.

 

We were discussing the layout of the interior, the center console and panel especially. I'd noticed that Nat's panel had a very straight forward no-frills appearance, yet he managed to use up most of his available panel space. I remember asking if he knew whether a BMA EFIS/One would fit in a Cozy panel, and he seemed to think it would. I knew the EFIS was pretty good sized, and having looked at the dimensions and specs of both the panel and the EFIS, concluded that it would fit, but only just. I then asked if having such a large hole cut out of the panel would weaken it appreciably. He replied that it might, a little, but didn't seem to concerned.

 

Well, I figured that if he wasn't concerned, then I didn't need to be, so I was going to leave it at that. So, in my ignorance, I made a comment that got me a strange response. I said something like "well, I guess it's not structural anyway so, yeah, sure." Nat immediately gave me a funny look and corrected me, saying that the panel was, indeed, structural.

 

Now, what I meant by "structural" may or may not have been what he meant. What I meant was that to my understanding, the panel wasn't critical to the integrity or strength of the fuselage. I was puzzled, but he seemed a little miffed that I might say such a thing and I promptly changed the subject. He was being kind enough to show me his aircraft on very short notice (he'd been doing something and I'd interrupted him), and I was worried I might say or doing something that might offend him or alter his disposition.

 

Anyhow, that coversation keeps bubbling up in my mind each time I think about putting holes in the panel. Obviously, it's been designed for that very purpose, and something the size of the EFIS/One isn't large enough to violate whatever limits are designed into it.

 

However, if I cut a hole that size, and later move it, fill it with something else, patch it over, etc., and cut another, similar sized hole elsewhere else, or two... You get the idea, I'm sure. At what point are there too many holes?

 

IS the panel critical to the strength of the fuselage? How much is too much when removing material from the panel? Would anyone need, at some point, to cut the whole thing out and replace it?

 

Another reason for asking this is I'm considering opening up the the underneath for a bit more leg room. The angle of the seats makes it difficult to get more than one of my long legs in and out at a time. This is really a non-issue normally, someting I rarely notice, since I've been getting in and out of things that way since high school. I noticed this the first time I climbed into Nat's plane, but thought little of it.

 

However, a recent embarrassing experience in a military vehicle caused me to realize that if the vehicle is on it's side and I don't have the leverage to lift my weight with my arms, it's next to impossible to get out. It made me think of the Cozy. If the plane (God forbid) were in an orientation other than upright, especially on it's side, I'm not certain I could free myself.

 

Since I don't have a completed aircraft handy, I just can't go check this out and see if my fears are justified (No, I don't want to turn a plane on it's side, I just want to see exactly how much leverage I need to have to get myself out). At this stage of contruction, it would be pretty simple to make these kinds of adjustments. A mere inch of diameter could make all the difference. That inch adds a lot of strength. How should I resolve this?

[mplafleur]

I'd been thinking the same thing regarding the hole for the legs. I'd rather the panel were not even there, but I can see it was designed and put there as a structural component. And then, "well if we really have to put our legs through there, well I guess we will allow you to put a small hole there".

 

I would like to try to build a panel for the legs that is opened up wider and higher but with some ribbing on the back for strength. But I'm one to talk, I only ordered my plans yesterday.

 

Regarding the inst panel: I can see how we would loose a lot of strength by cutting holes and leaving them open, but we fill them and secure the instruments in them. That I believe puts the rigidity back into the panel that was lost. So I would not worry about it.

[John Slade]

However, if I cut a hole that size, and later move it, fill it with something else, patch it over... At what point are there too many holes?

A good fiberglass patch is as strong as the original, and holes in something don't reduce the strength all that much. The structural aspect of the panel is in tension / compression, not bending. There's very little left of my original panel, but it still seems pretty strong. True, there isnt much of the upper panel left with an EFIS installed, but there are stiffeners above and below. The instruments, especially a thin al walled EFIS circuit board, wont put much strength back. It would definately be a good idea to beef up the stiffeners if cutting an 11 * 8 hole in the upper panel.

 

As for making the leg hole bigger - I'm sure it's been done - check the archives (and Rick Maddy's search engine) for discussion on this. Personally, I wouldn't want to trade ANY panel space (either on the sides or above) for the unlikely event of trying to get out while lying sideways. The leg holes are big enough for large people. Don't worry. If the plane's on its side and you need to get out... adreneline will more than make up for any difficulty.

 

A mechanic working on a Jet Provost in UK was once in a contorted position under the panel half sitting on the seat when he heard the ejection seat timer running. Keep in mind that this timer runs for something like 2.3 seconds waiting for the canopy to clear before firing the seat itself. On hearing the timer he got himself off the seat and out of the way by the the time the seat fired. He had a nice burn on his back to prove it. Later, when asked by investigators to get back into the same position under the panel clear of the seat, he couldn't do it at all, never mind in 2.3 seconds. Fear is a wonderful motivator

[Nat Puffer]

First let's address the "vehicle on its side" concern.

A Varieze, Long EZ, and/or a Cozy overturning is an extremely rare event. We are talking upside down. I can only remember one Cozy that turned upside down, and that was caused by landing on a muddy field. With both the canard and the wings sticking out to both sides, I can't imagine how any of these designs could end up "on its side", so I think we can dismiss that concern.

How big a hole can you cut in the panel? Remember, the panel is structural, but it was designed to cut holes in it for instruments. At what point does the hole become "too big"? That is sort of like the question "how strong should the roll-over structure be"? The only way to answer that question is, "how hard are you going to land up-side-down". I don't know when the hole becomes "too big". Everything is a trade off. The more you cut into structure, the more you weaken it.

As far as a hole for an EFIS is concerned, obviously Greg Richter (Blue Mountain Avionics) has one mounted in the instrument panel of his Cozy. I think his unit is about as large as they come. Then there are many other EFIS designs. Some even mount in a 3-1/8 inch instrument hole.

As far as the leg holes are concerned, I sit on 4-1/2 inches of foam and still have plenty of leg space. I designed my last seat cushions in several layers or sections, so I could accommodate pilots from small to large. I haven't seen a builder yet who didn't fit after the seat cushions were adjusted for him. I keep telling people that once they are airborne, they should take their feet off the rudder pedals and extend them, legs straight. Of course you can make the leg holes larger, but you give up panel space. That isn't too much of a problem if you are prepared to use miniature instruments, or use an EFIS like the new Dynon, which contains all the flight instruments including solid state gyros, which fits into a standard 3-1/8 instrument hole, and one of the new electric engine monitoring systems (like the Stern Pulsar) of a similar size which replaces all the old analog engine instruments.

We find that some builders are concerned about things which they will later discover should have been of no concern. For most builders, all they have to do is to follow the plans.

[mplafleur]

Uh oh, caught by the man himself tinkering with his design.

 

I thought you were going to Minnesota?

[ekisbey]

Good to know he's watching over us...

[Joe Patterson]

at the risk of getting in big poopoo caca................

 

 

I was thinking about an Aluminium frame for the Instrument panel/bulkhead, so that I could easily change out an Instrument Panel , or Upgrade to IFR............

 

I thought if I made the stiffners out of 1/2 inch alum "c" channel, it might be easier to form a solid sheet alum. panel that screws on to that...Radios could mount on some Verticle "C" channels.........Kinda like a Cessna, or Bowing..

 

anyone ever considered anything like that???

 

am I a Quack?

 

Almost ready to proceed to Ch. 4.................Going to look at my first Cozy Thursday.

[shender1]

Check out Brian Deford's web site at www.deford.com/cozy

He has an aluminum panel in his.

[Jim Sower]

I've heard of folks (Ez, Cozy, Velocity) who have installed various departures from the plans panel. I first became interested in this when I needed to change the panel on my EZ. Couldn't be done since it's a "structural bulkhead", right? Turns out a number of folks don't see it that way. I heard of various folks who had cut out all but an inch (or less) around the perimiter of their panel and bolted in another with different layout. Another fellow cut his out and replaced it with a new [structural] bulkhead that had a different layout. Others cut it down to the periphery and installed aluminum or whatever panels.

 

There are several bulkheads in the vicinity of your knees. They are all "structural" but the pivotal one is F22 IMO. I am not an expert in structures, but I do know a little about them. If I'm not badly mistaken, the instrument panel's "structural" mission, aside from supporting the instruments, has a whole lot more to do with crashing than flying. It's part of the "compartment" that allegedly protects us when the airplane crashes. The loads on it during normal flight are not severe at all.

 

That said, I plan on reinforcing my panel for an inch or so around the periphery and across it just above the leg holes with several plies of carbon BID. That reinforcement, in the event my panel undergoes significant modification, will tend to compensate for the [structural acerage] lost when I cut out the original panel and replace it with another new one with a different layout.

 

I don't believe the panel structure is a life or death issue. I can't imagine any kind of accident in which a panel crushing because I compromised it would be the difference between surviving or not, or even account for significantly more serious injury. That's my personal view. If I am wrong and crash and my panel collapses needslessly, I have lived an eventful life.

 

Ya' gotta' die of somethin'. .... Jim S.

[Marc Zeitlin]

Originally posted by Jim Sower

.... If I'm not badly mistaken, the instrument panel's "structural" mission, aside from supporting the instruments, has a whole lot more to do with crashing than flying. ..... The loads on it during normal flight are not severe at all.

The concept of "structural" involves two basic ideas - strength and stiffness. While you are certainly correct that the IP (and, in fact, almost ALL the bulkheads) are very lightly loaded in normal use, and therefore the stresses are low and the strength requirements are also low, there's stiffness to be considered.

 

The fuselage, especially of the COZY, is an open "C" shape (opening "up"), and has very little intrinsic torsional stiffness. The bulkheads provide most of the torsional resistance to "racking" of the fuselage, and this is important to maintain the relative positions and angles of the canard and main wing.

 

That being said, wrt replacing the IP with something else, as long as the Aluminum (or whatever) seperate IP piece is bolted to the fuselage in such a way that it CANNOT move wrt the fuselage under any loading, it will fullfill it's job and stiffen the fuselage. Just ensure that the mounting system (bolts, pins, etc.) is reinforced at the mounting points and that there's no slop.

[Joe Patterson]

Chapter four, says:

One of the Firwalls is to be mabe of 1/4 Inch Birch.

And a temporary Firewall ,for assembly purposes from Fir.............It can't be so important to use fir, I have some extra 1/4 inch birch...........any reason I can't use that.

 

I am Really wanting to get this done tomorrow.

 

??????????????????????????????????????????????

[Jim Sower]

<... fuselage ... is an open "C" shape (opening "up") ... very little intrinsic torsional stiffness ... bulkheads provide most of the torsional resistance to "racking" of the fuselage ...>

Agreed. The finer points of stress analisys are about 40 yrs behind me, but it seems that the "outside" portion of a bulkhead provides a lot more of the stiffness than the "inside". That is to say that if you cut most of the center out of IP leaving an inch or two around the periphery you would still have pretty substantial torsional stiffness - stiffness disproportionate to the amount of material you left in place.

 

But I am a little murky on the quantitative aspects .... Jim S.

[dust]

go ahead with the birch, just write "fir" on it and the plane will be fooled

 

enjoy the build

 

dust

[Joe Patterson]

Thanks big brother,

 

Thou art truely a beacon to mankind.........

 

Peace out.............

 

 

What about this Low density blue foam...Can I use HomeDepot.blue.....?????????

[John Slade]

What about this Low density blue foam...Can I use HomeDepot.blue.....?????????

That was a joke, right?

[marbleturtle]

Home Depot pink?

[Jim Sower]

Originally posted by John Slade

That was a joke, right?

Actually, I don't think so. I believe there might be something to all this Home Depot foam bit. There's a recent thread on the Cozy list around alternative "flying surface" foam from a guy in Europe or somewhere who can't get the blocks we order from ASS, Wick's. A few years ago I was talking to Jeff Russel about that and he said that if some marking on the billet said some certain category or formulation or something, it was the same stuff and you could use it. I have seen blue "floatation billets" for boat docks that I'm convinced were the exact same stuff that ASS and Wick's sell but was around half the price.

 

I think there are legitimate alternatives to wing core foam but we have to be careful about which of the possible sources are legitimate and which are not. I know my memory is pretty hazy and we need specifics, but I think there's something out there that's well worth pursuing.

[dust]

there was a thread somewhere on this forum about a builder that found huge blocks of the wing foam, at a large reduction in price and even went so far as to have it tested for compliance, can't find the thread

 

enjoy the build

 

dust

[John Slade]

even went so far as to have it tested for compliance

If you're not using the recommended part number from Wicks or Spruce, I would have thought a test of the foam would be absolutely essential. This is what holds you in the air, after all.

[Norm M]

<<This is what holds you in the air, after all.>>

 

Oh, so wrong!

 

What keeps you in the air is the vacuum caused by all the money being rapidly sucked out of your wallet!

 

 

But seriously-

 

Check the 3rd paragraph: http://www.canard.com/cp/stet/CP10-8.html

 

"If you are searching for substitutes do not accept any material which has lower strength or other physical properties than the recommended materials shown as follows:

 

Blue Styrene: Dow Chemical Co. Brand F.B. Styrofoam, 2 +- 0.2 lb/cubic feet density, cell size 1.4 to 2.4 mm."

 

Note- FB ==>either Floatation Billet or Fabrication Billet, depending on which source you believe.

[John Slade]

What keeps you in the air is the vacuum caused by all the money being rapidly sucked out of your wallet!

Well - you did decide on a Lycoming to get in the air faster. Now you pay the piper....

[Norm M]

<<Now you pay the piper....>>

 

Yeah, that's the problem with actually finishing one of these planes. The guys who build for 15 years save so much money!

 

I should put a pencil to what the engine installation really cost me. The biggest issue with Lycomings is that you have no clue what your total cost of operation is until you sell it! Some people have made out great, others have lost their shirts.