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post #91 of 337 Old 02-08-2016, 08:10 AM
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Originally Posted by Augerhandle View Post
It is interesting that he compares his product to the "industry standard"-MDF. Usually, something becomes industry standard for very good reasons.
That's true. MDF is an OK material and its CHEAP thereby cost effective but its not the best material. Most speaker manufacturers are building to a price point. If you're into DIY then those cost restraints don't have to apply to you since you're saving $$ by building your own speakers.
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post #92 of 337 Old 02-08-2016, 09:22 AM
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Originally Posted by rajacat View Post
Here's Albert Von Schweikert's take on speaker design. http://www.vonschweikertaudio.com/#!designer-bio/cjbm
Notice that he favors constrained layer damping in his speakers. I don't think that it can argued that he, a Cal- Tech trained engineer, hasn't done the research to support his theories on speaker design and his speakers have been very successful in the marketplace.

Next time why don't you take extreme doses of vitamin C because a double nobel prize winner thought very strongly that it cured among other things, cancer. He died of cancer of course because that's how the universe works.
Argument from authority is well and good in a church but not here. If using mdf or something else makes sense or not can't be justified without name-dropping, it seems like not a very good idea.

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It is interesting that he compares his product to the "industry standard"-MDF. Usually, something becomes industry standard for very good reasons.
Well, yes, good reasons, but not necessarily the reasons you would think up. Good reasons don't have to be good reasons for me or you, but good reasons for the company. Cheap material made from otherwise unusable wood is the perfect kind of ingredient for profit-motivated entities.

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I'm going to eject from this nonsense. Next time Pascal is promoted as "word of the week" on dictionary.com, could someone please post a warning? I hope the OP got what he needed.
Hey, some of us are trying to add some view points to OP. This post of yours is literally to tell everyone you aren't bothering to add anything. And trying to seem superior in doing so. If you can't deal with the fact that not everyone will bow down to your opinion that you don't bother justifying then the internet isn't the place for you.
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post #93 of 337 Old 02-08-2016, 11:25 AM
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Originally Posted by ronny31 View Post
Next time why don't you take extreme doses of vitamin C because a double nobel prize winner thought very strongly that it cured among other things, cancer. He died of cancer of course because that's how the universe works.
Argument from authority is well and good in a church but not here. If using mdf or something else makes sense or not can't be justified without name-dropping, it seems like not a very good idea.



Well, yes, good reasons, but not necessarily the reasons you would think up. Good reasons don't have to be good reasons for me or you, but good reasons for the company. Cheap material made from otherwise unusable wood is the perfect kind of ingredient for profit-motivated entities.



Hey, some of us are trying to add some view points to OP. This post of yours is literally to tell everyone you aren't bothering to add anything. And trying to seem superior in doing so. If you can't deal with the fact that not everyone will bow down to your opinion that you don't bother justifying then the internet isn't the place for you.
How does vitamin C relate to the topic at hand? LOL
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post #94 of 337 Old 02-08-2016, 01:29 PM
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This is a very inefficient, expensive, complicated, and not particularly effective way to brace speaker enclosure panels. Glass fiber in this application is a waste. Much, much better methods of panel bracing have already been spelled out in this thread.

MDF is a fine material, especially for full range or high frequency (midrange up) enclosures. I personally like plywood for subs especially for ease of driver mounting, but both plywood and MDF will need good bracing.

My next speaker enclosure (baffle, rather) might actually be GRP, but not because of some inherent material properties, but instead for the relative ease of creating compound curves repeatably with glass fiber.

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post #95 of 337 Old 02-08-2016, 03:38 PM
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Originally Posted by ronny31 View Post
...Well, yes, good reasons, but not necessarily the reasons you would think up. Good reasons don't have to be good reasons for me or you, but good reasons for the company. Cheap material made from otherwise unusable wood is the perfect kind of ingredient for profit-motivated entities...

Not just A company, the whole INDUSTRY. Actually, they ARE the same reasons I thought up, and the very reason I went DIY. Cost efficiency. You mentioned cardboard and paper earlier. What material do you think Sonosubs are made of? Why? Cost efficiency. It's all about price vs. performance. Your pickup truck might have a separate steel chassis and be able to haul train cars uphill, but a cheap family sedan will beat you up that hill, and for less money. I very much doubt that the OP built his HT subwoofer for SPL drag racing the neighbors (though I could be wrong).


Your computer would be nice in a Steam-punk-ish walnut case with brass fittings, but plastics are cheaper (and lighter). Every car could have padded leather upholstery, but plastics are cheaper (and lighter). Every subwoofer could be build like a concrete bunker, but MDF is cheaper (and lighter).

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post #96 of 337 Old 02-08-2016, 04:14 PM
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What most use is irrelevant, what most winners use is steel reinforcement directly on the chassis which is then filled in with fiberglass and concrete (concrete ceilings and walls is getting popular, with internal steel mesh wired in place first its really easy to do, just lay the concrete with the car on the side or roof, no form needed and you use all the space out to the edge of the chassis panel). Steel beams you see are there in addition to this reinforcement you don't see, because the largest surfaces (roof and floor) will flap like a bird under 170db+ even if they're made of steel, fiberglass and concrete. The steel beams that cross the space will be bolted through the floor and ceiling with the same bolts as the doors. And act both as a pre-tensioned steel wire and load-bearing column depending on which way the pressure is trying to force the surfaces in that particular fraction of a second...
I just remembered that I forgot to comment on this. Steel cannot act as pre-tensioned anything unless it is actually pre-tensioned. The steel beams mentioned act in flex and compression, similar to re-bar.

One can find actual pre-tensioned steel cables in concrete bridges. Put simply, these cables are stretched like rubber bands in order to do their job (supporting the live weight of vehicles upon the bridge). During the pre-tensioning procedure, the crew has to over-tension the cables a certain distance in order to have room to release the stressing machine from the cable chucks. If the cables are less than 90 feet long, it is very difficult to do this procedure, as the 5/8" required overstress can be enough extra for the cable to yield or fail at that length. That is why pre-stressed concrete forms are usually hundreds of feet long. Steel certainly cannot be pre-tensioned in such a short span as a car.


I don't want this to detract from the thread topic or your other opinions, I just want to clarify the facts.

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post #97 of 337 Old 02-08-2016, 09:49 PM
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How does vitamin C relate to the topic at hand? LOL
He made an argument from authority. Argument from authority is the reason we think big doses of various vitamins is beneficial.
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post #98 of 337 Old 02-08-2016, 09:53 PM
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Originally Posted by Augerhandle View Post
I very much doubt that the OP built his HT subwoofer for SPL drag racing the neighbors (though I could be wrong).
I don't presume to know what OP wants I just lay forth a general concept he can use to scale to his needs, be they 180db or 108db. Do you explain how to build a paper plane when you can just explain how all planes fly so that OP can build any he wishes?

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I just remembered that I forgot to comment on this. Steel cannot act as pre-tensioned anything unless it is actually pre-tensioned. The steel beams mentioned act in flex and compression, similar to re-bar.

One can find actual pre-tensioned steel cables in concrete bridges. Put simply, these cables are stretched like rubber bands in order to do their job (supporting the live weight of vehicles upon the bridge). During the pre-tensioning procedure, the crew has to over-tension the cables a certain distance in order to have room to release the stressing machine from the cable chucks. If the cables are less than 90 feet long, it is very difficult to do this procedure, as the 5/8" required overstress can be enough extra for the cable to yield or fail at that length. That is why pre-stressed concrete forms are usually hundreds of feet long. Steel certainly cannot be pre-tensioned in such a short span as a car.


I don't want this to detract from the thread topic or your other opinions, I just want to clarify the facts.
Person, a steel bar acts as a pre-tensioned steel wire in that its initial low stress stretching is very very low. Hence, its like if you pre-tension a steel wire, in that it keeps it together like a rope and like a column in that it prevents compression.
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post #99 of 337 Old 02-09-2016, 07:49 AM
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Originally Posted by ronny31 View Post
I don't presume to know what OP wants I just lay forth a general concept he can use to scale to his needs, be they 180db or 108db. Do you explain how to build a paper plane when you can just explain how all planes fly so that OP can build any he wishes?



Person, a steel bar acts as a pre-tensioned steel wire in that its initial low stress stretching is very very low. Hence, its like if you pre-tension a steel wire, in that it keeps it together like a rope and like a column in that it prevents compression.

I'm sorry, but you really have no clue as to what you are talking about. My apologies to the OP for letting this go this far. Ronny31, I wish you all the best, but I am done.

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post #100 of 337 Old 02-09-2016, 12:24 PM
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post #101 of 337 Old 02-09-2016, 04:52 PM
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Yeah, crazy stuff. Craig Butler has hit over 182. I think that's the current world record.
I think the current world record is 184.6db @ 71Hz set in 2014 by HAL.
http://www.termpro.com/asp/worldreco...4&Org_Select=1

It was not beat in 2015.
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post #102 of 337 Old 02-09-2016, 06:50 PM
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Originally Posted by ronny31 View Post
Person, a steel bar acts as a pre-tensioned steel wire in that its initial low stress stretching is very very low. Hence, its like if you pre-tension a steel wire, in that it keeps it together like a rope and like a column in that it prevents compression.
That makes no sense. Based on your suggested bracing scheme, and explanations of it, I cannot help but conclude you simply have no idea what your talking about.
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post #103 of 337 Old 02-09-2016, 07:17 PM
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post #104 of 337 Old 02-09-2016, 11:28 PM
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That makes no sense. Based on your suggested bracing scheme, and explanations of it, I cannot help but conclude you simply have no idea what your talking about.
What is so bleeding difficult about it? Its the practice in your house, your offices, your stores, your roof, your floor, your bridges, skyscrapers, ships and airplanes.

Only you use polyester resin, glassfiber and "sticks" of proportional size because its cheap and low skill requirement to work with. "Sticks" is anything you have handy that you don't need to expend more money on. Cut-offs from the edge of your sheets, bits and pieces from previous projects, junk from a nearby construction container. The amount of glassfiber you need is microscopic. If you take two 400 gram chopped strand mats and lay them on top of each other on the form of lets say a dinner plate bottom, the finished product is so strong you can stand on it without damaging it. And glassfiber is laid so fast you wouldn't know it. Just out in a sunny day brushing on resin and then applying the glassfiber over some sticks, wetting the sticks and glassfiber with resin with the brush, then let it set. The sticks don't need exact measurements, neither does the glass mats, you don't have to measure twice and cut once you just do it quick and easy. You don't need a plan you just eyeball how much to put on each surface. More on the bigger surfaces and less on the small ones. Then you eyeball where you can have some sticks crossing the span between two big surfaces that you also just glue in place with resin. Don't even have to measure that stick exact, just jam it in where it fits when you have cut it close. it will be set in glassfiber when you're done anyway.
Throughout all the bloody years am I the only person to suggest this way of structural reinforcement? I think some here are too focused on it looking neat during the job. Neat mdf bracing evenly spaced with complex cut-out shapes to get rid of material (that gets paid for and then time wasted to cut it out to be thrown away). Pre-laid plans of how to cut each sheet for the reinforcement, exact measurements and cuts, figuring out where all of them goes and what order to put them in. Each glued in separately with wood glue and secured with staples or screws. Possibly also tools for pressing them together for better glue joint. What a laborious process.

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post #105 of 337 Old 02-09-2016, 11:56 PM
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... you use polyester resin, glassfiber and "sticks" of proportional size because its cheap and low skill requirement to work with....
I have no dog in this fight, but I have a real question - does the method you're describing offer anything additional in the way of sealing? I've never glassed anything but I'm familiar with the concept. It's too late to change the build I'm currently working on but I'll be doing another soon. and likely quite a few more. I love trying new methods and bucking convention, if it gets me some tangible benefit. I'm willing to do some experimentation and prove you right (or wrong, whatever happens). With as much time as I spent on sealing this evening... if glassing it in would do that for me, I'd be a lot more excited about trying it.
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post #106 of 337 Old 02-10-2016, 12:07 AM
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Some SPL build pics.





More pics of the last build here: http://www.gmfullsize.com/threads/ou...-build.278835/
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post #107 of 337 Old 02-10-2016, 02:43 AM
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Some SPL build pics.

More pics of the last build here: http://www.gmfullsize.com/threads/ou...-build.278835/
Sweet, winning results speak for themselves (speaking of the thread you linked to). But have you used a vibration meter in your build? They cost in the ballpark of what a termlab unit costs. Or about one battery worth.

I would hesitate as a rule to use the term "high spl build" if they use duct tape :P

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I have no dog in this fight, but I have a real question - does the method you're describing offer anything additional in the way of sealing? I've never glassed anything but I'm familiar with the concept. It's too late to change the build I'm currently working on but I'll be doing another soon. and likely quite a few more. I love trying new methods and bucking convention, if it gets me some tangible benefit. I'm willing to do some experimentation and prove you right (or wrong, whatever happens). With as much time as I spent on sealing this evening... if glassing it in would do that for me, I'd be a lot more excited about trying it.
Sealing an enclosure with some gaps here and there takes the amount of time it would take you to paint the seams with a big brush. Spanning gaps more than a few millimeters requires application of some glass but its applied as quickly as you can wet it with resin with your brush. Since you're using the speaker enclosure itself as a form you won't take away, and apply the glass inside it out of sight, the look of it is unimportant you just need to remove most of the air and wet the glass enough. Superfluous resin isn't too bad (weight isn't a concern, and its not going to need the flexibility of a canoe or boat so excess resin hardness isn't a problem either). So its possible to work extremely fast by the time you finish up the last enclosure.
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post #108 of 337 Old 02-10-2016, 03:11 AM
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Btw, I know its my opinion and yours that either material is best. I would love to do a vibration meter test to see how much vibration each method produces with a series of different amounts of material, to do a proper cost analysis. But until then it will still be my opinion that its superior with glassfiber. Because I think there's less need for planning and time-consuming assembly, and I think it will be stronger if we performed such a test. Maybe glassfiber mats in the necessary quantity for it to be stronger, is slightly more expensive if mdf is very very cheap in the US, but here mdf isn't a lot cheaper than anything else. And I'd wager polyester resin is dirt cheap in the US if you don't buy it in microscopic cans in hobby-stores and the like.
Glassfiber in woven mats also allow a lot more control over strength direction. Align the strands along the longest direction, out from the center of the sheet, etc. This makes it possible to save tons of material (or add insane strength with the same amount). And reinforcing glassfiber with glassfiber, with the correct use of fiber direction, is immensely strong.
The kind of strength they're building spaceships and A380 wings with. Only they use lightly better fibers (carbon fibers).

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post #109 of 337 Old 02-10-2016, 08:36 AM
 
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What is so bleeding difficult about it?

It's not that it's difficult to understand, it's that where speakers are concerned it simply makes no sense. All of your complicated constructions are fine if there is a need to make panels stiffer where cross-bracing isn't possible. But speaker cabinets don't have that restriction. The only item in your illustration that applies to loudspeaker construction is the stanchion. That's what you seem unable to understand.
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post #110 of 337 Old 02-10-2016, 12:29 PM
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What is so bleeding difficult about it? Its the practice in your house, your offices, your stores, your roof, your floor, your bridges, skyscrapers, ships and airplanes.
All of those applications mentioned have one very important thing in common - they require large open spaces where no bracing is allowed to penetrate. You can't have 2x4'x criss-crossing the rooms in your home, or office, or store. You can't have them criss-crossing lanes of traffic on bridges. Ships and airplanes even need open unobstructed spaces for passengers, crew, cargo, etc. Panel stiffening techniques using hollow core sections, beam stiffeners, hat stiffeners, etc. are used when you MUST have panel spans of a certain minimum for other reasons. There is no such minimum span for the majority of the panel area of a sub box, and no restriction on unobstructed internal volume beyond the relatively small area and volume required for the driver itself. The rest of the box can have as many internal braces in whatever arrangement is most efficient.

Look, I worked in naval R&D designing standard ship hulls, advanced double hull concepts, as well as large carbon and glass composite structures for submarines and surface warships. Look up the DDG-1000 destroyer. The entire topside structure of the original DD(X) design is composite, and I worked for years on its structural design. Believe me, if I would have been allowed to cross mechanical and living spaces of the interior with braces like we are talking about, life would have been much easier.

I know all about GRP. I know all about structural design. What you are suggesting looks cool, but is a waste of time, money, and material to achieve an inferior result. But don't let post-grad degrees in mechanical engineering or years of experience in composite structural design discourage you... keep lining your boxes and be happy.
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post #111 of 337 Old 02-10-2016, 12:33 PM
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[QUOTE=ronny31;41418449]Sweet, winning results speak for themselves (speaking of the thread you linked to). But have you used a vibration meter in your build? They cost in the ballpark of what a termlab unit costs. Or about one battery worth.

I would hesitate as a rule to use the term "high spl build" if they use duct tape :P



/QUOTE]

Sorry not my build.
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post #112 of 337 Old 02-11-2016, 12:02 AM
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Look, I worked in naval R&D designing standard ship hulls, advanced double hull concepts, as well as large carbon and glass composite structures for submarines and surface warships.
Sweet. Then you could theoretically do the math for us. Or make an excel sheet so that we can do it ourselves. Is there a formula which tells us how much I-beams strengthen a sheet material given different dimensions and spacing of the I-beams?
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Sweet. Then you could theoretically do the math for us. Or make an excel sheet so that we can do it ourselves. Is there a formula which tells us how much I-beams strengthen a sheet material given different dimensions and spacing of the I-beams?
I'd imagine the software he uses is light years beyond an Excel spreadsheet. I think I know what you're wanting. Know the density of the wood at a certain thickness, get the area by height and width, and find the areas needed for bracing. An Excel spreadsheet can't tell you where to put a brace. We're only building sub boxes here. Keep it simple. Follow the proven designs for bracing; and the music plays on...with some great bass.
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post #114 of 337 Old 02-11-2016, 01:31 AM
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If time was of the essence I'd just copy proven designs. But it isn't.
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post #115 of 337 Old 02-11-2016, 06:14 AM
 
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Originally Posted by ronny31 View Post
Is there a formula which tells us how much I-beams strengthen a sheet material given different dimensions and spacing of the I-beams?
There is, and it's existed for roughly 3,000 years. Google 'beam deflection'. Where panels are concerned the difference is that one is considering three dimensions versus two.
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If time was of the essence I'd just copy proven designs. But it isn't.
The same can be said of re-inventing the wheel. No matter how many times it's done it always ends up being round.
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post #116 of 337 Old 02-11-2016, 07:05 AM
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Hm, time to start that free trial for hobbyists in Autodesk Fusion 360.
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post #117 of 337 Old 02-11-2016, 09:16 AM - Thread Starter
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Originally Posted by Bigus View Post
Look, I worked in naval R&D designing standard ship hulls, advanced double hull concepts, as well as large carbon and glass composite structures for submarines and surface warships. Look up the DDG-1000 destroyer. The entire topside structure of the original DD(X) design is composite, and I worked for years on its structural design. Believe me, if I would have been allowed to cross mechanical and living spaces of the interior with braces like we are talking about, life would have been much easier.
Was that the one up at BIW? I read an article on that, very cool. I remember something like it has the radar signature of a small fishing boat. Hats off to you and your hard work.
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post #118 of 337 Old 02-11-2016, 10:10 AM
 
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Originally Posted by bob_m10 View Post
Was that the one up at BIW?
+1. The most interesting aspect of the USS Zumwalt isn't its use of stealth technology, though. Scuttlebutt has it that it's a test platform for next gen weaponry. It's capacity for generating electricity seems to be quite a lot higher than what's required for propulsion and all of the other conventional shipboard power needs. It will probably be the first ship of the line to be equipped with lasers and rail guns.
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post #119 of 337 Old 02-11-2016, 01:23 PM
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Originally Posted by ronny31 View Post
Sweet. Then you could theoretically do the math for us. Or make an excel sheet so that we can do it ourselves. Is there a formula which tells us how much I-beams strengthen a sheet material given different dimensions and spacing of the I-beams?
Well, yes and no. The equation for stiffness of a beam of a certain cross section is straightforward, and could certainly be put in excel form if not already done and floating on the web. And the displacements involved are rather small, so you don't have to worry about anything more complicated like flange or web buckling. And you can probably ignore any stress related questions.

And that can be compared to the equivalent stiffness of a stanchion to get a grasp on what we're trying to say here. It's been a decade since I put any of this into practice, and am not inclined to go look up the MOI equations and calculate deflection myself, but I would suggest this would be a good exercise for anyone interested. Take the equation for a constrained end beam of a pretty damned rigid stiffener for the sizes we are talking about, like 2x4 dimensional lumber turned on side to produce a blade stiffener of a panel, say 2 feet long. Calculate the deflection with a load applied in the midspan of the beam, say 100 pounds to make it easy. Now do the math for how much compression you get in that same 2x4 turned on end, pretending it is an internal brace spanning to the opposite panel 2 feet away. With that same 100 pound load, the percent of compression will be a fraction of the deflection midspan if used as a stiffener on the panel... same volume of wood. Now find the minimum size of internal brace spanning to opposite panel that will have the same deflection under a 100 pound load as your 2x4 panel beam stiffener. You will find it to be quite small.

That's the simple math, and good enough to prove the point. There are closed form solutions for plate/panel stiffening, but the math is horrendously complex (I hated the advanced applied mechanics courses in grad school) and the solutions depend on the boundary conditions at plate edges (how stiff are the corner joints?) and types/number of stiffeners, and the more complex they get the more unwieldy the math is.

Any sane engineer just whips up the proposed plate/stiffener combo in his FEA software of choice and lets the magic happen. Hell, it would be easier to solve the FE equations by hand than to attempt the closed form solutions! But that doesn't lend itself to something as simple as an excel spreadsheet equivalent. Not an easy way to give you a tool that produces real results for real life practical designs, apart from the FEA software itself.

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post #120 of 337 Old 02-11-2016, 01:26 PM
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Originally Posted by bob_m10 View Post
Was that the one up at BIW? I read an article on that, very cool. I remember something like it has the radar signature of a small fishing boat. Hats off to you and your hard work.
Yeah that's it. "Hard work" is an interesting way to put it... working for the DoD/Navy was eye opening. I personally produced about 5 iterations of that topside structure design, scrapping it each time the Navy changed their minds and started over, only to find out about two years into it another design group in California had also been working on the topside design, directed by a slightly different management group in the Navy. Sort of a case of "the thumb doesn't know what the pointer finger is doing".

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