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  #11  
Old 11-17-2012, 09:11 PM
RVguy RVguy is offline
 
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Quote:
Originally Posted by pierre smith View Post
Steve, it's a TAS matter, NOT an indicated airspeed matter.

Van wrote an article entitled, "The gauge that lies" and was directly addressing VNE issues and that they're related to TAS.

A search should turn up the article.

Best,

Thanks Pierre, I will look it up.
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  #12  
Old 11-17-2012, 09:18 PM
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Ron Lee Ron Lee is offline
 
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By "proper construction" I am also implying proper engineering as well. That gets it beyond my ability.
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  #13  
Old 11-17-2012, 09:25 PM
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Quote:
Originally Posted by Sam Buchanan View Post
The question begs to be asked..........WHY?
Hey Sam, the best way for me to answer this question would be to say FUN! For me a big reason for embarking on this, my first homebuilt project is all the fun and joy experienced in the pre-planning, planning and researching aspect of this long educational endever. Yes it would be very easy for me to follow the status quo and build something exactly like everyone else but customization just seems better to me. Of course I do not want to re invent the wheel but its really cool to hear all of your ideas hear on VAF. This stuff really gets my brain in gear and Ive always been a dreamer.
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Last edited by RVguy : 11-18-2012 at 02:07 AM.
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  #14  
Old 11-17-2012, 09:38 PM
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Quote:
Originally Posted by Jerry Cochran View Post
Article by Ken Krueger here...http://www.vansaircraft.com/pdf/hp_limts.pdf

Thanks Jerry, yep thats the article I originally read. Was researching more about flutter after re-reading Kens article and found this: http://members.eaa.org/home/homebuil...0Problems.html

It addresses other reasons for flutter that I found interesting.
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  #15  
Old 11-20-2012, 09:20 AM
chrish chrish is offline
 
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Reading between the lines, the 14 looks like Vans trying to standardise things in an attempt, amongst other things, to improve the safety record of homebuilding. Bolting a big engine on an aeroplane is not like building a hotrod in the garage. Big mods like this make you an engineer and a test pilot. Regarding the process of experimental modification that led to the RV-1 - Vans is an engineer and modded the Stitts based on sound engineering decisions. His design philosophy is 'total performance', along with safety. designing an aircraft (or anything for that matter) you should have clear design goals and the skill to make the appropriate engineering decisions to achieve them. 'Just for fun', is not a precise enough goal. Aviation is an extremely unforgiving environment - I know, I have lost quite a few friends in the industry. One modification, error, mistake etc can have a whole set of flow on effects that end in a smoking hole in the ground. That smoking hole does not equate to 'fun' for you or the poor sod sitting beside you.

If the 14 does not meet your mission goals and you don't have the skill to engineer a proper modification, then you should pick an aircraft that someone else has designed and proven that does meet your needs.
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  #16  
Old 11-20-2012, 12:00 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by chrish View Post
Reading between the lines, the 14 looks like Vans trying to standardise things in an attempt, amongst other things, to improve the safety record of homebuilding. Bolting a big engine on an aeroplane is not like building a hotrod in the garage. Big mods like this make you an engineer and a test pilot. Regarding the process of experimental modification that led to the RV-1 - Vans is an engineer and modded the Stitts based on sound engineering decisions. His design philosophy is 'total performance', along with safety. designing an aircraft (or anything for that matter) you should have clear design goals and the skill to make the appropriate engineering decisions to achieve them. 'Just for fun', is not a precise enough goal. Aviation is an extremely unforgiving environment - I know, I have lost quite a few friends in the industry. One modification, error, mistake etc can have a whole set of flow on effects that end in a smoking hole in the ground. That smoking hole does not equate to 'fun' for you or the poor sod sitting beside you.

If the 14 does not meet your mission goals and you don't have the skill to engineer a proper modification, then you should pick an aircraft that someone else has designed and proven that does meet your needs.

+1, Two Thumbs up, etc.....

I agree that the freedoms of the experimental category are what got us to where we are today, but there is far to much TLAR engineering that goes on.

Over the years I have seen countless #'s of highly modified RV's where the builder wasn't an engineer, but said all of the "calculations" had been done (though I can't think of a single instance were a builder / modifier ever offered any documentation or other information that would substantiate that claim).

There is so many factors that can be effected by a seemingly simple modification. Without a very detailed look at how the mod. integrates with the whole design, it is very easy to miss something that might be significant.

Example: In the near future, the RV-14 design will be put though dynamic testing of the landing gear. A change such as a 6 cyl engine would cause major moment of inertia change (among other things) that would most like totally negate any testing that was done based on the IO-390 being the biggest/heaviest engine. Considering the amount of effort required to complete these tests, it is highly unlikely that anyone would repeat them after doing such a modification.
The main point of this, is to emphasize that someone may be pushing much farther into the experimental fringes than they would at first believe.
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  #17  
Old 11-20-2012, 12:32 PM
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miyu1975 miyu1975 is offline
 
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I can only imagine these are the same type of arguments/discussions held when someone first decided to put a 540 on front of a 6, 7 or 8... I suspect it will happen with the 14.
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  #18  
Old 11-20-2012, 05:25 PM
chrish chrish is offline
 
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Quote:
Originally Posted by miyu1975 View Post
I can only imagine these are the same type of arguments/discussions held when someone first decided to put a 540 on front of a 6, 7 or 8... I suspect it will happen with the 14.
I am sure it will happen, but I just hope that whoever does it makes an informed decision, and that the modification does not have serious unexpected consequences. I understand there needs to be a balance between the freedom to do what you like and sufficient regulation to prevent people from unwittingly injuring themselves or someone else. I don't live in the USA, but the latest kitplanes magazine seems to infer that the FAA are starting to look at the accident rate of homebuilt experimental aircraft. I also see that Vans is leading the group of experimental kit manufacturers trying to improve the safety of the industry. I see the standardisation of configurations of the '14 as piece in that picture. In fact, I have been 'lurking', wanting to build an RV for about 20 years. Life's circumstances have gotten in the way and it has not happened. I will be able (I hope, if my airline does not implode in the next year or so) to finally start. What made me say 'the 14 is the one' is the very standardisation discussed above. I have seen various accidents and incidents caused by what would appear minor aircraft modifications or minor changes to procedures.

I don't want to 'rain on anyone's parade'. If you have the skill and talent to modify an aircraft, and you are informed about the risks, and you accept that - then go right ahead. As a professional aviator for the last almost 30 years, I have seen that it is 'what you don't know' is what has the potential to kill you.
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  #19  
Old 11-21-2012, 06:44 AM
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Captain_John Captain_John is offline
 
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Sam,

I have a good reason why. 540's rated at 230 hp and 260 hp are commonly available. I like the 390 ALOT (initially wanted one for my -7 but at almost $40,000 it is cost prohibitive).

If one were to locate a 230 hp (derated for mogas is a good thing) 540 on the cheap wouldn't that be a good cost effective fit?

I do know that the 540 would be slightly more hp and somewhat heavier than the 390 that Van suggests, but probably not a bad choice if CG issues and proper diligence is given to the change.

Now, I know that I am an armchair engineer with no real experience in the matter... but how bad would that be?

CJ
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  #20  
Old 11-21-2012, 08:06 AM
chrish chrish is offline
 
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A quick google shows about 130lbs difference in weight. This extra weight is well forward. What would your new 'G' limits be? - with the reduced useful load, could you do aeros 2-up? With the higher fuel flow and reduced useful load, would range be acceptable? What is the effect to A/B ratio? All that weight forward could significantly change the spin characteristics of the aircraft. So, putting a bigger motor in may make it go faster, but will you still be able to do aeros in it safely? If it flicks into a spin when manoeuvring, will it recover? Who is going to test it to find out?
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