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Old Dec 31, 2009, 12:02 AM
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United States, MI, Detroit
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you got some space in the tail how about helium balloons
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Old Dec 31, 2009, 12:55 AM
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Waterloo, Belgium
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Originally Posted by dag214 View Post
That is some great info, thank!

I am designing a APU cart that will have 4 parallel deep cycle marine 12 volt batteries. I will have 3 Bantam BC8DX Charger, I know there are other, I just love these chargers.

The A123 will not take much time to top off at the field, my calcs show I can get 15 flights before they are 50% down on my A123.

It looks like I can turn the plane around in about 90 minutes. Plenty of time to get my knees to stop shaking. I bet I will never fly it more then 2-3 times in a single day.

Thanks, DAG
I use regularly 12s2p a123 packs. I charge them at the field with a MasTech HY5020E at 20A 43.2V in 15min, strictly following a123 specifications. Brushless are in the 50cc category (3500W).
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Old Dec 31, 2009, 06:07 AM
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DAG, I have been following this thread for a while and now finally come forward to express my amazement and appreciation for your dedication and craftsmanship. As a former pipe organ restorer, I can appreciate the combination of fine woodworking and electronics skill you abundantly possess.

So here's my "stupid" question, and I hope it's not too derailing: Regarding Carbon Fiber, I see it used many times in strips as a lightweight reinforcement; so, why not build a plane using mostly, if not all, carbon fiber?

Anyway, congratulations on getting this project near completion. I know you are going to really enjoy flying it!

Scott
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Old Dec 31, 2009, 07:04 AM
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United States, CA, El Cerrito
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Originally Posted by thpppttt View Post
Regarding Carbon Fiber, I see it used many times in strips as a lightweight reinforcement; so, why not build a plane using mostly, if not all, carbon fiber?
Scott
My guess is that it's very expensive.

Jerry
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Old Dec 31, 2009, 12:33 PM
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Well don't forget that wood has a lot of excellent qualities for this application too. It's very easy to work with. Easy to cut and shape and glue. Balsa is very lightweight and strong pound for pound and dollar for dollar, and the same holds true for aircraft ply. Building a mold of the entire fuselage, for instance, is very expensive and labor intensive prospect. It's a great way to go if you're going to make many copies. Building the plug for the mold is a LOT like building the entire airframe from scratch. And a fuselage of this size would still require a lot of internal structure anyway. The all wood structure might easily be lighter. It's definitely cheaper and faster to build. DAG has identified where composite materials make the most sense to accomplish his design goals, and he added the carbon fiber tow where needed. Rather than replacing the wood, the composite of wood and carbon fiber enhances the engineering properties of the wood in very beneficial ways with very little weight penalty. Wood is good!
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Old Dec 31, 2009, 12:55 PM
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Originally Posted by ska2000 View Post
Rather than replacing the wood, the composite of wood and carbon fiber enhances the engineering properties of the wood in very beneficial ways with very little weight penalty. Wood is good!
Wood schmood, if it was affordable of course he'd rather have a full carbon structure, where applicable and in conjunction with other materials if needed. The US Military has a mini remote controlled flying plane, saw it at SEFF last year, about 28" wingspan, folds in half and shoves in a little tube, very slick. It's made out of 100% CF and is $3,500 just for the airframe :-o

Jack
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Old Dec 31, 2009, 01:08 PM
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One of the probelms with carbon fiber is if used for the full structure it is a completely diffrent build...Just like a making a fiberglass plane! it requires making molds and plugs most of the time..all can be done just not the same type of build...the others problems are cost and the fact it is a waist of money unless you have prepreg carbon and an auto clave to Cook it..most of the gain is lost by useing normal fiber glass constructin methods..the excess resin kills a lot of the strenght gains from carbon...it really only helps when used in tension only in this type of contruction..
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Old Dec 31, 2009, 01:12 PM
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Well the question was why not 100% CF, I am sure the number one reason is price, not skill as I'm sure it could be learned. I was just agreeing with the original answer, not saying the rest isn't valid...

Jack
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Old Dec 31, 2009, 02:12 PM
Hey Guys, Watch This.......
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USA, TX, El Paso
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Originally Posted by jfetter View Post
Well the question was why not 100% CF, I am sure the number one reason is price, not skill as I'm sure it could be learned. I was just agreeing with the original answer, not saying the rest isn't valid...

Jack
There's another issue with radio equipment in a full CF airframe. Seems to me cost would be a major issue as well.
Mike
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Old Dec 31, 2009, 05:30 PM
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United States, CA, West Sacramento
Joined Jul 2007
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if this plane was made of CF i would have little interest in it , even if it is my second favourite plane .1. Tigermoth
2. b-36
3 . predator b aka reaper
woodworking is a skill moulding not so much even i can do it , woodworking is much more difficult ,its an art , that I thing Dag has pretty much perfected .
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Old Dec 31, 2009, 05:53 PM
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Sydney Australia
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That for sure, very robust and I'm sure the fact that they are a little heavier also helped in the choice as they will offset some of the excess tail weight this beauty will have.
Found this out myself when I recently converted my little (110 inch) B-36 to lipos.

The B-36 has a lot of 'junk in the trunk' & it was hard to get everything far enough forward to get the CG correct.

Still, with the almost 1 1/2 pounds I've saved (plus more horsepower) the old girl is almost sprightly! - John.
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Old Dec 31, 2009, 05:57 PM
This is high school for you...
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Longmont, CO
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Its coming along great!
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Old Dec 31, 2009, 06:27 PM
I fly, therefore, I crash!!!
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San Jose, CA
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Quote:
Originally Posted by jfetter View Post
Wood schmood, if it was affordable of course he'd rather have a full carbon structure, where applicable and in conjunction with other materials if needed. The US Military has a mini remote controlled flying plane, saw it at SEFF last year, about 28" wingspan, folds in half and shoves in a little tube, very slick. It's made out of 100% CF and is $3,500 just for the airframe :-o

Jack
Of course it's $3500.00 for the U.S. government....but then they pay $2500.00 for a toilet seat.... Like what was alluded to in the movie "Independence Day".... How do you think they pay for covert and black ops, and other secret projects??

SteveT
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Old Jan 01, 2010, 05:58 AM
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Originally Posted by bdelapen View Post
That for sure, very robust and I'm sure the fact that they are a little heavier also helped in the choice as they will offset some of the excess tail weight this beauty will have.

Regards,

- Birger
Based on the continuing on-going examples of Dag's superb engineering, I defy you to identify ANY "excess tail weight" in this model NO doubt every gram in it is there because it has to be....
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Old Jan 01, 2010, 06:18 AM
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Springfield, VA
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Originally Posted by Draknkep View Post
Of course it's $3500.00 for the U.S. government....but then they pay $2500.00 for a toilet seat.... Like what was alluded to in the movie "Independence Day".... How do you think they pay for covert and black ops, and other secret projects??

SteveT
As it turns out, as part of my USAF career, I got the correct info on the "$2500.00" toliet seat. First, it was not $2500, I forget just what it was, but I want to say it was about $1600, and second, what is always forgotten or never known by the folks who repeat this story, is that it was also required to be a pressure seal in the aircraft (it was on a P-3, by the way). I submit the engineering and tolerances, and required manufacturing skills, for a part that if it fails will crash the aircraft, requires a bit more than a Home Depot solution (and price).

Another intersting story--back when smoking was still very prevalent. The Navy had a requirement to install an ashtray in an aircraft, the procurement officer let the contract for $600 a copy--and promptly got called on the carpet for the cost. Again, what is not added (the rest of the story), is he checked with the government back shops and they said it would cost them $900 each to do--so he thougt he was doing great saving 33% on the cost.

The services have a program called Education with Industry where serving officers/civilians get to essentially be a contractor for a year, in order to learn the other side of doing business. It was one of the most interesting years of my career, and really gives you an understanding of just how mis-informed people are sometimes. You would be appalled at how much money is wasted just because the appearance of waste has to be avoided--not to mention the number of parts that don't get made because a company can't afford the publicity on what a small production run would cost.

Not to say there aren't some abuses out there, of course there are--but my experience indicates 99.9999% is completely aboveboard. It's just that the amount of money involved is so huge that .0001% still looks outrageous in the paper.

Anyway, apologize for going off-track from this stupendous project, but after a 30 year career in the USAF, I get a little peeved sometimes when criticism is unjustified. After all, there are enough times when it is valid--lol. But those times I won't talk about--while the guilty don't deserve the discretion, the innocents involved do...
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