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Old Sep 10, 2008, 05:15 PM
Time for another motto!
Utrecht, The Netherlands
Joined Jul 2006
1,413 Posts
Quote:
I was thinking maybe it wasnt enough Amps to keep the wire hot while I was cutting as the wire in the foam cooled the wire outside the foam heated up and melted.
That may very well be the cause. The resistance of steel increases with temperature. Cool down the wire, and more current will flow. The parts that are not cooled will see the most voltage drop, meaning they heat up more. The resulting increase in resistance locally is not enough to offset the lower resistance in the rest of the wire. The hot spot will create a local bottleneck concentrating where the power is dissipated: that is where the wire burns through. From that point of view, it would be a good idea to use longer wires if your powersupply can deliver the voltage. It makes quiet a difference if you cool down 90% of the wire or say 50%.
Or use a regulated power supply and set a fixed current.
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Old Sep 10, 2008, 05:21 PM
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Joined Oct 2004
789 Posts
Quote:
Originally Posted by Cybernaught
So many hobbies. So little time. www.tranquilityisland.com

Steve.
Looked at your website Steve, very nice boat you've built. A bit of a shame that you haven't put any pictures of you're latest (flying) build on there
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Old Sep 10, 2008, 06:02 PM
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Joined Oct 2004
789 Posts
3-blade 8040

I am going to try this one as well. First time with a 3-blade prop, looking forward to trying it. Why are so few people using 3-blades? Apparently you should have less Amps but same pull as a prop that is one size larger
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Old Sep 10, 2008, 06:10 PM
AMA 14680
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Northern Nevada
Joined Mar 2007
1,581 Posts
Quote:
Originally Posted by MadDuc
I am going to try this one as well. First time with a 3-blade prop, looking forward to trying it. Why are so few people using 3-blades? Apparently you should have less Amps but same pull as a prop that is one size larger
For me.... they cost more and are easier to break. Mainly I go with what the similar real life plane would use. Bob
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Old Sep 10, 2008, 09:51 PM
AKA Don
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United States, MI, Houghton Lake
Joined Dec 2002
7,563 Posts
On models and full sized planes 3 and 4 blade props are only used when needed for clearance. Three blade props are less effecient than 2, and 4 blades are worse yet. Some racing planes used single bladed props with just a counter weight on the other side.
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Old Sep 10, 2008, 10:14 PM
I'm not flying backwards!
Tony65x55's Avatar
Oshawa, Canada
Joined Sep 2004
3,753 Posts
Quote:
Originally Posted by Cybernaught
I bet it would be a floater with the 60" wing. TNX for the info, Tony. Would the stabilizers need to be enlarged too or would stock size work OK in your opinion?
Stock stabs are fine.

Tony
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Old Sep 11, 2008, 12:09 AM
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Joined Oct 2004
789 Posts
Thanks for your comments on the props guys. Strange that they are less efficient, can't remember where I read it..... will try to find it, will try the props anyway since I have got them now.
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Old Sep 11, 2008, 01:58 AM
Onward through the fog.
Cybernaught's Avatar
Bohol Philippines
Joined Aug 2008
1,566 Posts
Quote:
Originally Posted by JelleB
That may very well be the cause. The resistance of steel increases with temperature. Cool down the wire, and more current will flow. The parts that are not cooled will see the most voltage drop, meaning they heat up more. The resulting increase in resistance locally is not enough to offset the lower resistance in the rest of the wire. The hot spot will create a local bottleneck concentrating where the power is dissipated: that is where the wire burns through. From that point of view, it would be a good idea to use longer wires if your powersupply can deliver the voltage. It makes quiet a difference if you cool down 90% of the wire or say 50%.
Or use a regulated power supply and set a fixed current.
I'm not sure what you mean by the part of your post that I highlighted. The voltage out of a regulated power supply is fixed. The current remains the same in all parts of a series circuit but changes as the total resistance changes. Simple battery chargers are not constant current sources. I think the best solution is to use a bit heavier gauge of wire with higher resistance such as SS or nichrome. You can get more resistance by using a longer wire too (as you point out) but you need enough heat to melt the foam and length has it's practical limits too.

I tried using thin tie wire and guitar string before but didn't like it personally. Seems to me to be too hard to work with.
Steve.
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Old Sep 11, 2008, 02:31 AM
Onward through the fog.
Cybernaught's Avatar
Bohol Philippines
Joined Aug 2008
1,566 Posts
Can anyone point me to a post with the pdf file that has details for the 60" polyhedral wing? I used the thread search engine but didn't find anything. Also searched for AP1 and AP2 but didn't find anything on the wing in the results. Is it a KFm3 with a 10" chord and 3 20" pannels?

Has anyone tried the Clark Y as shown in the article at:
http://www.ncflyingtigers.org/combat...%20Study21.pdf
(See screen capture below.)

Tony said: "Stock stabs are fine."
Thanks I got the guides for the hot wire cutter made. I did the elevator with it and it makes a beautiful clean cut. Elevator on and hinged. back decking cut and fit.

Thanks,
Steve.
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Old Sep 11, 2008, 04:51 AM
Postcards From The Purple Edge
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United States, OK, Sand Springs
Joined May 2007
3,919 Posts
Hello

Hi, everybody. I feel like I need to introduce myself again...Wow! My last post in this forum was back in April--about 250 pages ago! I don't have the time or the bandwidth to play catch-up right now and I still won't be able to check in regularly. I just wanted to pop in and say "Howdy" to my fellows in the BB fan club. So--"Howdy!"

Tony, after five and a half months out in the middle of the Afghan desert we're finally back in near-civilization. Right now I'm sitting on the boardwalk outside the Timmy's trailer, surrounded by your countymen, and surfing the free wireless internet (can you believe that?!). I still have a few weeks to hang out here, but it's almost time to dust off those plans you promised.

kendall
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Old Sep 11, 2008, 06:29 AM
I'm not flying backwards!
Tony65x55's Avatar
Oshawa, Canada
Joined Sep 2004
3,753 Posts
Kendall!!!!!! Whoo-hoo!!! How are you Buddy. It's great to hear from you. I figured you were lost in a sandstorm. Thanks for the periodic updates from the sandbox though. It's good to know you're OK.

The plans are still waiting for you to beta, as promised. I bet that Timmy's tastes like heaven after 5 1/2 months of sand. You tell those Canadians that Tony said to treat you good and give you extra Timbits.

When are you coming home?

Tony
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Old Sep 11, 2008, 06:34 AM
I'm not flying backwards!
Tony65x55's Avatar
Oshawa, Canada
Joined Sep 2004
3,753 Posts
Quote:
Originally Posted by Cybernaught
Can anyone point me to a post with the pdf file that has details for the 60" polyhedral wing? I used the thread search engine but didn't find anything. Also searched for AP1 and AP2 but didn't find anything on the wing in the results. Is it a KFm3 with a 10" chord and 3 20" pannels?

Has anyone tried the Clark Y as shown in the article at:
http://www.ncflyingtigers.org/combat...%20Study21.pdf
(See screen capture below.)

Tony said: "Stock stabs are fine."
Thanks I got the guides for the hot wire cutter made. I did the elevator with it and it makes a beautiful clean cut. Elevator on and hinged. back decking cut and fit.

Thanks,
Steve.
Steve, go to post 1120 http://www.rcgroups.com/forums/showp...postcount=1120

It has all the plans for the BBAP2 and a description on the wing. Yes, it is three panels. The original is designed to come apart in the middle for easy transportation but you can easily build it as one piece. Flies great too.

Tony
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Old Sep 11, 2008, 08:11 AM
If it flies, I will crash it
mxspode's Avatar
USA, CO, Westminster
Joined Jan 2008
3,022 Posts
Quote:
Originally Posted by tuppertn
Hi, everybody. I feel like I need to introduce myself again...Wow! My last post in this forum was back in April--about 250 pages ago! I don't have the time or the bandwidth to play catch-up right now and I still won't be able to check in regularly. I just wanted to pop in and say "Howdy" to my fellows in the BB fan club. So--"Howdy!"

Tony, after five and a half months out in the middle of the Afghan desert we're finally back in near-civilization. Right now I'm sitting on the boardwalk outside the Timmy's trailer, surrounded by your countymen, and surfing the free wireless internet (can you believe that?!). I still have a few weeks to hang out here, but it's almost time to dust off those plans you promised.

kendall
Wow, nice to hear from you again Kendall and very nice to hear you are doing well. We have missed you around here. So give us all the info, like Tony said, are you coming home soon?

My, what a pleasant surprise for today. I am glad I decided to check my mail this morning.

Rob...
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Old Sep 11, 2008, 08:13 AM
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jhtitan's Avatar
Washington MO
Joined Jul 2008
567 Posts
Ok so I have a BB question. I finally got a scale so I could weigh my planes and see where I was at. been curious about how much weight I added with the printer decal camo. I thought someone had posted there AUW on a 42" BB at 450g as being a bit heavy. well after weighing mine in mast night it was over 600g I dropped a bit of weight by removing the decal camo and any extra box tape I thought I could get away without having. that dropped little over 60g or 2.2oz. not sure where the rest of the weight is coming from unless the Popular Dowels I used weight that much more than Spruce would. I am now down to an AUW of just under 540g (sorry got the numbers wrote down at home and forgot to grab them so I am trying to remember) I am curious if the new props I have ordered will weigh in less than the seemingly indestructible ones I have on it now. she flew fairly good before the weight loss. I probably shouldn't with it at all lol but I would still like to see if I can get a few more mins in the air with her. I would like to have to bring her down cause my neck hurts not cause the batts died lol.

also is there a ratio of AUW to thrust I should be shooting for? I keep thinking if my plane weighs in at 21oz I should be looking for 21oz of thrust. not sure if I am thinking right on that or not. Its not unheard of for my to be wrong "Sometimes".

Thanks again for your help.

Jon

P.S. Kendall its good to see you posting. I have read a lot of your posts lately and seen many of your fine builds. looking forward to seeing more wonderful builds from you soon. Stay safe over there. Thanks for everything and come home safe.

Jon
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Old Sep 11, 2008, 11:35 AM
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maguro's Avatar
United States, DE, Bear
Joined Apr 2007
1,720 Posts
Cybernaught, the photo you showed is no Clark Y. It's not even close. It is just a flat bottom airfoil shape. I've attached a drawing of a Clark Y for reference, in case you want to build one.

I did actually build a Clark Y from FFF. I cut FFF ribs from the airfoil template, glued the spar and ribs to the bottom foam, and folded the top over. The wing was for my Slow Stick. I wanted to add ailerons and a "real" wing. The wing worked OK, but was heavier than the equivalent KFM3, faster, and had less lift. The KFM3 is also a lot easier to build.
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