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Old Nov 10, 2011, 03:56 AM
big bruce is offline
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F5B from Big Bruce Racing


Now I am hooked on the potential of electric powered competition, my next step is to develop an F5B version of my F5D model.
All I need is some guidance on likes and dislikes of current models.
From what I see so far my dislikes would be not enough room in the battery compartment and servos built into wings that you can't replace at the flying field in the event of surviving a failure.
1 piece wings??
My sketch pad so far is a 1.9m span, 26.75 dm wing area, modified MH42 airfoil and a 3dm area tail. Configuration would be the same as my F5D for the body shape and 4 bolts for holding the wing on. Kontronik KIRA FAIF5B/6S motor
Would be grateful for some feed back from those with experience and opinions.
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Old Nov 10, 2011, 04:38 AM
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interchangable nose section where you can choose longer or shorter for heavy and light setups?! or even a glider nose.

Old Nov 10, 2011, 04:59 AM
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3 dm2 is much to big for a tailplane on current models. something like 2.2 is more common.
Old Nov 10, 2011, 05:22 AM
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26.75 dm2 might be a bit tight also only 1.5in2 to spare does allow much for processing errors.
Old Nov 10, 2011, 05:25 AM
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Originally Posted by David H View Post
26.75 dm2 might be a bit tight also only 1.5in2 to spare does allow much for processing errors.
Thanks for the feed back Dave. Should I go bigger than the 1.9m span or just up the area to high 27's ?
Old Nov 10, 2011, 06:12 AM
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Livin it UP when Im goin DOWN
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Old Nov 10, 2011, 07:42 AM
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Quote:
Originally Posted by David H View Post
26.75 dm2 might be a bit tight also only 1.5in2 to spare does allow much for processing errors.
not if you add the 3dm2 tail....
Old Nov 10, 2011, 09:50 AM
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Quote:
Originally Posted by David H View Post
26.75 dm2 might be a bit tight also only 1.5in2 to spare does allow much for processing errors.
Not so. the B9.5 is a B08 reduced from the mid 27s down to the limit. People say they see the difference in flight, only about 3mm less chord. The WC measurers are never under, usually over, but you can't guarantee that. But it not a problem, our lipo weights are so low.
Old Nov 10, 2011, 10:06 AM
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2 piece wings with the strength (or close to it) of a one piece.....easier traveling and packing.
Edit: and a removable tail...same reason.

Old Nov 10, 2011, 03:10 PM
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Originally Posted by arcticflyer View Post
2 piece wings with the strength (or close to it) of a one piece.....easier traveling and packing.
Edit: and a removable tail...same reason.

tail is easy removed of course, no problem there, but was thinking strength wise that a 3 piece could be better with the center piece being 1m span then 2 x 450mm tip pieces. ( join would be at the break between flap and aileron sections)
Old Nov 10, 2011, 08:12 PM
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Thanks go to Steve Neu for some PM's to get me on track also and advise of the pack size for the new 10s packs legal next year.
Old Nov 11, 2011, 12:58 PM
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+1 on a three piece wing.
Old Nov 11, 2011, 01:00 PM
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Bruce, i think you will have to make the choice here so either end with a competative plane that will push the Avionik to the side, keeping in mind most serious competitors are now flying an Avionik, or go for the Hotliner/F5B market and accept that your plane will only be flown in competition by a hand full of people. Depending on that you will have to then pick who you are listening to and think about the practicality of things. Personally i think you did a great job on the F5D from what i have seen so far, please don't get to far away from that. I don't think a 3 piece wing is going to cut it in hard competition for 2 hard reasons, the added weight, the lower strength. You can always do a 3 piece wing in the same moulds for those who want it.

The minimum legal area of an F5B is 26.67 for the whole plane, so wing and elevator together. If you look on the german website you will see some figures for the models out there, probably pritty accurate. http://www.f5b.de/modelle.html
I'd say anywhere between 26.7 and 27 total area would be fine, the less the faster the model will be but the more we may have to argue with the officials who measure it.

Battery pack wise, to small is not good, but to big is equally bad. Nobody wants to fly a fridge in competition because you just know it's going to be slower. For me there is really only one pack size out there and it's 6S 3000-3300mah. The new 10S brick pack from Neu has about the same dimensions. You could think about splitting the pack up in 3S+3S like the German Go One 6/7 has 2S+2S.

Drive wise, nobody is flying a Kontronik drive in the top. Lucky it's pritty similar in size to the Hacker. The Neu 1500 series motors are a few mm bigger in diameter and they fit snug in the Avionik B08+ nose, they don't really fit well inside the old B1L nose, Sergey changed the nose to fit the bigger diameter motors. Only a couple of mm but it's enough. Since the Neu motors are pritty popular, you'd probably want to work with that and then the Hacker will fit no problem. You could offer various firewalls for the big brands ready installed on request. This is another job that is so much more easy to do in production then at home. I'd gladly pay 10 euro more to have this job done.

Lastly, back to the servo's.... I'd say everybody hates having to do the linkages, it would be nice if the wing was RTF and also knowing that it's done right unlike the early RW4. You could draw some lines in the paint so we know where to cut if we need to. That's about it i am afraid, any hatches or even just a strip of tape will increase the drag as it will function as a turbulator and likely to change the air flow from laminar to turbulant in certain AOA ranges. Right when in those ranges we should be able to have laminar flow to a point past the hinge line. But hey, if you don't want to challange the Avionik then this is not a problem.

Last little tip, i'd say that wings with an overriding eliptical planforms (so the corde at the start of the aileron is much less then at the root) don't seem to be working as well as the much more constant cord, rounded tip planform of the Avionik and RW4. However it seems atleast the Avionik does have a different airfoil near the tip region that i think helps to make it safe in high AOA situations like we have in the turns. The Avionik is pritty much impossible to stall at speed. Maybe worth seeing how your F5D goes in serious competition before you move on to the F5B.
Old Nov 11, 2011, 04:47 PM
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Quote:
I don't think a 3 piece wing is going to cut it in hard competition for 2 hard reasons, the added weight, the lower strength.
Definitely agree with this, the big challenge with 3 piece wing is torsional stiffness in the high speed turns of F5B.
Re wing area it appears that most of the top model are all under 27dm2 and therefore 26.8 is quite common. Look like George was correct.
Old Nov 12, 2011, 12:56 AM
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wing would be made from a full span mold, so can make 1 piece wings or do 3 piece with the same mold.
As soon as I get the graupner 9mm thick servos I can play with built in servos in my F5D model ( servos are set int the wing just ouside the body and the 9mm servos will fit inside nicely.


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