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Old Jun 26, 2012, 06:10 PM
Time for me to Fly...
Mr. Wiz's Avatar
United States, MI, Fenton
Joined Jan 2000
8,522 Posts
My launch preset is nothing more than a flight mode with a different trim setting on the elevator. Flap mixing is a true mix but if I'm carrying down trim to fly straight and level and suddenly I change that, dosent the amount of flap to stop change too?

When flying in wind and such all I ever do is click down one or two on the elevator. Camber.... I generally leave that about the same. Are there more advanced uses of trims that I could use and take advantage of? Probably but the time to implement those isn't right before my very first big contest. I'll have enough to concentrate on without adding all that to my list right now. That said, after the fact, I might like to explore those further.

Thanks!
Mike
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Old Jun 26, 2012, 06:44 PM
G_T
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Joined Apr 2009
5,725 Posts
Flaps is flaps. You adjust the camber to be optimal for the flight loads on the wing and the airspeed (lift coefficient desired). For landing, you use more than optimal camber (which we now call flaps) to deliberately increase the drag coefficient as a method of glide path control. If you have added down trim then yes your approach will be slightly faster. Slightly. The higher drag when flaps are down beyond the maximal useful thermal setting prevents the buildup of speed.

If you added down trim then there are a few possible reasons.

(1) You decided the plane was flying slower than optimal. In this case you needed to retrim anyway just to get back up to normal speed. Thermal drift or pull string stretch can put you in this situation.

(2) Turbulence level is higher. Optimal airspeeds are now very slightly faster than for calm conditions, for the same camber settings. So a touch of down trim may be appropriate. In turbulence, you want a slightly higher landing speed as well just to maintain adequate control. So no cost.

Go too slow in turbulence and the plane gets mushed around, greater pilot input is required for control (therefore more control drag) and you come down way too fast. Go too fast - just pull up to convert the extra speed back to altitude.

In turbulence the airfoils on our modern wings and probably for all DLGs perform their best at slightly higher airspeeds. Proper trimming for cruise in moderate turbulence for instance is probably about 1/2 M/s faster than optimal in dead calm air. So you have two reasons to fly slightly faster in turbulence.

(3) Wind is high. You need to be able to move and are willing to sacrifice a bit of efficiency to do so. When landing, won't wind still be high? You want higher landing airspeed on approach.

(4) Or you need to add up trim for dead air flying. You'll retune your float and/or cruise settings for min sink.

In normal flying, cruise would be tuned more towards max L/D as your general purpose in cruise is to get to better air. Odds of that improve if you cover more air, hence max L/D. Yes, you come down slightly faster if you fail. But you'll lose anyway to someone else if you fail.

Min sink is somewhere around 0.2 M/s slower than max L/D for a fixed camber setting. It appears much more than that in practice, because usually we don't use these two settings in constant conditions. Min sink in dead air, max L/D in more active air. More active air has more turbulence, so optimal airspeeds have increased more. So what the pilot sees is a change in desires speed of the sum of these changes - something closer to 1M/s. Then there is ballast, and it goes up some more.

...

So in general, if you needed to adjust elevator trim for level flight, the same adjustment is also quite appropriate for landing approach.

Gerald

PS - Mike, I'm not trying to change your decision to not mess with this stuff until after your first major contest. I'm just providing some additional info for you and any others who may have interest. CU at the Bruce!
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Last edited by G_T; Jun 26, 2012 at 08:36 PM.
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Old Jun 26, 2012, 08:51 PM
Time for me to Fly...
Mr. Wiz's Avatar
United States, MI, Fenton
Joined Jan 2000
8,522 Posts
Quote:
Originally Posted by G_T View Post
PS - Mike, I'm not trying to change your decision to not mess with this stuff until after your first major contest. I'm just providing some additional info for you and any others who may have interest. CU at the Bruce!
Fair enough... Gerald. I don't want to sound unappreciative either. You've provided me with a lot of good advice so far and I will continue to respect, enjoy and hopefully absorb everything you have to offer. It will be my pleasure to meet you in person at the Bruce.

Mike
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Old Jul 03, 2012, 09:28 AM
Time for me to Fly...
Mr. Wiz's Avatar
United States, MI, Fenton
Joined Jan 2000
8,522 Posts
Well, I never did get the Fr3aK dialed in after the boom repair so I only flew it a couple times at the Bruce. Hopefully now that the big push is behind me I can find some time to get it flying the way I want it to. At some point I'll probably just want to replace the fuse, assuming you (Tom) have any extras for sale.
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Old Jul 06, 2012, 10:28 AM
Horizon Hobby Employee
United States, IL, Mahomet
Joined Jun 2006
608 Posts
I left The Bruce very happy with Fr3aK in hand. This is a top quality product and it's great to see it being made in the US. Started working on it last night and hope to have it done next week some time. Installing wing mounting hard points and tapping holes brought back memories of building Polecat XP models, has been a while and we sure get spoiled with the completion level of most European models.
Looks like a straightforward assembly, really looking forward to throwing and flying it. Thanks to Tom and all involved (Phil/Brian?) for the great work and making these available.

Craig
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Old Jul 12, 2012, 07:25 AM
Father of Fr3aK, DLG Pilot
tom43004's Avatar
USA, OH, Worthington
Joined May 2002
6,709 Posts
Funny retrospective from exactly three years ago in my "Zone Clone" build log...

***quote***

I'm not trying to be anyone's hero. I just tend to build alot after the wife and kids are in bed. Sometimes I'm a bit obsessive and build alot to compare layups, airfoils, epoxies, building techniques, etc.

My next few airplanes will focus on higher quality and cleaner finished product. I will be venturing into CNC work soon of both wings and fuses. I may not get deeply into that until the winter.

For now, I have four more sets of CNC cores that will complete my stable for the rest of the year. I am diggin Kevlar again so I may dump some glass and glass disser wings at NATs or the Bruce.

Paul, I have no desire to ever produce kits or parts for $$$. I build more than I crash so I will dump a part here and there like the next guy, but building is fun until you have to do it, then it becomes work.

Tom Siler
Columbus, OH

***end quote***

Funny how things change and how they stay the same.

Craig, I hope your build is getting along nicely. UPS tried to tell me that you live in the "boonies" and wanted to charge me $13 to ship a regulator/switchjack in a small box. Explaining that you have an interstate running right through didn't help. USPS sent it for the usual $5. I think I sent a similar box to Europe for about the same money recently.

Fr3aKs are popping up alot lately. I've recently shipped another wave of airframes and many are taking to the skies. I have a big pile of new fuselages in the basement after a week long building binge and now I just need to get them trimmed and matched to wings for shipment.

There has been alot of conversation about a new wing and solid molding... some of that is my fault. I likely will concentrate on refining what we already are making and save the major breakthroughs for the winter. Yes, it's quite true that I'm re-drawing the wing to make a one-piece mold to eliminate the center wrap, but that will likely be the only major change you'll see before the Team Selections. I will be staying with the airfoils and planform that we have now. It's just too good to stray away from at this point, and chasing "better" could leave alot behind if we're not careful.
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Old Jul 13, 2012, 12:01 PM
Time for me to Fly...
Mr. Wiz's Avatar
United States, MI, Fenton
Joined Jan 2000
8,522 Posts
I know, I get it... Some days I'm the hammer and some days I'm the nail. It seems like the last few times I've flown the Fr3aK, I've been the nail... In fact, I'm a bent nail. Then I go out next time and fly the B3 and all is right with the world. This didn't use to be the case. I've fiddled with the stab incidence and I have it matched to the wing. I have it set up as 0. Is that right?

Or

Are the B3 and Fr3aK so different that I'm just confusing my thumbs and generally making life difficult for myself?
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Old Jul 13, 2012, 01:14 PM
G_T
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Joined Apr 2009
5,725 Posts
1) Yes, they are that different.

2) If your Fr3aK uses one of the Freak-Horizontal airfoils for the horizontal stab (which it should), then you have it set up wrong. First off, forget the 0 degree concept. It is meaningless with any stab setup. For the specific case of a FreakHorizontal V2 stab, when trimmed for level cruise flight - that is with CG set, everything - then the elevator portion of the stab should be down. It should look like this: http://www.rcgroups.com/forums/attac...mentid=4389808 This is important with this airfoil. It gives better performance than any other hinged horizontal stabilizer, but ONLY if set up this way. If not, then it may well give worse performance than most any other hinged horizontal stabilizer.

Gerald
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Old Jul 13, 2012, 01:45 PM
Time for me to Fly...
Mr. Wiz's Avatar
United States, MI, Fenton
Joined Jan 2000
8,522 Posts
I'm completely baffled at this point. No surprise, right Gerald. How do I properly set up the angle like that? Just have the elevator hang down one or two degrees when trimmed for level flight?
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Old Jul 13, 2012, 01:49 PM
Father of Fr3aK, DLG Pilot
tom43004's Avatar
USA, OH, Worthington
Joined May 2002
6,709 Posts
Mike,

A good approximation is to set the horizontal so that the "fat" part of the bottom of the fixed horizontal and the trailing edge of the elevator both touch a straight edge, and the straight edge is about 1/32 below the hinge gap.

In normal cruise flying, the wing carries about 3.5 degrees of angle of attack, meaning that with your cruise settings, if you put a hobart meter on the wing with the tail level, you should see the LE a few degrees higher than the TE. When you reflex this for launch and speed mode, you're effectively removing this AoA by moving the TE of the flapperon upward, and getting the wing very near zero lift which should nearly "zero" it up with the tail.
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Old Jul 13, 2012, 01:56 PM
Time for me to Fly...
Mr. Wiz's Avatar
United States, MI, Fenton
Joined Jan 2000
8,522 Posts
Alright, back to the pool table with it and my incidence meters. I've been following that crazy 0 thing in the Radio Carbon Art video with everything. Of course, that makes no sense with a B3.
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Old Jul 15, 2012, 09:35 PM
Registered User
United States, MD, Baltimore
Joined Feb 2007
682 Posts
Am I seeing double?

The new kids are at home awaiting clean up and electronics. Huge thanks to Tom for bringing moldies to the US, Gerald for coming up with a killer foil, and Phil for generally being the man, albeit Big and Dirty, and builder extraordinaire.

Time to neglect everything in life and build planes!

Austin
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Old Jul 15, 2012, 11:33 PM
Will fly for food
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Bellevue WA,
Joined Dec 2003
6,843 Posts
I got to see one of these up close yesterday at the contest in Olympia WA. Very nice.
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Old Jul 16, 2012, 06:05 AM
Father of Fr3aK, DLG Pilot
tom43004's Avatar
USA, OH, Worthington
Joined May 2002
6,709 Posts
Excellent Austin...

T-shirts are being printed and soon will be available for Fr3aK drivers and fans. They're a bit obnoxious but I'm sure you guys wouldn't want it any other way.
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Old Jul 16, 2012, 07:19 AM
Aurora Builder
United States, MD, Lusby
Joined Nov 2003
3,437 Posts
Quote:
Originally Posted by austinhlg View Post
The new kids are at home awaiting clean up and electronics. Huge thanks to Tom for bringing moldies to the US, Gerald for coming up with a killer foil, and Phil for generally being the man, albeit Big and Dirty, and builder extraordinaire.

Time to neglect everything in life and build planes!

Austin
Mmmmm, RDS. Any chance you have dimensions on the pockets?
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