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Old Oct 12, 2005, 06:00 AM
D Hauch
Guest
n/a Posts
top or bottom driven ?

hi all,
I've been asked this a few times, and I give my opinion,
but i want to see what you guys have to say.

What gets better mechanical advantage, top or bottom
driven linkage, and how much does the drag of bottom driven
really effect things, if any ?

My vote goes towards bottom driven.
I can always get the throws I want, easy to set up and adjust,
and gives a solid control surface.

Dave Hauch
www.git-r-built.com
RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to soaring-request@airage.com. Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Old Oct 12, 2005, 06:00 AM
Harley Michaelis
Guest
n/a Posts
Re: top or bottom driven ?

For what it's worth, some years back a German modeler, whose name I can't
now recall, and who apparently had the means to evaluate it, determined that
4 covers over exposed linkages (clevises, rods, horns, etc.) added 5-10% to
overall airframe drag.

This was of interest to me since I was then working out the details of an
all-internal system of moving flaps and ailerons which became the Rotary
Driver System, detailed in File 6 and File 3 of the Genie pages at
http://genie.rchomepage.com/.

While extensively experimenting with the RDS, I found out it did not matter
if the "pocket" that the "drive shaft" enters was high or low in the thin
surfaces we deal with. However, it was much easier to mount a pocket inside
the bottom surface so I usually stuck to that whether for flaps or ailerons.

I've now used some form of the RDS in over 60 airframes. They are
particularly quiet, suggesting that it is worthwhile to use an all internal
setup for moving surfaces.

An RDS installation is easy to do in home built, built-up or composite wings
or pre-built composite wings that can be purchased without wells cut in
them.

Pre-molded wells in moldies, however, are an obstacle to an RDS
installation, since it is preferable that the servos be angled relative to
the hingeline. 45 degrees is a very practical orientation and makes it easy
to get full down flaps.

----- Original Message -----
From: "D Hauch" <djunruh@qtm.net>
To: <soaring@airage.com>
Sent: Tuesday, June 21, 2005 6:24 PM
Subject: [RCSE] top or bottom driven ?


> hi all,
> I've been asked this a few times, and I give my opinion,
> but i want to see what you guys have to say.
>
> What gets better mechanical advantage, top or bottom
> driven linkage, and how much does the drag of bottom driven
> really effect things, if any ?
>
> My vote goes towards bottom driven.
> I can always get the throws I want, easy to set up and adjust,
> and gives a solid control surface.
>
> Dave Hauch
> www.git-r-built.com
> RCSE-List facilities provided by Model Airplane News. Send "subscribe"
> and "unsubscribe" requests to soaring-request@airage.com. Please note
> that subscribe and unsubscribe messages must be sent in text only format
> with MIME turned off. Email sent from web based email such as Hotmail and
> AOL are generally NOT in text format
>
>



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Old Oct 12, 2005, 06:00 AM
AMA3655@aol.com
Guest
n/a Posts
Re: top or bottom driven ?

I like bottom driven flaps and ailerons for various reasons. According to
Dr. Hepperle a properly faired set of 4 linkages on the bottom of a wing add
around 3% total drag to a typical F3B airframe. You can go dig around his
website and find a number of interesting tidbits.
_http://www.mh-aerotools.de/airfoils/index.htm_
(http://www.mh-aerotools.de/airfoils/index.htm)

happy trails - Rob Glover





hi all,
I've been asked this a few times, and I give my opinion,
but i want to see what you guys have to say.

What gets better mechanical advantage, top or bottom
driven linkage, and how much does the drag of bottom driven
really effect things, if any ?

My vote goes towards bottom driven.
I can always get the throws I want, easy to set up and adjust,
and gives a solid control surface.

Dave Hauch
www.git-r-built.com

RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to soaring-request@airage.com. Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Old Oct 12, 2005, 06:00 AM
Jim Laurel
Guest
n/a Posts
RE: top or bottom driven ?

Dave,
I would have to say bottom-driven gives the best advantage. On the Icons,
this has proven itself time and again. However, I would add that I have
assembled a number of planes lately with top-driven linkages, including a
Tragi 705x and Graphite Standard.

In actual use, I found the top mounted linkages on these planes to be
perfectly adequate. I was able to set up both so that the ailerons and
flaps have no slop at all, and the whole assembly feels strong. Also, it
depends on the plane design. The Tragi, for example, seems to have a
particularly well-designed top mounted linkage for the flaps, with adequate
mechanical advantage.

I am now assembling a Pike Superior, and I can already see that the
top-mounted linkages on this plane were not as well thought-out or as strong
as the Tragi. The thin wing leaves little room for a linkage with some
mechanical advantage to help the servos in their work. On the plus side,
however, protrusions from the wing surfaces are slight and the whole thing
is aerodynamically very clean.

Gordy feels strongly about this topic and has admonished me not to use the
top-mounted linkages on my Pikes and encouraged me to adopt his
bottom-mounted system.

--Jim Laurel


-----Original Message-----
From: D Hauch [mailto:djunruh@qtm.net]
Sent: Tuesday, June 21, 2005 6:24 PM
To: soaring@airage.com
Subject: [RCSE] top or bottom driven ?

hi all,
I've been asked this a few times, and I give my opinion,
but i want to see what you guys have to say.

What gets better mechanical advantage, top or bottom
driven linkage, and how much does the drag of bottom driven
really effect things, if any ?

My vote goes towards bottom driven.
I can always get the throws I want, easy to set up and adjust,
and gives a solid control surface.

Dave Hauch
www.git-r-built.com
RCSE-List facilities provided by Model Airplane News. Send "subscribe" and
"unsubscribe" requests to soaring-request@airage.com. Please note that
subscribe and unsubscribe messages must be sent in text only format with
MIME turned off. Email sent from web based email such as Hotmail and AOL
are generally NOT in text format

RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to soaring-request@airage.com. Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Old Oct 12, 2005, 06:00 AM
John Erickson
Guest
n/a Posts
Re: Re: top or bottom driven ?

Rob,

That's an interesting page. I especially like the drag summary at the
bottom. For a mid Cl the airfoil is responsible for 55% of the drag,
induced drag is another 20%, the fuselage is about 18%, the linkages about
3% and the stab is worth about 4%.

In almost all cases the linkages on the bottom were a better choice. In all
cases faired were the best (other than internal) and the shorter the linkage
(and fairing) the better.

No wonder everyone puts so much into the wing. Worth about 75% of the
overall drag at average flight speeds.

JE
--
Erickson Architects
John R. Erickson, AIA


> From: AMA3655@aol.com
> Date: Tue, 21 Jun 2005 19:16:51 EDT
> To: Soaring@airage.com
> Cc: djunruh@qtm.net
> Subject: [RCSE] Re: top or bottom driven ?
>
> I like bottom driven flaps and ailerons for various reasons. According to
> Dr. Hepperle a properly faired set of 4 linkages on the bottom of a wing add
> around 3% total drag to a typical F3B airframe. You can go dig around his
> website and find a number of interesting tidbits.
> _http://www.mh-aerotools.de/airfoils/index.htm_
> (http://www.mh-aerotools.de/airfoils/index.htm)
>
> happy trails - Rob Glover
>
>
>
>
>
> hi all,
> I've been asked this a few times, and I give my opinion,
> but i want to see what you guys have to say.
>
> What gets better mechanical advantage, top or bottom
> driven linkage, and how much does the drag of bottom driven
> really effect things, if any ?
>
> My vote goes towards bottom driven.
> I can always get the throws I want, easy to set up and adjust,
> and gives a solid control surface.
>
> Dave Hauch
> www.git-r-built.com
>
> RCSE-List facilities provided by Model Airplane News. Send "subscribe" and
> "unsubscribe" requests to soaring-request@airage.com. Please note that
> subscribe and unsubscribe messages must be sent in text only format with MIME
> turned off. Email sent from web based email such as Hotmail and AOL are
> generally NOT in text format


RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to soaring-request@airage.com. Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Old Oct 12, 2005, 06:00 AM
ejfranz
Guest
n/a Posts
Re: Re: top or bottom driven ?

You know it's kind of funny. We spend all this time trying to build the
cleanest plane possible with internal linkages and as little drag as
possible trying to get that last bit of performance. Then we strap on the
large drag inducers know as skegs to stop us on landing. What's wrong with
this picture? :-)

Ed Franz


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Old Oct 12, 2005, 06:00 AM
D Hauch
Guest
n/a Posts
Re: Re: top or bottom driven ?

Thats good Ed. :-)
dh

> You know it's kind of funny. We spend all this time trying to build the
> cleanest plane possible with internal linkages and as little drag as
> possible trying to get that last bit of performance. Then we strap on the
> large drag inducers know as skegs to stop us on landing. What's wrong with
> this picture? :-)
>
> Ed Franz
>
>
> RCSE-List facilities provided by Model Airplane News. Send "subscribe"

and "unsubscribe" requests to soaring-request@airage.com. Please note that
subscribe and unsubscribe messages must be sent in text only format with
MIME turned off. Email sent from web based email such as Hotmail and AOL
are generally NOT in text format
>
>


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Old Oct 12, 2005, 06:00 AM
ama3655@aol.com
Guest
n/a Posts
Re: Re: top or bottom driven ?

Ed -

If your shark tooth and skeg are large drag producers something is wrong. Try aligning the skinny axis of the skeg with the flight path of the airplane.

I'll gladly give up any drag the skarks tooth generates for the landing points they generate.

happy trails - Rob Glover



You know it's kind of funny. We spend all this time trying to build the
cleanest plane possible with internal linkages and as little drag as
possible trying to get that last bit of performance. Then we strap on the
large drag inducers know as skegs to stop us on landing. What's wrong with
this picture? :-)

Ed Franz

Old Oct 12, 2005, 06:00 AM
Michael Lachowski
Guest
n/a Posts
Re: Re: top or bottom driven ?

Well why don't you put a retractable skeg on your model. That way you can
have the best of both. While at it. also do a retractable tow hook.
And don't forget to slim down that fuse.
RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to soaring-request@airage.com. Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Old Oct 12, 2005, 06:00 AM
Jo Grini
Guest
n/a Posts
Re: top or bottom driven ?

Ok I see there were plenty replies after I wrote this but anyhow...

The name is Martin Hepperle.... he has a nice article about drag and linkage
http://www.mh-aerotools.de/
Direct link http://www.mh-aerotools.de/airfoils/linkage.htm
It might seem small but with the small differences in todays models the drag
is very important.
Might not be that important to a slow TD model. But for F3B/F on top
level....

The linkage on the Superior/Brio is not super. There are solutions that are
much better but most of them with more drag. But it is hidden and gives and
drag advantage when flying fast (and also zoom). It is offcourse up to each
customer to build a better linkage. Personally I change out the flap horns
to more secure ones in 2mm carbon (because I land VERY hard). It comes down
to that Samba wants a ready solution that works and with small drag.
Customer just screws the horn in the correct angle and all is set to go (or
atleast the customer will ahcive the 90 degree flap etc. without reinventing
the wheel).

Hilsen (Regards) Jojo
www.grini.no


>
> Date: Tue, 21 Jun 2005 18:24:15 -0700
> From: "D Hauch" <djunruh@qtm.net>
> To: <soaring@airage.com>
> Subject: top or bottom driven ?
> Message-ID: <005501c576c9$1beabd80$6970b3cf@oemcomputer>
>
> hi all,
> I've been asked this a few times, and I give my opinion,
> but i want to see what you guys have to say.
>
> What gets better mechanical advantage, top or bottom
> driven linkage, and how much does the drag of bottom driven
> really effect things, if any ?
>
> My vote goes towards bottom driven.
> I can always get the throws I want, easy to set up and adjust,
> and gives a solid control surface.
>
> Dave Hauch
> www.git-r-built.com
>
> ------------------------------



RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to soaring-request@airage.com. Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Old Oct 12, 2005, 06:00 AM
Paul Emerson
Guest
n/a Posts
Re: Re: top or bottom driven ?

I recently setup top driven flaps and noticed two things:

A little trickier to setup, especailly if there is a secondary TE spar
and the servos are mounted to the servo cover (are they all this
way?).

The benefit of the top driven is the linkage is pushing on the fat
part of the horn, instead of pulling on the small end of the horn,
which may reduce the stress on the horn when you drag the flaps across
the rocks on landing ;-) [called "desert skegs" here in Arizona].
But this benefit is minimal if you have good horns.

I would go with bottom driven if I had to choose. I really would go
with RDS if I had better building skills and the parts/plane to do it.

On 6/22/05, Jo Grini <jo@grini.no> wrote:
> Ok I see there were plenty replies after I wrote this but anyhow...
>
> The name is Martin Hepperle.... he has a nice article about drag and linkage
> http://www.mh-aerotools.de/
> Direct link http://www.mh-aerotools.de/airfoils/linkage.htm
> It might seem small but with the small differences in todays models the drag
> is very important.
> Might not be that important to a slow TD model. But for F3B/F on top
> level....
>
> The linkage on the Superior/Brio is not super. There are solutions that are
> much better but most of them with more drag. But it is hidden and gives and
> drag advantage when flying fast (and also zoom). It is offcourse up to each
> customer to build a better linkage. Personally I change out the flap horns
> to more secure ones in 2mm carbon (because I land VERY hard). It comes down
> to that Samba wants a ready solution that works and with small drag.
> Customer just screws the horn in the correct angle and all is set to go (or
> atleast the customer will ahcive the 90 degree flap etc. without reinventing
> the wheel).
>
> Hilsen (Regards) Jojo
> www.grini.no
>
>
> >
> > Date: Tue, 21 Jun 2005 18:24:15 -0700
> > From: "D Hauch" <djunruh@qtm.net>
> > To: <soaring@airage.com>
> > Subject: top or bottom driven ?
> > Message-ID: <005501c576c9$1beabd80$6970b3cf@oemcomputer>
> >
> > hi all,
> > I've been asked this a few times, and I give my opinion,
> > but i want to see what you guys have to say.
> >
> > What gets better mechanical advantage, top or bottom
> > driven linkage, and how much does the drag of bottom driven
> > really effect things, if any ?
> >
> > My vote goes towards bottom driven.
> > I can always get the throws I want, easy to set up and adjust,
> > and gives a solid control surface.
> >
> > Dave Hauch
> > www.git-r-built.com
> >
> > ------------------------------

>
>
> RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to soaring-request@airage.com. Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
>

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Old Oct 12, 2005, 06:00 AM
Daryl Perkins
Guest
n/a Posts
Re: Re: top or bottom driven ?

On this note....Question for Mr Drela, or any of the
aero guys out there...

I believe MH's study was geared more towards F3B and
higher performance flying, and he came up with a
figure of 3%. So let's assume, at TD speeds... linkage
hanging out the bottom adds 2% drag to the airframe.

If our model has a 15/1 LD, does this now translate
directly to a 15/1.02 LD?

What does this really mean to the performance of our
model? And what is gained in real world performance by
going completely internal?

Thx,

D

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Old Oct 12, 2005, 06:00 AM
Michael Lachowski
Guest
n/a Posts
Re: Re: top or bottom driven ?


At a high Cl, the linkage drag relative to everything else is pretty small.
For a straight TD model, it would be nice to reduce drag a little during
the zoom. He who launches highest......

And FWIW, Mark Drela does have internal linkages on his Supra. Or course,
some of us also wonder if he selects the electrons with the best spin when
charging a DLG flight pack. ;-)

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Old Oct 12, 2005, 06:00 AM
Richard Hallett
Guest
n/a Posts
Re: Re: top or bottom driven ?

The biggest benefits of RADS for the average flyer are
1. storage and handling and
2. much less landing damage.

Rick
Richard Hallett Pittsfield ME

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Old Oct 12, 2005, 06:00 AM
Steve Meyer
Guest
n/a Posts
Re: Re: top or bottom driven ?

I would have to argue number 2.

Damage to linkages does not happen because they are external. It happens
because you do not get the flaps up before dorking a landing.

However similar damage could occur with either method.

Steven Meyer
SOAR
LSF IV


At 04:16 PM 6/22/2005, Richard Hallett wrote:
>The biggest benefits of RADS for the average flyer are
>1. storage and handling and
>2. much less landing damage.
>
>Rick
>Richard Hallett Pittsfield ME


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