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Old Sep 16, 2003, 04:01 AM
Grant
Guest
n/a Posts
Help choosing Airfoil for 60" DS Plank

Hello All,
Ive been having a great time lately with my JW's but i feel like
trying something a little different. Ive scaled up a 48" Zipper to 60"
and cut the wing and fuse planforms last night. Im now ready to cut
the cores. The wings are being build out of high density styrofoam and
the fuse is cut out of EPP.

Ive basically got thinned my choices down to two, possibly three
airfoils. They are in order of preference at the moment.

- EH-2010
- MH 45
- MH 61

I believe these are all quite good plank foils. I need some help to
make my final decision. Can anyone tell me which one would be the
better choice. Keep in mind this is being build mainly with DS in
mind.
The original Zipper uses the EH foil however planes such as the gulp
use the MH foil. Both are great performers so im not sure on what the
difference is.

Any help in choosing the best foil is greatly appreciated.

Cheers Grant
Old Sep 17, 2003, 04:01 AM
Robert Steinhaus
Guest
n/a Posts
Re: Help choosing Airfoil for 60" DS Plank

> -----snip
> Ive basically got thinned my choices down to two, possibly three
> airfoils. They are in order of preference at the moment.
>
> - EH-2010
> - MH 45
> - MH 61
>
> I believe these are all quite good plank foils. I need some help to
> make my final decision.


Comment - - -

Pitch stability on a plank flying wing is provided by the airfoil alone
(there is no tail to help provide pitch stability). For planks you have to
use an airfoil with a positive coefficient of moment [cm0/4](the more
positive the coefficient of moment the easier it is to achieve good pitch
stability on a plank). Unfortunately, it is not easy to design real high
performance airfoils with exceptional lift to drag that have large positive
coefficients of moment. If you examine listings of airfoils you will find
relatively few airfoils that have a positive coefficient of moment (the vast
majority of airfoils end up with negative cm0/4). You have to balance
tradeoffs to get good performance with positive coefficient of moment. You
can cheat a little toward performance when designing a positive coefficient
of moment airfoil and sacrifice some stability by choosing an airfoil with
only a very small positive cm0/4. You can go for solid pitch stability by
choosing a larger positive cm0/4 airfoil but the lift to drag of the foil is
probably lower. All of the airfoils you have mentioned have relatively small
positive coefficient of moment. You will tend to have a plank that
emphasizes performance at the expense of stability with these foils. Of the
group of three foils that you called out MH61 has the largest positive cm0/4
and eh2010 has the smallest positive cm0/4 at almost zero. MH61 is a
relatively low risk choice for a successful plank that will have good sport
performance. MH45 is thinner and will probably perform better and have
greater speed potential. EH2010 is probably a better choice for a swept
flying wing because it just does not have enough positive cm0/4 to have
decent pitch stability.



One small adjustment that should be added to the above discussion is that
frequently we do not build the exact airfoil with our plank flying wings.
The span-wise elevons are usually added to the wings and are not always
shaped in the exact shape of the airfoil (just slabs of balsa carved to an
approximate trailing edge shape). Often the final 10% of the airfoil (near
the trailing edge) contains most of the airfoil shape that makes the airfoil
have a positive cm0/4. If you just chop off the final 20% of the trailing
edge of the wing off and install a generic balsa trailing edge you stand a
good chance of losing the positive cm0/4 characteristics of the airfoil.



A second adjustment to the earlier discussion is the fact that
simultaneously actuating the elevons (producing an "up" or "down" control
deflection) effectively changes the airfoils shape and the airfoil's cm0/4
and the plank's stability. Many modelers introduce some small amount of "up"
deflection in both of the span wise elevons while trimming a flying wing.
Simultaneous up adjusted in each of the elevons gives the airfoil more
effective positive cm0/4. As you make pitch commands (up and down commands)
you effectively dynamically alter the stability of the plank.



I would add a couple of additional foil to your list of candidates



E184 - A thinner and lower cambered plus cm0/4 foil for plank flying wings -
the Eppler foils are good and are often skipped over these days



S5010 thinned to 8% thickness - Dr Selig's flying wing airfoil thinned for
improved speed with plus cm0/4 - a little more

extreme than I like with good straight ahead speed but not as much
performance in turns at higher lift coefficients as MH45



MH45 one of the best balanced flying wing airfoils for small models
(especially good for models under 2 meters in span). Above 2 meters MH60 may
be slightly superior. MH45 is a fine sport foil but is a little low on plus
cm0/4 for a plank. MH45 would be usable on a plank if you are willing to
give up some stability for performance. I have found MH45 to perform better
than typical commercial foam airfoils as are used on the Zaggy in light
lift. MH45 is a little thick for real high performance DS. Still one of the
best choices available.



TRY2B - The root airfoil for the Bowman JW. Another very good foil with
relatively high cm0/4 and so a good candidate for a plank. Not as good as
MH45 in light lift. A little thick for great DS performance. Coordinates
available on the xfoil Yahoo eGroup in the file section.



EH1210 - Not enough plus cm0/4 for plank applications - the Zipper used a
modified version of this good sport foil that moved the maximum thickness
point on the airfoil rearward to achieve better range of speeds.



Overall I like MH45 the best for your project but I feel MH45 is not as good
as it could be for DS and energy retention. When flown at mid range Cls when
flying with ballast and turning and banking MH45 has a little more drag than
one would wish.



I feel the ultimate DS flying wing airfoil has yet to be designed.



You can find a listing of good flying wing airfoils, coordinates, and
performance information (some of it in German)



http://www.aerodesign.de/profile/profile_s.htm



on the www.aerodesign.de web site as well as design sketches for many
interesting flying wing gliders.



Best wishes!




Old Sep 17, 2003, 04:01 AM
Grant
Guest
n/a Posts
Re: Help choosing Airfoil for 60" DS Plank

Gday Robert
Thanks a heap for the reply, that was very informative. I was told the
Zipper used the EH-2010 and was going to cut the templates tonite,
probably better I didnt

Im using a feather cutter so ill try to get my cuts as acurate as
possible. As for the elevon, it will be sanded to the shape of the
airfoil so I can keep it as close to the original airfoil shape as
posible.

I posted this on another msg board
(http://www.rcgroups.com/forums/showt...36#post1300936)
and another bloke replyed and mentioned this airfoil.

HS130x - Its apparently great for DS planks. Check out the post, Also
check out the wing that uses it, videos show it flying sho I guess it
proves it works.

If it doesent fly to well , it will be interesting to play with
differnt foils and see how much they differ so I guess it doesent
matter to much if I make the wrong choice.

I couldnt find much on the HS130 foil though. Do you think this would
be a good choice? Failing that do you think i would be wise to go with
the MH45 or mabey give the old E184 a go???


Once again, thanks for your help Robert, its much appreciated.

Cheers Grant



"Robert Steinhaus" <steinhausq@earthlink.net> wrote in message news:<8dA9b.5621$BS5.1838@newsread4.news.pas.earth link.net>...
> > -----snip
> > Ive basically got thinned my choices down to two, possibly three
> > airfoils. They are in order of preference at the moment.
> >
> > - EH-2010
> > - MH 45
> > - MH 61
> >
> > I believe these are all quite good plank foils. I need some help to
> > make my final decision.

>
> Comment - - -
>
> Pitch stability on a plank flying wing is provided by the airfoil alone
> (there is no tail to help provide pitch stability). For planks you have to
> use an airfoil with a positive coefficient of moment [cm0/4](the more
> positive the coefficient of moment the easier it is to achieve good pitch
> stability on a plank). Unfortunately, it is not easy to design real high
> performance airfoils with exceptional lift to drag that have large positive
> coefficients of moment. If you examine listings of airfoils you will find
> relatively few airfoils that have a positive coefficient of moment (the vast
> majority of airfoils end up with negative cm0/4). You have to balance
> tradeoffs to get good performance with positive coefficient of moment. You
> can cheat a little toward performance when designing a positive coefficient
> of moment airfoil and sacrifice some stability by choosing an airfoil with
> only a very small positive cm0/4. You can go for solid pitch stability by
> choosing a larger positive cm0/4 airfoil but the lift to drag of the foil is
> probably lower. All of the airfoils you have mentioned have relatively small
> positive coefficient of moment. You will tend to have a plank that
> emphasizes performance at the expense of stability with these foils. Of the
> group of three foils that you called out MH61 has the largest positive cm0/4
> and eh2010 has the smallest positive cm0/4 at almost zero. MH61 is a
> relatively low risk choice for a successful plank that will have good sport
> performance. MH45 is thinner and will probably perform better and have
> greater speed potential. EH2010 is probably a better choice for a swept
> flying wing because it just does not have enough positive cm0/4 to have
> decent pitch stability.
>
>
>
> One small adjustment that should be added to the above discussion is that
> frequently we do not build the exact airfoil with our plank flying wings.
> The span-wise elevons are usually added to the wings and are not always
> shaped in the exact shape of the airfoil (just slabs of balsa carved to an
> approximate trailing edge shape). Often the final 10% of the airfoil (near
> the trailing edge) contains most of the airfoil shape that makes the airfoil
> have a positive cm0/4. If you just chop off the final 20% of the trailing
> edge of the wing off and install a generic balsa trailing edge you stand a
> good chance of losing the positive cm0/4 characteristics of the airfoil.
>
>
>
> A second adjustment to the earlier discussion is the fact that
> simultaneously actuating the elevons (producing an "up" or "down" control
> deflection) effectively changes the airfoils shape and the airfoil's cm0/4
> and the plank's stability. Many modelers introduce some small amount of "up"
> deflection in both of the span wise elevons while trimming a flying wing.
> Simultaneous up adjusted in each of the elevons gives the airfoil more
> effective positive cm0/4. As you make pitch commands (up and down commands)
> you effectively dynamically alter the stability of the plank.
>
>
>
> I would add a couple of additional foil to your list of candidates
>
>
>
> E184 - A thinner and lower cambered plus cm0/4 foil for plank flying wings -
> the Eppler foils are good and are often skipped over these days
>
>
>
> S5010 thinned to 8% thickness - Dr Selig's flying wing airfoil thinned for
> improved speed with plus cm0/4 - a little more
>
> extreme than I like with good straight ahead speed but not as much
> performance in turns at higher lift coefficients as MH45
>
>
>
> MH45 one of the best balanced flying wing airfoils for small models
> (especially good for models under 2 meters in span). Above 2 meters MH60 may
> be slightly superior. MH45 is a fine sport foil but is a little low on plus
> cm0/4 for a plank. MH45 would be usable on a plank if you are willing to
> give up some stability for performance. I have found MH45 to perform better
> than typical commercial foam airfoils as are used on the Zaggy in light
> lift. MH45 is a little thick for real high performance DS. Still one of the
> best choices available.
>
>
>
> TRY2B - The root airfoil for the Bowman JW. Another very good foil with
> relatively high cm0/4 and so a good candidate for a plank. Not as good as
> MH45 in light lift. A little thick for great DS performance. Coordinates
> available on the xfoil Yahoo eGroup in the file section.
>
>
>
> EH1210 - Not enough plus cm0/4 for plank applications - the Zipper used a
> modified version of this good sport foil that moved the maximum thickness
> point on the airfoil rearward to achieve better range of speeds.
>
>
>
> Overall I like MH45 the best for your project but I feel MH45 is not as good
> as it could be for DS and energy retention. When flown at mid range Cls when
> flying with ballast and turning and banking MH45 has a little more drag than
> one would wish.
>
>
>
> I feel the ultimate DS flying wing airfoil has yet to be designed.
>
>
>
> You can find a listing of good flying wing airfoils, coordinates, and
> performance information (some of it in German)
>
>
>
> http://www.aerodesign.de/profile/profile_s.htm
>
>
>
> on the www.aerodesign.de web site as well as design sketches for many
> interesting flying wing gliders.
>
>
>
> Best wishes!

Old Sep 21, 2003, 04:01 AM
Robert Steinhaus
Guest
n/a Posts
Re: Help choosing Airfoil for 60" DS Plank

The Austrian respondent at the alternate forum provided a very interesting
information of which I was certainly unaware.

HS130x appears to be a new airfoil by Hartmut Seigmann that could very well
have excellent properties for DS planks. I would suggest you consider
emailing Mr. Seigmann at

siggi@aerodesign.de

and ask him whether coordinates for this airfoil have been released. I and
many other readers of this forum would be grateful to learn if you obtain
any information regarding this airfoil (either coordinates or design data
such as zero angle of attack or coefficient of moment).


Old Sep 22, 2003, 04:02 AM
Grant
Guest
n/a Posts
Re: Help choosing Airfoil for 60" DS Plank

Gday Robert,
Yeah Ive emailed him and obtained a few dat files, there is the
HS128X, HS130X And HS132X.

I have alredy cut my plank wings and nearly finished the plane so its
to late to try them on this version. Ive gone with the MH45 alredy and
is looking like its going to work well (well throwing the plane it
accross the loung room anyway ..

Now ive got all the fuse planform templates cut im going to knock up
another one useing the HS130x foil and see how much difference there
is. It only takes a week or so from start to finish to build one of
these things.

ALso here is a quote from the designer saying how versitile the series
is.

"You can reduce thickness to 6.5% if you like and you can rise
thickness
up to 12.0%. Doesn't matter! It is a very uncritical airfoil regarding
these modifications but normally you have not to modify anything. The
original airfoil has astonishing allround performance I never thought
of. That is the reason why I did not test yet the 'inofficial allround
airfoil' HS132 of this series! The HS132 was designed for allround
performance, but actually HS130 do the allround job very well. So I
attach the interesting part of that airfoil series that you can check
out what you like. HS130 planks normally use -1.5 washout because it
does not take any speed performance but raises allround performance!

Be careful if you use different airfoils on a wing: use the higher
cambered one as tip airfoil! E.g. root HS130X, tip HS132X (washout
0.0
or -1.0). Never try the old style using the lower cambered as
outboard
airfoil! This is very critical and cuts much performance just due to
stall behaviour. You have to fly high aerodynamic stability - doesn't
make any sense!"

As u can see, sounds like a dammm good foil, if my new plank flys
well, i want to cut it at 8% and vac bag it this time. Foam is great
for making prototypes but youll never get the speed from a block of
form u will from vac bagged hard surfaced wing.

Ill keep everyone posted with some pics of the plank soon, so far so
good. Also as soon as this is done, ill cut up a wing using the HS
foil and let everyone know.

Cheers Grant
Old Sep 30, 2003, 04:01 AM
Grant
Guest
n/a Posts
Re: Help choosing Airfoil for 60" DS Plank

Gday Rob,
Ive emailed Hartmut and asked his permision befour im willing to
release them on here, they are in beta stages and he may not want them
out into the public yet, as soon as i get permsision ill post them and
also email them to you.

Cheers Grant
Old Oct 01, 2003, 04:01 AM
Bob Steinhaus
Guest
n/a Posts
Re: Help choosing Airfoil for 60" DS Plank

That's more than fair Grant (and what I would do myself).

Best wishes and the best of luck with your project.

Robert Steinhaus
Email: steinhausq@yahoo.com

> Gday Rob,
> Ive emailed Hartmut and asked his permision befour im willing to
> release them on here, they are in beta stages and he may not want them
> out into the public yet, as soon as i get permsision ill post them and
> also email them to you.
>
> Cheers Grant

Old Oct 20, 2003, 04:00 AM
Grant
Guest
n/a Posts
Re: Help choosing Airfoil for 60" DS Plank

For anyone who was following this thred, here's some pics of the finished bird.

http://www.vision6.com.au/~gockwell/rb/plank.php
 


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