The tension brace is a simple post that is mounted at the center point of
the hook-to-hook distance on the motor stick. It should be roughly 1/10th
the length of the hook-to-hook distance in height. You will route a wire
from the prop hanger end, over the post, and then to the rear hook. This
will aid in reducing bow. Tension wires are usually only used when a hollow
rolled balsa tube is the construction method for the motor stick. They are
not needed on heavier models because you can make the motor stick strong
enough to carry the compression loads from the rubber just from the cross
sectional area of solid balsa.
Refer to simple crane design to get inspiration for motor stick design. The
tension wire method is similar in its static loading to a tower crane boom.
You can use tungsten wire as this is very thin. One strand of Kevlar fiber
will also work well.
On Mon, Jun 15, 2009 at 11:04 AM, Sameer Tiwari <deevana_2001_at_yahoo.com>wrote:
>
>
> Hi Gentlemen,
>
> You are absolutely right... the rubber is 1/16 (NOT 1/32).
>
> I am currently looking at pigtail bearings, and see how to not to use the
> stock Ikara, prop mounts, and hoping to hear from you on how to make the
> balsa tension brace for the top of the fusestick.
>
> Thanks,
> Sameer
>
> --- In Indoor_Construction_at_yahoogroups.com<Indoor_Construction%40yahoogroups.com>,
> lcordes <lcordes_at_...> wrote:
> >
> > Ben, when I first read your reply about grain direction I thought ???
> > Then after thinking about it a minute or so saw what you meant - never
> > thought of vertical grain orientation - just one more of those little
> > details that adds up - thanks for that insight. Now, if only I can tell
> > the difference <G>
>
> >
> > LeRoy Cordes
> > AMA 16974
> > Chicago, IL
> > In God We Trust
> >
> >
> > On Fri, 12 Jun 2009 11:56:17 -0700 Benjamin Saks <bensaks_at_...>
> > writes:
> >
> >
> >
> > You also mentioned that the wood grain runs lengthwise. This is the
> > normal direction for the grain to be oriented, however what I was trying
> > to convey was that in looking at a cross section of the motor stick the
> > wood grain should be oriented vertically and not horizontally. This will
> > help to reduce deflection in the motor stick.
> >
> > Some other reasons the plane would dive under power:
> >
> > Improper location of the center of gravity(too far forward)
> > Too much down-thrust (probably the most important)
> > Improper horizontal stabilizer incidence
> > Improper wing wash
> >
> >
> >
> > On Fri, Jun 12, 2009 at 10:26 AM, lcordes <lcordes_at_...> wrote:
> >
> >
> >
> >
> > Sameer - is it really 1/32" motor ? With a 1/4 x 1/2 inch motor stick
> > you should have little trouble with rubber up to at least 1/8". It's
> > hard to believe that a 1/32" motor will bend a stick of that mass.
> >
> > LeRoy Cordes
> > AMA 16974
> > Chicago, IL
> > In God We Trust
> >
> >
> > On Thu, 11 Jun 2009 19:53:07 -0000 "Sameer Tiwari"
> > <deevana_2001_at_...> writes:
> > > Hi,
> > >
> > > Thanks LeRoy and Benjamin for the replies...
> > >
> > > After some more experiments over the last two days, I realized that
> > > even though the MS bows, its the prop holder which is bending way
> > > more.
> > > I am using the Ikara gray plastic prop assembly.
> > >
> > > I do the back off everytime to get the corrrect torque on my home
> > > made torque meter, but the plane still dives :-(
> > >
> > > The length of MS from prop to hook is 7 inches
> > > Rubber is Tan 2, 1/32 - about 16" long, brass ring attaches the
> > > rubber to prop.
> > > MS is 1/4" X 1/2" grain running lengthwise.
> > >
> > > Maybe I should make the MS with two sticks and pass the rubber in
> > > between?
> > >
> > > Thanks,
> > > Sameer
> > >
> > >
> >
> > > --- In Indoor_Construction_at_yahoogroups.com<Indoor_Construction%40yahoogroups.com>,
> Benjamin Saks
> > > <bensaks_at_> wrote:
> > > >
> > > > It would help to have some key information:
> > > >
> > > > Length of your motorstick from the prop hanger to the rear hook
> > > > The cross sectional area of rubber that you are flying on
> > > > The grain orientation of the balsa wood that you have built the
> > > motorstick
> > > > from
> > > > The cross sectional dimensions of the motor stick
> > > >
> > > > Keep the following in mind:
> > > >
> > > > The motor stick will bow when loaded with a fully wound motor. You
> > > should
> > > > expect this to happen and use it to your advantage.
> > > > You can build in some slight upthrust to counter-act the down
> > > thrust from
> > > > the bowing motorstick.
> > > > You can also use balsa to make a tension bracing for the top of
> > > the MS.
> > > > Balsa is strong in tension and does not stretch.
> > > >
> > > > With more information I think we can help you out.
> > > >
> > > >
> > > >
> > > > On Mon, Jun 8, 2009 at 12:25 PM, Sameer Tiwari
> > > <deevana_2001_at_>wrote:
> > > >
> > > > >
> > > > >
> > > > > Hi folks,
> > > > >
> > > > > Having built several of the indoor models over the last year. I
> > > kept
> > > > > bumping into the issues of a the plane taking a nose dive,
> > > whenever I put
> > > > > turns in the rubber exceeding a 1000.
> > > > >
> > > > > I am sure the folks on this forum know what I am talking
> > > about...
> > > > >
> > > > > The fusestick warps/buckles under the stress and causes an
> > > unwanted
> > > > > upthrust from the prop, causing the plane to nose dive. Once you
> > > pick it up
> > > > > and let it run a few seconds, it will fly beautifully once again
> > > giving
> > > > > close to 2 mins of flight time.
> > > > >
> > > > > But, I want to stretch more to exceed 3mins, and stuck on the
> > > fusestick
> > > > > design, it has to be balsa - no boron/fiber/tubes etc.
> > > > >
> > > > > BTW, I did try a box design with two 1/32 X 1/2 for a pair of
> > > sides and
> > > > > 1/16 X 1/16 for the other, and it was equally weak as a solid
> > > 1/4 X 1/2.
> > > > >
> > > > > Any ideas?
> > > > > Thanks
> > > > >
> > > > >
> > > > >
> > > >
> > > >
> > > >
> > > > --
> > > > BEN SAKS
> > > > Project Designer
> > > > bsaks_at_
> > > >
> > > > WET
> > > > 10817 Sherman Way
> > > > Sun Valley, CA 91352
> > > > T 818.769.6200
> > > > F 818.301.6111
> > > > www.wetdesign.com
> > > >
> > >
> > >
> > >
> > >
> >
> > > ------------------------------------
> > >
> > > Yahoo! Groups Links
> > >
> > >
> > >
> > >
> >
> > LeRoy Cordes
> > AMA 16974
> > Chicago, IL
> > In God We Trust
> > __________________________________________________________
> > Click here to find the right stock, bonds, and mutual funds.
> >
> http://thirdpartyoffers.juno.com/TGL2141/fc/BLSrjpTFOGdPitqxMv2tLQ3LVVLbB
> > oV9OWVTJ8OpBKWvdIpfBtrscXCf2Hu/
> >
> >
> >
> >
> > --
> > BEN SAKS
> > Project Designer
> > bsaks_at_...
> >
> > WET
> > 10817 Sherman Way
> > Sun Valley, CA 91352
> > T 818.769.6200
> > F 818.301.6111
> > www.wetdesign.com
> >
> >
> >
> >
> >
> >
> >
> > LeRoy Cordes
> > AMA 16974
> > Chicago, IL
> > In God We Trust
> > __________________________________________________________
> > Digital Photography - Click Now.
> >
> http://thirdpartyoffers.juno.com/TGL2141/fc/BLSrjpTDvmTDP4Gjg8LviLk3QQ0A9ujBpNbceEW88ornxftaAbZ6Oz9gPT6/
> >
>
>
>
--
BEN SAKS
Project Designer
bsaks_at_wetdesign.com
WET
10817 Sherman Way
Sun Valley, CA 91352
T 818.769.6200
F 818.301.6111
www.wetdesign.com
Received on Mon Jun 15 2009 - 11:16:20 CEST