A bunch of
goodies on tail booms from the early 2000's
From: ScrollSander [chris@scrollsander.com]
Sent: Friday, June 29, 2001 9:27 PM
To: shink@m.alta.jordan.k12.ut.us; RCSE
Subject: Re: [RCSE] DHLG booms
The tailbooms currently being used are of three-four general
types. There
are Skyshark booms, G-Force Avia Booms, Allegra Booms, and
Godinov (sp?)
booms. The SkyShark
and Avia booms are thin, OD about 5/16" tapering to
abouot 1/4" over approx 36". Avia G-Force are avaialbe for $8 for
PoleCatAero.com. these have flex. The Alegra Booms go from 9/16" to
5/16"
over 33" (approx) and sell for approx $25. The Goodinov booms are a CF-Al
laminate and are 36" long. 17mm down to aprrox 5 mm over 36". these are
$30 each. The Alegra
and Goodinov Booms are quite stiff. I
have flown the
Avia's and Allegra's and they are different. I have the CF-Al boom to try,
but I konow on person who has 6 planes with these and loves
them
I'll have pictures of these booms and the planes they are on
on my CD of the
contest, hopefully done soon.
Chris
----- Original Message -----
From: "Scott Hinckley"
<shink@m.alta.jordan.k12.ut.us>
To: "RCSE" <
Sent: Friday, June 29, 2001 9:37 AM
Subject: [RCSE] DHLG booms
> I have heard that the booms used on older HLG aren't
stiff enough for
> the new DHLG. What tubes are being used now? Straight?
Tapered? Custom?
> Where can they be purchased?
>
> Scott Hinckley
> RCSE-List facilities provided by Model Airplane
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Mark Drela kindly did some testing of booms. Here is his results:
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Carbon boom stiffness measurements
Mark Drela
7 May 01
Booms tested:
1) Avia Skinny Super-UL
27" 10.5g, 0.305" OD -> 0.205" OD
(trimmed off 5.5" from small end of 32.5" 11.8g
boom)
2) Skyshark Allegro-Lite 27" 13.5g, 0.625" OD
-> 0.365" OD
The Avia boom is nearly the same in dimensions and weight
as the Skyshark 3PT boom used in HLG's, and is expected
to have comparable stiffness properties as well.
The Apogee 36" HLG uses a lighter Avia boom (Skinny UL)
than the one tested here.
Testing procedure:
Each boom was mounted by clamping 3" of big end in a
split wood block.
Weights and torques were applied at the small end, 24"
from clamp.
Deflections and twist angles were also measured at the small
end.
Nomenclature:
EI = average bending stiffness
GJ = average torsion stiffness
Bending tests:
Load Deflection EI EI_relative
EI/boom_weight
------- ----------
------------ -----------
--------------
1) 0.54 lb 1.625 in
1540 lb-in^2 1.0 66500 in^2
2) 2.00 lb 1.250 in
7370 lb-in^2 4.8 248000 in^2
Torsion tests:
Torque Twist GJ GJ_relative
GJ/boom_weight
---------- --------
------------ -----------
--------------
1) 0.85 lb-in 10.6 deg
111 lb-in^2 1.0 4800 in^2
2) 3.24 lb-in 7.2 deg
622 lb-in^2 5.6 20900 in^2
Observations:
A) The specific stiffnesses closely match the theoretical
results...
EI ~
boom_weight * diameter^2
GJ ~
boom_weight * diameter^2
Extrapolating the Skyshark's stiffness down to the Avia's
diameter,
predicts that for the Avia...
EI = 7370
* (10.5/13.5) * (0.305/0.625)^2 = 1365 lb-in^2
GJ = 622
* (10.5/13.5) * (0.305/0.625)^2 = 115 lb-in^2
which isn't too far off the actual values of 1540 lb-in^2
and 111
lb-in^2.
B) The Skyshark has a smaller bending stiffness and a larger
torsional
stiffness than the theory predicts. This is easily explained by the
Skyshark's significant +/-45 glass
content.http://auctions.yahoo.com/
From:
Sent: Saturday, June 30, 2001 3:38 PM
To:
Subject: [RCSE] Re: DHLG booms & Taboo
> I spoke with Oleg at Mid-South and he said that he has
the SkyShark
> boom (3P or 3PT I believe) on his Taboos. Very (VERY) nice planes!
>
> - David
> david@enete.org
David,
thanks for the kind words. I am using Avia Composites booms
on my
Taboos. The G-force SUL is the largest tapered kite spar
thay have and
it is quite adequate for the job. With the gyro the plane
does not
suffer any disatvantage compared to an Allegro tail boom
plane. Without
the gyro a stiffer boom would probably help a little, but
again not
dramatically. Maybe 10ft extra altitude. The gyro helps to
get those
extra 10ft back.
Oleg.
see www.geocities.com/olgol/taboo.html for pictures of
Taboo...
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Glass/Carbon/Glass Boom Layup
This type of boom is composed of unidirectional carbon, with
glass on the inside and outside to provide hoop stiffness
and torsional stiffness and strength. It is similar in
principle to the Al/CF/Al booms, except glass (or Kevlar)
are used instead of the Aluminum.
For small HLG's, 1 layer of 3 oz Uniweb carbon and 0.75 oz
glass is sufficient.
Full-size HLGs will require at least
2 layers of carbon and perhaps an extra layer of glass or
just 1 oz Kevlar instead of the glass.
A non-stick tapered mandrel is required. A 0.4" to 0.5"
diameter at the big end is about right. The small end
wants to be about 0.25" to 0.35" diameter.
Layup procedure:
Cut the carbon to size. Lightly spray it with 3M-77,
and
stick it down onto the glass (or Kevlar) stock at 45 deg.
Cut the glass to twice the width of the carbon +
1/8".
The 1/8" of glass sticks out past the carbon along one
edge,
and the full width sticks out past the carbon along the
other edge.
In cross-section:
==============
------------------------------
Wet out the carbon only (and the glass under it). Remove excess
resin by putting down a paper towel on the carbon and
rolling
over it with a hard roller.
The exposed glass is left dry
since there will still be enough excess resin in the carbon
to wet out the glass after rolling. With Kevlar you may
want to wet out everything, but blot it as much as possible.
Wipe a thin stripe of highly cabosil'd epoxy onto the
mandrel,
and stick it down onto the edge of the dry glass. If the edge
of the glass doesn't somewhere, dab on more thickened epoxy
in that spot so it does.
Roll the mandrel on the table, wrapping the glass and
carbon/glass
onto it:
---
<---- / \
| |
\ /
============== ---
------------------------------
I spirally wrap the layup with a strip of 1/2" wide
heat-shrink tape,
overlapping 2/3 of the tape width (effectively 3 layers of
tape are
applied). You could
also wrap it with a polyethylene strip, and then
compact it with a vacuum bag or wrapping with a long strip
of rubber.
For strength, it's important to get the carbon fibers
straight.
I leave about 1" of extra carbon on each end extending
past the glass.
This allows me to pull hard on it after rolling before
spiral wrapping.
- Mark Drela
From: Dick Barker [dickb@eskimo.com]
Sent: Saturday, June 30, 2001 8:26 AM
To:
Subject: Re: [RCSE] DHLG booms
>The tailbooms currently being used are of three-four
general types. There
>are Skyshark booms, G-Force Avia Booms, Allegra Booms,
and Godinov (sp?)
>booms. The
SkyShark and Avia booms are thin, OD about 5/16" tapering to
>abouot 1/4" over approx 36"......
Skyshark booms come in both tapered and non-tapered. The
non-tapered work
well for me as I can get two UpLinks from one boom. The 3P
booms are
very stiff but tend to split lengthwise when abused. The
p300 has a bias
wound layer that prevents this failure mode. Old non-DLG and
the small
toy DLGs can get by
with the 2p or p200 booms. You can use the tapered
ones (with the -t in the name) if you wish and pick the
portion of it
with the stiffness and weight you need. The downside is that
it is *much*
harder to replace a broken tapered boom.
Red at http://www.tgworks.com/ has them or you can check
your local kite
shop.
--
Dick Barker
Seattle, WA
- Turning HLG Around -
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