Mcnulty, J. F.

Taylor, R. T.

English

NASA Technical Reports Server

(PARAC-_.Tn_ LO&DS/_ER0_SfICITY AND M&T_J_
By Robert To Taylor and James F. McN_lty
https://ntrs.nasa.gov/search.jsp?R=19730061711 2020-03-17T13:38:20+00:00Z
INTRODUCTION
!mprovem,:ntsin paraglider aerod_m=dcperformanceckaractarist._cs indlca'_ed
by recent wind-tanuel tests hav_ _romptedthe I_ngley Research Center to _n_e_ti-
gats paraglider loads a_ a function of the aerod.vnsmic parameters InvolveU _n
th_ performance increases. An effort is also u ._.rway to at%erupt te calculate
both the aerodynamic loads and performance as_,-iated _dth these co,Jfiguration
changes, to s/low the evaluation of parametric changes without the _eed for
extensive tunnel testing.
qtructur,il analyses have been cont_nuln_ which ooint up som_ interesting
results as regards the prob]_ws ol _.ight and _aterials_
It is the purpos_ of the preseat paper to present some c.f the hig,,_ights
of recent research concer_ing loads, structures and mate_'ials, and to d_d4cR+_
by i_ication, the _ype of data which are available for use in the d_al _=n of
parsglide:'s.
DISC,TSSION
Unoertainti_s in the exact s?ape of the cloth m,_mbrane of the p_regl_-.,r
have been the b_gest obstacle in calculatirg the air-load dis _ibution _ez
a representative canopy. Some early pressure data obtalned on rigid conical
models has suffer_-d in application because of the sfocementioned shap_ uncer--
tainties. Recent force test measurements h_ve been m_de on a semispa,, glider, model
with a cloth wing_, wh_oh is s.__m in th_.first slide.
SLIDE I
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The mod_-l,showL here was mounted on _wo bal_nces_ one semispan balance
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which allowed the measurement of to_al i_-._ a_1 another six-component balance
wh_.ch m_su_ed the load ,_:_the leading _ge.
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v,-,x4ables cc.vered 1rare aspect ratio 2.5, 4.0, 6.0 and twist dlstrl-
b_,t£on Indl¢_l be.lov by the values of _a_" oot at the .80 opan s%tion.
Loade -_-lod Lu t_e paraglider stmec_ure c&a be divided into two classes:
(1) _-_s ncr,_ to the p_ to_-ed by the vtn_ _ _d t,_l. s_d (_) Zoac'p.
p__-allel _o the plane of the _!z_ tip "_d keel. Z:_e lords may _m tre_-_d
sepm'ntelw mad _Ided v_ _-i_ll_ 1;o _rive a_ a ;_inal loading, on which the
de_ _i-the s_tcture ._ be based.
_be next s_Ltde shoes a c_oa of the measured spam_se 1_% dtstri-
but_.on ob#_ned f_ _wssure our_e, s
walues _uain_ the twist d_ s+_ibut!on o£ the _xtels. As mightbe e_ted t_-_
_r,lated ealu_ _w weJL! [t_ the measure_t_ _Je.n the twist is known.
_m_lse lift cam*_r; are also sbevu on the slAdc, _ere we have +.h_ li:
c_nter _ven by _=-r,_ te_,*s.._he calculated li__t ee.Pter, and opotted on for
compa._son _z the ii1_ center obt_.ine_.f_xm _ne semispan fo._ee test _odel.
l_le _n_ one po._n_ is sl_o_-_, here, gc_ agreement _£th bo',.htheory and
presa,_re G,s_ "_a_ obtains<! "J_roughout _ "=-_.ncar_ angle-,:,!'-atl;a_k range and
agreement is shown _th th_ pressu_ measur___,.- i_si <-,hestall.
The lower _ of the figure sho_s _he ex_ reme loadlr ""due _: _w_st st
a llf_ e.oetf_eien_ of zero.
Iiotmmeh ._ore Ce._ be said about :h_-.normal or lJ_ _Istributlon of l_td
].r _ _der membars wlthou% .kno_ =_h_ placement a_l m_her of _-.. shrot-_
fi_,es, so le_- tm look ._t the moments ebcut the a_ex, in the plane of t_e le_ding
edg_ and keel.
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_LII_ III
Here we have nlot:ced .-:pexbinge m_aent a_ a 1_,_nctionof -ugle of attack
fur an as___: r _i_-2.5 glider _i+h canopiea having different values of washout.
'_he sketches show _he .-elatlve degree of flatnes_ of the canopies under load.
The darkened symbols i_-,_te the augl_ of attac_ at _.Ich (CL)ma x u_c_rred.
_..ese data s.er.v_to i!l_trate a number of points: _i_ increases in washout
are asscclated _th decreasing In-_l_e ape_ moment, ax_ dec_ _simg li-_-dr_
L_tlo if the leading-_ge sweep e,- _ng spar, is _ eld fixed_ (2) the design
cf the glider frame for _tren_th is fixed by the J_udmml lift-,a_fficient point.
The .:a__ w_r_ +_:en th_-o_h an angle of attack o£ 90 °, and ,,h_le not shown here
the level of 8pc}: m_ent at _ or stall is not exee_ed.
Below the stall you _ii_ _otice that th- slcre of Cn with a _s negative
for the full cr._nopyand positive f_r :.ho fl_._,can._py. In %h_ ca_e where the
wing is flexible (e.g. cmn change sweep or span _gth changes in ansie of attack)
the slope of thi._ line may effect the gust r_s_onse of _b_ g__d_r. Ncte that
with thi_ full canopy a positive chan_ in a red_c_c the _2_icnc_ t(. close
which mlght lucre ._e the span somewhat making the glider more sensitive to gusts
w_ile with the flat canopy positive angle-e_-atteck cban_s reduce sp_u possibly
allevlatir_ the _aot r_ponse.
Paragllder win&_ with 1_exible frames have been tested at Langley in
cc_ne_.tio_,with gc_e_me_.t suoasored programs for (I) thc r_eovery of the Saturn
booster in which U_e P_rsz_d! Spac_ Flight Center is ic.terested and (2) in
connection with the recover 7 and launching of the Gemini spececraft, which Is
of tntermat to the _nncd _ecraft C_uter.
i.i
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Generally speaking the in_roductlon of flexib._lity into f.he btructu_e
results in sc_e saving in weight. The next slide (slide IV_ shows so_ _rvea
which indicate para_der structural efficiency, _e_e is l_otted the retio of
_paraglider weight to gross weight for r_gid and flexible .-_te_s. The scale
On the right represents the volume requi_ed _o stow the par_lider syatme, end
xs obtained by assuming a stowed der_ity of 23 pou_e _er cubic foot.
Decreases in v_ight ._?_ "._ _ch_e_.ed if structural flexibility is allowed
in-the parmgllder frsme as shown he_. it should be no#_d, howler, _nat
flexible glide:_ are much more difficult to analyze bot_ aerodyna_ical!y and
structurally because of thz Interdepeudence of aerod_u_c 1.oad _d configuration.
Elasticai_¥ and dym_.Ical!y-scaled inflatable models of both relatlve]y
r_id a__.flexible paragiiders are being febric,_ted under contra, "_th G. Ao C.
These modes _.will be ,u_ed to study the peraglider _eployment charac_cxs-ics along
"_th the ','ffectsof ael_elastlcity. In ad,iition these _lels rep_duce _:he
becki"ng in the inflated structural tubes which is impor-_nt in def_ninE_
aer,_dyna_ics.
Thee dat_ should be available tc evaluate th,_ trad,:-_x_s be_.,m,_,, weight
sx_ /_rlor_nce pre_iously mentioned.
_ne last curw, on the slide shows furthec improvement in the weight picture
through _e u_e of _ifferent gas tight materials, in this case ___ilm-fah_c
constm_ctlon of dacron and _lar similar to the sa_ple I bare here. _ould
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such a _aterial prove feasible ond ._llow _he c_ts_ton of the elast_er which
weighs as inch as the fabric, si_.-nificant weight ._mvings _tld resu_.
Ve wall discuss more about _aterials later.
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i_ addition ÷_ bei._ mor_ diffic,_', _o analyze, ._'la_ib]e paraglide_s
u_ually suffer some de_radatior, in pe,-for=s_c,. The next 3]id,_ shows aplot
of _/D agtd_rt CL for the (_mini-paraglider =Onfigu._ation. l_t_ three
2urves repre_mt the ,_,-Jodynagics of gliders havi_ three stiffnes_s. The
degradation in _I./D)=ax is ebb%us but note tl_t at higb_,- CL the curves
tend to merg6_ so that it t._uchdcwn cenaiti¢.ns are :_ore i=portant in a partt_olar
applicv _icn _._an range _o_id_r_tions the _rqai_._ent for s-_iffness jn the glider
fr_e _y be relaxed _r _'e!c _ a sol,nat ll_ht_r wei_ot and _cre readily storable
recov_ .ry _.ya tern.
Ki_, temFera_ure ._+.er_al_ are also under investit?,ati..n by Langley Research
Ceu_er i_ c_nuecti_n w,_th ?.he minr_neSvoz_.id paraglider _r_eri_ent _hich _11
hay,TM to s'az_ri_ reentry t_mpe_atures ( !0OO ° F). For the L_lated memL_rs of
f
the pacaglider: Lar_ley L,_search Csuter is _vestigatlug _b? feasibility of a
fiberg._s-silicone comb -nation. Sl_ce silicoae is d_f_mu't to "work", seams
a_d j_nvtt_res represent a comsid_.-able problem w___ch is being studied. F__rimgs
from White Sazd._ :A,z;,,iieP,an_e, a'e sch_Suled _r next summer.
In _o_jumction with the aer_ljma_c vnd materi_ls _tad_',_, Lauglty Re_areh
'Jen,_ercontinues im#est!ga_ior_ in structural analy_i_. _ile structural desl_n
an_lysls proc_dure_ have been developed for pe_mg]Iders wxtn -,o-plauar leadimg
edges and keel (these p_'ocedures _e b_n _we_, for free-flight models. Wir._-
tunnel models and the micrometeoro!,i paraglider), ,.'.erecent i_cvation of the -
utiii_atlon cf helic_ ]ead_g edges_ d_scussed ry Mr. S]e_man, repr_se_ts __
z _w st_zctur.-1 probl_u. Langley Research Cer+_r ha_ a program underway to
define t+_ strv_mral probl_ are_s_ it is hoped that the m_terial aud gco_etrlc
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coefti_tents heine de_e_'oped by testLng by Goodye_ and North Ameri.;au u_e:
a MSC eo_tra_.t will suffice to allow an ewLluation ¢,f the probles. Should a
fav_,rable solution to this Droblem be i_d_cated, it is an.+,icipate__ -','_a_ scaled
mo_.el,._ __'!1 b_ _,sed for tes'- purposes since it ha_ been fou_ that ,_esi_ can
be scal_ without use of _tic" n_teria!s.
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SEMI-SPAN WIND TUNNEL MODEL
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Paraglider loads, aeroelasticity and materials

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