Hi All,Not being an engineer (I've always seen myself of more of an artisan and
lover!), you'll need to take my following comments with some caution.
I have never flown the Mk2 so unable to give a comparison on aileron circuitry
from the piloting perspective. We do have a set of Mk2 wings for sale as an
aside. Since we first started flying GYT, the thing that struck me from the
beginning was the extra resistance in the side to side movement of the stick
compared with conventional glass aircraft.
My understanding is that this is a function of the installed spring tension and
can be varied by changing the spring tension. I also thought that ours was that
way as an assist to long distance, higher speed touring. Correct me if I am
wrong Rob. The aircraft is very stable in this configuration. Never noticed any
snatching Macca or oscillation/feedback of or from the ailerons as mentioned by
Michael, under the full range of flying conditions. Despite the resistance YT
is a delight to thermal and was doing some hands off soaring today
incidentally, made possible I assume via the extra friction.
Another assumption was that the even upward ailerons deflection at higher
speeds (around 20mm as Ian W. mentioned) is a rigging adjustment designed to
improve performance along the lines of reflex flap settings on sailplanes.
I would be quite concerned about any H36 needing full or close to full forward
trim and it may well be at least partly associated with the snazzy new paint
job Michael as its hard to believe that the Dimona could have been in service
for very long previously with that characteristic. It wasn't reweighed after
the paint job?
Re the thrust line inclination, I assumed this was for improved prop clearance.
There is a noticeable difference in tail height in three point between the
fixed tail wheels and the suspension tail wheel assemblies installed which
impacts on the thrust line so some variation there. The resulting unusual low
nose attitude even when climbing is a huge boon to visibility ahead when
otherwise the nose would be obscuring much of the sky, especially during
descent. I have wondered if this was also an intended consequence of the engine
mounting.
I often get things wrong so pleased to be corrected on any of the above.
PS Where are those bloody cutout pics Macca?PSS Don't be too upset Rob and Nige
as being an engineer doesn't necessarily exclude you from being artisans and
lovers also.
Regards
Laurie Hoffman
From: Ian Mc Phee <[email protected]>
To: DOG LIST <[email protected]>
Sent: Saturday, 23 May 2015, 22:50
Subject: RE: [DOG mailing list] Engine mount for Limbach
What Ian says is true I believe. I do know the later version is nicer to fly.
Earlier version wanted to snatch the control.
Ian Mc Phee 0428847642
On 22/05/2015 1:03 PM, "Ian Williams" <[email protected]> wrote:
Hi Michael, Thanks for your reply. I still think NZ is not too bad, thoughnot
so much of it. I thought a quick response was necessary based on my
thoughtsabout your friends aileron issue. However I will also try and get you
up tospeed with the aileron changes. I am the engineer for 2 Dimona’s and 2
Grob 109’s here in NZ. OneDimona (ZK-GCB) is ex Thai Air Force which I have
“restored” over a 5 yearperiod. During that time I have had a lot of help and
good advice from NigelBaker Ian McPhee Laurie Hoffman, Rob Thompson and John
Callaghan … all fineupstanding Australians. If I have made any errors in this
discussion I am sureit will be corrected. The difference between the systems is
that if you consider thereis a load pushing both ailerons up, the aileron push
rods are in compression(old system) and in tension (the later system). The old
system uses 5 bearingsets in each wing and the new one only 3. They can be
clearly checked which iswhich because the outer aileron bell crank of the old
system is made from tubesteel while the later one is made from flat steel. I
have some photos I can sendto you showing the difference. As I indicated, the
ailerons on GCB lift about 20mm or so at100Kts. If you attempt to duplicate
that on the ground manually, the loadyou have to put into the aileron to lift
20mm is VERY high. That indicates theup load in flight is also very high. So
it is a logical improvement to changethe aileron push rod to a tension mode).
Even with the 5 bearings, there is stillenough up force from the ailerons to
bend the aileron push rod betweenbearings. (where the 20mm lift comes from).
Nigel indicated It is not apractical idea to modify the aileron circuit of the
older Dimona’s. On GCB I also found all 10 (3 bearing) bearing sets inside
thewing were seized. Because the ball bearings used at the time had their
entire outerballrace made from nylon. Maybe OK short term but as you may know,
nylon doestend to absorb water and slightly expands…. Hence seizing all the
bearings. Theyare not easy to replace as 5 large holes need to be made under
the wing andtheir associated repair schemes, however can be done. Diamond
supplied the newbearing sets which were a complete steel bearing but with a
nylon “tire” in theouter edge. A much better system and the same as used on the
Diamond DA 40elevator rod. Re your friends Dimona, An issue like that would set
off a bigalarm. There could be a few issues. Some Dimona’s didn’t have any
push rodbearings at all .. just bushes so if there was any radial play that
couldcause a problem. Also the bearing sets were mounted in plywood brackets
buttglued to the inside skin … not really that strong. I am thinking that
maybeone or more of these wooden brackets has come off. Also based on my
abovecomments regarding the high flight loads put back thru the aileron
circuit inflight, maybe you should make a closer inspection (try using a USB
enderscope). Also note that the older aileron push rod has a joint about 5
feet or so intothe wing from the root rib. This can make things a bit confusing
as well. I will put together some photos for you .. .also will show the holeswe
made to replace the old bearings and also of the new and old bearing sets. Is
there anything else you would like a picture of. Best regards Ian WIlliams
From: [email protected][mailto:[email protected]] On
Behalf Of Michael Stockhill
Sent: Friday, 22 May 2015 12:59 a.m.
To: [email protected]
Subject: Re: [DOG mailing list] Engine mount for Limbach Ian Williams I follow
DOG from Montana, one of the prettiest of the GreatSatan's 50 states. I own
an H-36, SN 3518, and maintain another for afriend. I read your post
discussing a modified aileron actuationmechanism. I am not familiar with that,
so wonder if you could enlighten me? My friend's H-36 has an odd
characteristic--at theonset of any disturbance or turbulence, the ailerons
oscillate. I'd callit aileron snatch, but it doesn't quite fit the formal
definition for thephenomenon. I'm headed his way in the next couple days to
check the rigging;last time I was there, we checked and there is no play in the
system. His birdis very tail heavy for some reason, so its CG is very near the
aft range. This may or may not be relevant. Best, Michael Stockhill On Thu, May
21, 2015 at 5:14 AM, Ian Mc Phee <[email protected]>wrote:Interseting your
observation about the tilt of the engineand may explain something. Ours points
up for some unknown reason but isgoes so well. We have bing carb and I had to
finally fit different jetsin each carb to even up temeratures (one 2.05mm and
other 1.90mm). Bingsonly adj is jets. Ian McPhee Ian McPhee On 18 May 2015
at 09:29, Ian Williams <[email protected]> wrote:HiAll, Interestingreading.
Nigel … rip into it, I am looking forward to seeingthe finished HK36.
Regardingthe engine mount for the H36, One thing I have noticed, looking at all
the picsof Dimona’s available on the internet is the thrust line of the earlier
H36’sseems to be different as compared with the later ones … I mean that ifthe
prop is vertical and you are looking at it from the side, the prop anglelooks
as if it is at the wrong angle ref the fuse … it pointing“up” The later H36’s
seem to have a lower “angle “ relative to thefuse. (Havn’t explained it that
well but you shouldunderstand). Our H36 is an earlier one (S/no 3537) We have
2 alloyspacers on the rear mounts which decrease the angle a bit which I assume
is thesame for all the ex Thai Dimona’s. Later h36’S seem to have a lower
angle. Ofinterest, we have just done 100hrs in GCB since its first flight in
June lastyear. It is a great little rocket and by far has exceeded
ourexpectations. It has the original aileron control configuration buta new
set of bearings in the wings (5 sets per wing) A mission to replacebut works
well. It is different in that the control forces than the laterones … the
stick is quite “firm” around the centre for a small lateralcontrol input but
max aileron control load at speed is actually significantlyless than a Grob
109 which I am involved with. It does take alittle to get used to but is
quite OK. With the new bearings there is no“sticking” at all. When cruising at
90 kts or more, the ailerons do liftup about 15mm or more. However both are
even. Looking at the wing sectionand the pressure distribution under the
ailerons it is quite clear that thecompressive load into the aileron push rods
is very high so the modifiedconfiguration was a logical one. Wehave had 2
problems … the first was a fuel blockage where there was some crapin the banjo
bolt at the bottom of the fuel tank which was impossible to see(looked like
grey cotton wool) .. ie between the finger strainer and the 3outlet holes of
the fitting … not helped by using some CRC rubber for a smallsealing job on the
tank (learn’t a real lesson there) However allreplaced, flushed out and
OK.Theother issue is at lower RPM and lower airspeed the prop tends to slip
into finepitch. Not a major problem as in cruise mode it is
OK.Otherinteresting things are· I have installed an MGL fuel computer
using the original VDOfloat and a new turbine type flow sensor … a great system
as you know exactly howmuch fuel is available and it also removes the non
linearity of the fuel tankcontents (5 calibration points)· The engine
indicates an oil temp around 65 to 80 degrees Ccruising. RHS rear cyl drops to
about 120degrees C and the LHS side around160. I think the variation is caused
by a slightly different mixturesetting of the carbs. Take off cyl hd temps
around 190 (depending on theOAT)· I have installed a 5 V regulator
supplying power to a small GPSplus a couple of USB sockets to keep ipads etc
charged (note if using USBsockets the 2 * signal pins need a specific bias
voltage to enable appleproducts to accept a charge … tricky people those apple
dudes. · I also connected the comm. Radio audio amplifier to double
asthe Intercom amplifier with a panel switch that turns it on or off. Very
simpleand works real well. Combined also with a MP3 socket so ad you
arecruising along, you can play music from your iphone thru the headsets.
Areal spin off also is if someone calls you the ringing and audio from
theiphone is directed thru the intercom so no problem hearing the person
calling. Soall good. If any of you happen to come to New Zealand I would love
bothto see you and can provide some accommodation if required. I think
WolfHoffman did a great job all those years ago. Bestregards IanWilliamsZK-GCB
From: [email protected][mailto:[email protected]]On Behalf Of
Ian Mc Phee
Sent: Saturday, 16 May 2015 10:53 p.m.
To: Laurie Hoffman; DOG LIST
Subject: Re: [DOG mailing list] Engine mount for Limbach I will take photos
tomorrow but it is a great (brilliant) mod & you musthave it in a L2400 to gain
access to oil filter. Engine in and out is a pieceof cake especially when you
remove front engine mounts AND the front Truss (2bolts). Engine goes in and
out with muffler exhaust all attached toengine. So easy. ImOn16/05/2015 7:29
AM, "Laurie Hoffman via dog" <[email protected]>wrote:Hi Ian,Re
removable front cowl panel.Did you find the template that you had?
RegardsLaurie Hoffman From: Ian Mc Phee <[email protected]>
To: DOG LIST <[email protected]>
Sent: Saturday, 16 May 2015, 7:21
Subject: Re: [DOG mailing list] Engine mount for Limbach Theyare VW part & will
check old box later for number or may have it written upin logbook. Front ones
need drilling and cutting. Back is as is ready touse. Do you have the
removable panel at front? Great mod.
Ian Mc Phee
0428847642
Box 657 Byron Bay NSW 2481
AUSTRALIA Ianm On16/05/2015 5:27 AM, "Angel Jimenez Martin"
<[email protected]>wrote:Helloeveryone,Couldsomeone tell me if it has the
same engine mounts Limbach flock of Dimona andDimona Mk 2.Greeting
