Conference vmszoo::rc

    Glass on the tail will probably be a lot heavier than the injected foam.
    Going this route will force you to add additional weight on the nose.
    That'll increase the overall weight of the fuselage, which would
    increase the stress on the wing center section, making it more likely
    that you'de fold the wing.  Keep it light.

    Glass on the bottom of the wing *WILL* be much heavier than carbon
    fiber.  Resin on the bottom of the wing will just add weight,
    structurally, it isn't worth a damn.

    Add carbon fiber to the leading AND trailing edge of the wing.  Use CYA
    to hold the fiber down.  You won't be adding more than one or two
    ounces.  The increase in strength will be significant.

    Use Carbon fiber along the sides and top/bottom of the fuselage at the
    area of the tail that is susceptable to breaking.  This will impart a
    considerable amount of additional strength, with much less weight than
    glass, or resin.

    Carbon Fiber is really great stuff.  It's incredibly strong for it's
    weight, and incredibly strong compared to other, more traditional
    alternatives.  It isn't hard to work with, nor is it dangerous (Carbon
    Fiber SPARS are.  The tape, made up of hundreds, if not thousands, of
    hair like strands, is very safe.  I use it all the time, and I've never
    had any trouble).

>< Note 1068.1 by LEDS::COHEN "Some limitations may apply..." >
>                            -< here's some opinion >-
...
    Use Carbon fiber along the sides and top/bottom of the fuselage at the
    area of the tail that is susceptable to breaking.  This will impart a
    considerable amount of additional strength, with much less weight than
    glass, or resin.

I like that idea - now I have lots of Dave Brown carbon fiber in strands
and can thin zap it to the tail - but I have to cover it with something
smooth before paint.  Normally I would glass over it but I think you
have something else in mind - what?

Bye          --+--
Kay R. Fisher  |
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================================================================================

    Install the fibers on the inside of the fuse. Not the outside.
    I'd still consider the foam. Seems to me that the foam would add
    dampening rather than strength. The dampening would serve to spread
    the shock load over a greater surface reducing the likelyhood of
    localized damage.
    
    
    Tom

>< Note 1068.3 by SA1794::TENEROWICZT >
>
>
>    Install the fibers on the inside of the fuse. Not the outside.
>    I'd still consider the foam. Seems to me that the foam would add
>    dampening rather than strength. The dampening would serve to spread
>    the shock load over a greater surface reducing the likelyhood of
>    localized damage.

Tom - I can't get inside the fuse - it's already one piece and ready
to paint.

OK - foam is still being considered.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
================================================================================

    Kay,

    After gluing the CF to the fuse, I'de just build up a little bit around
    it with something like Magic Model Filler, and sand it down smooth
    (without cutting the CF with the sandpaper).  The CF tape should lie
    quite flat, and thin, so you won't have to do a lot of buildup.  This
    will prevent you from getting an unsightly bulge around the work area,
    and leave you with a strong, super light reenforcement.  After you're
    done, paint the area with a thinned down coat of epoxy.  That'll keep
    the MMF from chipping off the fuselage.

    If you put the CF on the left/right-top/bottom, and also on the four
    "corners" (add another 4 strips, one between each of the first 4), you
    can forget about the foam.  Even if the tail fractures completely around
    it's circumference, the CF will hold it rigidly.  There's no stretch in
    CF tape.

    Remember, I'm talking about running the tape along the length of the
    fuselage, longetudenally (?), not radially.  you only need to go a few
    inches to either side of the recommended reenforcement area to be
    effective. 

    Kay,
    
    the foam does not add structural reinforcement, but is used to
    support the glass fuse so that it can't buckle. The glass is forced
    to keep it's nearly cylindrical shape which is the strongest shape
    it can have. There is no way to bend it unless you reach the tensile
    strength of the fiberglass. This is basically the same as what the
    foam does to your (wood or glass) sheeted wing.
    
    Can't say something about the weight. A friend of mine bought a
    used glider about ten years ago, and for weight reasons he pulled 
    out the foam the previous owner hat put into the rear.
    
    If you should decide to go "the foam way", make sure to clamp down
    the rudder while the foam cures. It expands incredibly and will
    try to make a bubble out of your beautiful rudder.
    
    Good luck with your wonderful ship!
    
    Hartmut 
     

I didn't get a chance to read your reply until this morning but last night
I started doing almost exactly what you said.

>    After gluing the CF to the fuse, I'de just build up a little bit around
>    it with something like Magic Model Filler, and sand it down smooth
>    (without cutting the CF with the sandpaper).  The CF tape should lie

I did that.

>    quite flat, and thin, so you won't have to do a lot of buildup.  This

Mine is not so flat - it is separate fibers - not tape and although I tried to
keep them flat by combing it out with a tooth brush - I still got a lot of
bunching and raising when I put the thin ZAP on it.

>    will prevent you from getting an unsightly bulge around the work area,
>    and leave you with a strong, super light reinforcement.  After you're
>    done, paint the area with a thinned down coat of epoxy.  That'll keep
>    the MMF from chipping off the fuselage.

I almost put Fiberglas on it last night but elected to put micro fill on
first to get it smooth.  Good advice about just using the epoxy as paint
but... Any reason to stick with epoxy instead of polyester resin?  It is
already thinner and more paintable.  If I do thin epoxy I'm suppose to
use alcohol right?  How thin - like polyester resin?

>    If you put the CF on the left/right-top/bottom, and also on the four
>    "corners" (add another 4 strips, one between each of the first 4), you
>    can forget about the foam.  Even if the tail fractures completely around
>    it's circumference, the CF will hold it rigidly.  There's no stretch in
>    CF tape.

I'd like to do both - especially as per the previous reply about foam - but
I really like the furnished Fiberglas pushrods and I put each end in a vise
last night and yanked on them to test for breakage - I don't see how they
could ever break.

>    Remember, I'm talking about running the tape along the length of the
>    fuselage, longetudenally (?), not radially.  you only need to go a few
>    inches to either side of the recommended reinforcement area to be
>    effective. 

I went from 1/2" from the tail forward about a foot.  I put twice as much
on the bottom as I did on the top and sides.  Picture this - I have
this tail section that is white Fiberglas sanded smooth as glass and I'm
Zapping on stringy black bunchy narley snaggy lumpy carbon fibers.  Sure
looked nice before I started.

P.S.  I sanded the plywood sheeting and wing leading edges last night and
      filled plywood chips with glazing compound.  Most if not all chips 
	  were there before I started sanding - probably caused by the machine 
	  that they used to cut out the lightening holes.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
================================================================================

    Kay,

    Magic Model Filler, and the like, won't stick too well to Fiberglass.
    The Epoxy suggestion is only to "coat" the filler enough so that it
    won't chip away as the fuselage flexes.  I'de thin the Epoxy down to the
    point that it brushes easily, ie. not quite as thin as dope.  Resin
    might not work as well, 'cause you want to keep the coat thin, but a
    thin resin coat will crack when flexed.  Epoxy maintains some
    flexibility, even when cured.

    Kay,
    	You might try Epoxy with microballons as a filler. Mix
    epoxy and then add the microballons until paste consistency.
    allow a day to cure and then sand. Once sanded then brush on 
    a coat of thinned epoxy as a gel coat.
    
    
    Tom

I guess I need some sanding lessons.

I had a layer of micro fill on the Hawk tail last night and I
just wanted to send it down.  Now I figure there will be some
low spots that I'll have to put more fill on later but I ended
sanding the cone into a really non circular goofy shape.  

OK - I put another layer of micro fill over most of what I just
sanded and figured maybe before I sand again I can get some good
advise from the notes file.

So picture this long Fiberglas tail that is basically round
(kinda oval at the forward end and rounder at the tail).
I have carbon fiber strips on the top, bottom and both sides
that I want to cover up.  So I put some micro fill on with a
putty knife.  

Now - How do I sand this mess off and not take
too much material off at the 4 corners - upper right, upper
left, lower right, and lower left?  Because of the taper - no
curved sanding block can be the correct shape.  Seems to
me that the best recourse will be to use a flat sanding block
and carefully rotate my block over the surface and go by
eyeball and keep redoing sections that go to far.

Anybody have a sure fire way to do this right?

Bye          --+--
Kay R. Fisher  |
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================================================================================

RE: < Note 1068.10 by K::FISHER "Stop and Smell the Balsa!" >

> Anybody have a sure fire way to do this right?

    Would you consider using a sanding sponge with the appropriate grade of
    sandpaper wrapped around it?

Later,

Don

    Kay,
    Use a piece of card stock and make a template of the shape in front
    of the filler. This can be used to give you an idea of what it should
    look like.
    
    Tom

    Kay,

    This may be too late if you went home already, but...

    Try this:  Take a strip of sandpaper 8 to 12 inches long (however
    long your sheet of sandpaper is) by 1/2 to 1 inch wide.  Then, use
    the sandpaper like you would a shoe shine cloth.  

    (For a picture of what I'm talkig about, see the November 1987 issue
    of Model Aviation in the Electrostreak construction article...)

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

>    Try this:  Take a strip of sandpaper 8 to 12 inches long (however
>    long your sheet of sandpaper is) by 1/2 to 1 inch wide.  Then, use
>    the sandpaper like you would a shoe shine cloth.  

Dan - I'll try that tonight.  Sounds like a great idea.  I really don't 
know how anyone can build and/or fly a model airplane without this notes file.

Bye          --+--
Kay R. Fisher  |
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================================================================================

    Hi Kay, glad to see you enjoying the HAWK.
    
    re: the foam in the fuse.  Thats right the tube of the fuse has to
    buckle-in in order for it to break and the foam helps it hold shape. 
    There is foam out there that is not expanding type.  There is the
    triple expansion stuff and then there is stuff that expands but not
    much.  Spray a glob out and watch it.
    
    About 10 of us have used the foam on our PANTERA's and I do think that 
    it does add weight of course but on mine it needed about 5-6oz in the
    nose to balance it out.  I would guess that most of that is because of
    the foam.  The advantage:  I cartwheeled my pantera off of a launch and
    it busted both wings at the poly joing and cracked the fuse just behind
    the wing.  But because of the foam it is just cracked....not completly
    severed and hanging by the control rods.  For control rods we used
    the metal rod inside the plastic tube method and it works OK.  
    
    
    For filling in the fuse.  dont use the model magic, spackeling compound
    stuff.  Go to your local auto parts store (Checker, etc) and get some
    of the BOND spotting stuff.  I call it BONDO in a tube.  It is about a
    6oz tube and sells for 1.59 or so and is great for filling in
    fiberglass pinholes and etc.  The model magic is just too soft and
    every time I put it on I sanded it all off before I knew it.

    Good suggestion for filling.  You want stuff called, generically, Body
    Putty.  It's big advantage is that it will stick to Fiberglass.  

    I had one of the original Hawks many moon ago and was as delighted
    as you are with the construction and look. I used the rods that
    came with it and otherwise built it exactly as specified. i covered
    mine with Solarfilm. I really looked great- White fuselage with
    red wings and tail.
    
    As for flying- well it sure did roll!! I proved that the wings are
    hard to fold several times. You really had to make sure you had
    airspeed before you pulled on the stick. Overall, I loved the way
    it looked but sold it because of the way it flew. 
    
    Good Luck with yours.

My Hobie Hawk won it's first trophy at the contest in CT this last weekend.
3rd place in Standard.  If I hadn't dumb thumbed it and blew a landing that
had a perfectly good approach it would have pushed it up to 1st.  But on the
other hand that was the 2nd round - if I had done real good there I would
have probably felt more pressure and blew the last round.

It is always fun to fly the Hawk because of all the attention it gathers.
There is always a group of guys that tell me stories about the Hawk they
used to have or a friends.  One fellow was talking to Shane about the
Hawk and saying he wished I wasn't always so high up so he could get a better
view of it flying.  Seconds later I was back around 50 feet and right in
front of the tent they were under and circled for about 3 minutes.  Shane
was telling me this on the way home.  I remember that flight because I 
launched into sink air and flew straight out sinking like a rock finally
I turned left and watched it sink till I turned back to the field to give
up and land.  As I arrived at the field there was suddenly no sink
and I circled ready to break away to land after the bottom fell out.  It
ended up I got just over 5 minutes with a goal of a 6 minute flight.

As an aside the contest in CT was great.  Three classes and 3 rounds in
each class.  Each 6 minute duration.  Day started with heavy haze and threat
of rain - but it never happened.  We started out playing with HLG's before
the contest (boy was the grass wet).  The first round was in the haze with
no real big thermals but some large masses of raising air so we could float
out 6 minutes from a good launch.  Then the sky started breaking up and
there were thermals popping up everywhere.  There were some launch windows
with gaggles of gliders in the same thermal and there were some launch
windows with solid sink air.  I managed two short (2.5 minute) flights.

I'll never forget one fellows launch.  He had a Falcon 880 and just
above the launch area someone was getting a good thermal.  So he launches
straight for him.  I figured he'd catch the same thermal and climb up 
with the original thermal owner.  But no his launch was awsome - he 
climbs up to the plane in the thermal and zooms launches and pops
up about 50-100 feet above the thermal owner - AWSOME!  Not only was
his launch incredible in height but he put it exactly on top of a known
good thermal.  Two minutes later he was an easy 10 minutes high.  Then to come
down he goes into crow and dives straight down - Double AWSOME!  He was
telling me after wards that he had a young fellow timing for him and
during the dive the young lad says "Wicked Sled Man".

Winners were at around 1200 points (one slightly above 1300), I managed
to get over 1000 in each class so LSF wise there were a log of point 
possibilities - unfortunately I don't need any more contest points for
my current level so it was just for fun.  There were about 20-25 in each
class - nearly everyone had entered all three classes.  Nice site - I was
there last year for an electric fun fly.  They ran one winch and retriever
and kept it going pretty good all day.  The few times a line broke the
winch/retriever operator would run to the break and fix it in no time.

One of the best thermal days I've seen at a contest.  There was seldom
a wind so if you caught a good thermal you went straight up.  A gentle
lady could have won all three classes.  Nice sight.  We threw HLG's after
the last official flight till my battery alarm on the Tx went off (and then
some) and the regular club flyers started cranking up the pylon racers.

Shane did well accumulating over 2000 points when the cumulative point
leader was slightly over 3000 (yes I was close).

He finally did his first winch launches by himself.  So he put in 9 good
flights on his Spirit with no damage.  I know I'm rambling a bit but
there were no DECies there to write for me.  You missed a good contest guys.

Anyway the Hobie Hawk finally received some gold.  Next weekend is the
CRRC contest - always a fun one to attend.  If you can only make one
glider contest a year - the CRRC contest is the one to make.  If you
don't fly gliders but would be interested in just watching one contest (or
part of one) stop by Sudbury this next weekend and look in on the CRRC 
contest.

Bye          --+--
Kay R. Fisher  |
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