[NSRCA-discussion] Genesis revisited

Sat Apr 10 21:35:51 AKDT 2010

John,
I had a Genesis (which flew great, BTW). As I recall, there was no down
thrust. However, that was 4 planes ago so I could be wrong. Anyway, no down
thrust is easy. Block up the fuse so the nose ring is perpendicular to your
table. A good square will take care of that. Then make sure the fin is
straight up and down to the table. Once you have both of those right, any
line on the fuse that's parallel to the table will be at 0 degrees to the
thrust line. 

I have a dead flat, slate, former pool table top that I know is flat and
level everywhere. I use a tool called a surface height gauge that is perfect
for making straight parallel lines off a flat surface. Just google it and
you should find plenty of examples from machine tool supply house. 

I actually go one step further. I have a sub-table I built years ago that's
about 2' long, 8" wide, and 5" high. The main part of the table is made from
some cheap hard board laminated to a piece of 2" foam, just like foam wing
construction with hard board instead of balsa. On each of the four corners
of the bottom of the sub table that will be sitting on my slate table, I
have an adjustable furniture caster from Home Depot. That's basically just a
1" metal disk with a threaded stud coming out of it. With those I can adjust
my little sub table (and anything mounted to it) from side to side and fore
and aft. The top half of the table has removable wooden saddles to hold the
fuse. Depending on the configuration of the fuse, I either screw the fuse to
the saddle through the holes for my landing gear or epoxy it to the saddles
after a couple of coats of paste wax on the fuse where it will contact the
saddle. If you have to epoxy it, just make sure it's kind of gobs of epoxy
rather than smears. The gobs pop right off (sometimes too easy) whereas
smears would require some picking to get it all off. I realize the epoxy
route sounds scary, but I've done it many times and learned about it from a
former kit manufacturer who was the best in the business at the time. When
you're done setting it all up, you just have to make sure to clean the fuse
very thoroughly with wax and grease remover like PPG or Dupont Prep-Sol
before you start filling and painting. Obviously, when you're gluing the
fuse to the saddles, you want the epoxy blobs to look like big spot welds
that only touch a nice smooth, waxed surface on the fuse and definitely not
something like a seam where it would get a good foot hold. 

Once you have your fuse mounted to the sub table and have the casters on the
sub table adjusted so the nose ring and fin are oriented properly compared
to your main table, you use the surface height gauge to draw new alignment
lines on the fuse as close as possible to the originals. Surface height
gauges are used to scribe lines, not draw them. I made a pointer for drawing
lines from a piece of music wire and a narrow strip of wood hollowed out to
fit a super-fine Sharpie pen. I just tape the pen to the wood and the wood
has a hole in it to mount it to the music wire. 

Once you've done this a few times, you'll realize how far off those original
marks can be, regardless of the manufacturer. They can make a perfect plug
and mold with perfect alignment marks and still pop out fuses where things
have moved a few thousands. A few thousands at the root will be about 1/8"
at the tip. The three most important tools in my shop are the dead flat
table, sub table, and surface height gauge. Now, if we can just get all the
manufacturers to let us glue in our own sockets. I'm getting tired of
cutting out and replacing the originals.....

Verne

-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of John Gayer
Sent: Sunday, April 11, 2010 12:09 AM
To: General pattern discussion
Subject: Re: [NSRCA-discussion] Genesis revisited

Verne,

Thanks for the good suggestions. I will set up to reference off the fin 
centerline.
Although we cut the holes  for the wing and stab tubes, no reinforcing 
has been done, no epoxy used- so modifications will be easy. Probably 
have to shim the gear slightly to get the plane to sit level. Sounds a 
lot easier and much more likely to work than trying to straighten the tail.
What are you using for a reference to establish stab incidence = 0 and 
check the downthrust of the nose ring if you are not trusting any marks 
on the fuselage?

Thanks again,

John

Verne Koester wrote:
> John,
> You may be far better off in the long run cutting out the wing and stab
tube
> sockets. Then jig up the fuse so the fin is straight up and down (90
degrees
> to your table). At that point, you just need to glue the new sockets in so
> the tubes are parallel to the table. I realize I'm over-simplifying the
> process, but I think it would give you the best chance for long term
> success. If you don't ruin the fin by bending it with a heat gun, it will
> almost certainly end up where it started after being out in the sun for
> awhile. BTW, I never trust alignment marks molded into a fuse. My first
> alignment steps are to make the fin perpendicular to my table and check
out
> the down thrust molded into the nose ring at the same time. Once those are
> set, I make my own marks (referenced off my table) as close to the
molded-in
> marks as possible. When you consider that two fuse halves are joined in
the
> center, even a few thousands shift somewhere can equate to things being
way
> out whack at the wing tips. One of many reasons I prefer kits where the
> builder glues in the sockets rather than the manufacturer.
>
> Hope this helps
>
> Verne Koester
>
> -----Original Message-----
> From: nsrca-discussion-bounces at lists.nsrca.org
> [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of John Gayer
> Sent: Friday, April 09, 2010 10:47 PM
> To: NSRCA Mailing List
> Subject: [NSRCA-discussion] Genesis revisited
>
> I'm helping someone from our club build an old Genesis kit. Everything 
> was going along just fine until it came time to install the wing and 
> stab tubes. The wing tube is just fine, ends up parallel to the belly 
> pan within a millimeter at the ends of the tube running through the 
> fuselage.
>
> The problem occurs at the tail end. The fin is 12 mm out of plumb and 
> the stab tube(using the indicated marking on the fuselage) is tipped 
> about 10 mm in the same direction as the fin. Also the marks on the 
> fuselage for the stab tube and the front pin are not the same distance 
> up from the fuselage bottom so it appears these marks were not 
> accurately set in the mold. Rather a mess.
>
> A long time ago when I ran into the crooked fin problem , I managed to 
> get it lined up by using a heat gun and gentle pressure. Then using 
> braces, tail post and a former, try to lock in the new fin position.
>
> Anyone have any experience with this netbox kit that ran into any of 
> these problems or were all the others perfect right out of the box?
>
> I would really appreciate any guidance on this that I can get.
>
> Thanks
>
> John
>
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