Sidewinder mods

Sidewinder mods

Post by Buzz McDermot » Sat, 21 Dec 1996 04:00:00



Quote:

> We are building a Sidewinder (Estes) and after following the posts,
> decided to use plywood for fins.  Would 3/32 ply be ok for the sub for
> balsa?  as well as balsa strips along the ply fins in place of
> cardboard?  Intend to use a c-6-5 for first flight, as all the posts
> about near crashes with A's and B's so what altitude would I be
> looking at?  Is a 12" chute to small?  We don't have lots of area, but
> have lots of trees.  We have launched others and had no problems, but
> don't want a ground level para discharge.

Be careful of weight gain. The model is a pretty anemic flier on a C
motor. It really wants a D12. Before substituting ply (and basswood
would be a lighter, better choice than plywood), I would first suggest
you investigate covering the fins with Jap tissue. If you have access to
a flying model airplanes (ie: R/C) store, they will sell Jap Tissue, Sig
Lite clear dope and Sig Thinner.

1. sand and shape fins
2. Apply one coat of 50/50 Sig Lite and thinner to fins. Let dry. Don't
coat fin root.
3. Cut out tissue a little bigger than fins all the way around. Cut
tissue for both sides of fins.
4. Lay tissue on one side of fin. Brush on full strength Sig Lite,
enough to fully soak tissue. Allow to dry. Trim off excess tissue with a
single edged razor.
5. Repeat for other side of fin, but don't trim off excess. Trim only
enough to leave ability to wrap around fin edges (except root) plus 1/4"
overlap with tissue on other side. Wrap around and dope that on.

6. If you insist on substituting for the balsa fins, use 1/16" basswood.

You'll be surprised at the strength of the tissued fins. You won't need
to replace the cardboard. And there is very little weight gain. Even
basswood is a lot heavier than balsa, and plywood is heavier than
basswood.

Buzz McDermott
Dallas, Texas

 
 
 

Sidewinder mods

Post by Fox » Sun, 22 Dec 1996 04:00:00


We are building a Sidewinder (Estes) and after following the posts,
decided to use plywood for fins.  Would 3/32 ply be ok for the sub for
balsa?  as well as balsa strips along the ply fins in place of
cardboard?  Intend to use a c-6-5 for first flight, as all the posts
about near crashes with A's and B's so what altitude would I be
looking at?  Is a 12" chute to small?  We don't have lots of area, but
have lots of trees.  We have launched others and had no problems, but
don't want a ground level para discharge.  

Thanks

Foxeye

 
 
 

Sidewinder mods

Post by Bob Kapl » Sun, 22 Dec 1996 04:00:00


Quote:

> ... I would first suggest
> you investigate covering the fins with Jap tissue. If you have access to
> a flying model airplanes (ie: R/C) store, they will sell Jap Tissue, Sig
> Lite clear dope and Sig Thinner.

> 1. sand and shape fins
> 2. Apply one coat of 50/50 Sig Lite and thinner to fins. Let dry. Don't
> coat fin root.

For the past 10 years or more I've been using the Sig Nitrate dope for all my
tissuing. Less warping and it fills faster. The one drawback is that some
finishes can't be put over Nitrate dope, including regular dope. Not a problem
on my BGs, which get nothing but dope and tissue. Could be a problem here
depending on what you paint the model with after tissuing. Acrylics and enamel
are probably OK, dope, laquer, and epoxy probably not. Test first whenever
mixing different paints in a model.

Quote:
> 3. Cut out tissue a little bigger than fins all the way around. Cut
> tissue for both sides of fins.

And remember that the second piece you cut must be a "mirror image" of the
first one. Tissue has a front side and a back side. The fuzzier dull side is
the back side that goes against the wood. Some tissue has grain. If yours does,
try to run it perpendicular to the balsa grain.

Quote:
> 4. Lay tissue on one side of fin. Brush on full strength Sig Lite,
> enough to fully soak tissue. Allow to dry. Trim off excess tissue with a
> single edged razor.

Here's a neat tissue t*** trick I learned from Guppy at least 20 years ago.
Take a fresh piece of 320 grit wet-or-dry sandpaper, and lightly sand at the
edge of the tissue / fin. It cuts right thru the tissue and leaves a real clean
edge.

Quote:
> 5. Repeat for other side of fin, but don't trim off excess. Trim only
> enough to leave ability to wrap around fin edges (except root) plus 1/4"
> overlap with tissue on other side. Wrap around and dope that on.

For the cleanest tissue job, try reversing these two. Wrap the first sheet
around, then flush trim the second sheet.

Regardless, afterwards put another coat of whatever dope you used over the seam
edges to be sure they are stuck down well.

Quote:
> 6. If you insist on substituting for the balsa fins, use 1/16" basswood.

... or 1/16 model aircraft plywood. Basswood still has grain and can crack. My
old rule of thumb is that plywood is about as strong and about as heavy as
balsa 4 times as thick. 1/16 ply would match 1/4" balsa.

Quote:
> You'll be surprised at the strength of the tissued fins. You won't need
> to replace the cardboard. And there is very little weight gain. Even
> basswood is a lot heavier than balsa, and plywood is heavier than
> basswood.

I find plywood and basswood to be pretty close. The one thing I would NOT use
for fins is Sig Lite-Ply. It breaks too easilly. It's OK for centering rings
and bulkheads in most LMR applications because all edges are supported. It
beats cardboard and isn't much heavier. But I've broken or shreaded just about
every fin I've ever made from the stuff.

        Bob Kaplow      NAR # 18L       TRA # "Abort, Retry, Fail?"

 
 
 

Sidewinder mods

Post by Frank J. Bur » Tue, 24 Dec 1996 04:00:00


I'd use basswood, as it is almost as light as balsa, but much stronger.
C-s are marginal even for the balsa finned version.  Consider changing
to a 24mm mount and D motors, or using Aerotech 18mm D motors.

Frank


Quote:

>We are building a Sidewinder (Estes) and after following the posts,
>decided to use plywood for fins.  Would 3/32 ply be ok for the sub for
>balsa?  as well as balsa strips along the ply fins in place of
>cardboard?  Intend to use a c-6-5 for first flight, as all the posts
>about near crashes with A's and B's so what altitude would I be
>looking at?  Is a 12" chute to small?  We don't have lots of area, but
>have lots of trees.  We have launched others and had no problems, but
>don't want a ground level para discharge.  

>Thanks

>Foxeye