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Aug 31, 2016, 07:47 AM
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Discussion

JW60" - The Quick Build Sessions


I'm starting on a plan to build 3 JWs by next Spring. The idea is to develop a quicker building, lower cost, lower weight, more versatile airframe than my usual efforts.

All three will be built from the JW "Classic" kit available from jwglider.com.
They will use standard sized servos and 4 cell AA nimh battery packs.
The current plan is to use only 2 layers of strapping tape and a simple covering design using Hobby King covering.
The fin will be the stock coroplast and the balsa elevons will probably not be glassed.
One difference is I will be building the first one with solid fiberglass rod spars instead of the stock carbon tube spars to prove if they are stiff enough and without a significant weight penalty for use in future builds.
Last edited by 1000MPH; Dec 30, 2016 at 11:44 AM.
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Aug 31, 2016, 10:51 AM
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Servo guidelines are drawn out.
.250" Fiberglass rods replace the .240" carbon tubes. The joiners were drilled out .01" to fit, not as easy as I expected.
So far, the added weight compared to solid carbon rod spars are approx .75oz for the bottom and 1oz for the top. I will compare to carbon tubes later.
4 cell AA nimh square pack will go in the fuse.
Servos are Tower Hobbies TS-64 (OEM versions of the now discontinued Hitec HS 635). They are faster than the HS 425/485's and $16.99 on sale.
Sep 01, 2016, 10:31 AM
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Weight differences for spar assembly.
Top Spar:
Hollow carbon tube (.240"): 58g
Solid carbon rod (.240"): 83g
Solid fiberglass rod (.250"): 109g


Lower Spar:
Hollow carbon tube (.240"): 50g
Solid Carbon rod (.240"): 70g
Solid Fiberglass rod (.250"): 91g
Last edited by 1000MPH; Sep 01, 2016 at 10:44 PM.
Sep 06, 2016, 04:41 PM
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No work performed this past weekend. I did prep the servos. A little mix n match on the wheels to get the holes lined up with no sub-trim. Notice it is stamped "HS-635" under the Tower emblem.
Sep 20, 2016, 12:27 PM
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FG spars are glue in. I heat up a spare joiner to relieve the foam at the root to accept the spar and joiner. I make sure it fits with no pressure and nothing sticks above the airfoil. This also requires a bit of melting along the spar channel, for that I use my 99 cent store sharpened screwdriver.
Spar is then spot glued using CA along its length. Then I use epoxy to pot the joiner and about an inch of spar, this is just added security for the spar/joiner joint.
thinned goop is then used for the rest of the spar with the hope that it will soak into the foam a bit.
I don't weigh down the spar, I think this contribute to a warped wing. I do weigh down the foam cores with sanding blocks while the goop dries.

Carbon tube spar JW is also being done this way.
Sep 20, 2016, 08:02 PM
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Looks great! Where are you sourcing your Fiberglass rods from? I seem to remember seeing a link at one point in time but am not having much luck finding it. Keep up the good work.

Chris
Sep 20, 2016, 10:16 PM
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Hey Chris, I hope you're not trying to follow along on this build as it will be sllloooowwww.
I get my FG and carbon from Goodwinds.com
Sep 21, 2016, 10:49 AM
Faster is Better
I'm a slow builder too.

Watching.
Sep 22, 2016, 01:22 PM
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More glue pics. Thinned Goop dripped over the spar and joiner.
I'm not sure if the new cores are cut differently but using the method in the instructions, flipping over the cores on a flat workbench to glue in the bottom spar, seems to now give too much dihedral. I ended up using top wingbeds, not sure if the difference in dihedral will be noticeable.
Last edited by 1000MPH; Sep 22, 2016 at 04:39 PM.
Sep 22, 2016, 03:29 PM
Faster is Better
So you use goop to glue the spars in the cores?

That's how I do it. I'm asking cause I've read other posts where they use Gorilla white glue to attach spars to cores.

I've never used gorilla white glue.
Sep 22, 2016, 04:37 PM
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Yes, I think goop yields the best bond. PU glue is very good as well, I haven't done enough crash testing to compare anything though. This one got three applications of the thinned goop then I will use the white PU on top as filler.
JB weld for the spar to joiner
CA to spot glue the spar in the channel
30min epoxy to pot the joiner/spar at the root
thinned goop for the spar to EPP
white PU for filler on top of spar
Not exactly part of the quick build plan but I wanted to experiment.
Sep 22, 2016, 06:44 PM
Faster is Better
That sounds good to me. I'm picking your brain cause of my upcoming FA build.

Like I said I've never used PU which i assume you're referring to white gorilla glue.

IMO Goop, is a safe bet thanks to its flexibility and proven track record.

I think that using a glue that was not very flexible could allow the glue joint to detach from the foam.

Never used jb weld on a spar joiner but that sounds much better than epoxy which can crack and detach. I will adopt that practice.

Thanks
Sep 22, 2016, 08:33 PM
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John Buxton recommended JB weld to me on my first JW build but of course I had to find out for myself.
You don't really want a flexible bond. PU actually has a little give, it's not brittle. White moreso than the amber. The reason white PU is popular is blends well with EPP, both visually and structurally.
Last edited by 1000MPH; Sep 22, 2016 at 08:48 PM.
Sep 22, 2016, 08:45 PM
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After spot gluing in the fiberglass spar I did a bit of flex testing. You can really see why you want a complete bond all along the spar, the foam compresses and releases and adds nothing to the stiffness. Once it's all locked together the stiffness is better that I hoped.
Sep 28, 2016, 10:49 AM
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First application of white PU...I'm still not good at achieving a smooth finish with no voids. I recommend using a new piece of 60 grit sandpaper to cut the PU, then a quick swipe of spackle will fill those air bubbles or another app of the PU if you are super picky. You can do it now to make it look pretty or wait until after the radio install is complete.


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