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Jan 08, 2019, 03:10 PM
Aka Magical Moonstone
balticS2's Avatar
Quote:
Originally Posted by JornWildt
Alec, how is it going with that Meteor?
OK, I take the point. Instead of soaking up this vicarious entertainment, I'll get off my backside and see if I can do something creative this evening

Alec
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Jan 10, 2019, 06:05 PM
Father by day, hacker by night
JornWildt's Avatar
Thread OP

Flaps


I did say earlier on that the flaps wouldn't be scale ... well I was wrong With the success from the retract mechanism, a little voice started saying "Flaps ... flaps ... at least you have to try ...", so I tried. After a few evenings behind the CAD program I got the geometry right and draw some templates for the project.

It is not complete yet as I haven't added the little arm that pushes and rotates the flap - and still need to find the best way to block it from sliding sideways. But the basic mechanism works fine with very little play in it.

The only drawback is the weight. Each hinge set weights about 6 grams and I'll probably add a few grams more. There are six of those, so there is approximately 60 grams in flap hinges all-in-all (plus a torque rod for each side). But then - it does look cool :-)

Wonder when I get ready to do some actual aircraft/airframe building ....
Last edited by JornWildt; Jan 10, 2019 at 06:21 PM.
Jan 10, 2019, 08:31 PM
Registered User
You could replace the steel and brass rods with carbon and tack them in place with a drop of CA. Where the rods have to rotate they can turn in ply bearings hardened with CA - just a thought, John
Jan 11, 2019, 02:21 AM
Father by day, hacker by night
JornWildt's Avatar
Thread OP
Carbon/plastic is a good idea, thanks - especially the big FG board wing mount could be made a lot lighter (but a few more lightening holes could probably help a lot too). But what about the load bearing points at the end of the arms (see photo) - I wouldn't rely on carbon alone for that?

I'll try to shave down the brass tubes a bit, drill a few lightening holes and see how much I can reduce the weight.
Jan 11, 2019, 04:35 AM
Registered User
Hi Jorn, I think that I would make the flat elements of the design in plywood of appropriate thickness and soak the ply parts in thin CA to harden their surfaces. I would replace the metal rods with carbon of appropriate dimensions. You can hold a carbon rod axially with a drop of CA at an appropriate point as long as it doesn't need to rotate. Or if it does you can CA a ply washer to the carbon shaft so that the shaft can continue to rotate. CA forms a fierce bond between carbon and wood. The ply parts hardened with CA will act as bearings and turn on the carbon axles. Any carbon powder that rubs off will lubricate the bearing pretty well. As long as the bearing only has to work intermittently it will last a long time. When the carbon rods begin to wear you just replace them with new ones, but I have never had to do that and carbon doesn't rust. That's what I meant, John
Jan 11, 2019, 09:42 AM
Father by day, hacker by night
JornWildt's Avatar
Thread OP
Thanks John - I'll investigate those options.
Jan 12, 2019, 08:20 AM
Father by day, hacker by night
JornWildt's Avatar
Thread OP
Tried a new version of the flap mechanics last night - this time with plywood and plastic pieces. That shaved about 50% off the weight - and seems solid enough for the intended use. In addition to that I'll use a carbon torque rod instead of a brass rod when time comes to mount it for real - and that should shave quite a few more grams off the final product.

Not to mention that it is way easier to build without the metal work.

Now back to the CAD program and get the retract mount laid out, so I can get the wing covered.
Last edited by JornWildt; Jan 12, 2019 at 08:42 AM.
Jan 13, 2019, 11:57 AM
Father by day, hacker by night
JornWildt's Avatar
Thread OP

Ready for sheeting


Back to the wing core - two half ribs plus a tiny sub-spar added and glued in with gorilla glue (using an expanding foam safe glue seems like a good choice for this kind of project). All pieces are flush with the foam surface and leading edge.

The trailing edge is really thin - and as can be seen, it also lost a few beads during the sanding process. I don't expect any problems from that as the sheeting on both sides are supposed to extend over the edge and merge into the actual trailing edge (the wing form is about 5-8 mm smaller than the final shape to make room for this).

I also added a sub leading edge. This may not really be necessary - but it was an easy addition that might help the sheeting bind to the front (although it should already bind fine with all that foam).

Balsa sheets are joined and ready to attach. Now I'll see if I can get the sheeting on to night
Last edited by JornWildt; Jan 14, 2019 at 02:13 AM.
Jan 14, 2019, 02:52 PM
Father by day, hacker by night
JornWildt's Avatar
Thread OP

One sheeted wing half


The wing half came out very nice today - no big issues, but some smaller mishaps like believing all CA glues are foam safe (leaving a void at the wing tip where the trailing edges didn't join) and being a bit too sloppy about the trailing edge shape before assembling ... nothing visible and nothing that cannot be fixed with a few drops of gorilla glue to fill some voids

I was a bit surprised about the the weight. The core itself was 46g. Then I added half ribs and sub leading edge and ended up on 64g. Then I weighted the 1.5 mm (1/17") balsa sheets - 67 grams more! Double up!

After a ton of sanding, trying to make the sheets about half a millimeter thinner, I ended up on a final weight of 140g. The wing is 58 cm long (approx 23").

The airfoil is a Selig8036 that someone recommended here http://www.rcuniverse.com/forum/aero...6-airfoil.html

Now I'll see if I can get that flap system rigged up for real.
Jan 14, 2019, 02:58 PM
Father by day, hacker by night
JornWildt's Avatar
Thread OP
Have anyone tried to fill the void between the foam core and the cradles with something like expanding isolation foam, plaster or other that would make it possible to get a perfect fit between the wing core, sheeting and cradles?

It seems like it should be possible to wrap core and cradles in plastic bags, spray a little bit of expanding isolation foam on the wing tips and then squish everything together and expect the foam to expand equally on both sides and thereby not twisting the wing core.
Jan 17, 2019, 07:22 AM
Gorilla glue rocks
Spit100's Avatar
Wonder if gorilla glue might work well. Dribble it in, let gravity draw it down into the gap. Stir it around in the gap with a wire. Let it expand and dry, add more were gaps remain.

Atleast it is a nice and light possibility for smaller annoying gaps.

Beautiful hand made custom hinge design. Being lazy, I use CA hinges... but seriously, your hinging is a work of art.

Spit100

P.s. I don’t even mind that you have switched to the dark side using foam for the wings!
Last edited by Spit100; Jan 17, 2019 at 07:55 AM.
Jan 17, 2019, 07:36 AM
Father by day, hacker by night
JornWildt's Avatar
Thread OP
Quote:
Originally Posted by Spit100
Wonder if gorilla glue might work well. Dribble it in, let gravity draw it down into the gap. Stir it around in the gap with a wire. Let it expand and dry, add more wee gaps remain.

Atleast it is a nice and light possibility for smaller annoying gaps.

Beautiful hand made custom hinge design. Being lazy, I use CA hinges... but seriously, your hinging is a work of art.

Spit100

P.s. I don’t even mind that you have switched to the dark side using foam for the wings!
Hey, there is still balsa on the wing - right

Personally I prefer the brass hinges, they actually look good by themselves - the wood and plastic hinges are boring. On the other hand, they will be hidden in the wing, so nobody will see them - and the weight saving is certainly worth it. Maybe I should just polish the brass version and put it on display somewhere

Regarding the foam - I have decided to try expanding insulation foam (see for instance https://www.familyhandyman.com/smart...tion/view-all/) when I skin the second wing half (if its foam-safe ... I have to verify that first). That cannot be worse than the balsa-stick-horror I tried first.
Jan 17, 2019, 06:00 PM
Father by day, hacker by night
JornWildt's Avatar
Thread OP

Working flaps


Got the flaps setup tonight - and it works! Its a somewhat delicate and rather complicated system with lots of easy ways to break - but then, flaps don't take much abuse as they are somewhat protected close to the fuselage, so I'll take them.

The flap, rod and hinges as shown on the video weights 28g total. Thanks to John (RFPJ) for the tips about carbon and plywood.

If you wonder about the middle hinge missing something then it's because I couldn't find the hinge arm at that time

P47 flaps demo (scale 1:10) (0 min 25 sec)
Last edited by JornWildt; Jan 17, 2019 at 06:06 PM.
Jan 17, 2019, 06:07 PM
Aka Magical Moonstone
balticS2's Avatar
That's really cool Jorn

I'm going to watch it a few more times

Alec
Jan 17, 2019, 08:41 PM
Balsa addict
Kev.au's Avatar
That looks nice, Jorn.


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