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Author Topic: P-30 Spitfire wing questions  (Read 5208 times)
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Crabby
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« on: December 08, 2018, 10:51:55 AM »

Good am brothers and sisters. I am going to build this Spitfire P-30. I am following the plan. My question is about the diagonals crossing the rib bays, you can see I have 'em at the bottom...Should I add 'em to the top as well?
The lightening holes are for balancing the wing from tip to tip...something I never consider doing but it makes sense to me. Even after stripping all lumber from the same sheet, the port side is a bit heavier. Total wing weight, 11.5 grams, target is around 50 grams total for plane.
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Glenn (gravitywell) Reach
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« Reply #1 on: December 08, 2018, 12:40:41 PM »

Hi Crabby, I can't help with your questions cause I no smarty!  But I just wanted to say that I love this ship, have looked many times at her and will build one some time.  Your work is as usual, superb.  Please keep the pics coming, cause I will need the info later!  Grin
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Duncan McBride
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« Reply #2 on: December 08, 2018, 02:24:11 PM »

I would put the diagonals in on top as well.  For very little weight you gain significant stiffness.  Try one panel and see.

I like this plane too.  Nice going.
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« Reply #3 on: December 08, 2018, 04:45:39 PM »

If you want greater stiffness and you do go ahead and put those extra braces in, I would put the top diagonals in in the opposite direction to the bottom ones to make an "X".
ian
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Crabby
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« Reply #4 on: December 09, 2018, 10:56:12 AM »

OK deed is done and significant stiffness noted...however still need to balance wing would like to do it without adding ballast! Still needs a good sanding will recheck balance afterwards
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Don McLellan
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« Reply #5 on: December 09, 2018, 11:54:17 AM »

Very cool pic Crabby.  Curious how much will have to be removed to get it balanced.  Did you try adding weight to balance, just to get a feel for how much you have to remove?
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Crabby
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« Reply #6 on: December 11, 2018, 04:09:53 PM »

Ok, Don to answer your question, I was able to balance the wing with a ball of plumbers putty, 1/5 gram way out on the tip. This business of balancing the wing is new to me, it just never occurred to me. In the plans it is mentioned to drill lightening holes to balance the spar. That got me going. Its no wonder some of my planes take to much fidgeting to get 'em in trim! Anyway I have nothing left to remove, so I am stuck ballasting the light side. Wing now weighs 11.5gr.

This plan is really simple looking, and I know a lot of guys and gals are turned on by it, but (thanks to bigbandito on the other thread for raising the flag) do not trust the plan! You really got to measure things and get 'em right or you'll pay later! I decided to build the wing first so I could get the wing saddle right. I really gotta give bandito the credit for jumping into the ice cold water first on this ship, and saving me the drama of fitting the wing into the fuse. Bottom line if you want to build this thing, do the wing first then get a tracing of the root profile for the wing saddle or a fun looking project will have you sitting at a bar stool or looking at the ocean!

Oh I should mention, that leading edge.... I stripped 6 pieces of 3/16 by 1/16, and tossed them on a cookie sheet filled with water then cooked 'em with the tuna casserole (350 degrees for 30 minutes) till they got nice and flimsy. Then I made a witches porridge of tite-bond and water and coated (3 strips a side) then wound em (laminated) on a waxed form to get the shape. A nights fitful sleep and they came out stiff as Moses's cane. Next the turbulator spar, tossed it into the hot tub. 104 degrees, and watched the Bears beat the Rams, at the 2 minute warning I took 'em out, wrapped em on the table lamp and got the shape. A Spitfire wing, P-30 or not, has got to look right. Everyone knows the shape!

I really like the idea of scaleish P-30's. If this Spitfire treats me right I might do a FW Ta 152 the sameish way.
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« Last Edit: December 11, 2018, 04:32:39 PM by Crabby » Logged

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flydean1
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« Reply #7 on: December 11, 2018, 04:46:13 PM »

Why is the left wing larger than the right wing?? Huh
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Indoorflyer
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« Reply #8 on: December 11, 2018, 07:46:28 PM »

Because he's holding the wing at nearly a 45º angle to the camera!

Crabby, I would have just put the diagonal bracing on one side.  The heavy side.  Then that way it will always dork in on the sturdy side.  Just kidding.

I get nervous hearing about putting a sheet spar on Slim Fast, if you know what I mean...
« Last Edit: December 11, 2018, 07:57:11 PM by Indoorflyer » Logged
flydean1
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« Reply #9 on: December 11, 2018, 10:56:36 PM »

I was just kidding too.  However some pre-war Italian aircraft did make the left wing slightly larger in chord than the right in order to counter torque and prop factor.
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Crabby
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« Reply #10 on: December 12, 2018, 09:24:25 AM »

Fly dean, you scared the b’jesus out of me because this plan has been copied and recopied so many times that every thing I do on this model has to be re-symmetricalled! After you said that I bolted for the shop and measured three times three ways...again! Like I said this build is really pretty simple, but can be a aborted wet dream if you just trust the plan! I have read the Bigbandito thread a few times to my benefit!
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« Reply #11 on: December 12, 2018, 12:17:10 PM »

That is a beautiful looking wing Crabby, and it will be really strong once covered and finished.
ian
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applehoney
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« Reply #12 on: December 12, 2018, 02:05:46 PM »

With respect, I've found that such wings can be built lighter than 'regular' wings of similar area and by virtue of  their shape are more warp resistant.   The P30 example depicted has 2 laminations of 3/32 x 1/16 for the trailing edge,  1/8 sq leading edge, spars 1/16 sq.  Ribs 1/20 centre,1/32 towards tip; very rigid now covered and well doped - 10g
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flydean1
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« Reply #13 on: December 12, 2018, 02:22:25 PM »

Fly dean, you scared the b’jesus out of me because this plan has been copied and recopied so many times that every thing I do on this model has to be re-symmetricalled! After you said that I bolted for the shop and measured three times three ways...again! Like I said this build is really pretty simple, but can be a aborted wet dream if you just trust the plan! I have read the Bigbandito thread a few times to my benefit!

Ahh...yes!  My work here is done. Grin Shocked Wink
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Crabby
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« Reply #14 on: December 12, 2018, 02:29:37 PM »

Hi Applehoney!
My wing is 11.4 grams right now. I am thinking about covering with mylar then maybe a coat of esaki. I hope I can stay under 15 gr.
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flydean1
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« Reply #15 on: December 12, 2018, 05:50:02 PM »

All kidding aside, I would use just Mylar.  A P30 wing doesn't have the torsional stresses of a power model or even some fairly high powered scale models.  I would try the Mylar first.  Then, since the wing is totally detachable, add some tissue later if required.

The elliptical planform also minimizes torsional loads at the tip, where uncommanded washout will bite you.

"Simplify, and add lightness"  Attributed to the late Anthony Colin Bruce Chapman.
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« Reply #16 on: December 12, 2018, 06:34:01 PM »

That is a neat looking wing Crabby. The TE is sheet? I'm a little surprised that the designer didn't use a laminated TE as well as LE.

That's a very light wing Applehoney - those light ribs and spars are interesting. I've noticed that this was common in the 40-50's for models as large as 40"WS but now it is rare to see anything lighter than 1/16 on ribs on similar size models.

John
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Crabby
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« Reply #17 on: December 12, 2018, 07:12:39 PM »

OK this is gonna be my first mylar wing. Whats the adhesive? I have the tack iron and the heat gun already. Where I fly the best time is early am and the tall grass is wet so I have been wanting to do a mylar covering for a while now. Also, in P-30 what are the rules concerning dethermalizers?
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flydean1
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« Reply #18 on: December 12, 2018, 07:28:00 PM »

No rule or restriction on any DT configuration.  This is not the FAC.

Best adhesive is at your nearest Jo-Ann Fabrics or equivalent.  Velcro adhesive thinned with MEK or Acetone to dope consistency.  Brush on, let dry, then have at it with the tack iron.

If you want some color (colour), spray one side with a very light coat of floral spray, and put the sprayed surface on the inside.
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Crabby
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« Reply #19 on: December 17, 2018, 09:45:00 AM »

I built the fuse last week and got a satisfactory wing-fit. There are some things that should be mentioned for the benefit of anyone attempting this build. One. the wing comes out a little wide chord wise, this supports John's wish that the trailing edge be laminated instead of sheet, plus as the pic shows I have a little trim detailing to do where the trailing edge is supposed to blend in with the fuse. Two, the pics don't show it but the wing saddle area is a bit wide for the fuse so I have to do something there. I am gonna use magnets to hold the wing on anyway. Three, I am not arguing with the designer here but the plan shows a hefty amount of wing incidence. I think its augmented by the degree of stab incidence. Maybe its set for a slow steady climb? All you professors can please speak up anytime.

Flydean, am I coating my ribs and diagonals as well as the perimeter? When I dope a wing I usually do but I don't "lock" up the inside area (ribs, etc,) till I have done the shrinking, a la Duco Guru. I could use a little advice and a mylar man's blessing here!
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flydean1
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« Reply #20 on: December 17, 2018, 10:49:40 AM »

You coat whatever you want the Mylar(tm) to stick to. 

It doesn't impart any rigidity, but your triangulated structure should be sufficient. 

Some put adhesive on everything the Mylar(tm) touches and after the initial shrink, go over all joints with the iron.  Adds very little weight and divides the areas of covering into smaller spaces which simplifies both repairs, and allows drawing up any stubborn wrinkles with local heat.
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Starduster
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« Reply #21 on: December 17, 2018, 12:01:55 PM »

As I mentioned in another thread, I did an experiment with Mylar and using "Gorilla Glue" (the clear regular glue, not the super glue) to attach it.

the good news is that once it's cured, it is a very good adhesive. The bad news is that it takes about 3 hours to set and about 24 to completely cure.

Next time, I'm going to try the Gorilla Glue "Clear Grip".

Just this past week, I put together a large (electric) Power ship fuselage (A Pimenoff #18) using the above Clear Gorilla Glue, and I am 100% sold on this product. Stronger than any other adhesive I've tried, sandable and paint and stainable. I also am sold on the Gorilla Glue Super Glue (mostly use the gel).

And the best part, Gorilla Glue is available everywhere.

And, no, I don't have any financial stake in the product!

 
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flydean1
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« Reply #22 on: December 17, 2018, 03:37:35 PM »

So Starduster, how does it compare with Titebond II and similar?  I'm looking for alternatives for my 2019 building projects.

I assume you used the regular Clear Gorilla Glue--the 3 hour setting type.
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Starduster
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« Reply #23 on: December 17, 2018, 03:50:00 PM »

So Starduster, how does it compare with Titebond II and similar?  I'm looking for alternatives for my 2019 building projects.

I assume you used the regular Clear Gorilla Glue--the 3 hour setting type.

Yes, I used the clear 3-hour stuff for the Pimenoff, and I really like it. I think the bond is better than titebond II, but that's just my impression.

I think it's at least worth the $5.00 or so to try it out. One thing, though: It does come out of the bottle pretty thick, so I lay it down, then take a popsicle stick and spread it so it's a thin even layer. On smaller joints, I squirt a puddle onto a piece of cardboard and then use a toothpick to spread an even layer on.

I really think that this is a great replacement for Duco and Ambroid
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Crabby
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« Reply #24 on: December 17, 2018, 04:17:08 PM »

OK Starduster, I am gonna try it out since you speak so highly of it. I assume I am gonna let it dry tack free before bringing on the mylar and heat? Roll Eyes
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