Logo
Builders' Plan Gallery  |  Hip Pocket Web Site  |  Contact Forum Admin  |  Contact Global Moderator
November 18, 2019, 06:33:45 AM *
Welcome, Guest. Please login or register.
Did you miss your activation email?

Login with email, password and session length
 
Home Help Search Login Register
Pages: 1 2 [3] 4   Go Down
Print
Author Topic: Re: Rockytop Stahl Spitfire  (Read 1317 times)
0 Members and 1 Guest are viewing this topic.
ZK-AUD
Platinum Member
******

Kudos: 50
Offline Offline

New Zealand New Zealand

Posts: 1,150



Ignore
« Reply #50 on: June 28, 2019, 06:28:33 AM »

Oh boy. I seldom get involved with these discussions because I know so little but logic would suggest that it’s the average incidence of the wing from root to top but with a weighting to take into account the effect of taper i.e. reducing wing area as you go outboard. Come on gurus there has to be a formula for this
Logged
billdennis747
Titanium Member
*******

Kudos: 52
Offline Offline

United Kingdom United Kingdom

Posts: 3,705



Ignore
« Reply #51 on: June 28, 2019, 06:48:23 AM »

Isn't nearly 1/4" rather a lot? It must be getting close to negative decalage.
Logged
ironmike
Platinum Member
******

Kudos: 87
Offline Offline

United States United States

Posts: 1,131



Ignore
« Reply #52 on: June 28, 2019, 05:06:26 PM »

Remember my Zero it had close to 3/8+ w/out ea tip.
Flew like gang busters
Logged
MKelly
Gold Member
*****

Kudos: 86
Online Online

United States United States

Posts: 880


Topic starter


Ignore
« Reply #53 on: June 28, 2019, 07:22:58 PM »

It does seem like a lot of washout when you look at the model.  The instructions recommend at least 3/16" washout - I overestimated how much the wing would spring back and ended up with another 1/32 per side.  It's the same on both sides and seems to be holding nicely, so I'm not going to mess with it before trim flights.  My main concern is getting a good starting decalage for the model.  On the T-28 and Little Gem (both of which had significant amounts of washout) I had trouble with nosing in as the model picked up speed, which got fixed by increasing the decalage and moving the CG slightly forward from the TVo-calculated position.  Given all the washout on this model I'm going to start trimming with the CG a bit forward and edge it back once I've got a feel for how the model flies.

Got the rest of the gingerbread on the wings (tip lights, walkway lines, gun port patches and landing gear) and finished up the noseblock and spinner assembly today, along with adding a second set of magnets on the lower wing root as insurance against the wings popping loose in flight.  Still have to paint the power unit and do final assembly on the tail group.

Mike
Attached files Thumbnail(s):
Re: Rockytop Stahl Spitfire
Re: Rockytop Stahl Spitfire
Re: Rockytop Stahl Spitfire
Re: Rockytop Stahl Spitfire
Logged
MKelly
Gold Member
*****

Kudos: 86
Online Online

United States United States

Posts: 880


Topic starter


Ignore
« Reply #54 on: June 29, 2019, 10:14:57 PM »

Thanks Ratz for separating this build from the Strutter thread!  In the future I'll attempt to be more disciplined with my topics.

The Spitfire is done!  Rigged the tail, painted the prop and spinner, finished up the lights and installed the antenna and antenna wires.  I had to play with the stab mount a bit - I built a Schmidt incidence meter (http://www.modelflight.com/incidence.html and checked the decalage, decided I needed to allow a bit more negative incidence in the stab.  The wing twist is dramatic when you measure the incidence: +2deg at the root, -.75deg at average chord, and -6deg at the tip - 8 degrees of twist across the span!  I set the stab for 1deg negative incidence compared to the wing at average chord as a starting point with adjustment to go another degree and a half if necessary.  We'll see how it flies...

It took about 5g noseweight to balance the model at the TVo-calculated cg (~47% of average chord, 2.25" back from the LE at the root).  I drilled holes in the noseblock well and embedded three fishing sinkers in the cowl to get things close, then added a bit of clay over the lead to get to the final balance.  Weight without motor is 68.7g.

Look forward to seeing how it'll do in the air.

Mike

Cheers,

Mike
Attached files Thumbnail(s):
Re: Rockytop Stahl Spitfire
Re: Rockytop Stahl Spitfire
Re: Rockytop Stahl Spitfire
Re: Rockytop Stahl Spitfire
Re: Rockytop Stahl Spitfire
Re: Rockytop Stahl Spitfire
Logged
FLYACE1946
Platinum Member
******

Kudos: 26
Offline Offline

United States United States

Posts: 1,550




Ignore
« Reply #55 on: June 29, 2019, 10:53:51 PM »

AMAZING to see this great project ready for the SKY. Maybe soooon I hope.
Logged
OZPAF
Palladium Member
********

Kudos: 180
Offline Offline

Australia Australia

Posts: 5,191



Ignore
« Reply #56 on: July 01, 2019, 10:32:19 PM »

Quote
Oh boy. I seldom get involved with these discussions because I know so little but logic would suggest that it’s the average incidence of the wing from root to top but with a weighting to take into account the effect of taper i.e. reducing wing area as you go outboard. Come on gurus there has to be a formula for this

The Mean Geometric Chord or as it is also known "Standard Mean Chord" does  allow for taper and plan form shape with it's actual chord length and it's span wise position. For all practical applications the Aerodynamic Centre can be located at 25% of the MGC from the LE of the MGC. The 50% chord of the MGC position should be located on the wing plan form centroid. Finding the centroid on wing plan forms such as the Spitfire is much easier now with CAD! Although you could hang a card copy of the shape from a couple of different points and the intersection of the plumb lines would give it.

Well hope that helps Mike (ZK AUD).

I think you should be close Mike with those settings. This nice spit deserves to fly well.

John

Logged
FLYACE1946
Platinum Member
******

Kudos: 26
Offline Offline

United States United States

Posts: 1,550




Ignore
« Reply #57 on: July 01, 2019, 10:36:34 PM »

AMAZING to see this great project ready for the SKY. Maybe soooon I hope.
Saw this Jewel take flight today. Really Nice to see up close.
Logged
skyraider
Platinum Member
******

Kudos: 93
Offline Offline

United States United States

Posts: 1,292

WWW

Ignore
« Reply #58 on: July 01, 2019, 11:40:09 PM »

Mighty fine looking Spitfire there Mike!  Very well done. I can really appreciate the
detailing that you've put into her. Great panel lines and the whole ten yards. I hope
she rewards you with some outstanding flights soon. Looking forward to your flight
reports. Excellent work!

Skyraider
Logged
MKelly
Gold Member
*****

Kudos: 86
Online Online

United States United States

Posts: 880


Topic starter


Ignore
« Reply #59 on: July 02, 2019, 08:30:40 AM »

Thanks Skyraider!  As Allen said, the Spitfire took wing yesterday on a short, fat motor (4x20" loops 1/8", ~14g).  Video at:  https://www.youtube.com/watch?v=PiFyDNOI0Ck

I had to take a huge amount of decalage out to make it fly - the washout made less of a difference there than I had anticipated.  Haven't measured the after-trimming incidences yet.

Mike
Attached files Thumbnail(s):
Re: Rockytop Stahl Spitfire
Re: Rockytop Stahl Spitfire
Re: Rockytop Stahl Spitfire
Logged
DavidJP
Titanium Member
*******

Kudos: 45
Offline Offline

United Kingdom United Kingdom

Posts: 2,894




Ignore
« Reply #60 on: July 02, 2019, 08:43:35 AM »

And very nicely too!  Well done.
Logged
steveneill
FAC Squadron Ventura Model Aviators
Silver Member
****

Kudos: 45
Offline Offline

United States United States

Posts: 235


WWW

Ignore
« Reply #61 on: July 02, 2019, 10:20:33 AM »

Great job.
Logged

ironmike
Platinum Member
******

Kudos: 87
Offline Offline

United States United States

Posts: 1,131



Ignore
« Reply #62 on: July 02, 2019, 10:32:16 AM »

Well done Mike well done.
Amazing that we put in too much stab that always
needs to come out during trim session.
Logged
Crabby
Titanium Member
*******

Kudos: 134
Offline Offline

United States United States

Posts: 2,181


I never met a modeler I didn't like



Ignore
« Reply #63 on: July 02, 2019, 10:57:18 AM »

Hi Mike That's just about how I had mine flying, only it never got better. Finally got a nice climb then she spilled off to the left and cartwheeled, amputating the wing. I decided it looked kinda heavy and clownish with all that camo and roundels and really not flying that well so I purged it with a bunch of others that were just taking up space! What is your stab setting? You are off to a great start!
Logged

The Threadkiller!
ironmike
Platinum Member
******

Kudos: 87
Offline Offline

United States United States

Posts: 1,131



Ignore
« Reply #64 on: July 02, 2019, 03:05:49 PM »

It is the wash out man, the washout that enhances the dihedral.
Logged
Don McLellan
Titanium Member
*******

Kudos: 63
Offline Offline

Canada Canada

Posts: 2,387




Ignore
« Reply #65 on: July 02, 2019, 04:07:05 PM »

Beautiful model, and very nice trimming flights Mike! 
Logged
OZPAF
Palladium Member
********

Kudos: 180
Offline Offline

Australia Australia

Posts: 5,191



Ignore
« Reply #66 on: July 02, 2019, 09:50:22 PM »

It looks like it is trimming out well Mike. Looks great in the air. The indications of too much decalage surprise me a little - - it's almost as though the outer section of the wing is providing little to no lift and that most is being provided by the root section. If this was the case then as you set the tail originally to -4.75 deg relative to the root it would definitely seem too much.
There is always more to learn or fully understand.
Congratulations on a model that flies a well as it looks.

John
Logged
flydean1
Gold Member
*****

Kudos: 20
Offline Offline

United States United States

Posts: 980



Ignore
« Reply #67 on: July 02, 2019, 10:05:11 PM »

Thanks for resisting the temptation to try to cure all problems by adding nose weight.  If you have to put in a lot of downthrust, the CG is too far forward.  It looks like you pretty well have it ironed out.

It is also an extremely well done model.
Logged
MKelly
Gold Member
*****

Kudos: 86
Online Online

United States United States

Posts: 880


Topic starter


Ignore
« Reply #68 on: July 03, 2019, 06:15:48 PM »

Thanks for all the kind words.

Crabby, here's a pic showing the post-trimming stab position.  I measured the incidences this afternoon, the stab is 2 deg negative compared to the root rib (about 2 deg positive compared to the average chord).  I noticed that the stab is starting to warp - going to have to do something about that...

Flydean, I did end up adding a pinch or two of clay (less than a gram) up front during glide trimming because the model started getting twitchy as I decreased the stab incidence.

The magnets to hold on the wings weren't giving me much confidence, so I spot-glued the wings on for trimming.  Still undecided whether to stay with that or retrofit a more rigid system than the two carbon rods.

Cheers,

Mike

Attached files Thumbnail(s):
Re: Rockytop Stahl Spitfire
Logged
DHnut
Gold Member
*****

Kudos: 14
Offline Offline

New Zealand New Zealand

Posts: 657



Ignore
« Reply #69 on: July 03, 2019, 06:41:25 PM »

Mike
Logged
DHnut
Gold Member
*****

Kudos: 14
Offline Offline

New Zealand New Zealand

Posts: 657



Ignore
« Reply #70 on: July 03, 2019, 06:49:40 PM »

Mike,
        Not sure what happened the post just vanished. The incidence difference is surely within the normal range and the model is flying. Perhaps the washout is working very well as it did on the original. I have used magnets on a FW190D and the reason it is still in one piece is that the wing was able to seperate when it arrived, which it did far to often. I am doing a larger version using the same approach. I use a short peg in the leading edge with one or two magnets on the trailing edge and locators on the side that to provide alignment.
   Ricky
Logged
TheLurker
Gold Member
*****

Kudos: 24
Offline Offline

United Kingdom United Kingdom

Posts: 743




Ignore
« Reply #71 on: July 04, 2019, 02:19:59 PM »

Great job.
+1
Logged
ironmike
Platinum Member
******

Kudos: 87
Offline Offline

United States United States

Posts: 1,131



Ignore
« Reply #72 on: July 05, 2019, 10:51:50 AM »

No biggie on the stab warp.
It will finally settle in, just may need to tweak the trim if flight gets affected.
I ve had many models with stab warps, I just re trim.
Logged
MKelly
Gold Member
*****

Kudos: 86
Online Online

United States United States

Posts: 880


Topic starter


Ignore
« Reply #73 on: July 28, 2019, 11:20:11 AM »

Took the Spitfire to Geneseo for the FAC Non-Nats and flew it in FAC Rubber Scale and the Battle of Britain Mass Launch.  Very pleased with how it flew, especially since I'd only had the one low-power trimming session and the model had been heat-cycled in the back of the pickup for 10 days prior to the meet.  Flew it on 4x33" loops of 1/8" rubber (22g, about 23% of flying weight) - given the performance shown I think it should easily take 36" or maybe 40" loops giving somewhat longer flights.  

Video at:https://www.youtube.com/watch?v=vJqAD4qcINU&feature=youtu.be

Ratz, this can be moved to the completed builds section.

Mike
Attached files Thumbnail(s):
Re: Rockytop Stahl Spitfire
Re: Rockytop Stahl Spitfire
Re: Rockytop Stahl Spitfire
Logged
Don McLellan
Titanium Member
*******

Kudos: 63
Offline Offline

Canada Canada

Posts: 2,387




Ignore
« Reply #74 on: July 28, 2019, 01:30:31 PM »

Nice flights Mike!
Logged
Pages: 1 2 [3] 4   Go Up
Print
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.21 | SMF © 2015, Simple Machines Valid XHTML 1.0! Valid CSS!