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Author Topic: P-30 Spitfire wing questions  (Read 4462 times)
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Crabby
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« Reply #125 on: July 29, 2019, 09:37:35 PM »

Hi Don, no my Spit did not survive my last heartless cold blooded purge. If I do another Spitfire it will be a version with a longer nose moment like the MK XXI(?) My Spit had lots of washout, downthrust and right thrust. I did get it flying somewhat, but jeez what a pain that plane was!
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flydean1
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« Reply #126 on: July 29, 2019, 10:43:17 PM »

I believe the MK XII was the clipped-wing version (anti-V1), the MK XIV the Fighter, and the MK XIX the Photo-Recon.

All 3 had the Griffon engine.  It required a longer nose, and a plug was inserted in the aft fuselage to compensate.  Also had a wider chord fin and rudder, all to handle the 2000+ horsepower.

The Griffon-engined Spitfires are my favorite.

If this is incorrect, I'm sure someone out there will chime in.
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OZPAF
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« Reply #127 on: July 31, 2019, 09:42:04 AM »

Good to see your P-30 Spit flying nicely. It looks like you will be doing a lot of chasing soon. Did you import all the KeilKraft grass from England? Smiley

John
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Crabby
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« Reply #128 on: July 31, 2019, 01:49:41 PM »

Is that where we got all the fire ants, snakes, and wild boar from?
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« Reply #129 on: August 01, 2019, 04:47:32 AM »

Possibly not the snakes! Grin we could give you some more if you are running out of them - but without KK grass Cheesy

John
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Crabby
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« Reply #130 on: August 03, 2019, 12:09:49 PM »

Before I head out to do anymore trim flights I decided it would be wise to rig up a DT for this plane. I have the viscous timer from Volare. I wrapped my mind around how the thing is supposed to work, but getting the right amount is tension between the timer and the stab is getting to be a bit of an art. Too much and you hurry the timer, too little and the timer won't rotate. I have a very strong rubber band holding the stab down, and it will snap up smartly when the pressure is off. I didn't think the spring supplied was gonna be strong enough so I have been using different strength rubber bands. So far I'm not there yet.
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Crabby
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« Reply #131 on: August 04, 2019, 10:34:28 AM »

Well not ever having to rig a DT before, I just realized the viscous timers must work better in a straight run to the stab. This epiphany arrived after a few hours in the morning, and a few hours in the evening of trial and error. I should have mounted the timer along the bottom of the plane. Instead, I dumbly mounted it where the plan shows the snuffer tube, which is not a straight shot to the stab. A snuffer/fuse setup would work fine if I wanted to light a fuse here in wildfire country. I doubt it is much to worry about but I don't want a wildfire even close to my screw up resume. Anyway, I was being a robot. Now for a source for springs. I found old acquaintance Alan Cohen on the web and he has plenty. Volare must be out of stock or quit selling 'em. Whatever. I could also wind my own which is another thing I have to buy, a spring winder. Whatever!  Roll Eyes
« Last Edit: August 04, 2019, 10:53:08 AM by Crabby » Logged

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« Reply #132 on: August 04, 2019, 08:47:18 PM »

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I have the viscous timer from Volare. I wrapped my mind around how the thing is supposed to work, but getting the right amount is tension between the timer and the stab is getting to be a bit of an art. Too much and you hurry the timer, too little and the timer won't rotate.

Are you using a capstan in the DT line between the timer and the tail  - the small peg shown in this article? By winding the line around the peg the friction helps to isolate the tension to hold the tail down from the line to the timer. The timer sees much reduced tension.

John
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Crabby
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« Reply #133 on: August 05, 2019, 08:25:24 AM »

Good am John, no I haven't tried the capstan yet, I am now awaiting more springs in the mail. I have plenty braided fishing line. This is a great article, I breezed through it a few nights ago but the brain wasn't absorbent enough to soak it up. It makes good sense, sewing thread is a pain to tie and was breaking, mono too springy, and the stuff I got from volare with the spring was braided I just didn't realize it. Simple gets harder everyday! Maybe I can try making some springs while I wait for the mail. This plane is a few winds short of flying away on me, flying without a DT is out. Meantime I have the wing for the FW-47 to cover. Another flyaway plane if I don't DT it!
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« Reply #134 on: August 06, 2019, 02:23:05 AM »

I'm sure you'll conquer this DT stuff Crabby. You wouldn't want a jar of Vegemite to carry you through all this brain labour? Grin

John
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« Reply #135 on: August 06, 2019, 10:58:24 PM »

Rob, stick some damn paper on that crate and bring it to the field.  We're waiting on you, buddy.  Smiley
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« Reply #136 on: August 07, 2019, 05:07:50 PM »

Crabby -

Congratulations on the successful trim flights of your Spitfire P-30.  Even at 55 grams, a P-30 can still be very competitive.

Learning how to properly set up a DT took me a number of tries until I mastered a few techniques.  I wanted to share them with you.  This is a long post but I hope that you, and others, will find it worth reading.
 
First, if you are going to use a viscous timer button you need to have a consistent pulling force.  Don’t use a rubber band or a piece of elastic line used in sewing. Use a good coil spring.  I buy mine from Stan Buddenbohm.  They are made from .009-inch music wire and are approximately 1 ¼-inches long, when unstretched.  See the attached photo.  I bought a tool from Volare Products for winding my own springs. I plan to learn how to use this tool once I use up the batch of 20 or so springs that I bought from Stan.

Second, use a non-stretch line such as Spiderwire that is apparently popular with fisherman. See the attached photo.  It warps nicely around a capstan to keep the TE of the stab from creeping up once you have the correct pulling force on the viscous timer.  I find that this force comes when the spring is initially stretched to about 2 ¼-inches in length when I use the large viscous timer button that used to be available from Volare Products.  

See the attached pictures of the DT set-up on my King Harry, which is representative of the overall layout of my typical DT system.  The single best piece of advice about setting up a DT is as follows.  Slide the Spiderwire through tiny segments of 1/16-inch or 3/32-inch Aluminum tubing and crimp the tubing when you have pulled the Spiderwire so that the spring is stretched the appropriate amount, e.g. 2 ¼-inches.  I used to try to tie tiny knots and was very frustrated in that I could not reliably achieve the correct amount of stretch of the spring.

Depending on the dimensions and configuration of the fuselage, you may use a tiny stub of a round toothpick for the capstan.  In the first picture of my King Harry you can see the toothpick capstan.  The Spiderwire is not wrapped around the capstan in this photo. In some cases, the Spiderwire can be wrapped a single loop around the motor peg.  Also, in some cases, the forward ends of the rubber bands that tilt the stab can be secured around the motor peg. This saves a little weight by not having a separate post and helps prevent the motor peg from inadvertently sliding out of the fuselage.  That will almost never happen if you reinforce the inside of the balsa wood motor peg mounts with 1/64-inch plywood panels pre-drilled to have the motor peg slide snugly through the same.
 
Here is another detail that is quite important.  As shown in the first picture of my King Harry with the stab down, I affix a tiny segment of black electrical wire insulation so that it wraps around the rear end of the fuselage. This insulation feeds the DT line to the lower portion of the TE of the fin.  The Copper wire has previously been removed from electric wire to provide this small flexible tube.  This tube is black in the picture of my King Harry with the stab down.  You can rough up the exterior of the wire insulation with an Emery board and glue it to the fuselage with CA.
 
I secured a small music wire hook so that it extends from the base of the TE of the fin in the case of the King Harry.  Normally this small hook extends from the TE of the stab in the center of the stab, but the King Harry has a V-shaped indent in the TE of the stab at this location. The rear end of the Spiderwire DT line is connected to the forward end of a segment of a very thin 6 pound test monofilament fishing line that feeds through the wire insulation. The rear end of the monofilament fishing line segment is tied to a small black O-ring which removably fits over the hook. This tiny O-ring is visible in the second picture of my King Harry with the stab popped up.  A small segment of Aluminum tubing is crimped over the monofilament fishing line segment that acts as a stop.  It hits the forward end of the wire insulation when the TE of the stab has pivoted upwards and the stab is extending at about a 45-degree angle relative to the thrust line.

The monofilament fishing line does not seem to stretch under the forces exerted on it in the DT set-up described above.  But it tends to retain a coiled shape if wrapped around a capstan and does not have the desired amount of friction when wrapped around a capstan.  Therefore, you need to use Spiderwire for the two front portions of the DT line and position the capstan so that the the aft one of the Spiderwire portions can be wrapped around the capstan, typically in a single loop.  You need to use monofilament fishing line for the rear portion of the DT line so that it can slide smoothly through a segment of small diameter wire insulation made from small- gauge insulated electric wire.

Make sure that the rubber bands pull on the stab with enough force to firmly pop it up.  You may need to put a tiny amount of light oil on the monofilament fishing line to ensure that it slides smoothly through the segment of wire insulation.
 
Viscous timer buttons do not always rotate at the same speed.  As the ambient temperature goes up, and/or as you rotate the arm of the button more and more, the viscosity of the fluid inside the button changes and the arm rotates more quickly when pulled with the same spring force.  Therefore, time a few test- runs of your DT system just before a competition flight to predetermine the “clock-face” starting position, e.g. 10:00 a.m., of the arm of the viscous timer button that will ensure that the stab does not pop up before your model has achieved a max.

Best of luck to you Crabby.  Please post another video of your Spitfire P-30 in flight, after installation of a DT on that model.  As we like to say, it shows a lot of promise in its trim flights!
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Re: P-30 Spitfire wing questions
« Last Edit: August 07, 2019, 05:27:23 PM by calgoddard » Logged
Crabby
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« Reply #137 on: August 08, 2019, 07:36:44 AM »

Good am Cal
Thanks for making the effort to get all that knowledge understandable in writing. Writing well is an art form I am still mastering. I am glad you put any idea of using rubber bands or elastics to rest. After a little searching I found Stan Buddenbohms address for more springs. The Volare spring winder is another gadjet that has my impulses aroused. The P-30 bug has bitten me and I just cleared the board for Applehoney's Ellipsis. I am lusting to build that pretty wing with the undercamber.

Back to the Spitfire though. As soon as I get my springs I will put this DT discipline into action and get back to the field for more test flights. I also noticed my AMA membership has lapsed. It has slipped down a few notches on my urgency meter since I hadn't felt the desire to compete (until lately) I lately don't see the point of building and flying without at least a bare modicum of sharing socially in friendly competitions. Thanks again Cal!
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« Reply #138 on: August 11, 2019, 03:54:21 PM »

Crabby -

Here is a link to a video illustrating the operation of my usual DT set-up as implemented on my Korda C Tractor:

https://www.youtube.com/watch?v=1y0X6Hvgkb0

Here is a link to a video of the beginning of a flight of my Korda C last June in a contest:

https://www.youtube.com/watch?v=A6cbyS8kJhc 

I believe this flight was a max.

I am looking forward to videos of more flights of your Spitfire P-30.
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Crabby
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« Reply #139 on: August 15, 2019, 01:29:08 PM »

Good afternoon comrades
As I mentioned earlier, I epoxied my timer per the plan, which intended to use a lit fuse and snuffer. I now want to run this cord from stab to timer in a straight run. So since I didn’t want to create drama by removing it, I bought another one from FAI. Does anyone know what this odd looking cord included with the new timer is used for? It seems too beefy and short for anything related to a dethermalizer!
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« Reply #140 on: August 15, 2019, 04:46:22 PM »

If it stretched when pulled it is for "powering" the timer.  A light spring is more reliable.
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