RE: P-51 Take off Tips  
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RE: P-51 Take off Tips - 6/13/2008 1:47:11 AM   
prop wash



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Joined: 1/1/2003
From: Griffith, IN, USA
Status: offline 		Sub,thats the way it's supposed to be done, not mod the plane. Tom

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RE: P-51 Take off Tips - 6/13/2008 3:31:08 AM   
KentuckyColonel



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Joined: 4/20/2007
From: Mission Viejo, CA, USA
Status: online 		True enough, but look at a real P-51 and then again at some ARF's. They often lack the correct angle of attack to the gear leaving them well behind where they should be. A simple shim can correct this. Having said that, I also agree that knowing how your plane acts and knowing how to make corrections during the take off run are vital aspects of flying an RC plane.

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RE: P-51 Take off Tips - 6/13/2008 5:22:18 AM   
Rip n Bank


 

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quote:

ORIGINAL: timothy thompson

are your wheels rolling easy? they should spin on the axles. add oil or drill out very slightly on a drill press the axle holes. Make them straight


Good point, Timothy. I was scanning down the thread to see if this had been mentioned.

Excessive rolling friction is often overlooked as a reason for tail-dragger nose-overs on take-off. Also, too much toe-in will create enough rolling friction (even if the individual wheels turn freely) to cause a nose-over.

This being said, I'm also in favor of SLIGHT shimming to move the extended gear axle location about 1/4" further forward from the "stock" location on certain models. My H9 Marie needs it, my H9 1.50 Frankie doesn't...

Rip

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RE: P-51 Take off Tips - 6/13/2008 2:51:23 PM   
Larry S



Posts: 443
Joined: 3/3/2004
From: Manteno, IL, USA
Status: offline 		I believe in shimming the gear also but the type of field will sometimes dictate whether that should be done. As an example, my flying field is grass where you have a lot of drag, especially when the grass is tall. Add wet conditions and the drag is greater. Yesterday I went out to our field to maiden a TF Spitfire. The grass was tall and wet and I had a hard time just taxing out. We have a paved runway but the wind was coming off the side of the runway so I didn't have much room to get airspeed. When I reached the grass, the plane started to nose over so I gave it up elevator and sorry to say, to much and it snapped, completely destroying the plane. Had the gear been shimmed more then I had it, I believe it would be still around today. I could have at lease started my runoff on the grass and compensated for the drag. Damn thing is, I know better. All of my warbirds have the axle at least even to the leading edge of the wing, the Spit was about two inches behind. On a paved surface, it was fine but on grass, it wasn't.
Larry

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RE: P-51 Take off Tips - 6/13/2008 4:46:56 PM   
US185Damiani



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Joined: 3/29/2002
From: Danville, PA, USA
Status: offline 		Shim the Gear,
It will help ground handling. Look at this profile shot of a real P-51, the gear is definitely canted forward.
Also add larger wheels. The foam wheels supplied with these arfs are usually too soft and stub the nose.

Learned the hard way on this one.
good luck and have fun with it.

Mike

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< Message edited by US185Damiani -- 6/13/2008 4:55:41 PM >

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RE: P-51 Take off Tips - 6/13/2008 5:11:40 PM   
paladin


 

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Status: offline 		Actually the angle of the gear is good on most ARF’s the problem is that its leaving the wing half a D section back from where it should be. As a general rule, that means I set up this way for a grass field, all main axles want to be directly under the LE of the wing when the plane is level (like in Mike’s pic).

Joe




< Message edited by paladin -- 6/13/2008 5:12:20 PM >

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RE: P-51 Take off Tips - 6/14/2008 2:06:46 PM   
Larry S



Posts: 443
Joined: 3/3/2004
From: Manteno, IL, USA
Status: offline 		Great advice Joe,
That is usually the way I set my planes up. On the Top Flight kit they had the retracts located behind the main spar and even then I had the retracts shimmed forward more then what the plans called for but it still wasn't enough. After the crash, checking the wing I saw that I could have located the retracts in front of the spars and had the axles even or in front of the leading edge. Is it scale? Nope, but I would be better off with a good ground handling plane then a wrecked scale one. Remember, I'm speaking of the TF Spitfire but I do fly a P 51 set up with the axles even with the leading edge and it handles nice on grass fields.
Larry

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RE: P-51 Take off Tips - 6/14/2008 9:11:14 PM   
paladin


 

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Status: offline 		Larry, If you are building the plain you have the opportunity to do it right. Break out your trig book from high school. You can measure on the plans the distance from the center of the retract(where the strut comes into it) to the leading edge, you know the strut length. So figure out how far into the wing the forward mount needs to be moved.
Or
On the plans where they show the retract mounts Draw the line perpendicular to the wing cord that you want the wheel axle on. Lay the retracts on the plans with the wheel axle on the line we just drew, then put the aft retract ear on the aft mount on the plans. Mark the location of the ears then draw in the best size maple you have available and now you have the correct mount angle. Notice the front mount has moved into the wing. We add shims to ARF’s because removing hard points is an ugly process.

I hope this is understandable.

Joe


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RE: P-51 Take off Tips - 6/16/2008 4:06:21 AM   
Larry S



Posts: 443
Joined: 3/3/2004
From: Manteno, IL, USA
Status: offline 		Joe,
I understand what you are saying. Normally I would do something like that. The only problem on the Top Flite kit is where the upper and lower main spar is located. There was roon to mount the retract ahead of the spar but not enough room for the wheel. What I did not do and should have done was go ahead and mount my retract between the leading edge and spar, then build a frame around the wheel opening connecting the ends of the bottom spar. I have a Pica FW 190 and had problems with those retracts until I shimmed the gears BUT that kit had the location of the retracts and wheels between the leading edge and spars. But also here is what I found by shimming the gears even or ahead of the leading edge, it takes more speed to raise the tail while the plane is still on the ground which is exactly what we want for take offs on our warbirds. As I said, if I had been flying off of pavement or very short dry grass, I would have been all right where Top Flite has the gears on the Spitfire but that isn't always the case with my field. As much as I hated doing it, I ordered a 120 size Spitfire ARF. My plan is to mount the gear as far forward as possible, shim the gears so the axles are at least even with the leading edge and hopefully have room between the spar and leading edge for the wheels. If there isn't room, I'll make room.
Larry

< Message edited by Larry S -- 6/16/2008 4:08:45 AM >

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RE: P-51 Take off Tips - 6/16/2008 8:47:54 AM   
JET FX



Posts: 1532
Joined: 1/20/2002
From: Sydney, , AUSTRALIA
Status: offline 		Lots of good tips here.... Maybe also consider larger diamater wheels, ideally the wheel axle centres should be as close as practical lining up with wing leading edge (note full scale P-51 pic above) it will also mean moding the wheel wells! but larger wheels and slight shiming "forward" should make a big difference. Funtional oleo struts such as from Robart would also help the matter.

Add power very "gradually" while holding full back stick and ease off elevator only when approaching flying speeds.... It comes with practice for sure and is applicable to all taildragger warbirds.

Cheers- Marty

< Message edited by JET FX -- 6/16/2008 8:49:14 AM >

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