Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Think I can do it? Magnum with retracts

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Old 02-15-2006, 10:58 AM
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erikpmort
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Default Think I can do it? Magnum with retracts

Hey guys i was bored last night, and i have no projects lately so I pulled my slightly busted up magnum (engine died after hand launch, busted up the front of the airplane only) and started ripping the covering off and rebuilding the front of the fuse.... i was suprised how far i got, and I think i'll have the wood rebuilding part finished today! I want to recover the whole thing and try to do retracts, but i need some advice as this will be my first retracts project... i think the nose gear will be no problem, but i'm still thinking about how to do the main retracts with those skinny wings.... any suggestions on what type or brand i should use? I'm going to go check out my lhs's inventory of retracts today and try to find some.... What do you think, can i do it? Its a pretty small plane... it will add weight, but i'm not in it for pure speed, and i got so sick of hand launching... and i hate fixed gear on an airplane that looks like this, it would just ruin it to me. So here we go


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Old 02-15-2006, 01:07 PM
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Default RE: Think I can do it? Magnum with retracts

oh and if anyone had some small mech. retracts for sale i'd be interested

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Old 02-16-2006, 01:45 AM
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Default RE: Think I can do it? Magnum with retracts

That wing I believe is only 1/2" thick at the thickest point (been a while since I looked at my magnum). The ONLY method you'll make work is if you built some massive blisters on the top of the wing, or built an under wing pod like the A4 skyhawk had. You're at a disadvantage in that if you did find small enough retracts to fit in the wing or at least relatively close to it, they will probably not be strong enough for the weight of the magnum never mind the speeds it lands at. Even putting a fixed gear in that airplane is difficult to do strongly, You're going to have a hard time even finding wheels that would fit into that wing with a wire gear, if you use 3/16" wire (which would be very small and probably bend easily at landing speeds) and a pylon racing wheel (which is still 1/4" thick at the axel portion) by the time you have the radius'd bend in the wire you're going to be at the VERY least 1/2" thick in the wheel and wire alone assuming you make a VERY tight bend and solder a washer on to retain the wheel. There are narrower wheels out there, but they're for park fliers and the like, I suppose you could machine some aluminum ones to 1/8" thick, but if you're going to go to that trouble you'd be just as far ahead to put a fixed gear on there since the drag from an open wheel bay is going to be the same if not more than a very narrow wheel with wire gear.
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Old 02-16-2006, 11:17 AM
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Default RE: Think I can do it? Magnum with retracts

By the way, there is no room with the fuel tank in there for a nose gear retract.
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Old 02-16-2006, 11:21 AM
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Default RE: Think I can do it? Magnum with retracts

yeah, its looking tough... i looked at some basic hobbico retracts yesterday, and the problem i see right now is the retract wire (that the servo pushes in and out) sticks out right where the wing is.... i would have to bend a Z in it and run it along the bottom of the wing.... anyway it does seem tough, but i'm going to look at a few other retracts and see if i can get any other ideas. With the nose retract, i have to run a retract servo, and a seperate servo to steer, right? those jr 331's looked like they could do the job... really small and have 43 ish oz torque.
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Old 02-16-2006, 11:48 AM
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Default RE: Think I can do it? Magnum with retracts

May be easier, but not as nice looking, to go with a taildragger design. I don't know though... don't own one (although I'd really like to!!)
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Old 02-16-2006, 11:50 AM
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Default RE: Think I can do it? Magnum with retracts

so I went and did some reading, and it sounds like most guys all up weight was 3-4 pounds... so if i used a .32 and small servos/reciever, think i could get between 2-3? robart has these small retracts that are for 2 lb models, but i don't know if they'd be strong enough... they're really small though.
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Old 02-16-2006, 04:40 PM
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Default RE: Think I can do it? Magnum with retracts

yeah i've thought about taildragger... i'd have to fix the rudder and do another servo anyway (cause it doesn't have rudder) so i figure one extra servo for nose isn't that big of a deal... a little more weight but not much.... the mains are the real problem right now anyway...
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Old 02-17-2006, 12:31 AM
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Default RE: Think I can do it? Magnum with retracts

a 32 and small receiver probably won't get rid of a pound, even if it did, those retracts designed for 2lb planes will not take the loads of a magnum. The plane lands at a very high speed. Anything but the most perfect of landing on the smoothest surface will rip them out. I just don't think you'll find a retract anywhere close to fitting in the thickness of that wing and doing a solid mount. But hey, if you can prove me wrong, awesome, I'd just hate to see you cut up a plane only to find it won't work. I can't see ANY way a nose gear will fit with wheel retracted in that bird, the tank takes up to much room. Add in retracts and servo's and you're going to add back the extra pound you might save anyway. And as I say, the drag of a retract well is going to be more than if you put on a wire gear with thin pylon wheels. JMO though
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Old 02-17-2006, 12:38 PM
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Default RE: Think I can do it? Magnum with retracts

i found some .30 size retracts made by hobby lobby, and i was thinking of removing some foam underneath and installing some good wood to secure the retracts in... they're an inch deep, but i was thinking i could take a balsa block and smooth it up to make an airfoil type shape in front of the extra part of the retract that stuck out.... anyway i think i'm going to try it.... call me crazy
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Old 02-19-2006, 02:07 PM
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Default RE: Think I can do it? Magnum with retracts

better off making a take off dolly. Thats what I use for my magnum . No extra weight and a clean take off.

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Old 02-21-2006, 12:54 AM
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Default RE: Think I can do it? Magnum with retracts

If you're still set on doing this, I think your best bet would be to use a set of FAI retracts from Lyle Larson. They can be found here:
http://www.calspeedpros.com/access.htm

I still think the biggest problem you'll have is a strong mount in the wing without losing any of the wings structure.
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Old 02-21-2006, 12:04 PM
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Default RE: Think I can do it? Magnum with retracts

thanks for all the help. are the fai retracts just mains or do they include the nose too for 60$?
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Old 02-21-2006, 12:07 PM
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Default RE: Think I can do it? Magnum with retracts

ah it looks like they are just mains, but they do look very small.... i emailed him for more info
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Old 02-21-2006, 11:45 PM
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Default RE: Think I can do it? Magnum with retracts

H&M Racing sells them as well. You can get an idea of what they look like [link=http://www.hmracinginc.com/catalog.php?id=24]here.[/link]
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Old 02-22-2006, 12:27 AM
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Default RE: Think I can do it? Magnum with retracts

man the gear legs are expensive too! do you have to buy both, or can i just use wire? whats so special about them? i don't see any specs on size, or weight
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Old 02-23-2006, 11:33 AM
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Default RE: Think I can do it? Magnum with retracts

I'm not totally sure, but I think you need to use their legs too, I'm sure they're designed to work together. As for the nose, don't bother, you'll never get a wheel in there with the fuel tank, the wings will be close enough to impossible, but the nose I think is impossible unless you plan on using next to nothing for a tank. Don't forget, a nose retract needs provisions for a steering arm, wheel, length of the strut, all that stuff. I just brought my magnum back from home and got looking at it and I can't see retracts working in it. Not if you want to mount them flush. All you're doing is increasing weight and drag. But still, best of luck, if you can figure out a way then kudo's to you!
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Old 02-23-2006, 02:20 PM
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Default RE: Think I can do it? Magnum with retracts

mini servos and tank on the CG. it can be done, i just need to raise funds
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