nacelle design
08-07-2003, 01:56 AM
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nacelle design
Dave:
Build a box with thick balsa and round the edges. The thicker the blocks, the more rounding you can do. Also, triangular stock in the corners will allow more rounding without extremely thick balsa.
Finally, you can use round formers and plank the surface.
Or any combination. Slab sides and formers top and bottom, so forth.
Picture attached is the bottom of the right nacelle on the Tiggerkitty, it has planked former construction.
Bill.
Build a box with thick balsa and round the edges. The thicker the blocks, the more rounding you can do. Also, triangular stock in the corners will allow more rounding without extremely thick balsa.
Finally, you can use round formers and plank the surface.
Or any combination. Slab sides and formers top and bottom, so forth.
Picture attached is the bottom of the right nacelle on the Tiggerkitty, it has planked former construction.
Bill.
08-07-2003, 03:10 AM
#5
nacelle design
William; the tiger kitty looks pretty good, for simplicity I will go with rounded corners. What area within the nacelle does a person need ply besides the firewall of coarse. I was thinking about installing two 1/16 ply half ribs from the leading edge to the spar located where the sides of the nacelle will slide over the wing also the nacelle itself built out of 1/8 ply sides with balsa top and bottom. this is what I have thought of mainly after research in this forum and by years of building experience please add any comments.
08-07-2003, 03:45 AM
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nacelle design
Dave:
Thanks for the comment on the Tiggerkitty. I call the blue and white one the C3/10, as I think it looks about three tenths like a Cessna 310. It is a bashed HobbiStar 60. The Tiggerkitty is scratch built.
You will not need the ply half ribs, if the wing is sheeted beyond the nacelles. The nacelle sides should be, for 30 engines, minimum 1/16"ply doublers inside minimum 1/8" balsa sides. The ply doublers should run from the firewalls back to the main spar in the wing. Use tri-stock to reinforce the joint between the firewall and the ply doublers.
Decide how much fuel you want to carry, get the tanks, and make the nacelles an appropriate size to hold them. The tanks, more than anything else, will dictate the nacelle size. Dont forget room for foam around the tanks, and the throttle push rods.
The C3/10 has pumped engines, the fuel tank (one) is in the main fuselage, with two clunks, one for each engine.
If you would like some "Professional" advice, (from Dave Platt) go into my gallery. The entire text of the instructions for the Duellist 2/40 is there, and the final design for the wing and nacelles for the latest Duellist version, the 2/15, is the very first image. Might get some ideas.
Bill.
Thanks for the comment on the Tiggerkitty. I call the blue and white one the C3/10, as I think it looks about three tenths like a Cessna 310. It is a bashed HobbiStar 60. The Tiggerkitty is scratch built.
You will not need the ply half ribs, if the wing is sheeted beyond the nacelles. The nacelle sides should be, for 30 engines, minimum 1/16"ply doublers inside minimum 1/8" balsa sides. The ply doublers should run from the firewalls back to the main spar in the wing. Use tri-stock to reinforce the joint between the firewall and the ply doublers.
Decide how much fuel you want to carry, get the tanks, and make the nacelles an appropriate size to hold them. The tanks, more than anything else, will dictate the nacelle size. Dont forget room for foam around the tanks, and the throttle push rods.
The C3/10 has pumped engines, the fuel tank (one) is in the main fuselage, with two clunks, one for each engine.
If you would like some "Professional" advice, (from Dave Platt) go into my gallery. The entire text of the instructions for the Duellist 2/40 is there, and the final design for the wing and nacelles for the latest Duellist version, the 2/15, is the very first image. Might get some ideas.
Bill.
08-07-2003, 06:57 PM
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nacelle design
Dave,
Here's another pic of a rounded box nacelle.
It houses a 46, but the methods are similar to what Mr Robison outlined. It is a Duellist 2/40
If you can mount your engines sidways with the mufflers on the bottom, you can achieve a relatively nice clean look. Inverted would be better, but could also introduce other operational problems.
cheers,
-E
Here's another pic of a rounded box nacelle.
It houses a 46, but the methods are similar to what Mr Robison outlined. It is a Duellist 2/40
If you can mount your engines sidways with the mufflers on the bottom, you can achieve a relatively nice clean look. Inverted would be better, but could also introduce other operational problems.
cheers,
-E
08-07-2003, 07:25 PM
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nacelle design
dalolyn:
mucksmear is being much too modest in posting only that one view. The pictured airplane is a highly modified Duellist, you might have a problem seeing the Duellist under his bash if he didn't tell you. Check it out here:
http://www.elliotfan.com/temp/duelist.html
Muck, I go back and look at it again every now and then, it just doesn't get old.
Bill.
mucksmear is being much too modest in posting only that one view. The pictured airplane is a highly modified Duellist, you might have a problem seeing the Duellist under his bash if he didn't tell you. Check it out here:
http://www.elliotfan.com/temp/duelist.html
Muck, I go back and look at it again every now and then, it just doesn't get old.
Bill.
08-07-2003, 07:42 PM
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King Air
Hi Bill,
I'm afraid the King Air is several months away. I've been sidetracked for the last several months, and am just getting back to it now.
Updates are always on my site. Thanks.
I'm afraid the King Air is several months away. I've been sidetracked for the last several months, and am just getting back to it now.
Updates are always on my site. Thanks.
08-07-2003, 09:43 PM
#14
nacelle design
nice airplanes guys although this is not my first this is my first twin trying to keep it as simple as possible I thing I'm going to laminate 1/8 " balsa to 1/16" ply for the sides and use 1/4" balsa for the top and bottam so I willkinda have a oval top with flat sides my dream is to build a 100" span p-38 someday
08-08-2003, 05:10 AM
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nacelle design
sounds good dalolyn.
If you like, instead of 1/8 sides and 1/4 top, increase the balsa thicknesses to 3/16 or 1/4 sides and 3/8 or 1/2 top - or some combination thereof, and you'll be able to get a real nice rounded form. Just as simple either way.
Post some pics when your done!
cheers,
-E
If you like, instead of 1/8 sides and 1/4 top, increase the balsa thicknesses to 3/16 or 1/4 sides and 3/8 or 1/2 top - or some combination thereof, and you'll be able to get a real nice rounded form. Just as simple either way.
Post some pics when your done!
cheers,
-E
08-08-2003, 11:13 AM
#16
nacelle design
that sounds about right after I drew it out I relized I wanted more thickness to get the rounded effect I am after thanks.I will send some pics. might be this winter though I have my tanks, mounts, and pushrods need engines and radio gear
08-08-2003, 10:52 PM
#17
nacelle design
I am getting nervous thinking about flying a twin even though its going to be a little while. I am trying to get everything right .there is nothing like building a kit or from scratch and not have to trim more than a couple of clicks on the first flight. I was going to put 3 degrees right thrust on the right engine and 1 degree on the left does this sound about right? no down thrust this plane is designed after a sr falcon I have the Plans and Kitted everything else. Added more rudder and the fuse lost a lot of weight by design I am sure I will come in about 6lbs or less I hope.
08-08-2003, 11:16 PM
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Dave:
You will get one person saying out thrust is good, the next will say it's a bad idea, and the next will say it doesn't matter.
My very first twin, the Tiggerkitty in my avatar, was built with 3 degrees out in the right engine and the left at 0 degrees. Both engines are at zero up and down. It works fine, and if you want to use out thrust it's all right. But all I've built since have been both engines 0-0 side and up/down.
Rudder authority is far more effective and important in flying engine out. If you go back and look at the Tiggerkitty you'll see the vertical area is far greater than scale, I went a lot bigger than I needed to. But VMC is just barely above stall speed as a result.
On the C 3/10 I didn't quite go big enough, if I ever redo the tail the rudder will get a one inch extension. It is still stock Hobbistar 60, down to the covering which I've never replaced.
So in your scratch design, draw the rudder to look right, then add 3/4-1" to the chord. You'll be fine.
If you want out thrust, do it. It will cut your speed a little because the two engines will be pulling against each other by the same amount, but you'll never notice it. And if it makes you more comfortable it's worth it. Set the engines on your next one dead away. If I were doing the Tiggerkitty now they would be dead away also.
Bill.
You will get one person saying out thrust is good, the next will say it's a bad idea, and the next will say it doesn't matter.
My very first twin, the Tiggerkitty in my avatar, was built with 3 degrees out in the right engine and the left at 0 degrees. Both engines are at zero up and down. It works fine, and if you want to use out thrust it's all right. But all I've built since have been both engines 0-0 side and up/down.
Rudder authority is far more effective and important in flying engine out. If you go back and look at the Tiggerkitty you'll see the vertical area is far greater than scale, I went a lot bigger than I needed to. But VMC is just barely above stall speed as a result.
On the C 3/10 I didn't quite go big enough, if I ever redo the tail the rudder will get a one inch extension. It is still stock Hobbistar 60, down to the covering which I've never replaced.
So in your scratch design, draw the rudder to look right, then add 3/4-1" to the chord. You'll be fine.
If you want out thrust, do it. It will cut your speed a little because the two engines will be pulling against each other by the same amount, but you'll never notice it. And if it makes you more comfortable it's worth it. Set the engines on your next one dead away. If I were doing the Tiggerkitty now they would be dead away also.
Bill.
