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Making my RC Seaplane, where to place the motors

Old 12-14-2020, 02:41 AM
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makehobbyrc
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Question Making my RC Seaplane, where to place the motors

Hi, I have a question for my RC Foam seaplane...: is their any better reason to put the DC motors (ducted fans) in front on the wing, or behind the wing? Concerning weight I think i'd rather place them in front (just in front ) of the wing, but is their any aerodynamic, or balance reasons to rather put them behind...? Thank!

They will be slightly above the CG, so they will give a nose down moment effect when accelerating (at least if they are placed in front the wing... I am not sure if they are placed behind...?) , I will try to put them as low as possible, but high enough from the water...
PS: i'll post pictures when I will be allowed to... after 10 posts
Thanks

Old 12-14-2020, 09:01 AM
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jester_s1
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Where to place motors depends on a lot of factors. The biggest one is how the affect the CG of the plane. Nose down or nose up effect depends on where they are in relation to your vertical center of drag rather than the vertical CG. The goal is to not have the create any pitch effect, which can be done by adjusting the thrustline. I'd think ducted fans would be pretty fragile when it comes to ingesting water, so putting them on top of the wings and a bit back would probably help quite a bit.
If you're new to the hobby, it would be smart to build a proven design first so that you can learn what works and how to create a good structure.
Old 12-15-2020, 12:50 AM
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Originally Posted by jester_s1
Where to place motors depends on a lot of factors. The biggest one is how the affect the CG of the plane. Nose down or nose up effect depends on where they are in relation to your vertical center of drag rather than the vertical CG. The goal is to not have the create any pitch effect, which can be done by adjusting the thrustline. I'd think ducted fans would be pretty fragile when it comes to ingesting water, so putting them on top of the wings and a bit back would probably help quite a bit.
If you're new to the hobby, it would be smart to build a proven design first so that you can learn what works and how to create a good structure.
Thanks, well I have already started a lot on this project so i didn't choose to make a proven design,.... which I might regret... but I am going on... but thanks for the tips, I didn't know about the Center of Drag. I really don't know if I should put the engines front or rear of the wing (they can either be ducted fans or propeller motors, I just received my 2 DC motors I can fit propellers to). But still this point remains on where I should place them... I shall have to see how much it affects the CG (maybe with the battery pack far in front, the motors at the back won't be that bad...) I will see...
Old 12-15-2020, 04:51 AM
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You didn't buy DF units already made? The motors are very different between the two. Seriously, look on Flite Test or Outerzone for some plans. That will prevent you from putting all this time and energy into it and then being disappointed.
Old 12-18-2020, 09:32 AM
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Originally Posted by jester_s1
You didn't buy DF units already made? The motors are very different between the two. Seriously, look on Flite Test or Outerzone for some plans. That will prevent you from putting all this time and energy into it and then being disappointed.
Yes I did my ducted fans are ready made... not with their ESC... I also bought 2 brushless motors I have received, and they might do the trick for this seaplane... I will see...

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