Reaction 54 Jet Kit
#3935
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aft cg in addition to make your plane more responsive, save some fuel also
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Because a lot of people read this thread and they maybe don't know why "aft cg save fuel", I give the short explanation for those who want to know.
The stab produce a NEGATIVE lift to counteract the effect of the distance betwwen the cg and the wing "lift centrum". If you move the cg more backward, the distance is less, meaning the negative lift generated by the stab to counteract the effect is less. Then the wing have to produce less lift ( the total lift the wing has to produce is the sum of the weight and the negative lift of the stab). If the wing has to produce less lift , it produce less drag. Meaning you save fuel........
I admit that in the case of rc jet , the difference is very small, but in airliners that's something we take care off to reduce trip fuel
because of my bad knowledge of english you maybe don't understand my short explanation, in that case just type " aft cg save fuel" on google and you will have the explanation in your mother langage
Last edited by SALMONBUG; 05-02-2018 at 01:01 AM.
#3937
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My decision to move the cg a bit backward is definitly NOT a attempt to correct the pitch changes induced by turbine trust management. If I move the CG a bit backward , it's to have a more responsive airplane. The effect of moving the CG backward will make the airplane more sensitive to pitch change induced by turbine ( if there is one) in my opinion
When you decide to move a CG backward, be carrefull and proceed with several step by step tuning, because this change the airplane behaviours
So my suggestion to tune your R54 to your particular taste is to proceed like that
1) set the turbine tilt to stock position and the cg in the middle of the cg margin for the first flights
2) tune your CG to make the airplane matching your particular taste and skills ( I suggest to remain in front of the aft cg limit)
3) finaly make the turbine tilt correction if required
This is only my opinion and maybe Bruce should knock a the door to give his opinion on the subject
I'll let you know the correction I will apply on the turbine tilt if I make one. The nose down effect I felt was so small that it need to be confirmed after some other flights before I decide to put one or two washers to correct it
Last edited by SALMONBUG; 05-02-2018 at 09:43 AM.
#3938
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Here is a view of my finished inside setup. In order to remain in the "adfordableé" philosophy of the design I solved my need of 10 chanels ( i like to have all the elements on a separate channel) by making a twin receiver setup instead of serial bus or powerbox system.
The "front receiver is in charge of everithing except the gear stuffs. The second receiver is in charge of gear extension control, brake and steering.
I made a effort to separate gear and brake power supply from the main power suply ( just in case) and as you can see there is a connection to place a second lipo in parallel with the ecu lipo during start.
each receiver is fit inside a homemade 3D printed receiver case.
the two wood plate in the front are there to hold batteries firmly in place. Because I turned without lead I need to be able to move my batteries easily to modify cg, those two bolted wood parts hold them in place
I consider this setup reliable, but Of course I have what I consider to be a weak point. Either the ecu and pump "floor" is held in place with six screws, a steering servo issue would be extremely anoying and would require to disconect nearly everithing.....
The "front receiver is in charge of everithing except the gear stuffs. The second receiver is in charge of gear extension control, brake and steering.
I made a effort to separate gear and brake power supply from the main power suply ( just in case) and as you can see there is a connection to place a second lipo in parallel with the ecu lipo during start.
each receiver is fit inside a homemade 3D printed receiver case.
the two wood plate in the front are there to hold batteries firmly in place. Because I turned without lead I need to be able to move my batteries easily to modify cg, those two bolted wood parts hold them in place
I consider this setup reliable, but Of course I have what I consider to be a weak point. Either the ecu and pump "floor" is held in place with six screws, a steering servo issue would be extremely anoying and would require to disconect nearly everithing.....
![](https://cimg1.ibsrv.net/gimg/www.rcuniverse.com-vbulletin/2000x1504/img_0328_c066dfce08fe698fd8002e174c5a3ada1e4474ee.jpg)
Last edited by SALMONBUG; 05-02-2018 at 06:27 AM.
#3940
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same here in belgium, hot temperature, and too much pollen in the air. Yesterday I let my car on a parking outside for 4 hours and when I came back it was literaly green from pollen dust. I suffer asthma and it's really not a good period for me
Last edited by SALMONBUG; 05-02-2018 at 09:56 PM.
#3943
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Joe, I strongly recommend balancing in the forward half (6" to 6.5") of the balance range for first flights. The R54 is okay back to 7", and in normal flight I don't think you would feel much of a difference. But I have sensed a bit of twitchiness/sensitivity on landing approaches with the CG at the aft end of the balance range. The approach feels much more solid with a forward CG. Add the weight and don't worry about it. Make it removable so you can experiment later by pulling some weight out if you wish.
Joe
#3947
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I will share what hapened to me with this particular building. I builded my first wing with the booklet next to me and made a good wing. For the scond wing I decided to go a bit faster. I placed the parts in the assembly order on a table and jumped in the building leaving the booklet in a corner of the shop. I was extremely proud of this second wing panel looking even better than the first one. When I cleaned the aera I found laying under the parts table............ The balsa wing dowel block glued to his hardwood partial rib. AAAAAAARGGGGGGGhhhhhhh
A delicate surgery on the wing sheeting has been mandatory to place it.........
A delicate surgery on the wing sheeting has been mandatory to place it.........
#3948
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I'm glad you got it fix, that's the beauty of building a balsa wood airplane, you can fix, change, add, modified all you want.
My build is not perfect, I've made about 4 mistakes so far, nothing critical and they got fix, I keep saying, the next Reaction build is going to be flawless.
My build is not perfect, I've made about 4 mistakes so far, nothing critical and they got fix, I keep saying, the next Reaction build is going to be flawless.
Last edited by CARS II; 05-03-2018 at 08:58 AM.