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FH Hawk 900 (First plan)

#1
Hiya,
I've drawn up some plans for a mini foamie I plan to cut out of two 400x900x8mm sheets of EPP. I've squeezed in almost every square centimeter of plane I could possibly use from the foam I have available since it's $12.50 a sheet plus shipping.
The wingspan will be just about 900mm and the nose to tail length will be 630mm. Everything is made of layered, glued, and shaped EPP template cutouts. A 3mm fibreglass spar will span the wing. Wing is a single assembly with no mid join. I will use bamboo skewers and toothpicks to reinforce the entire wing, all control surfaces and pin the fuselage together. Since the wings are made of three layers to create an airfoil shape, it is possible to conceal reinforcement between layers. I may use a triangular latticework of glued toothpicks as internal reinforcement for the fuselage electronics cavity, as I have tried making a small 'tower crane' style tube of toothpicks and found their stability impressive.
Control surfaces are flaps, ailerons, elevator and twin rudders. I have not yet ordered servos but my idea is for all the surfaces to be using HXT or Turnigy 9g servos except for the rudders, which because of their split duty and tiny area will use 5g HXT micro servos to save the tail from the extra weight and form disruption.
The things I am not entirely confident about are: The size/areas of the control surfaces, the stability of the fuselage and my biggest one which is the shape of the wing airfoil. The airfoil tapers towards the wingtips. I am not sure whether this is a good idea, but I am considering reducing the area across which the tapering occurs (i.e. make a sharper bevel). Obviously I have created an ostentatious, visually appealing hawk-wing form. I expect this to complicate and potentially hinder the performance, but if I wanted a conventional shaped plane I would order one from hobby king and save myself some money, after all. This is my primary indulgence.
Almost needless to say, I will sand down the sharp 'steps' of the wing layers to form a smooth airfoil and shape the corners of the fuselage into an aerodynamic tube. In the plans you can see I have left openings in the fuselage layers for the purposes of wing insertion, tail insertion and installation of the electronics.
I am replacing my Bixler 2's motor with a more powerful 1800kv NTM Prop Drive so I will have a Bixler 2 stock motor spare. I am also purchasing a Dynamic-S which by popular consensus, has an underpowered ESC for a motor of its calibre. As such, I will replace the Dyn.-S ESC with a 30A plush and salvage the stock ESC for the FH Hawk scratch build.
Since the aircraft will be significantly smaller and, in theory, consequently lighter than the Bixler 2, this motor should provide more than sufficient thrust.
Please tell me what you think of the whole thing and give me some constructive criticism if I need it. This is my first scratch build plan, so my overconfident beginner's naïveté (and the fact that I drew these from 11pm to 2am in a furor of creativity and sleep deprivation) will probably be visible.
One particular question I would like some advice on is whether I could get away with using entirely 5g servos. Thanks :D
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HIGH RES PLAN IMAGES:
https://dl.dropboxusercontent.com/u/25803839/DSC02695.JPG < Wing sheet
https://dl.dropboxusercontent.com/u/25803839/DSC02696.JPG < Fuse sheet
https://dl.dropboxusercontent.com/u/25803839/DSC02697.JPG < Finished projection
 
Last edited:

pgerts

Old age member
Mentor
#2
Good Looking!
The rudder areas are small - i think that you can use the HXT 500 to all surfaces as they are used to indoor models with a lot larger surfaces and the weight of the foam is almost nothing until you fill it with glue ;-)
 
#3
Thanks :) I realised that as I will end up with two big, high power glider type planes, I might as well go for small and aerobatic with this one, so I'll increase the control surface sizes, scrap the flaps and the third wing layer. 5g servos all round.
 
#4
Resketched the plane with smaller overall size and bigger control surfaces. Made a paper mock up of it. Seems to all work well, just need the foam to make it now :D
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