Experimental KFM 3D project.

[Hai-Lee]

I have a number od 3D aircraft including my latest addition a HK Mini Saturn which was gifted to me.

Whilst I do like the concept my thumbs are really old and hard to educate even though my brain knows all of the theory. Yes I manage to crash one from time to time still!

Anyway I was cruising through my library of FB designs and realised that I have not designed a profile 3D model as yet so this is my first attempt to come up with a working design.

Parameters/features. (Updated as the build progresses)
Wing Span: 800mm
Overall length: 800mm
All up weight:
Flight endurance in hover:
Motor/ESC/Prop:

Goals: Use FB for as much of the structure as possible without adding too much or any reinforcing.
No powerpod setup and therefore definitely not a swappable design.
Servos 3.7 or 5 gram - 3 of

Step one I have started collecting the largest offcut pieces of 5mm FB that I have, (Both new pieces and old pieces which have paper peeling or other surface imperfections).

This will be a spare time project so it will progress slowly especially where i strike an issue where the solution is not to my immediate liking.

Feel free to jump in with suggestions or questions!

Have fun!

 

[Hai-Lee]

Here the FB is rather heavy. From previous experiments it was noted that each layer of paper weighed approximately 30% of the weight of the same area sheet. Which means paper 30%, Foam 40%, paper 30%. In this build I will be removing as much of the paper as is possible and the external finish of the craft will be bare, (unsealed), foam except for hinge tape where fitted.

With the weight or the paper in mind I found 3 pieces of FB of suitable length and a width of around 150mm. These pieces will suffice for the fuselage. I just need to decide on the fuselage profile. Perhaps something similar to the HK Reaktor.

Anyway no time to be indecisive so I stripped the paper off of both sides of one of the pieces and from a single side on the 2 other fuselage pieces. Ready to start hacking out a rough profile design. Pic will be available soon but need to get more glue as this time I want a lighter and stronger/better glue than I used on the KFM wing finished earlier. The glue must also be able to secure the motor to the firewall in case the 1/16 ply does not have enough meat to hold the motor mounting screws permanently.

Fuselage lateral braces subject to the flexibility of the bare fuselage but if required will be made from paperless FB.

I had been worrying about the hinge makeup for the control surfaces and have convinced myself that the best option will be to use some fibre tape strips to make tape hinges.

Control horns will be home made from thin plastic from a take away food container or similar subject to material strength and weight. The elevator and rudder pull/pull control wires will be made from braided fishing line. Ailerons yet to be decided! Push rods (If any used) to be made from straightened paper clips.

The Battery, ESC, and Rx will be jam fits into the Fuselage cutouts. (Possibly locked in with a little Hotmelt excluding the ESC of course). Servos will also be jam fit with a little hotmelt to lock them in place. May include cutout for battery monitor/Alarm, (subject to weight).

NO LANDING GEAR!

Prop to be largest SF prop that the motor selected can handle!

Vortex generators Etc subject to build weight.

Wing plan form TBA but leaning towards a minor LE sweep with Aileron dimension max at root of wing and around half at tip. Possible saw tooth step in wing LE to act as a minor vortex gen, (outside of direct prop disc). wing root cord approx 1/3 of fuselage length (subject to confirmation).

Wing/tail incidences 0/0. Engine downthrust zero, side thrust Zero.

That is the target list so far! Will leave motor selection until last when plane weight is known.

Have fun!

 

[Hai-Lee]

Did a quick hack job on the fuselage outer layers to see how it would go. Wow I could have really used a laser cutter or similar but then I needed to do something to stay awake whilst the flight batteries I used today were charged.

Here is a pic. Sorry about the perspective, (poor camera angle), but I assure you that both side pieces are almost identical though the mirror image of each other.

Anyway so far the parts are incredibly light but I will not have a bare weight until the glue is applied and dried followed by a dressing up, (sanding).

I may see about the wing planform tomorrow as I have a few large pieces not allocated for any builds as yet.

Have fun!