How to extrapolate the curve that connects airfoil coordinates for aerodynamic shape carved into foam by hand without CAD?

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

wizzardworks

Well-Known Member
Joined
Nov 8, 2011
Messages
317
Location
murfreesboro NC USA
MotoFarang, First guess at the rounded nose. Is this what you were thinking or do you want a bigger or smaller radius. This bit
would need one inch thick foam slices. This is the elliptical cross section continued. I am thinking you will be poking out just
around template 6. Let me know the distance from 6 and the top of your helmut above the top of 6. If you need to resize the
template holes we can print a filler piece that will press into whichever template line you are using with a smaller inside shape.
The canopy needs to be flat wrap in the area of the glass but the rest of the shape can be convex. Just try not to have abrupt
shape changes where it meets the upper fairing shell.MotoFarang44.jpg
 

MotoFairing

Well-Known Member
Joined
Jul 9, 2020
Messages
46
It will be short wheel base.

Approximately
Wheelbase: 115-120cm.
Rear axle to bottom bracket: 115cm
 

MotoFairing

Well-Known Member
Joined
Jul 9, 2020
Messages
46
Yes I sent you an email.
I did some measurements, I will need to update red parts.
Measurements bike.png
I had the 16" wheel for long wheel base but I decided against it. I will use the 16" wheel front and rear for this frame iteration because they are on hand.

As for the nose, it would follow the airfoil used. Deviation interferes with the pressure.

Widths are
Pedal box: 41.5cm
Shoulder: 43cm
 
Last edited:

nickec

Well-Known Member
Joined
Apr 22, 2010
Messages
275
Location
Los Angeles, CA; Houston, TX
BOR with wedge.jpg

It was earlier posted that a body of revolution could be spliced to wedge.

I am uncertain the actual steps were discussed.

A makeshift hotwire lathe produces the the BOR which is cut in half. The edges serve as a template to cut the foam wedge.

To quicken construction an option is to only make 1/4th of the BOR. Less foam, less sanding.

Joggles are formed on the partial BOR - one overlay, one underlay.

This allows making 4 copies and the rest is obvious.

It is the mechanical that thwarts many would-be high speed bike building teams. Steering, brakes, transmission.

You might consider compromising on the shell and placing emphasis on the mechanical aspects.

It is alluring to perfect the shell. IMHO the first forays into HPVs can be daunting.

Very rewarding nevertheless.

P.S.: It is no coincidence that the image strongly resembles very high performance sailplanes. There are subtle differences. Still this simple method can bring you a long way toward your speed goals.
 

wizzardworks

Well-Known Member
Joined
Nov 8, 2011
Messages
317
Location
murfreesboro NC USA
MotoFarang, I sent the template files, including a 90% of scale outline inside the full scale outline. Well I backed up to last
weeks model and superimposed the dimensions you sent me. There is one in red I need a number for. The model matches
the full scale templates I sent you. Ignore the round nose it is borrowed off another model just as a place holder. The wheel
fariings are off a later version of this model you hadn't seen, so the ground clearance shown is not set to your dimensions yet.
If you are satisfied with the wheel fairings I can match them up to your 11Cm ground clearance and make them airfoil shaped, as
shown they are just extruded surfaces . I have a BB, pedals, and sprocket model for this sketch but pulled it off so you could
make out where the BB is sitting.MotoFarang47.jpg
 

wizzardworks

Well-Known Member
Joined
Nov 8, 2011
Messages
317
Location
murfreesboro NC USA
MotoFarang, Need a little help here. I tried the little man in the model and he fits, however using him to get a guess on knee position
I noticed that the BB is near the tire diameter which makes for a lot of overlap between the chainring and tire. Actually interference and no ability to steer if the front wheel is the steering tire. The 58.99Cm measurement is to the BB not the pedal, 45Cm to the pedal axel.MotoFarang49.jpg
 

MotoFairing

Well-Known Member
Joined
Jul 9, 2020
Messages
46
I have done some more measurements.

I have not done any limb measurements.
measured bike.png
Yes large wheels have crank overlap and chainring overlap if the chainring is large which is why I have the 16" wheel.
 

wizzardworks

Well-Known Member
Joined
Nov 8, 2011
Messages
317
Location
murfreesboro NC USA
Motofarang, I was looking at canopy shapes with 3 options. First is do the mouldMotoFarang53.jpgMotoFarang52.jpgMotoFarang51.jpg and blow form PET-G into it for a 1 piece canopy
and paint the inside where you don't want glass. Second do a glass layup in the mould cut out a flat wrap windshield and glue it on
flush with isocyanurate. Option 3, mount the same windshield from option two set back into the fiberglass shell canopy leaving an
annular air intake. At these piper cub type speeds it should gather considerable ventilation flow, be less suseptible to condensation
fogging, and the fiberglass section leading edge (radiused a little) could possibly reestablish laminar flow going aft. The thought
about laminar flow might be similar to the early MIG fighters which had an open nose air intake for the jet engine with a center cone
set inside the opening. Any thinkers out there with an opinion? Keep in mind the speed range is under 90 MPH.
 

wizzardworks

Well-Known Member
Joined
Nov 8, 2011
Messages
317
Location
murfreesboro NC USA
MotoFarang, I did a couple wheel farings to see what the steering angles would be with 16 inch and 26 inch wheels.
All these add on pieces need to be sliced for 1" styrofoam, probably the main fairing top could be faired easier with 1" foam as well MotoFarang54.jpgMotoFarang50.jpg
 
Top