recomendation fin material

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bobby_hamill

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I hope to be doing 3 different up scales of some Estes kits to 4 inch diameter phenolic air frames
These will be for sport flying NOT for scale
would you use Birch Plywood or G10 to prevent fin breakage . The up scales will be using only 38mm motors


Birch Plywood or G10 ?


Thank You for your input


Bobby
 
I hope to be doing 3 different up scales of some Estes kits to 4 inch diameter phenolic air frames
These will be for sport flying NOT for scale
would you use Birch Plywood or G10 to prevent fin breakage . The up scales will be using only 38mm motors


Birch Plywood or G10 ?


Thank You for your input


Bobby

Canvas:smile:
www.macperformancerocketry.com

Mike Crupe
MAC

What's In Your Rocket?
FLY CANVAS!
 
I hope to be doing 3 different up scales of some Estes kits to 4 inch diameter phenolic air frames
These will be for sport flying NOT for scale
would you use Birch Plywood or G10 to prevent fin breakage . The up scales will be using only 38mm motors


Birch Plywood or G10 ?


Thank You for your input


Bobby

I've flown 3-4" rockets up to mach 0.8 all using birch plywood with no problems. But we'd need more info. What's the max speed simmed? Mach buster? What's the fin shape? Thickness intended?
 
Canvas phenolic is not a bad suggestion. Nearly zero surface prep for painting. Won't warp. On par or lighter than good quality birch plywood. And if you are nice to Mike they may even come beveled.
 
It depends on the fin shape and size. If you were building an upscale of a Mosquito with the proportionally huge fins I would be more concerned than if the fins were a more normal or traditional size.
 
I've flown 3-4" rockets up to mach 0.8 all using birch plywood with no problems. But we'd need more info. What's the max speed simmed? Mach buster? What's the fin shape? Thickness intended?

Here is what I have so far
fin root = 13.8106"
fin tip = 9.0277"
fin span = 22.3603"
Max Velocity = 939 f/s
Max Velocity off rod = 94 f/s
acceleration = 1355 f/s
Apogee = 4135
motor J570W

I am leaning towards the G10 material
 
Last edited:
What are you comfortable working with more? Ply is easier to work with, but if it sits in a field for a while it will warp a bit.

Depends on the thickness of the material too. Stiffness scales to the cube of the thickness. Twice as thick is eight times stiffer (first approximation anyway).

I personally would generally favour the G10, but it makes me itch more.
 
Here is what I have so far
fin root = 13.8106"
fin tip = 9.0277"
fin span = 22.3603"
Max Velocity = 939 f/s
Max Velocity off rod = 94 f/s
acceleration = 1355 f/s
Apogee = 4135
motor J570W

I am leaning towards the G10 material

The span on those fins is massive. I would be looking at either some type lightweight but thick plywood (balsa ply), or a nomex core composite.
 
Is there a known sweep distance? Do you know the true OD of the airframe? You say 4" but is it really something like 4.15"? Is the span you list the span of one fin or is it the fins and airframe (overall width)? 22" is a lot...

I've run this through FinSim, assuming a 0 sweep distance as it wasn't given and I've assumed an initial altitude of 1000ft > MSL. Some possibilities (which are pretty funny):

.5" fiberglass
.5625" aircraft plywood
.325" aluminum

These do not take into account possible reinforcement options like T-T glass or CF.

For reference, this is what the fins look like as sim'd:

bigfins.png
 
Maxi Icarus Airframe is BT-60
BT-60 Inside diameter is 1.595
PML 4 inch inside diameter is 3.90
3.90 divided 1.595 = 2.4451
first attachment is maxi icarus actual fin size

Second attachment is full size for up scale
It shows a 22.3603 fin span

The last attachment was the sim results I got

max fin accual size.JPG

Maxi Icarus Up scaled fin.jpg

Maxi Icarus sim up scale.jpg
 
PML inside diameter = 3.90
BT-60 inside diameter = 1.595

3.90 divided by 1.595 = 2.4451 upscale factor

----------------------------------------------------------

PML outside diameter = 4.024
BT-60 outside diameter =1.640

4.024 divided by 1.640 = 2.4536 upscale factor

-----------------------------------------------------------

Using inside diameters or outside diameters to calculate upscale
Give a difference of only .0085

Bobby
 
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