building the "afternoon delight"

[blackjack2564]

what do you think of this? the idea is to try and create a 3D airfoil with three layers...

i experimented with the various FG cloth i have. the hobbico stuff is JUNK! it was stiff as a board. luckily i have some 6oz from PML that is real nice.

No!

Foiled fins created before installation by using a thicker G-10 and removing material or doing a build up then.
Not after the fact by building up thickness, you are just adding unnecessary weight at worst place [rear of airframe] & shifting the CG. Nigh on impossible to get even foils after fins are mounted.

Besides after running all the sims, it will not matter that much in this application. Removing launch lugs & flying out of a tower will give you more performance.

At this point I would be more concerned with finding it & getting it back after flight. [tracker]

 

[dixontj93060]

No!

Foiled fins created before installation by using a thicker G-10 and removing material or doing a build up then.
Not after the fact by building up thickness, you are just adding unnecessary weight at worst place [rear of airframe] & shifting the CG. Nigh on impossible to get even foils after fins are mounted.

Besides after running all the sims, it will not matter that much in this application. Removing launch lugs & flying out of a tower will give you more performance.

At this point I would be more concerned with finding it & getting it back after flight. [tracker]

OK, Jim now the guy's head is spinning!!! He may or may not recover... Let's see?

 

[joebot]

too late, but i was going to glass it anyway. the only difference is that there is a third, narrow strip in the middle of the fins. the weight difference with that little strip shouldnt be a big deal (vs. two strips), and i based my idea off of tfish's KestreL layup (biggest sheets on top for smooth transitions). the whole point of this rocket is to teach me lessons, so it's more important that i learn how to t-t than it is to gain a few extra hundred feet in altitude.

Nigh on impossible to get even foils after fins are mounted.

BTW, it's not impossible to shape the edges after they are attached. i came up with a pretty cool technique that results in perfect knife edges. basically, i bought a $5 manual v-groove knife sharpener from home depot and ran it along each edge the same number of times (i forgot to take pics after i did it a few days ago). i'll post pictures of the edges after this first layup hardens.

 

[dixontj93060]

Why all the blue tape above? In the past normal painters tape has not been immune to epoxy setup/hardening, at least for me. Hopefully you can get that off. When I want to protect an area I typically use packing tape--epoxy doesn't stick to it.

 

[joebot]

good to know. the idea is that i'll score the fg along the tape, and then lift the rough edge along with the excess epoxy before it hardens.

 

[joebot]

first layup, pre-finishing (looks nicer irl):

fin edging tool (cheap knife sharpener):

fin detail:

those edges are almost perfectly symmetrical. i just bought a better sharpener with deeper v's. i'll use it once i have all the fins glassed.

 

[dixontj93060]

I might have to try that knife sharpener idea.