carbon mast question

[Edge19]

No worries, I had one of my fusalge halfs bend in my oven. Had it in to speed up curing on some internal work. Trouble is it was supported on two points qen I took it out I was sick as a dog!!! Just like how you felt!!!

I thought to myself, this has happened when heat was applied and un even support. So I thought if I apply more heat and compression/tension it my revert back ..... Thank the lords of carbon it did lol

It's worth a shot, it won't take very long to do either.

[windfreak74]

hello Edge,
followed your advice and i decreased the bend by a good margin, did it with my wife blowdryer!!
Tomorrow ill borrow a profesional heat gun to apply more heat evenly thru the whole strut and take the rest of the bend out !!
im so happy great tip!!!
thanks,
Pedro

[Edge19]

Hi Pedro,
that's aaaaawesome dude I can just feel your happiness lol. So pleased it helped a bit and hopefully it will help some more with the heat gun. I'm well pleased for you, keep us informed

Cheers

[zfennell]

hi pedro
be careful with the heat gun.

there will be nothing uniform by using high and very localized heat on epoxy, carbon and wood (all having very low thermal conductivity).

there's a good chance you will set the epoxy on fire before you can get a uniform change in temp thru the thickness anywhere.
a simple test on one of your small 'off-cuts' could prove that to you one way or the other

cooking small patches of your foil a bit a time could easily make things worse and/or limit you options later on.

it sounds like the original cure was a room temp.
yes/no?
a post cure at elevated temps (while softening the epoxy) is still plausible
look at the spec sheet for your resin to pick suitable cure temperatures


perhaps a simple insulated box where you can place your strut ( clamped between two straight steel bars/brackets ) ?
use a space heater or the heat gun to raise the temp in the box.
a small fan to mix air.
a thermometer to monitor temps

if 6mm deflection is close enough for you to consider trying it "as is".
i think that would be a better option until you are more confident in how you want to fix it..

i'm old, so negativity is what i do best.
but considering the dollars and time you have invested, you should weigh the risks / rewards.
good luck,
-bill

[windfreak74]

hello Bill
i will cook the the masy in a box and put some weight on it to try to eliminate the residual curvature.
ill post a pic of what i got right now and with what i end up with.
i have a 3mm gap right now!
i hope to bring it dow a little but im quite happy at the momment.
Pedro

[windfreak74]

Almost done!

[windfreak74]

final mast profile ultrasecret naca xxxx!
after sanding i got 15mm thick , 110mm chord and 1mm in final mast !
im happy dude!

[zfennell]

good job!
you are now the wizard

[windfreak74]

Hello Bill,
I followed the path of least resistance.
im happy it was posible to fix the mast with so little effort.
i definately learned that it pays of to do the molds.
the cutting and sanding process on carbon is nasty!
thank you for sharing and your view it is most welcomed!
i forgot to respond to some of you earlier questions.
Epoxy resin that i fot is not sold with the spec and curing instructions.
unfortunately i cannot choose the resin. there is only one type. take it or leave it!
but the guy who sells it uses it for carbon too so i use it also!!:)
He is a mechanical engineer so i got to trust what he is saying.
the post curing i have a heating blanket which alows me to heat up to 85 ºC in a box for 8hours.
its probable that with the heat gun the resin got hotter than 100ºC.
the rest is guestimate.
this is the reason i did so many layer and such a thick laminate.
after trimming and sanding i get 2.1 kilo which i believe is heavy.
im sure ive could have used 300-400 grs less of carbon and a better core geometry and still get away with a thinner strut(14mm).
im happy i could lessen the problem and use the mast!
im definatelly will build closed mold for my next wings.
this has been and is a great hobbie!
so far my budget is really small with 1000 bucks in machinery and supplies. and lets not forget one zillion man hours obsesing and troubleshooting!!
ive learned a lot!!
wishfull thinking ill be able to top 18knots with this new mast!
Pedro

[windfreak74]

almost done but fot to finish mast to plate connection.