Opened the molding plates 21 hours after lamination. Surface appears rough. This was expected and this is why I added glass fiber layer of 48g/m². Sanding and probably some primer needed.
Curious to see the final weight after removal of the excess of lamination.
Removed all excess of lamination. Weight down to 127g .
I’m pretty sure that this fin will not be rigid enough and addition lamination may be needed after previous sanding.
Waiting one week for complete polymerization before deciding what to do.
Actual surface (both faces) + one additional carbon layer will be : 7.8dm² x 1.6g/dm² x2 epoxy = 25g + 127g actual Fin = 152g or a bit less because of previous sanding.
Yes, very old !
After the deception about the flexibility of the second balsa core Fin and 2x160g/m² carbon tissue only, a new Fin design started with a plywood core, not only but also decided to increase (power of 4 oblige) the profile thickness up 7.5/8.0%. My friend Pierre persuaded me that 7 or 8 % is no matter versus performances at this Reynolds level as well additional 20/30g in the total budget, therefore I decided to make a new Fin.
Lot of precision sanding waiting for me !!!
Of course I will adds 1 additional 160g/m² carbon layer to the first Fin. Certainly I will gain in rigidity, but also increase the weight !
Stay tuned the saga continue…
x 4 carbon tubes Fin out of clamping tool.
It was 128g at post 25.
I do not think will come out at the end with less than 160g thus 30g above my specification and not yet tested for bending.
PS : Some calculations based upon the actual weight for the not finished FIN, and assuming to shorten the FIN by 3cm, the weight will probably go down below 155g.
This is confirmed by the theoretical added Carbon/Epoxy layer of 30.4 g from calculations. 128g + 30.4 = 158.4g
It remain the rigidity verification in one week time
Contrary to my expectations !!! the 4 square carbon tubes Fin is weighting 159g as is, with shortening could go down to 150g, but not foreseen for the moment. Anyhow still above the 130g specified.
I have made a mistake, the expected weight of plywood core Fin is much more than expected and with the additional 2x2 layers of 160g/m² the final weight will be close to 200g, thus no need to continue in that direction. A lot of sanding for nothing !!!
I will keep the Fin I have and going to concentrate on the Hull and Rig.
Andrew, just forgot that the carbon layers were supposed to be 4 (2+2) and not only 2.
It may be possible to come back with a full balsa core of 6mm thick to get a profile of 8% instead of 6.5/7.0%.
Actually a friend told me that I could ask a manufacturer to make it for me, they use special manufacturing processes.
Being silent for a while, main reason my back pains.
This gave me the time to think about !
The Fin affair was discussed with a Master in the Fin-Rudder domain like Dave Creed and for him the failure to met the flexural rigidity is due to the ‘non use’ of UD carbon tissue.
Ordered therefore UD carbon tissue of various weights : 300g/m², 250g/m² and 200g/m². The core will balsa. All in stock now.
Need to recover a bit before starting manual work.
I have also reviewed the Esterel 45 design to see if something could be changed before starting ‘cutting metals’.
The major parameter considered is the Hull Wet Area against Draft.
Came to the conclusion that the actual design could be improved.
See below images of Main shadow:
Updated Esterel 45 with model 1b. A bit narrower than previous design ending up with a DSPL of 3852g against previous 3801g.
Thus narrower but with 51g extra volume.
Since nothing is for nothing, the draft is passed from 47mm to 50mm.
Note:
Shadow 6 immersed perimeter is 1.8% shorter than previous design indicating smaller wet area although not measured yet.