Here below the basic tool retained to laminate both faces of a ‘parallel’ Fin.
Tool under construction.
The tiny plywood of 0.8mm will be bonded to the shadows, care shall taken to ensure a uniform and good bonding. Light sanding as needed.
Shadows number as function of length to avoid deformation of the plywood bed.
For 500mm long Fin I will use 10 shadows of the same form.
The Plywood surface is then covered with Plastic adhesive Film to avoid lamination sticking and obtain a mirror surface. Roller shall be used to avoid bubbles under the Film.
ClaudioD
That’s a good way of doing it.
Would you need to soak the ply to get the shape?
Hi Andrew,
the 0.8mm plywood I have is very flexible in one direction.
It may depend on the type of tree, mine is birch.
Once I used plastic pockets filled with sand to exercise a soft pressure to let balsa sheets adhering inside the hull and with the female mould as support. Was later laminated with kevlar
Soft foam and water bottles on top, etc…
The tool I presented is for a ‘preformed sheet’ that is different from the use of a flat sheet and forced to bend as I’m preparing to do with lighter Carbon sheet lamination (2 x 160g/m²) since the one I have already done is too stiff.
Here below an example with the use of longitudinal stringers to distribute pressure on the shadow edge only and not in between other wise there is the risk to get an undulated surface. It may be good, who knows, heheh!!
I do not exclude the use of balsa sheets, eventually two layers of 1mm or something like that…
Cheers
lamination of 2 layers of carbon of 160g/m² is ready.
Cutout 4 panels : 2 of 8.5cm x 61cm and 2 of 7.5cm x 61cm.
Assembled, for trial and picture purpose, with adhesive paper including tube of 5.5mm and 3mm rod for leading edge.
Before bonding 85g.
Still missing the aluminum perforated band of 0.4mm x 1cm x 61cm for trailing edge. Measured weight 5.5g.
Replaced the 5.5mm carbon tube with the 8mm tube and the weight raised to 120g. I did used the 8mm tube in order to force the carbon sheet to bend more during continuing polymerization. In a week time will more rigid.
I do have recovered also the first lamination with carbon and glass and the preliminary assembly show a weight of 160g before bonding, but it look also very stiff !!!
The back light picture shows multiple micro holes. This should be recovered with diluted transparent polyurethane. Resin surface tension is responsible for the phenomenon. Several crossed carbon sheets can cure the problem, but spending more money since the carbon tissue of 93g/m² is at 80€/m².
Anyhow here some pictures …one is funny since I’m appearing in the mirrored surface plenty of micro holes…with some fantasy it look like NY skyscrapers in the background …
more pictures with 8mm carbon tube !
Went back to my old school books and recovered that figure about the flexural strength of various sort of beams. It is evident that the use of a square tube is much better than a round one unless the round tube thickness is increased. The square/round tube is a good choice to make the Fin. The second choice could be the 5.5x3mm.
Based on previous Table this is what I could try to do …
As can be noted the carbon circular tube is the one has less strength !