DIY Mast Construction

[kjorn]

How do you figure out how much carbon to put inside the mould? How many layers?

[downunder]

Making a mold for a solid carbon mast , cheap and exciting method:
...

Cheers Dirk, awesome.

How do you make a tuttle? Looks like the fuselage is molded at the same time but you've got bolts as well, I'm thinking just for strength and not for separation?

Ta

[faklord]

tahoedirk
Ok got this now. Nice lateral thinking on table saw use! Thanks for the clarification.
I guess it must be a bit tricky to set up the angles/depth of cut for each pass?

Thought I might give this a go using mdf. Any thoughts?

For a simple shape like a mast, Is there any reason why you can't line the mold with a thin polythene sheet rather than waxing? This should ensure an easy release and smooth surface and also ensure no wax residues on the carbon part, which might otherwise affect any additional layers or finishes.

Cheers
Dave

[tahoedirk]

All fine ideas, Dave. Yes , a bit tricky. MDF would be ok, it tools very easily but it is so flexible. If you use a straightedge when clamping it would likely be fine. I have found that a select piece of hardwood can remain perfectly straight with no additional support while clamped or vacuum bagged.

As far as lining the molds , this would work too but wax has always been kind of a standard with molds and it is very simple to use. Also , just sand before adding any more cloth later, wax does not leave much residue like other mold release.

[tahoedirk]

I got a cheap Chinook Tuttle box , cut it in half with a Japanese pull saw for the mold.

Fill the mold halves up with cloth until just past full, check with a straightedge.

[Denisesewa]

Just in case anyone wants to know about the validity of Divinycell / corecell as a core material, this is a cross section of an MHL Lift strut I shortened.

[boardjockey]

Which model year is that piece from?

[Denisesewa]

Which model year is that piece from?

Its early 2014 , the later 2014's have a longer chord to achieve a better thickness to chord ratio, construction is the same for both . for myself I am liking a 125mm chord which allows a slightly thicker foil section for stiffness and still get a good foil profile( my 3 DIY's are 14 to 18mm thick).
Going to a longer chord has eliminated the strut ventilation issues I had with 100mm chord.
Watch the vid at 1.10 or so, sucking an air bubble down the strut, this happened 3 times during this ride, after lengthening the chord and reshaping a more gradual entry this problem disappeared.

[bigcane]

I have been having the same problem with mast ventilation on one tack, when you reshaped the profile did you make the leading edge slightly sharper? Also what is the view on the exit of the mast foil, is a bit of concave in the back half better than straight?

[Denisesewa]

I have been having the same problem with mast ventilation on one tack, when you reshaped the profile did you make the leading edge slightly sharper? Also what is the view on the exit of the mast foil, is a bit of concave in the back half better than straight?

These are 4 mast profiles , the liquid force, my original DIY profile which I purposely made pretty blunt for safety while learning, my present DIY profile which works very well( notably faster and very quiet with no ventilation) and the early 2014 MHL. these drawings are all about 20 percent thicker than they should be since I traced around the outside but you get the idea.