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Tips for blunting up mast and foil?

Posted: Mon Nov 06, 2017 9:48 pm
by merl
My mast (aluminium) and fiberglass wings are way too sharp. I tried a bit of sandpaper on the wings and a file on the mast but life is too short. What do you diy wizards recommend to smooth these out?

Re: Tips for blunting up mast and foil?

Posted: Mon Nov 06, 2017 10:32 pm
by tegirinenashi

Re: Tips for blunting up mast and foil?

Posted: Tue Nov 07, 2017 3:27 am
by juandesooka
What's the worst that can happen? KIDDING, don't use a grinder! I may do the same for sup foil, I'd think sandpaper or file and some patience.
a-worker-uses-a-grinder-with-sparks-flying-off-it-AXWGJ9.jpg

Re: Tips for blunting up mast and foil?

Posted: Tue Nov 07, 2017 1:27 pm
by NYKiter
Heres what I use...
Image

Re: Tips for blunting up mast and foil?

Posted: Tue Nov 07, 2017 3:08 pm
by revhed
sand paper by hand slowly and PERFECT as possible.
Fold around edges and "feel" the sanding!
ANY machine is just way to much!
I have NEVER seen an alu STRUT that needed to be more round, on the contrary most could use sharper L E.
Also would seem that if alu STRUT is treated some how that ANY sanding would destroy coating?
R H

Re: Tips for blunting up mast and foil?

Posted: Tue Nov 07, 2017 5:18 pm
by tegirinenashi
revhed wrote:
Tue Nov 07, 2017 3:08 pm
...I have NEVER seen an alu STRUT that needed to be more round, on the contrary most could use sharper L E...
LF Rocket/Happy strut LE is as sharp as trailing edge -- filing and then sanding was the first thing I did a year ago. There are two effects of the mod: the underwater drag should actually diminish with blunt LE bringing strut profile closer teardrop shape. The water spray from blunt LE should have been increased. Both effects are minuscule.

Then their "shovel" front wing had sharp LE as well -- compared to stab which has blunt LE. Filed and sanded it to the bigger curve radius shape too. It exposed the wing core (glass?), but had no effect on wing structural strength.

As for the alum coating, I asked this question to somebody who rode a DIY-build full alum HF at my salt water local spot almost every day the past season. He just made a face, which I interpreted as the alum oxidation might be a problem in aviation, but not in our puny sport activity. One can always spray some primer+paint over exposed area if worrying too much about it.

Re: Tips for blunting up mast and foil?

Posted: Tue Nov 07, 2017 7:00 pm
by plummet
phpBB [video]

Re: Tips for blunting up mast and foil?

Posted: Tue Nov 07, 2017 7:33 pm
by revhed
tegirinenashi wrote:
Tue Nov 07, 2017 5:18 pm
revhed wrote:
Tue Nov 07, 2017 3:08 pm
...I have NEVER seen an alu STRUT that needed to be more round, on the contrary most could use sharper L E...
LF Rocket/Happy strut LE is as sharp as trailing edge Both effects are minuscule.
Only POS LF alu STRUT I ever saw and unfortunately rode was a very blunt, thick, heavy discontinued "funny".
A sharp LE bravo LF on their latest attempts :roll:
As most here know to avoid L F like the plague never even seen Rocket and, or happy, no problem!
And as you posted effects of sanding if one does not know how to will be minuscule and probably a waste of time unless making T E squarer and
L E rounder for safety.
HUGE thanks to MR PLUM :thumb: for posting vid from DELTA as he for sure know MUCH more than most!
R H

Re: Tips for blunting up mast and foil?

Posted: Wed Nov 08, 2017 1:56 am
by tegirinenashi
Once again, sharp leading edge contributes nothing to the foil performance. I understand that you are from the homeland of Jules Verne, who popularized sharp nosed Nautilus. However, 19th century has been long time ago, and submarine designers moved on since then. All atomic (and diesel) submarines for the last 60 years feature blunt (round) noses, and I assure you that boat builders know little more about hydrodynamics than some hydrofoil craftsman in a workshop. And, finally, Delta Hydrofoils never mentioned that sharp leading edge possesses any advantage [except being dangerous for the user].

Re: Tips for blunting up mast and foil?

Posted: Thu Nov 09, 2017 10:07 am
by merl
Thanks everyone - I'll keep on (wet) sanding.