I was reciently interviewed by High Octane One Designs for their site, the full interview
is available here.
Original post by Bruce McLeod and software by Elliott Back
You are currently browsing the monthly archive for November 2006.
After a really great fun handicap race today I am now fully comitting to building
a new boat. And the first step of that commitment is to put my current boat up for
sale. I am asking $2900, the full details are as follows:
- Homebuilt axeman style design
- Carbon Kevlar construction
- No leaks !
- Thorpe carbon mast and pocket luff sail
- Alloy wings and boom.
- 2 centreboards, one with cover.
- 2 rudders (One t-foil and one regular), one with cover.
- No hydrofoils (they are going onto the new boat)
- Trolley.
- Boat cover (Covers foredeck and front half of the boat.
Now I just need to get moving on the replacement.
Original post by Bruce McLeod and software by Elliott Back
In my last post I
talked about how the wing dragging was being caused by insufficient angle of attack
on the main foil, well I was wondering how the heck that could have happened (again).
To setup the angle we rolled the bottom of the boat upside down and set the hull up
so it was level at the centerboard case.
As it turns out, that wasn’t the right thing to do. The centerboard position of my
boat is a little further back than the current Hungry Tiger, as the measurements were
based on the ones that Andrew Landenberger was using successfully at the time. The
fact that the case is further back, means that I have not set the foil angle relative
to the waterline, but relative to a point on the curve at the back of the hull.
This has resulted in a setup error in the order of somewhere up to five degrees in
the wrong direction. At the nationals last Christmas, it must have been something
like 10 degrees the wrong way ! No wonder VR is hard to get out of the water
!
The diagram above shows exactly how the error occurs. The blue line is parallel to
the waterline of the boat, whilst the red line is the one we used to set the boat
level and configure the angle of the main foil. You can clearly see that there is
a significant amount of setup error that has occurred, especially when we are trying
to get around +ve 2 degrees of lift on the main foil.
A good thing about this is that after the issues at the nationals, I have deliberately
left things in a semi-finished state do I can make exactly these sorts of adjustments
on the boat. This also shows that if you are planning a foil conversion or building a
new boat getting the angles correct (or having them adjustable) is
absolutely critical.
Original post by Bruce McLeod and software by Elliott Back
Well today was another completely disheartening day sailing the “semi-foiler” that
I have. After installing the new gantry, I managed to get out for a few runs before
the race. With little success I asked resident foiler test pilot Luka
Damic to jump aboard an help sort out the set-up. The results were … interesting.
Luka after the first couple of runs came back in and hesitated before he spoke; “You
aren’t going to like this, it feels like a fat boat. It’s very heavy and it just is
not behaving like the new boats do.” Luka knows that I would rather hear the truth
than some sugar coated answer, even if it is hard to take, and I think his assessment
is bang on. The wings for my boat are double sleeved alloy and way something like
15-18KG by themselves, so this doesn’t not come as a huge shock.
The boat did foil though. Luka managed to get it out 5 times, however the results
are anything but pleasing. To get VR flying you need to seriously hang right down
the rear to get any altitude. The hull is simply not designed to be sailed like that, and
the wings drag in the water, which slows things down. When the boat does get out of
the water, the flap isn’t reducing the lift as intended, so the boat will rise
until it ventilates and crashes back down.
So what are the solutions? To solve the weight problem, a new low freeboard hull is
required with carbon wings. I will need to get this happening sooner rather
than later, budget permitting. Whilst I could add carbon wings to the current hull,
I am not too keen to invest anything more in the current boat when I am planning to
build a new one in the near future.
To solve the wing dragging problem, I think the best approach will be to add some
more angle of attack to the front foil. One possibility is that our measurement was
incorrect and we are still running with the angle of attack slightly the wrong way.
That is an easy fix with my current setup.
To solve the height adjustment problem, I will need to go back to the geometry of
the wand, and change the setup so that it reduces lift more aggressively. With more
angle of attack on the main foil, I should need less flap anyway.
I also had a minor problem with the new gantry, which caused a DNF, but it can easily
be fixed. I must say though it was much easier to adjust than the previous version,
and looks like it will do the trick.
Original post by Bruce McLeod and software by Elliott Back
I have finished constructing the new gantry to replace the one that destroyed itself
last week, so, assuming there are no installation issues, I am good to go tomorrow
once it is installed and the angle has been sorted out. The only thing that I didn’t
manage to do is to get it covered in a spot of black paint. In the end I went with
an almost identical design to the last one, as the filled box style simply won’t suit
the back beam arrangement on Virtual Reality.
The new developments I was planning will have to wait until the next boat.
Original post by Bruce McLeod and software by Elliott Back
Some people who shall not be named recently gave the club a face lift. Nice one !
Original post by Bruce McLeod and software by Elliott Back
I have launched a third blog, Teknologika
Soapbox. The Soapbox is where you will find my thoughts on anything and everything
that does not fit in with the theme of this blog, or my software
development and testing blog.
Original post by Bruce McLeod and software by Elliott Back
Sam Pascoe clocks a new moth speed record.
“Hi, sorry to do this to you Rohan
Took the P&B sail out for the first time today. It is a very quick sail. I had
a top speed of 33.4 knots and a 500 meter averge speed of 31.5 knots.”
Looks like KA Sail might
have some new competion.
Update (Thur 16th Nov): It appears that Sam’s download had a bug in it, and the max
speed was only 25.7 knots.
Original post by Bruce McLeod and software by Elliott Back
The GPS trace of one of Sam Pascoe’s recent runs has been posted here.
GPS Action replay as some nice features and one of them is to produce polar graphs.
Here are some screenshots of the sort of numbers a state of the art moth is capable
of producing.
 |
 |
| Maximum speed | Average speed |
Original post by Bruce McLeod and software by Elliott Back
I have been meaning to post this image for ages. This is a shot of me at the 05-06
Sunshine nationals, in never going to foil mode. You can clearly see that despite
good breeze and hanging off the back corner, the bird just won’t fly.
Hopefully that is all going to change this weekend.
Original post by Bruce McLeod and software by Elliott Back
According to the November issue of Mothballs the
US Modern Moth Class Association have almost unanimously voted to keep their spinnakers
and not adopt the international rules. This decision doesn’t really surprise
me given that Americans have a long history of doing things differently like: driving
on the right
side of the road, not adopting the metric
system and having their own style of motor racing that only involves turning
left.
Personally I think it’s a shame as it would be great to think of the International
Moth as truly international, and an active fleet in the US would be a great thing
for the class. Oh well, there’s always Canada.
Original post by Bruce McLeod and software by Elliott Back