[hpv-boats] New Boat

[Rick Willoughby]

Happy new year to all.

Rick, is that a hand drill gearbox being used in V15 or something  
else you
found? Looks a lot more compact and lightweight than some of your  
previous
models.

Here is a reference to graphene, a very new possibly stronger and  
lighter
material that I thought you might find interesting. It is already  
available
in powder form and can aparently be tweaked for marine applications:
http://www.plastemart.com/Plastic-Technical-Article.asp? 
LiteratureID=1433&Paper=graphene-automotive-aerospace-wind%20energy- 
electronics

Might be a way for a lighter hull down the road a bit...

Cheers,


Vic
I have a couple of these boxes and have used them before.  They are  
designated DZ2.  They have similar rating to an R-082 Mitrpak box but  
have slightly thicker shaft.  They weigh 1kg.

With my present method of construction I have been adding more than  
1kg in fairing the hull.  If I were to vacuum bag over a male mould  
with a silicone bag I will get fairer finish.  It would save a lot of  
effort and reduce weight.

As it is the boat is quite easy to carry with stabilisers attached.   
They fold up over the seat once the brace is unclipped. This is how I  
transport the boat.

This boat now looks good enough such that some people actually ask  
"Where did I buy it?" rather than asking "Did you make it?".  So some  
progress on the finish but still not commercial quality.

There is a fellow who has seen Mike racing his V15 boat who has  
approached me about making a plastic version with a view to  
commercial production.  It is early days yet but will see how it  
progresses.

I have gone back to the side mounted prop for a variety of reasons.   
The instigator was a semi-professional cyclist, Matt Johnson, from  
Seattle who has built a V15 style hull 6.5m long with the original  
intention of bettering the 24 hour record.  I have since convinced  
Matt that he should join Mike in the Sound Rowers races.  Matt can  
sustain around 330W, which is around 3 times what I can hold and  
about twice what Mike can hold.  In looking at the drive train I  
found I could not come up with a suitable shaft design for aft  
mounted prop for this power level  so went back to the side mount  
design for him.  It prompted me to use that set up on the new boat  
and he can now copy what I have done.  I will probably supply a prop  
and maybe shaft.  Also Mike still gets a bit of bother clearing weed  
from his folding prop and that is simply not an issue with a prop you  
can reach by hand and clean if it is badly fouled.

The reason I can get higher speed from this boat is the low torsional  
compliance of the drive train.  I am spinning a lower pitch prop at  
7X cadence.  The prop is on an 8mm diameter spring steel shaft that  
is only 1.4m long.  The drive dynamics are much improved over my  
V15-6m boat with the aft mounted prop on the CF shaft.

The CF shaft with aft mounted prop has worked very well but it is so  
long and at 4X cadence spinning a high pitch prop the torsional  
compliance is noticeable above 14kph.  It eventually limits top speed  
due to shaft recoil at the crank deadspot.  Mike Lampi is limited to  
about 8mph due to his shaft dynamics so he cannot do the high speed  
sprint to the finish line he could do in the Cadence despite his V15  
boat being faster over the course.

I did a lot of drive analysis for a guy, Dave Giering, who eventually  
wound his own CF shaft.  He has a very heavy boat but is pleased with  
his new shaft.  So CF shafts are a good way to go but they need to be  
purpose made to have bending compliance but torsional stiffness.

Rick Willoughby
rickwill at bigpond.net.au