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[Leo Lazauskas]

Originally Posted by Rick Willoughby

Leo
Here is the .mlt file. The draft is set to 130mm. The design draft is 97mm. That is where I am when light.

Most testing is done in a freshwater lake with depth from 5 to 15m. Temperature up to about 15C this time of year.

Rick

No luck, again. The offset table in the Michlet file produced by Delftship has junk at the top, e.g. offsets of 1.039143E21.
I have had this sort of problem many times with Delftship and Freeship.
Shame, it is a great program for many things, but these sort of problems and its occasional inaccuracy are very disappointing.

Leo.

[portacruise]

Originally Posted by Rick Willoughby

Vic
I have been thinking along the same lines with the hook. At least for easy transport to stop the prop from bouncing about.

For reverse it is not a big deal to use my hands. I can get 3 to 4kph just by paddling with my hands. In the temperature up there I try to stay wet all the time to get the evaporative cooling.

I am thinking of trying to diagonally wrap an aluminium shaft with fibreglass tape or CF tape to get some bendy but good in torsion. The CF tube pictured does not seem to have any diagonal strands. It is close to the right size and price is reasonably so could be worth a look. I wonder if they have actually measured the torsional compliance?




That wrapping idea might be the way to go. If you can raise a ridge on the shaft and thus provide for an upward feed screw effect, might help keep the bark and weeds away from the prop.





Rudders and prop now added. With building it was as easy as drawing it.




Will the prop still be accessible from the rider's position? Looks like a stretch.




Rick

Vic/Porta

[Guest625101138]

Leo
I checked this one. Delftship had waterlines higher than the aft deck when I generated the last .mlt file. I deleted all the stations and waterlines from Delftship and just set them for the export to Michlet.

Attached works in Michlet. Should have checked the first one. I cannot go deeper than 130mm because the aft deck does not have much freeboard.

Rick

[Guest625101138]

Originally Posted by portacruise

Vic/Porta

Vic
I never had to touch the prop this year. Just momentary stop and the leaves/weed just peels off. Even stuff that wrapped around the prop when I cut corners and went shallow into growing weed. A couple of back and forth motions with the pedals, blade flick in and out and the weed gets thrown off.

The folding prop is a big step in overcoming weed. It gives me more design freedom with locating the prop.

Rick

[kengrome]

The minimum drag hull for human power uses about 90% of the power to overcome skin friction. There is only 10% going into making waves. If skin friction could be reduced there would be a huge gain in speed.

I have considered the possibility of incorporating straws or coroplast into the hull so that the low pressure created via the venturi effect sucks air onto the hull surface as the hull moves through the water. Technically I think it might work without the necessity of a pressurized air system ... but if there were a surface treatment that would trap tiny bubbles of air at the hull surface it might be easier and more effective than drilling lots of holes in the hull and gluing straws into them.

[portacruise]

Bubbles do work and this is a clever approach. Sometimes there is marine life we can mimic to increase efficiency. Like the olympic swimsuits that have ridges which mimic sharkskin?

Porta

Originally Posted by kengrome

I have considered the possibility of incorporating straws or coroplast into the hull so that the low pressure created via the venturi effect sucks air onto the hull surface as the hull moves through the water. Technically I think it might work without the necessity of a pressurized air system ... but if there were a surface treatment that would trap tiny bubbles of air at the hull surface it might be easier and more effective than drilling lots of holes in the hull and gluing straws into them.

[kengrome]

I have considered the possibility of incorporating straws or coroplast into the hull so that the low pressure created via the venturi effect sucks air onto the hull surface as the hull moves through the water.

In light of this report that Rick posted in another thread (it's a PDF file, see figure 15) it seems that my straw concept might work best in the aft portion of the hull bottom since that's where the low pressure on the hull will create suction:

http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?action=rtdoc&an=8895319&article=0〈=en

[I57]

Just changing the subject for a moment, have made a new seat and am using an inflatable cushion for lower back support. Tried it for the first time today and went for 1.5 hours with no aches. The cushion gave good support but also allowed movement when pedalling, the problem with the old one was sitting in one rigid position all the time. Does anyone else have seat problems?

Ian

[Clemens]

Originally Posted by Tiny Turnip

and a few more. The longitudinal spars are held to the Dart cross members with u bolts. The 3 deck panels bolt down to the spars via captive nuts in the little blocks screwed and PURed to the side of the spars. The whole thing is designed to demount and travel on the original trailer. The red rope is my steering arrangement, to avoid the Dart's original great long tiller sweeping any passengers off the deck. The seat subframes are the final bit to finish. They will have a very simple fore-aft adjustment by clamping the seat base (not in the photos) to the deck through a small cut out, with two small G cramps. The seats themselves are a bit of an extravagance - from Trice engineering for their recumbants, but I thought a good comfortable position was pretty important for long cruises. I will fit new pedals with spds on one side, but the manufacturer of the unit has threadlocked the existing pedals in, so it is a bit of a tough job! I will also put adjustable webbing loops round the front crossmember, as hand restraints to pull on when pedalling hard.

Hello TT,
found your description and photos by chance. Seems we share a lot of ideas and preferences!
I did some work on my seacycle twin in order to make it fit for multi day excursions.
Best greetings
Clemens

[Clemens]

Hello,
I'm new to this forum, signed in today, after Rick sent me the link to this very interesting thread.
Thrilled about your modified Dart catamaran!

Three years ago, I modified my seacycle twin in order to transform it into cruising vehicle. After a 2 day trip to the canal connecting the rivers Rhine and Marne I added another platform section to put up a small tent on the deck. I made several 3 day excursions on Lake Konstanz, Germany.
Next I'd like to make a lighter and wider platform of foam, epoxy and fibre glass / carbon fibre.

Enclosed you'll find a report in Velo Vision.
Cheers Clemens

Originally Posted by Tiny Turnip

The longitudinal spars are held to the Dart cross members with u bolts. The 3 deck panels bolt down to the spars via captive nuts in the little blocks screwed and PURed to the side of the spars. The whole thing is designed to demount and travel on the original trailer.

[Guest625101138]

Clem
Have you made any plans for the deck modification?

Are you only in the thinking stage or have you got a finish date in mind?

Rick W

[Clemens]

Rick,
so far, I only did some sketches.
It would be great to test the new configuration in June.
Will send layout soon.

My goals:

• bigger platform / deck - 230x140 instead of 190x90
• lighter (20 kg less)
• lower profile (-8 cm)
• less parts to assemble
• faster to put together
• more appeal to my son to come along on a boat trip

Best greetings
Clemens

[Guest625101138]

Clem
There is some free 3D CAD software called Delftship that can be used for drawing up things like you propose so you can visualise them. It also allows you to get accurate measurements of pieces.

Takes a little bit of learning but is worth the effort if you do not have access to other CAD software.

It can be a challenge to get children to join you in the things you like doing. As they get older they have their own interests. I think you would have a special child who enjoyed pedalling on the water.

Rick

[blisspacket]

Great report, great effort. Thanks for sharing, Rick.
Is there any merit to a pulling folding prop that might not require a strut?

[Guest625101138]

Originally Posted by blisspacket

...
Is there any merit to a pulling folding prop that might not require a strut?

Believe it or not (I can show video) a pushing prop is self stabilising. As long as the prop pushes and is on a curved shaft it will align itself with the flow. A pulling prop would want to dive.

Rick