Building Paterson 8 in Dubai

[roland_trim]

Which uni?

[doug1720]

Oxford.
 

[roland_trim]

Nice place, sadly the head shrinking probably rules him out for a few weeks ;-) If he or yourself are free (and in the UK) do shout...

[doug1720]

Will do.

Doug

[doug1720]

Ok, so back to the build!
(Spent most of the year so far travelling across and around the Middle East.)
I spent the weekend leveling off the decks and bulkheads.  Took a long time.  Fitted the daggerboard case and cut the foam for the crew deck.
I hope I can get the crewdeck on this coming weekend.

Doug

[doug1720]

There are a couple of areas where I have still not finished my thinking and any ideas welcome!

My current thinking on the mast stump is to have a tall stump and bring back the shround loads under compression back to the top of the stump through some struts (like moth).

Put gooseneck on the stump and have a strut to the bow.

In terms of mast strut layup thinking of 8 layers of 200g uni and helical and 0-90 weave.  I am not sure of the mast to mast stump connection point.  Should I make a socket on the mast stump for the bottom of the mast?

Any thoughts welcome.

Doug

[Banshee Ambulance]

Something like this? As for layup check out the build of EJ pages.

[JimC]

Ergonomically I much preferred a free standing stump: makes it far easier to get crew weight forward. On Halo I used the bottom of a Finn mast. But that was with a full height foredeck and bulkhead: the structural issues are completely different with the layouts you use now.

[doug1720]

Something like this? As for layup check out the build of EJ pages.

Yes this was my thinking.  Thanks for the photograph.  How about a strut that goes to the bow or is this not required.

Doug

[Banshee Ambulance]

I have not seen a strut to the bow used. I presume that it would make for a difficult self taking jib arrangement. If you were to do it like the boat in the photo you would have some form of strut under the foredeck from stump to stem. If you were going for a foredeck less solution the floor would be higher and the spine would do the same job.

[doug1720]

Thanks for that.

In terms of the mast to mast stump join is there a preferred approach....thinking of using the same mandrel for both and with more carbon in the stump then it will be thicker.

I am also interested in the height from the deck of the gooseneck.  Presumably needs to be as low as possible to reduce heeling moment from the mainsail.  Thinking of a GNAV to provide more room to get under the boom.  Any thoughts appreciated.

Looking to make the stump and then put the crew deck on this weekend coming.

Doug

[Banshee Ambulance]

Gnavs have their fans but not everyone likes them. Have a read of the rigging article on the site as that may be of some help. For my boat I am working on just under a meter from the crew deck to the gooseneck which I think is what Atum Bom is. C-Tech sell the fittings for the bast base and stump join so it might be worth getting hold of those first so you know what diameter to use for the tubes. Alternatively you could make your own to measure after.

[Phil Alderson]

If you are going for a tall stump with solid lowers, you need to make sure that the stump is angled back in the boat enough so that the rig compression puts the lowers into compression.  putting a strut going forward will stop a self tacker from working, and will make it likely that the jib will catch if using std sheets.

I like gnav's and have had them on two different boats. I think the combination of a gnav and stump is not a good idea as the gnav is working on a short section of mast so bends will have a smaller radius.
I think that there is less need for the gnav in the modern boats as in sub trapizing the crew should be in front of the mast, and once trapizing the T-foil is working so you are further back in the boat.
Have a look at

http://www.sailingsource.com/cherub/test/doku.php/boats/2688

for a tall stump,

[JimC]

Surely if you've got a push kicker there's no point in having the stump? The reason I had the stump at least was to take the kicker bend loads out of the mast.

[doug1720]

Thanks for the thoughts.   

I will do some more thinking.

I am travelling back to Dubai tomorrow and should be able to start work on Wednesday.

Doug