Piranha Deck Modification.

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cweed
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Joined: Tue Sep 08, 2009 8:09 am

Piranha Deck Modification.

Post by cweed » Tue Sep 08, 2009 8:29 am

Hi, All.
I know this subject is covered by a thread 'Piranha Mk 2 Rudder wanted' back in 2006/07, but the links to the images submitted don't seem to work for me.....
I am thinking of removing most of the foredeck aft of the mast turret back to the seat carriage on my mk 2.
I'm concerned that the remaining edge of the deck may need reinforcing; the shroud anchor plates may need to be reinforced to stop the hull being squeezed inward and what the layout of the repositioned control cleats should be. The current layout with the access area to the daggerboard and mast step area iis through chipped jagged edges of the existing deck and is a tiger trap waiting to happen....
Does anyone have thoughts or experience on this, please? Alternatively does anone have details of the cover I presume was originally fitted to the aperture aft of the turret, with the necessary access for the daggerboard and kicker arc?
Thanks again.

wee mcp
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Re: Piranha Deck Modification.

Post by wee mcp » Tue Sep 08, 2009 11:29 am

Welcome to the forum cweed.

It would probably be useful to know the sail no. of your boat and also to know if the “dancefloor” (the crew deck) runs all the way to the bow or is there a bulkhead in front of the mast. It'll help to give suggestions for a way forward.

I’ll get back to you, hopefully later today, with some scanned pics and descriptions of the mods I did to K196 way back in, I think, 1989.

Ian McP
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"Sometimes its a boat, sometimes more of an accident .. It all depends" - Pooh Bear
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chrishampe
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Re: Piranha Deck Modification.

Post by chrishampe » Tue Sep 08, 2009 1:41 pm

Here is a picture of the setup on my boat. As you can see there are two small alu tubes running from the shrouds to the mast base with the deck cut from the shrouds to the mast gate. Hope this helps.

Chris H
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wee mcp
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Re: Piranha Deck Modification.

Post by wee mcp » Tue Sep 08, 2009 5:38 pm

Alan Powell's take on things.
Moonshadow K203. Alan's bracing was wood wrapped in Kevlar/carbon cloth. Kevlar tape strenghtens and protects the edges of the deck where it's been cut.
Note the buttresses under the mast gate as 203 did not have a bulkhead in front of the mast.

K196 still to come
Ian McP
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jimc
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Re: Piranha Deck Modification.

Post by jimc » Wed Sep 09, 2009 8:12 am

So basically Piranhas have worked fine without structural problems given some support for the lateral loads from the rig tension? That's good to know. Looking at the photos far IIWY I'd be tempted to replicate the set up on Chris Hampe's boat, but use a full height carbon bulkhead in place of the alloy beams, which would also give deck support.

Folks, what is the construction likely to be: epoxy or polyester? I know that it will be obvious as soon as an angle grinder hits it, but it still helps planning.

Cweed, could you measure the height of the topside and foredeck above the deck: I'll check out the collection of carbon panel scraps down at my parents left over from doing 257. There's just a chance I may have some pieces that would be suitable which would save a lot of work.

wee mcp
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Re: Piranha Deck Modification.

Post by wee mcp » Wed Sep 09, 2009 10:38 am

Jim,
The layup was, from memory, epoxy with a polyester or vinylester gel. :shock:

Cweed,
I've now been into the loft and dug out the photo album from that time
Here's a photo of the almost completed conversion of K196 . I quite liked the vert. sides of the deck running back so decided to keep them. As this conversion was undertaken when the boat was only a year or so old I took some time and extra effort, as a product designer it's built in to me I can't help it I'm afraid. :D
Also the boat had already been converted to having a bulkhead and a new, lighter, fordeck so I reckoned that the less I messed around with it the better.

All the parts were prefabricated off the boat using Dyvinicell foam glued together, then Kevlar/epoxy on the outside. When fully cured things were bonded into place. Why kevlar? I had some lying around.
The buttresses formed a base for the control cleats with the jib cleats going on the flat area on top.
In the photo the mast gate is unfinished. Eventually a marine ply piece was fashioned and coated with the blue gel to blend in with the rest.

BTW The Pyranhas had no internal structure, but they are strong. Don't be afraid to make the cuts, just keep in the back of your mind the need to be aware of where the loads are going.
Best regards

Ian McP
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cweed
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Re: Piranha Deck Modification.

Post by cweed » Wed Sep 09, 2009 8:51 pm

Many thanks to you all for the advice and photos. Your end products are such an improvement on the original.
In reeply to the comments so far made:
The boat number is K208, although the only verification I have is that this is as bought as, the sail is 208 with the 6 doctored into an 8;
The 'inner floor' of the boat extends through beneath the foredeck to the bow with no bulkheads, although there are two small knees strengthening the inner floor hull / sides in the vicinity of the forestay anchorage.
Jim C ~ thanks for your thoughts. The distance from inner floor to outer deck is 21 cms.

wee mcp
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Re: Piranha Deck Modification.

Post by wee mcp » Thu Sep 10, 2009 9:03 am

cweed does your boat have light blue decks, darker blue hull?
If so it's almost definately 208, originally called "Out of the Blue"
206 was a Tony Miles wooden creation.

Ian
"Sometimes its a boat, sometimes more of an accident .. It all depends" - Pooh Bear
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cweed
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Re: Piranha Deck Modification.

Post by cweed » Thu Sep 10, 2009 6:32 pm

Hello again.
Apologies for the abrupt end to my previous post; I was attempting to attach a photo (still am) and submitted before accomplished.
Wee MCP... Yes, that's the colour scheme.Thanks for the name, as I thought it was called 'Bluebell'.
Photo(s) will follow in due course..........

chrishampe
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Re: Piranha Deck Modification.

Post by chrishampe » Thu Sep 10, 2009 7:14 pm

the photos need to be under 256k try resizing to 800 pixels wide and jpg format. Hope this helps.

chris
IC GBR 238
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cweed
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Re: Piranha Deck Modification.

Post by cweed » Thu Sep 10, 2009 8:08 pm

Thanks, Chris, that's done the trick!
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There are two sets of shroud anchor points as the mast has lowers; I was wondering about using only the forward most chainplates for both shrouds on each side as then bracing between the gunwhales could be one transverse trut which will clear the daggerboard case.
The light blue / white mess on the gunnwhale is a poorly repaired stress crack where the original gunwhale strengthening hasn't been continued up to the cross brace in front of the seat carriage.
There is a gap of some 7 years between photos as I have recently re-acquired the boat in a semi abandoned condition.
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jimc
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Re: Piranha Deck Modification.

Post by jimc » Thu Sep 10, 2009 9:19 pm

cweed wrote:There are two sets of shroud anchor points as the mast has lowers; I was wondering about using only the forward most chainplates for both shrouds on each side as then bracing between the gunwhales could be one transverse trut which will clear the daggerboard case.
To my way of thinking you are better off if the transverse bulkhead from the gunwhales goes to the mast, or as close as possible, because that way the major loads between mast foot and shrouds are straight down a bulkhead/frame. The alloy beams on Chris boat do the same function, but personally I'm happier if its all bonded into the structure because there's less potential for it to work loose. I'm dealing with the consequences of that happening at the moment with my vintage Cherub. Whilst you have to consider the daggerboard loads as well they tend not to be of the same magnitude. The other issues is that as the shrouds go forward then the tension on them for a constant forestay tension increase very dramatically.

How would folk with experience of Piranhas feel about deck stepping the mast? If you are going to have lowers anyway - and I think you do unless you go for really radical stuff like I did with 257 - then it could make sense to actually step the mast on the intersection of the V bulkheads to the shrouds provided that you can build in enough vertical support.

Mudman
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Re: Piranha Deck Modification.

Post by Mudman » Fri Sep 11, 2009 1:10 pm

cweed does your boat have light blue decks, darker blue hull?
If so it's almost definately 208, originally called "Out of the Blue"
206 was a Tony Miles wooden creation.
Certainly is - 206 is mine! Though now the original wooden hull is flush decked with foam/carbon and has many more carbon bulkheads inside to beef it up. The centreboard case has been replaced with a daggerboard.
The main revision is the lack of a foredeck, or most of it. There's a short foredeck running to just behind the forestay fitting, with a bulkhead behind. A tube through this allows the kite pole to emerge from the stem. The open deck allows for all the gear operating the pole, together with the kite sock, to run along the deck and be readily accessible. The kite 'chute' will be a simple quadrant shaped bar.
The reasons behind this layout were:
1. The old deck was showing signs of age.
2. The centreboard case was a source of unfixable leaks
3. Having played with a traditional spi chute last year, I found that it really didn't like the short chop that Brightlingsea gets. Despite drain holes, it was filling up and making the bow heavier, and the pole arrangement was unnecessarily complex.
4. The new layout was fairly simple to do as an amateur - though my friendly local Olympic Tornado and carbon guru, Graham Eeles, did the layup and provided much technical advice.
I came to the conclusion that as the spinnaker was going to get wet anyway, I might as well make it as easy for the water to drain away as possible. The 'dish' shape of the deck at the front is pretty shallow, and won't retain much, if any water. It's very like a Musto Skiff.
The whole arrangement is incredibly strong. There's plenty of life left in the old hull, which had been epoxied and was in pretty good shape. It's just undergoing painting - the deck is to be clear coated (no point in hiding all that carbon) - before I find out if my theories are hits or misses.
Pics here show various stages of renovation - daggerboard case is now trimmed flush, support for the forestay and 'foredeck' has been added.
Cheers,

David
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cc284
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Re: Piranha Deck Modification.

Post by cc284 » Thu Feb 04, 2010 8:34 am

Mudman, have you yet managed to sail 206 with its new deck layout?

Keep us up to date with findings please, its always struck me that this deck layout could make things so much more simple. Only question is, how will it go in waves with so little freeboard?
GBR 284 (AC) - 'Outlaw'

Mudman
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Re: Piranha Deck Modification.

Post by Mudman » Thu Feb 04, 2010 8:47 am

Not yet. Last year was one of those years....The joys of self employment.
However, the boat is now decked - carbon throughout - and is ready to get wet, though still needs some fittings and tweaking. The freeboard hasn't really changed - up to the forestay and a bit behind it's just the same as the old foredecked layout, which I figured would be enough to shed moderate rough stuff. Where I sail at Brightlingsea we get a short chop in a blow and the old boat behaved like a submarine in that, foredeck or no. And then the chute filled up, and the boat went further down, and so on... I figure the water will still come aboard, of course, but it should run away more quickly with no tubes to fill up. The kite's going to get wet whatever.
The new layout is certainly simple. The pole runs freely through its tube between bow and forestay bulkhead (and is easily removed) and there's no problems with access for the string. The kite just runs in a sock from a hoop on the port side, roughly where the chute opening would have been.
I'll sort out some pics soon and post back current progress!
David
"No easy way to be free..."
IC 206 sailing out of Brightlingsea

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