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Bow sprit DIY help please!


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Can anyone help with a basic carbon engineering question.

 

I've got an Elliott 10.5.

 

Current set up is A frame alloy sprit which holds the forestay out 55cm with a bobstay to the knuckle (see pics)

 

I then have a carbon selden sprit to run the FR0 and Gennakers off going out another 120cm.

 

I got given a (Thanks BooBoo - bloody legend) a section of 120 OD x 5mm wall carbon tube (probably around 120cm of usable length.)

 

So my questions are:

 

1. will the tube support the forestay/bobstay in compression?

 

2. If how would you reinforce inside the boat, is this a over engineer it and DIY job? I'm comfortable working with glass and composites but not vacuum bagging etc?

 

3. I'm thinking with the reverse sheer the tube will need to be merge into the deck.

 

The selden sprit can then slide up the middle of the bigger tube to run the big sails.

 

What are your thoughts? 

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Is there a reason why you cant change it back to standard like the other 10.5’s?

 

Chain plate on the stem and then a nice tidy prod?

That is an option, but I think the set-up is to balance the rig out and carry more sail area as the chain plates were moved to the gunwales, preventing the use of  overlappers.

 

She can be a handful reaching sometimes so suspect that was to reduce the rounding up that can happen.

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That is an option, but I think the set-up is to balance the rig out and carry more sail area as the chain plates were moved to the gunwales, preventing the use of overlappers.

 

She can be a handful reaching sometimes so suspect that was to reduce the rounding up that can happen.

I believe the other 10.5’s have had keels moved aft which would assist with that?

 

Do you struggle getting forstay tension with that setup?

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Keel job is probably a future task (big$$$) and I sail in shallow harbour so the T-keels are probably a bit to deep.

 

Forestay tension is no biggie the rigging is 7mm Dieform and the bobstay is 8mm, both are strapped done hard. the forestay is fixed quite high on the mast so the backstay off the boomkin really tightens it up.

 

The rig itself is a bit of a beast. with the A-frame the weakest link by far.

 

The thinking is to laminate the carbon tube section super strong so it effectively extends the bow out 550mm then have a retractable sprit section in side it.

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This was Pork Chops move...

 

Wow quite a move.

 

I want to stick with a J -keel if possible and stay around the 2.3m draught so will probably stick with the current keel for now but maybe a project for the future.

 

Have conatcted and engineer re. the Sprit setup.... It feels doable for now. My keel leading edge sits directly below the trailing edge of the mast which looks a bit different to your original setup too?

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so you could do a similar set up to the one that Kick and Sniper have gone for.

We've both built cedar core carbon prods with static tubes. 

I was pretty comfortable building the prod and beefing it all up enough to hold gennakers and code zero's. I'm not sure I'd want it holding the rig though although I can't see why it wouldn't if its beefed up enough. 

Snipers prod is based around an Elliott 7 prod, which has around a 4mm wall thickness, with 4 laminations of 4mm cedar on both sides. There is a layer of carbon in between each lamination. Its then wrapped in 5 layers of carbon uni's and finished off with a layer of carbon double bias. All vacuum bagged.

 

THe inside of the anchor locker is beefed up was well with carbon plate, carbon uni's and DB's.

 

Have look at the "beware sniper in action" face book page for a few more pics of the finished prod.

20190708_083459_resized.jpg

20190708_084354_resized.jpg

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That looks like a pretty good.

 

I’ve had a chat to an engineer and will try to use what I have.

 

Retracting would be good as 1.7m out the front makes the LOA closer to 12.5m which is a hassle for berths etc.

 

I have the tubes now so I guess beefing up the anchor locker and reinforcing the big tube to take the loads with some margin will be the go.

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