Retractable Bowsprit 35 foot sports boat

[robbo007]

Im looking at building an after market retractable bow sprit for our 35 foot racing sports boat. It is a flat deck and i was hoping to be able to simply bolt it to the deck, toe rail etc without to much fiberglass work and penetrations to the front of the hull. Adjustable from 20mm to 1200mm.

Alluminium or Carbon?
Any suggestions?
Are there any after market products?
Any designs?
Looking at carrying 500 sq meter mast head asymetrical kites.

[charmc]

Aftermarket removable bowsprits:


http://www.sparcraft.com/uk/main.asp...re=actualite_7

[Vega]

You have also the one from Selden.

http://www.seldenmast.com/firstpage.cfm

[Robin Larsson]

Yeah, the Selden bowsprit should be able to take your A-sails. There should even be a carbon version of it now. If you use a bobstay you can have a longer bowsprit, but if you only need 1200 mm, you shouldn´t need one.

//Robin

[Paul B]

Originally Posted by robbo007

Im looking at building an after market retractable bow sprit for our 35 foot racing sports boat. It is a flat deck and i was hoping to be able to simply bolt it to the deck, toe rail etc without to much fiberglass work and penetrations to the front of the hull. Adjustable from 20mm to 1200mm.

Alluminium or Carbon?
Any suggestions?
Are there any after market products?
Any designs?
Looking at carrying 500 sq meter mast head asymetrical kites.

This summer I had the same idea for my 28 foot sportboat. I looked at all the after market offerings and thought I could do better, less expensive myself.

I bought a tube from a local spar shop, had a couple of bearings machined from 6061 Aluminum, and added a 3:1 purchase to push the pole out. I lined the bearing surfaces with teflon tape.

I've bolted the bearings to the deck. Remember the front bearing is tring to tear itself off the deck, and the rear bearing is trying to drive itself into the deck. My bearings and bolts are overkill, no worries there. I am concerned with the deck ripping off the boat, so I have tied down the front bearing into structure inside the boat.

Why only 1200mm? On my 28 footer I am out nearly 2000mm.

[robbo007]

Why only 1200mm? On my 28 footer I am out nearly 2000mm.

Im no engineer so im worried about spar strength. What is your spar rated to? How much pressure should i expect on the end, with say a 500sq meter kite, realising that the further i go out the heavier the spar required?

[Paul B]

You might want to contact matthew at CST in NSW. He can probably help you with your requirements.

matthew@cstcomposites.com

[tuks]

Is it possible you made an error, 500sqm is huge?


Stomp 38 kite about 160sqm if im not mistaken.

[Robin Larsson]

Yeah, I also felt that 500sg meters sounds extreme, isnt the Volvo 70s A-sails something like that?

I´m planning to get a 150-170sgm a-sail for my 44feet modern "skerrycruiser" long and narrow, the sailmaker thought that sounded extreme.. with about 2m sprit.

The dimensions of the bowsprit is really all down to the RM of your boat, check Seldéns website, they have a good list there. For example, I could have their 99mm OD alu tube to stick out 1.6m, without bobstay, and the boat weighs like ~5.5tons, RM is ~27KN/m. Longer sprit with bobstay of course.

But dont you want a sprit like the Minis(open 650)? I dont know how much gain there is in articulating the sprit, but it should be something?

Regars
Robin Larsson

[nflutter]

if you are using a bobstay dont forget that the pole may load up in the opposide direction ie down. we snapped a pole recently (set up like the mini, articulating) on an 8m boat that was ample if not overengineered for normal loads in normal directions. We had a bit of a moment and dropped 100m2 in the water and sailed past it, pole came straight off, taking the front corner of the boat and nearly the forestay.

The articulating pole does improve your pace marginally when you are trying to run square, but they are a lot of hassle, and in the long run theyre probably more trouble than they are worth for around the buoys racing. at sea different story.

[robbo007]

500 Square feet, Sorry!