Does anyone think that I will have problems with an 85 mm diameter 4.2m long aluminium Spinnaker Pole protruding 550mm forward of the bow fitting unsupported but for a lashing to the bow fitting and clipped into a deck padeye at the rear?

In my opinion based on the input you will have problems with this plan due to the stainless steel of the bow fitting side plates digging into the softer aluminium of the kite pole - and damaging it as regards making a progressive notch so as to make a strength and fatigue resistance reduction which will bite you down the track of time. Also the tack of the asymm kite so set will be offset to one side which is not a big deal for 550mm extension but needs to be understood. On my Farr727 (which I should never have sold in 2016, the best harbour day sailer and close offshore 1/4 tonner to the old IOR rule ) I set up the symm kite pole off the deck with a large ss saddle back at the inboard kite pole end but with a supporting saddle for the pole diameter made out of "timber decking plastic wood" a bit back from the bow mooring roller and off to one side so that when it was extended to 1.25m the outboard tack end was on the hull centre line. It worked perfectly. Obviously your 38fter is a different beast than the Far727 but the concept would work as long as the length out from the bow and the securing point on the deck aft of the forestay were engineered suitably. Numerous yachts run a similar system including a 30fter we race against.

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r13 said..
In my opinion based on the input you will have problems with this plan due to the stainless steel of the bow fitting side plates digging into the softer aluminium of the kite pole - and damaging it as regards making a progressive notch so as to make a strength and fatigue resistance reduction which will bite you down the track of time. Also the tack of the asymm kite so set will be offset to one side which is not a big deal for 550mm extension but needs to be understood. On my Farr727 (which I should never have sold in 2016, the best harbour day sailer and close offshore 1/4 tonner to the old IOR rule ) I set up the symm kite pole off the deck with a large ss saddle back at the inboard kite pole end but with a supporting saddle for the pole diameter made out of "timber decking plastic wood" a bit back from the bow mooring roller and off to one side so that when it was extended to 1.25m the outboard tack end was on the hull centre line. It worked perfectly. Obviously your 38fter is a different beast than the Far727 but the concept would work as long as the length out from the bow and the securing point on the deck aft of the forestay were engineered suitably. Numerous yachts run a similar system including a 30fter we race against.

Thank you very much for that answer. Yes I do appreciate that I will need to provide some sort of abrasion buffer between the bow roller and the pole as there are point loadings rather than a nice cradle fit. Not quite sure what I will lay in there yet (or wrap around the pole) as the obvious candidates like cut up ice cream containers and dense exercise mats would probably destroy themselves each outing. I could put a proper cradle (and top strap) back from the bow fitting but then I would lose another 250 and even though the pole is 85 mm diameter I would start to worry about the sideways and upwards forces on an unsupported extension of 800+ mm. I'm even worried about the forces a (13m luff) gennaker tack can exert on an unstayed 550mm extension although eyeballing it it seems as though it won't be too bad especially if I only use it in fairly light winds. However if run shy I'm sure pretty large forces can quickly be generated.

Also Im not familiar with the "timber decking plastic wood" but you mention. Have you got a link a source for it? Thanks.
Julian

Hi Jules,
I had a similar thought as you, only I used a 1" schedule 40 (thicker walled, about 4mm) 304 stainless pipe with a hook attachment that locked in under the bow roller. I tack welded a length of 20mm x 5mm angle along the top for added support.

It was a work of art!!! I thought !! "A Cav 32 with a bow sprit that'll put the fear of God into the fleet"

Aysso bent it no worries, first time out. OK, we gave it a bit of a work out to see what it could take, in about 15 knots. I'd rather have it break when it suits me not it. I had 500mm unsupported from the bow roller. Apart from the unplanned bending it worked great.
There's a lot of load there with a big aysso.
Give it a go, what have you got to loose!!!!

Mike

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Magpiemike said..
Hi Jules,
I had a similar thought as you, only I used a 1" schedule 40 (thicker walled, about 4mm) 304 stainless pipe with a hook attachment that locked in under the bow roller. I tack welded a length of 20mm x 5mm angle along the top for added support.

It was a work of art!!! I thought !! "A Cav 32 with a bow sprit that'll put the fear of God into the fleet"

Aysso bent it no worries, first time out. OK, we gave it a bit of a work out to see what it could take, in about 15 knots. I'd rather have it break when it suits me not it. I had 500mm unsupported from the bow roller. Apart from the unplanned bending it worked great.
There's a lot of load there with a big aysso.
Give it a go, what have you got to loose!!!!

Mike

Yes there are very significant forces involved and every inch I can shorten the pole extension helps but I run into the coach house roof at shorter than 560 mm although if I sit it on the forward hatch I can get back further. Interestingly the attached picture is from a selden advertisement for their expesive as hell dedicated bowsprit and you can still see the upward bending moment!

Interesting experiment Jules. I'll look forward to hearing how it works out. I have one of those poles sitting idle 99.9% of the time. Is installing a bobstay out of the question for you?

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2bish said..
Interesting experiment Jules. I'll look forward to hearing how it works out. I have one of those poles sitting idle 99.9% of the time. Is installing a bobstay out of the question for you?

I'm pretty sure that if I can keep the unsupported length down to around 500 mm I won't need a bobstay in light of the fact that my pole is 85 mm diameter. Of course a bobstay only braces against upward movement and there is sideways movement to consider. I could also brace to a padeye low on the stem but then this would introduce forces pushing the pole back which would require a bigger padeye at the rear.
I spent a while down at Whitworths and BCF today and bought another bow roller and quick release pin for it that I can quickly fit/remove it above and behind my existing bow roller with the pole sitting in a decent veed soft bearing surface. I got a rubber roller rather than nylon to help with grip. All I have to do is drill a hole in the other side of the bow fitting because there are a series of holes already well above the existing roller on the port side.
I also bought a chunky "V" shaped rubber thing which I will try as an alternative and which I also attach a picture of.
I have furthermore located a cheap second-hand pole of 80 mm diameter which is a metre shorter than mine which may be more convenient but I think every millimetre of diameter is important.

I had to make a new bow roller for my boat. It came with one of those Whitworth Chinese jobs that was bent out of shape, I extended it out a bit further as well so the boat sits better at the mooring. The centre loop I made a little higher and that's to take the tack line for the cruising chute [no block]. On the Currawong there was tack line that kept the tack about 50cm off the bow but with the SS34 I intend hauling down the tack right to the loop. The extension is 316ss 80mm x 10mm bar and bolted to the stem fitting with one large titanium bolt. SS bolt across to the fore stay base. With the headsail furled this should work fine.

Used a bit of Modwood left over from a deck;

www.barrenjoeytimber.com.au/modwood-decking

Ekodeck is another one;

www.bunnings.com.au/137-x-23mm-5-4m-decking-backbeach-leatherwood-composite-ekodeck-designer_p0109382?store=7302&gclid=EAIaIQobChMIr5aVnub29AIVQJFmAh2v6A3xEAQYASABEgLFUfD_BwE&gclsrc=aw.ds

See below 3 photos of the Farr727 set up. Very agricultural but it worked. The Modwood piece is cut so there is a tongue on the bottom which slides in and under the middle of a plastic horn cleat and the red rope secures it. The blue rope around the pulpit finishes the securing. Aft end of pole in saddle on deck. If I recall right extension out from the bow about 1.2m. No bobstay or lateral stays needed. Forget what the pole diameter was maybe around 60mm - wall thickness and alum material unknown. Kite luff around 9.6m, foot around 5m. For a Ross930 we made a carbon fibre prodder extending 1.5m out and that uses a 6mm Dyneema bobstay to the bow cutwater eyebolt but no lateral stays. The alum one which the carbon one replaced needed lateral stays and struts as well as the bobstay - it looked terrible.

See paper here with loads measured on J/80 tack line; not sure why the paper did not simultaneously record the apparent wind speed and boat speed with the load and apparent wind angle data - true wind speed could be calculated and plotted rather than just noted in the text as an average and gust peak. The kite area is noted as 63.1sqm. The rule is 65.
www.researchgate.net/publication/266477724_Dynamic_measurement_of_pressures_sailshape_and_forces_on_a_full_scale_spinnaker

There is another more effusive version of the paper here - suggesting a kite area of 68sqm.

hal.archives-ouvertes.fr/hal-01582953/document

Figure 3 of the first paper shows a kite halyard load of about 1320N at the assumed highest true wind speed during the trials which was noted in the text at 16kts or 8.25m/s. The tack line load is a bit less - say 80% of the halyard load as the clew load will have some vertical component. So 1056N.
From this the tack line load per sqm kite area (63.1sqm) =16.7 Newtons/sqm or 1.7 kgf/sqm. So this is at 16kts. The load will increase with the wind speed squared. So at (say) 25kts the load will be 4.2kgf/sqm. At 30kts 6.0kgf/sqm. A post on Sailing Anarchy on tack line loads has an input from someone suggesting 5kgf/sqm so this is in the ballpark. Of course all sorts of other factors need to be used in suggesting a general rule of thumb including the stability of the yacht in question, gust responses of the running rigging and the yacht, "upset" load case factors to account for murderous gusts and numerous other operational issues. So a 50% margin on top of this 4.2kgf/sqm at 25kts or 6kgf/sqm at 30kts would be prudent.

For the lateral loadings on the prodder end a 10% of the tack line vertical load assumed for the lateral load corresponds to a 6deg tack line angle off vertical. Maybe 15% or 20% could be used as a design value.

Would expect that for your 85mm alum pole only 800mm out from the fwd securing point you won't need a bobstay or lateral stays. If you had the wall thickness the section modulus of the pole could be calculated and the stress at the bow securing location calculated from the bending moment force x length. This stress could be compared to the 0.2% proof stress of the aluminium material the pole is made from. For 5083 H116 around 200MPa is expected. A margin of 2 to 3 on this would be advised.

www.atlassteels.com.au/documents/Atlas_Aluminium_datasheet_5083_rev_Oct_2013.pdf

A Eureka 30 yacht uses their normal symm kite pole for a prodder with about 800mm extension out with no bobstay or lateral stays.

Since mod wood/ plastic composite wood has been mentioned, has anyone tried to glue it with epoxy ?

Why risk the whisker pole? You could go to a nearby metal merchant and get a thick-walled aluminium tube for the spar. Cut it to length (you mentioned the length of the pole clashed with the coach-house roof), and apply the end-fittings. Two to three metres of the stuff is not very expensive, and aluminium is easy to work with hand tools.

A really quick internet search provided the following list of sizes ... www.ullrich.com.au/aluminium-extrusions/hollow-tube/

I previously got some 35mm (?) aluminium tube for my mast-raising A frame from a local metal merchant, see here theboattinkerer.blogspot.com/2018/06/episode-18-pole-son-of-pole-and-twin.html

Don't go the the Big Green Shed - the stuff there is too small and light (hence my experiments with my A frame).

My understanding is that Modwood is similar to Ekodeck as regards being based on the use of HDPE plastic in it's composition. The Modwood TDS and more details are here;

www.modwood.com.au/assets/Uploads/MOD-TechSheet-JUN-20-WEB.pdf

www.modwood.com.au/assets/Uploads/WPC%20-%20Building%20Contractor.pdf

I have had excellent responses back from Ekodeck as regards a project I had planned to use it in, for to add steps onto the transom of a Whiting 26 quarter tonner with the old diabolically sloped transom/stern shape, so I could get on board out of a 6ft dinghy without falling into the water.

As such, with HDPE in it, Ekodeck advised that no paint or glue will stick to it - they advised mechanical fasteners are needed.

I searched further and this glue apparently will do it but it is very expensive.

swiftsupplies.com.au/news/hdpe-drain-pipe-glues-and-sealants-guide/

swiftsupplies.com.au/weicon-easy-mix-pe-pp-45-adhesive-polyethylene-polypropylene-45ml-cartridge

I ended up making the steps out of Merbau from the big green shed and glueing and sealing the timber with Norglass epoxy glue and resin, then their shipshape epoxy primer, then their nonskid deck paint.

Thanks again guys. You have given me the confidence that my pole should work unstayed particularly as (usually effectively being singlehanded) I plan to use a light asymmetric only in light conditions and probably rarely shy. I can make the existing pole length work and this is good because I'm not sure that current readily available stock sections would accommodate my beaks.

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r13 said..
My understanding is that Modwood is similar to Ekodeck as regards being based on the use of HDPE plastic in it's composition. The Modwood TDS and more details are here;

www.modwood.com.au/assets/Uploads/MOD-TechSheet-JUN-20-WEB.pdf

www.modwood.com.au/assets/Uploads/WPC%20-%20Building%20Contractor.pdf

I have had excellent responses back from Ekodeck as regards a project I had planned to use it in, for to add steps onto the transom of a Whiting 26 quarter tonner with the old diabolically sloped transom/stern shape, so I could get on board out of a 6ft dinghy without falling into the water.

As such, with HDPE in it, Ekodeck advised that no paint or glue will stick to it - they advised mechanical fasteners are needed.

I searched further and this glue apparently will do it but it is very expensive.

swiftsupplies.com.au/news/hdpe-drain-pipe-glues-and-sealants-guide/

swiftsupplies.com.au/weicon-easy-mix-pe-pp-45-adhesive-polyethylene-polypropylene-45ml-cartridge

I ended up making the steps out of Merbau from the big green shed and glueing and sealing the timber with Norglass epoxy glue and resin, then their shipshape epoxy primer, then their nonskid deck paint.

Thanks r, I've got a toe rail to replace & am tossing up between composite & merbau

Thanks R13. I've been contemplating a similar setup, but my current pole is a light section (only about 60mm and 2mm thickness, IIRC) only designed to use to pole out the jib. So I can mess with different lengths on the assy kites I extended it with a spare bit of 6061-T6 I had lying around..... the joys of being a Laser sailor!

I may chase up RM, kite size etc to see if you wouldn't mind working out what sort of pole diameter and wall thickness would work as a prodder on reaches and heavy-air runs.

At the moment I just go straight from the bow when gybing or cruising, and on squares I just use a conventional pole on the assy. While there is an extra step involved in gybes, the assy and conventional pole setup seems to be a really good combination in many ways. You get excellent projection at deep angles, the head of the sail stays very controllable, and it's quite easy to ease off the brace and wind in the tack line onto the bow to allow you to move into "assy mode" for gybes or reaches.

Thanks Chris.

60mm diameter and 2mm wall thickness is certainly light on for a 36fter as you say, and good for jib poling out only I would expect as you indicate. Yes can see how your use of any asymm on the pole running square would work well. The 2 asymm kites on our Ross930 as bought 6 years ago were ~30yrs old and fine as such but late last year we got a 2nd hand (as new) Ullman asymm off a Tiger10 to go between them and it runs a lot deeper than the other 2 when set off the prodder - set on a symm kite pole it would work essentially as a symm kite as you say.

For sure I can assess your future plans for a prodder but the data I have in as per the prior post does not include RM just kite size in sqm. And need to know what length of the prodder you are planning out from the bow securing location - 1.5m works well with our Ross930 and should work ok on your boat. If you plan to include a bobstay this needs to be factored in also - so then the critical load case would be the lateral loading not the vertical loading but both need to be assessed.

Stolen from Sailing Anarchy. You might get some pointers here!

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Ramona said..
Stolen from Sailing Anarchy. You might get some pointers here!

is it just me, or does that sail look like they have the clew on the pole and the sheet on the tack ???

cheers,

Agree it certainly appears that they are reversed.

My apologies. It was just my poor taste in humour. I thought it was obvious they had it arse about!

Maybe they took inspiration from this beauty....


Merry Christmas to all!

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woko said..

r13 said..
My understanding is that Modwood is similar to Ekodeck as regards being based on the use of HDPE plastic in it's composition. The Modwood TDS and more details are here;

www.modwood.com.au/assets/Uploads/MOD-TechSheet-JUN-20-WEB.pdf

www.modwood.com.au/assets/Uploads/WPC%20-%20Building%20Contractor.pdf

I have had excellent responses back from Ekodeck as regards a project I had planned to use it in, for to add steps onto the transom of a Whiting 26 quarter tonner with the old diabolically sloped transom/stern shape, so I could get on board out of a 6ft dinghy without falling into the water.

As such, with HDPE in it, Ekodeck advised that no paint or glue will stick to it - they advised mechanical fasteners are needed.

I searched further and this glue apparently will do it but it is very expensive.

swiftsupplies.com.au/news/hdpe-drain-pipe-glues-and-sealants-guide/

swiftsupplies.com.au/weicon-easy-mix-pe-pp-45-adhesive-polyethylene-polypropylene-45ml-cartridge

I ended up making the steps out of Merbau from the big green shed and glueing and sealing the timber with Norglass epoxy glue and resin, then their shipshape epoxy primer, then their nonskid deck paint.

Thanks r, I've got a toe rail to replace & am tossing up between composite & merbau

Is this worth a separate thread? Whenever I have gone into Hammerbarn to look at the composite timber, I have found it only comes in lengths of several metres, and costs an arm and a leg. I'd like a short off-cut to see how it saws, drills, paints (or not) etc.

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Achernar said..

woko said..

r13 said..
My understanding is that Modwood is similar to Ekodeck as regards being based on the use of HDPE plastic in it's composition. The Modwood TDS and more details are here;

www.modwood.com.au/assets/Uploads/MOD-TechSheet-JUN-20-WEB.pdf

www.modwood.com.au/assets/Uploads/WPC%20-%20Building%20Contractor.pdf

I have had excellent responses back from Ekodeck as regards a project I had planned to use it in, for to add steps onto the transom of a Whiting 26 quarter tonner with the old diabolically sloped transom/stern shape, so I could get on board out of a 6ft dinghy without falling into the water.

As such, with HDPE in it, Ekodeck advised that no paint or glue will stick to it - they advised mechanical fasteners are needed.

I searched further and this glue apparently will do it but it is very expensive.

swiftsupplies.com.au/news/hdpe-drain-pipe-glues-and-sealants-guide/

swiftsupplies.com.au/weicon-easy-mix-pe-pp-45-adhesive-polyethylene-polypropylene-45ml-cartridge

I ended up making the steps out of Merbau from the big green shed and glueing and sealing the timber with Norglass epoxy glue and resin, then their shipshape epoxy primer, then their nonskid deck paint.

Thanks r, I've got a toe rail to replace & am tossing up between composite & merbau

Is this worth a separate thread? Whenever I have gone into Hammerbarn to look at the composite timber, I have found it only comes in lengths of several metres, and costs an arm and a leg. I'd like a short off-cut to see how it saws, drills, paints (or not) etc.

Indeed, I have some scraps and intend to test it, but I can tell you now it saw & drill superbly

Ekodeck provide a free sample kit posted to you. Many of the other suppliers do also. The Ekodeck samples are 70mm long cuts off their normally supplied 5.4m lengths of 137x23mmmm cross section. For sure it saws and drills well but for the many I have checked can't be glued (except for possibly the glue I outlined above) or painted.

www.ekodeck.com.au/request-a-sample