Biplane rigs

Discussion in 'Multihulls' started by cutawaycafe, May 15, 2013.

  1. he b gb
    Joined: Feb 2014
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    he b gb Junior Member

    Hi Groper, I have'nt had the boat weighed but by the displacement of the hulls I would estimate it at between 3.5 and 4 tonne sailing with minimal water ,fuel and basic gear on board. The rigs are of my own design but are balestron style as Robs are. They are actually constructed out of two 7 mtr lengths of aluminium tube (4.75 mm wall) internally sleeved,(150mm dia),to which I laminated divinycell foam up to the hounds,then tapered the foam from 20mm at base to nothing at the hounds. Then laminated carbon uni's (toray 6oz) at 12 layers up to a metre above the deck bearing tapering down to 1 layer at the hounds. This was consolidated with d/bias glass,one layer after 6 layers of carbon then another after 12 layers,also one layer over foam before the carbon. All the laminating was done by hand(no vacuuming etc,all very low tech). Because the tubes were joined I decided to put spreaders at the join (for diamond wires) as the 14 mtr tubes seemed quite floppy. In hindsight this was probably not the best way to go as the diamonds transfer all the loads below the spreaders so it bends at the lower half of the mast instead of from the top down as a full tapered carbon tube would. Despite this the masts work very well and appear to be mega strong, being only 40' above deck helps alot in this respect.We've had it out in 30kts a few times,been hit by a few big gusts without any scary noises or abnormal bending happening.The masts weigh about 170 kg each. hope this might be of some help with your project. As yet I have'nt heard of a biplane motorsailor either, probably because of expense but if you can do every thing yourself it would be quite feasible.
     
  2. groper
    Joined: Jun 2011
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    groper Senior Member

    Thats great gerald... can you tell me some more about the bearings and deck and sole reinforcement? I need to plan these out first - im not going to build the masts until the boat is in the water, so ill work that out later... I do need to get the bearings and reinforcement planned out tho so i can finish fairing it all in and get it painted... :D
     
  3. he b gb
    Joined: Feb 2014
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    he b gb Junior Member

    Hi Groper, My bearings are pvc pipe of around 10mm wall which I sourced by going around to every plumbing or irrigation store in Bundy before finding what I needed! I then took them to this retired lathe guy who machined them so inner and outer bearings had about a 1 mm clearance,this he did for $40. The inner bearings were then glued to the mast using a straight edge to align them.I made a conduit out of 3 layers of d/bias glass using some larger pvc pipe as a mould,the outer bearings were then glued to the conduit in situ on the mast which allowed the bearings to align. When cured the conduit was then removed and fitted to the boat knowing that the bearings were aligned. So to do it this way you need to build the masts before fitting outer bearings to the boat. I can't think of any way of aligning the bearings correctly if you fit the outer bearings to the boat first. My bearings are 80mm high and I have fitted s/s grease nipples (3) around each set, Innox make a grease which is suitable for use with plastics. They spin freely but the top bearings(which are more highly loaded) start to make noise when under load. I am in the process of fitting s/s shims to the top inners to hopefully stop this noise. As for beefing up deck and sole its a bit hard to explain in words, my conduit passes through what would be mast bulkhead(if standard rig) which is quite substantial giving it plenty of support sideways, to support it forwards and at 45 deg I have heavily glassed tapering timber ribs.(internal only) on the outside (deck) I glassed heavily (uni's and d/b) about 750mm out from mast,also if your decks are balsa remove the core for around 500mm around mast and replace with ply.The main things you should be aware of with beefing up decks and sole is that the major loads on freestanding rigs at deck level go sideways and forwards with smaller loads going aft and at sole level the loads go backwards and sideways with smaller loads going forward and there is bugger all compression load.(you're probably aware of this anyway) I have a drain at the bottom of my conduit into a small bilge (about 2 litres of space) this after 2 years has never needed emptying, I think the small amounts just evaporate. I have done a pretty good job of sealing the conduit.One day when I learn how to I'll post some photos.
     
  4. groper
    Joined: Jun 2011
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    groper Senior Member

    Cheers for that! You explained that well...

    To post pics, click "go advanced" instead of the "quick reply" dialogue box. When the screen refreshes with the advanced menu icons directly above the dialogue box, click on the paperclip icon which brings up another screen which allows you upload "attachments". Once your there, navigate to the pictures on your computer hard drive (or USB, or whatever) and then click the upload button. This will attached the pics to the bottom of your post where people can click on them and view them. They wont be visibly imbedded in the post iteself, this requires a few extra steps. Ill explain that next time :)

    Did you research the suitability of PVC plastic as a load carrying bearing material? I know many multis use it in the rudder post conduit type bearings, but the loads on these unstayed mast bearings must be huge in comparison, i would have thought PVC wouldnt last...? The other guys are using machined Acetal/stainless steel for the bearings to give a long service life... I think id spend a few extra dollars on the acetal aswell - although it would have to be done a little differently to the way you approached it as acetal is difficult to bond so instead its usually bolted in place. But if yours are going strong, more power to you!
     
  5. rob denney
    Joined: Feb 2005
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    rob denney Senior Member

    Very cool. Would you make them in one piece or mount them on stubs? This is a bit heavier, but allows the halyards to be lead aft or sideways and does not require a deck seal. It does require pretty good bearings as the top one is inaccessible after the mast is built.
    Another option is to make them hinge just above the boom, which would eliminate the potential for sailing round at anchor that Barra is concerned about. Unless you have a bridge to get under, I suspect it is not worth the effort.
    I like the idea of a motor sailor, but not so sure about the fuel and maintenance cost of 2 x 60 hp outboards.
    Your boat is looking good. Any idea of launch date?

    Gerald,
    Welcome to the forum. Thanks for the build explanation. I would have been surprised if you had built it the same way as anyone else, ;-) but even more surprised that you managed to combine alloy, foam, glass and carbon! 7 grand is pretty good going, although 170 kgs is a bit high. Most of it is down low, so not that big a deal.

    Look forward to seeing some more videos at some stage.

    We use UHMWPE for bearings on harryproas, it is lasting well. I have pvc drainpipe on my 25' proa and it has worn through. The other surface is fibreglass, fairly rough on the little boat so not a reliable test. I would have thought the grease would ensure very long life. For Mike's boat we made some very flash ss/acetal self aligning bearings which work very well. However, another client has sourced some low cost slewing bearings from China. If these work, they may become standard.

    rob
     
  6. he b gb
    Joined: Feb 2014
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    he b gb Junior Member

    Hi Rob, Hows things, long time no see. Are you back in Qld now? Yeh it's quite a mix of materials in the masts,I would have liked to do them out of carbon only but 6 years ago when I built them carbon was way more expensive and quite hard to get. I worked out it would have been more than 7 grand per mast in those days, and this boat being a bit of an experiment I didnt want to spend heaps in case I reverted back to a normal rig if I didnt like it (my boat was built with a full strength mast b/head in case I didnt like it) but after a couple of years sailing I can assure you that I'll be staying with the bi rig . With the greased pvc bearings I'm pretty sure I'll get mega years without them wearing out and with the s/s shims I should get even more(hopefully without the plastic on plastic squawking) I did research other plastics as a bearing choice but came back to pvc mainly because of it's high density, I felt that poly ethelene might start to compress under continued high load .( the price of exotics came into it also as this was an experiment) I dont have any other vids but heaps of photos, which I dont know how to get out of the folders,sorry Groper, on to here.
     
  7. groper
    Joined: Jun 2011
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    groper Senior Member

    No idea of launch date rob, hopefully late this year... I was planning on one piece masts... build a plug from hot wire cnc cut foam and glass it. Take a 2 piece split mold off it and infuse the whole thing in 1 shot. Talking to some people overseas about infusing heavy carbon laminates.... the need for internal webs at the boom connection will make it a 2 step job tho. Will have to catch up via email soon...
     
  8. rob denney
    Joined: Feb 2005
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    rob denney Senior Member

    Back in Qld, on the Gold Coast of all places. Still designing/building harryproas, selling carbon masts and playing with boats. Life is good.
    I agree that the grease/pvc/ss will last pretty much for ever. Glad it all works so well.
    Carbon has certainly come down in price. My last shipment was $45/kg for 300 gsm uni. In carbon with glass for the off axis, your masts would weigh about 100 kgs (?), so a tad over $3,000 for materials per mast.
    Look forward to seeing your boat sometime. Are you doing the 50th Gladstone?

    Groper,
    Bulkheads can be included in the infusion (we include full length sheer webs in the wing masts), which is a lot easier than making them in 2 pieces and joining them. Another option is to increase the laminate where the bulkheads go. Adds a little weight and expense, but saves a lot of mucking about. Can also add it externally, which increases the diameter, making it easier to step.

    If you are going to include an integral track (easier than adding one), split the mould along the max chord, rather than the leading and trailing edges. To eliminate bridging on the te, it is probably better to spilt it at max chord regardless.

    rob
     
  9. groper
    Joined: Jun 2011
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    groper Senior Member

    Why? I know they engineer wind turbine blades like this, but i wouldn't have thought it nessesary for these wing masts... My gut instinct tells me that there would be little weight advantage in doing so instead of building the wall thickness to sufficient thickness to simply let the wing section modulus do the work ( as opposed to splitting it up into tension/compression caps with shear web between).... I'll have to run some numbers and check out this approach to see if it's its worth it for my needs...
     
  10. rob denney
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    rob denney Senior Member

    Sorry, wrong wing masts. I was referring to the stayed ones we built for the Toro cat and the Essential 8 tri. Not sure if the biplane masts have them or not. At a certain size, any wing mast will need core and a sheer web. An 18m high, 600 mm chord wing mast for a 15m racing harry has both.
     

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  11. brian eiland
    Joined: Jun 2002
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    brian eiland Senior Member

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