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Alternative build


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Decided to use up my old stock of cedar planks ( at least 3 boats worth) and build a modern One Metre. Thanks Brad, have gone for your "Alternative" design. Super efficient looking lines and looks a little tricky to plank up.

Picture of starting point. Note the string passing through the 2mm datum holes in each shadow, each one is aligned by shining a bright light from the end and sighting down the hull.

Richard

 

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Thanks for the comment Mike.

Thinking of a lowered deck aft of the mast to avoid a mast well. I know the current fashion is back to flat aft decks but It is easier, lighter and stiffer for a timber boat than a multi part well or inserting an Ikon or similar moulding.

Some more pics of progress. Rough trimmed and sanded hull.

Richard

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Good work the photos are very helpful. I'm about to start planking an Ellipsis and am a bit concerned about the process, I understand the planking but not sure about what epoxy to use etc etc. Please update as you move forward.

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  • 2 weeks later...

Stephen, sorry for delay in responding. Boat has been on "back burner" for last few weeks.

Everyone has their favourite adhesives. I use the following:

SP 106 for structural filleting etc.

XCR coating epoxy from Easy Composites for coating. It has built in UV protection.

Aliphatic resin from Deluxe adhesive for planking. Easy clean up so all excess can be removed with the usual eye to keep weight off. It sets waterproof.

Picture to date. Ready for deck.

Richard

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Hull finished, just requires tidying up and a final thin coat of epoxy, which will be flatted back with 1200 wet and dry. Then setting the trim for ballasting the fin.

Note that I have straightened out the centre line of the fore deck. Brad's drawing shows a sharp curve towards the bow. The sheer retains the sharp upturn but the deck would have been tricky in wood and heavier to achieve; requiring intermediate deck frames. The drawing does show these however.

Richard

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Hi Richard,

I've just finished building my Alternative and I am in the process of rigging it. I have used a planked balsa wood contruction sheathed both sides in fibre glass mat using light weight epoxy resin. Weight of painted hull with winch, servo,pot, battery and receiver is 855 gm's. I wanted a total weight under 4 Kg. In a test tank the boat floats perfectly on her waterline. I am having a problem fitting a mast ram at the moment, there isn't enough room between the bulkhead and the mast.

I have attached 3 photos but the resolution is greatly reduced in order to send them.

Roger

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Hi Roger, looks stunning really beautiful finish.

I achieved practically the same weight. My bulkhead in front of the well gives me nearly 15mm to mast leading edge so I have plenty of room for ram. Picture attached. May be a bit of surgery to your deck for a recess to accept the ram screw. Let me know your solution.

My problem is the kicking strap fouling the winch lines emerging from the bulkhead. All as the drawing so I will have to devise a wire kicking strap with the tension screw inside the boom or something. All ready to sail apart from this hiccup !

Richard

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Hi Richard, looking at your picture, one change you could make would be to lower the bulkhead exits so the lines come out below deck level. There is little friction added where the lines rub on the edge of the recess but it allows the kicker to swing free. Also use a kicker with a slim rigging screw.

Also from your picture I would say that your jib sheet deck eyes are a little too tall which will give you problems with sheets getting wrapped around them - an easy way to put unnecessary strain on the winch.

Cheers,

James

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Thanks for your comments James, the solution was indeed easy. I have re positioned the fairleads right in the corner of the foredeck side deck transition.

Just wish I had checked before slavishly following the drawing. I already had the lines only 1mm higher than the deck. I have removed the knurled wheel from the Sails etc kicking strap and all is clear now. Point taken about the sheet eyes, probably look a little higher because of the picture angle, but could be lower I agree.

Richard

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Hi Richard,

You're more advanced with your Alternative than I am, I'm still fiddling around with the rigging. Regarding my mast ram problem of insufficient room between the mast and ram.The reason is because I positioned, by mistake, the fin/mast box 5 mm further forward than the plan so I hope this dosen't affect the balance too much.

I notice your ram takes up less space but doesn't provide lateral support, this may be my only option.

I also have the same problem as you with the kicker strut fouling the winch line. One reason is that the SAILSetc plastic compression strut has a very large knurled adjustment in line with the edge of the cockpit. Also initially I used the SAILSetc fixing point on the boom instead of Brad's position which is much closer to the mast so I shortened the wire and repositioned it, this gives more clearance however it didn't cure the problem completely so I have ordered a SAILSetc reverse strut which has the adjusting screw nearer the boom.

Can you tell me what the final total weight of your boat was before correctors were added and does the boat feel balanced? Also how much rake have you set?

Regards,

Roger.

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Hi Roger,

As long as the finbox and mast are all 5mm further forward the balance should be similar; the rectangular rudder reduces the effect of the hull rocker on the lateral position so the main effect will be to change the trim a little. But do note that Brad has placed these components deliberately and not where I would have expected; which is what has made this build particularly interesting.

I went for the simple ram and accept that there is no lateral support. I have tried extending the deck on other designs to form mast partners but the horrific snags on lines were not worth the bother.

The kicker problem: easily solved. I re positioned the fairleads as shown on the picture and filed off the Sails etc knurled top (using a drill and file) The lower plastic locking wheel just clears the fin bolt. I may reduce this also. The yellow tape provides grip to adjust. All clears now. I did consider the Sails etc reversed kicker however.

I set the mast vertical, by measurement and set the forestay accordingly. Then I drilled additional holes at the forestay attachment on the mast at 6mm intervals down. See Lester Gilbert's comments on mast building. This gives 1 degree of rake per hole. First sail experience was very encouraging. Perfect balance but a tad twitchy in gusts. This could be more to do with sail settings - must experiment more.

Total weight ready to sail is 3795grm so I have 110grms of lead in the bow. A shame to have to put it there but that trims the boat exactly as Brad has drawn. Not as light as my epoxy glass hulls but much much stiffer, which may count for something.

Any comments, advice or just critique, welcomed.

Richard

National championship race costs.xls

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  • 2 weeks later...
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Quote

Second picture here. Cannot download more than one at a time. Preview shows both but after submitting one is deleted.

Richard i will look into this in the morning you should be able to post more than one picture (think limit is around 3 per post)

Garry

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  • 1 year later...

I’m relatively new to the hobby, having raced at club level with an Isis and now a Lintel for about 3 years. My next project is building an ‘Alternative’, so this thread is obviously of interest. I notice some use cedar and others balsa planking; what are the pros and cons for each? Do both need finishing with fibreglass and is there a generally preferred plank thickness and width? I have built planked balsa and ‘glass hulls for mtb’s etc in my scale modelling days - usually 6mm x 3mm planks.

Howard 

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Hello Howard.

I am not a scale modeller but I do know that the approach needs to be different. Weight and strength makes it much more of an engineering task.

For this reason I make all the planks full length with no "closing" planks just my way, but it means that each tensioned plank contributes to the stiffness. This will result in an odd looking plank line and not like a model.

I use cedar planks; 10 X 3mm. I precut only 3 different shaped planks  with a parallel in the centre tapering to the ends with the parallel part reducing in each of the batches of 3.

I have one of those little razor planes and it is perfect for tapering the planks a pair at a time.

Each plank only requires edge sanding to fit snugly to its neighbour. I usually do the layup 3 planks at a time on each side, leave for a few hours and do the next 3.  Really quick and I find the hull the quickest part of making a One Metre. 

Cedar versus Balsa !  I don't want to start a debate, since each builder has a preference. I prefer Cedar. It is much more tolerant to being pulled down hard whereas you cannot do this with balsa because it bends too easily and it difficult to avoid dips between the frames and you cannot tension balsa at all.  It is the tension locked up in the tortured cedar planks that results in considerable strength. The bare hull shell should "ring" like a violin. Glue is important here and you need a quick grab aliphatic resin. It is vital that any excess glue is wiped off immediately, it swiftly adds to unnecessary weight. I use Deluxe Aliphatic resin; available from model shops. Also about ten rolls of 10mm insulation tape. 

Balsa also hoovers up resin when coated. I coat the whole shell with SP106, light and very strong epoxy. The same I use for filleting and all bonding.

Although I do not always glass a hull, I did line the inside of Alternative because it is quite a tight shape. Only the inside though and I use very fine woven glass: about 50gsm.

That is what I do, Howard. I am sure that you will get a different approach from whoever you ask though. Each just as good for them.

Building a modern boat like Alternative is a huge saving on a purchased hull and I can assure you that this design, carefully built will see you at the front of the fleet.

Richard

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Thank you very much Richard - there is some really helpful advice in your reply and I appreciate you taking the time to make it. I’d like to try cedar; other club members have used balsa also, and perhaps this is the best way to compare. I’m looking forward to the project!

Howard

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  • 3 weeks later...

Having received the plans last January I've finally managed to start on my winter project. I've decided on trying to complete this using the  foam / GRP option vice planking as my fibre glassing skills are probably a little better than my woodwork  ones . Now the decision is vertical split, hull/deck split, after making a mould or a one piece wrap on the plug

I'm sure there will be trials and tribulations along the way but hopefully another Alternative will be hitting the water eventually!

All advise gratefully received.

Shaun

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Hi Shaun,

Loads of work for a one off!  I like composites also it is just that cedar planking a hull only takes 2 or 3 days and is really simple. Also possibly more accurate unless used to foam shaping and avoiding the usual pitfalls.

One piece wrap works;  assuming you will be using fine twill weave and epoxy. Still you will be surprised at the weight to add with the fairing filler at 30-40grm per coat. 

Don't forget to colour pigment  the coats ! I use U pol, by the way.

Add some pics as you go.

Richard

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  • 2 weeks later...

Disaster avert! Too little epoxy midships ended with the hull in 2 halves, liberal amount of epoxy for the second attempt only to find the mark one eyeball didn't quite have everything aligned as it should (oops!). A cut and shut operation followed with a new 6th section inserted.

Now for lots of filler to cover the dents in the foam, bit more sanding then hopefully it'll be ready for a nice coat of glass.

A slow burner of a project but I'll get there in the end (hopefully!)

 

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