Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Yachts and Sail => Topic started by: goBulawayo on August 27, 2012, 07:55:31 pm
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So here goes my first foray into model yachts, other than the damaged yacht I bought some years ago shown in this thread - http://www.modelboatmayhem.co.uk/forum/index.php?topic=39116.0 (http://www.modelboatmayhem.co.uk/forum/index.php?topic=39116.0) -
The yacht I am planning to build a model of is called 'Force 8' which was designed by Angelo Lavranos in the 1970s, the yacht was built in Rhodesia (where I am from) and was used in the 1979 Cape to Rio yacht race, I believe it placed 14th. The yacht was crewed by eight members of the Rhodesian security forces, hence FORCE 8 - The yacht still exists in New Zealand.
I have recently been in touch with Angelo Lavranos, who has kindly agreed to supply me with plans of the boat. i will not be able to post them on forum, but you can see the basics that were published in "South African Yachting" plus some photos of the yacht here - http://www.apolloduck.co.uk/feature.phtml?id=235124 (http://www.apolloduck.co.uk/feature.phtml?id=235124)
This will be a long time in the making but I will post progress as I go along - It will probably be a few weeks before I get the plans anyway.
Wayne
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looks pleasing to the eye , what size are you thinking of biuldnig too ?
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Hi Triumphjon, the plans are drawn at 1/15 and this is the scale I will build the yacht - Makes a model about 930mm long, which I reckon is a manageable size both for the construction and handling / display
Wayne
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Hi Wayne
It's really nice that Angelo Lavranos has provided you with plans of the boat.
I'm sure you'll do a great job - and meanwhile I'll do a great build watch O0 {-)
Dave
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I'm really looking forward to watching this Wayne, as Dave says you're lucky to have been allowed to use the plans and at the size you're building it, it will be a practical size to sail.... Keep us of informed as to progress :-)
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I've put this on your other thread, but you may as well have it here too... A good source of info regarding rigging model yachts.... http://www.theamya.org/my/138-SampleWebEdition0801.pdf (http://www.theamya.org/my/138-SampleWebEdition0801.pdf) :-)
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Thanks Guys, I am looking forward to this build - I recall making a small yacht as a kid, solid shaped balsa hull with a mast and main sail, remember floating it in the local pool, I don't recall how well it worked though. This time will be different if I can get my head around all the workings needed!
Artistmike - Thanks for the link, now to get my head around it all!
Wayne
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Plans have arrived and as soon as I can get into town next week I will have them printed and then its time to get building - Oh I had better order in some wood, I think I will go with ply for the formers, not sure re the hull covering yet, probably thin balsa - The plan was to use the wooden hull but it may be better to make a fglass female mould then a fglass hull, any suggestions? If the fglass mould/hull does not work, at least I will still have the wooden hull to work with.
Cheers
Wayne
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Would 0.8 balsa be sufficient for the hull covering? I assume I should glue it in diagonally?
Thanks
wayne
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Would 0.8 balsa be sufficient for the hull covering? I assume I should glue it in diagonally?
Thanks
wayne
You need to consider that you will hit things, or they will hit you.
Also if you use something thicker you have surplus material to sand to lose the planking effect. You can then put a layer of 'J' cloth inside the hull and impregnate with resin. Or you can use glass cloth and resin on the outside for extra strength, or do both.
If you diagonally plank, you can use two layers of planking at opposite angles and sandwich cloth between the layers.
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Thanks Tigertiger, I was thinking along the lines of using the wooden hull as a former for fibreglass mould then make a fibreglass hull - However I think this may be too much for my skills so I reckon I will try the double layer of planking with "J" cloth - By "J" cloth do you mean the stuff used for washing dishes?
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Yup, dishes.
Have a look in the Masterclass section. A couple of the builds have the double skinned diagonal planking techniques set out on there.
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Can anyone suggest where I might be able to buy a yacht wheel like the attached please, with the steering post if possible - needs to be around 60-65mm diameter
(http://i297.photobucket.com/albums/mm223/gubulawayo/Yachtwheel.jpg)
Thanks
Wayne
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To be honest, I've not seen one like that so this may be the time to think about scratch-building one yourself.... when you get involved with making a one design scale model, even a stand-off one, it's inevitable that you're going to have to make much of the items yourself, how's your silver soldering technique ?
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Mmm I don't have any technique, my brother has said he will try though that would be in brass. What white metal can one solder to make one that looks like chrome / stainless steel?
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Hi Wayne.
The yacht steering wheel you are looking for is the kind used on the Robbe and Graupner yachts. You may get one on line or E-Bay.
Frank :P
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Thanks Frank, I have seen the robbe wheel but it has what looks like wooden cross struts - I will have a look for the graupner one
Wayne
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some modification might be a lot easier for you than scratch building
Dave
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Hi Wayne.
They come in both wood and plastic here a pic
(http://s9.postimage.org/z9zd7e7i3/S5000064.jpg) (http://postimage.org/image/z9zd7e7i3/)
Frank. :P
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Thanks Frank I will keep an eye out for them
Wayne
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Anyone got any idea where I can get oval aluminium tube please, shape like pic below, long length about 24mm
Thanks
Wayne
(http://i297.photobucket.com/albums/mm223/gubulawayo/ProfiledMast.jpg)
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Hi All, another question here - The plank on frame builds I have seen so far have the edges of the hull flush with the deck - The yacht I am going to build has the sides coming up above the deck, ranging from a few inches to about a foot or so (dimensions as on the full size yacht) - How would I go about doing this? I thought of carrying the planking past the deck line and then trimming it but how do I get the line cut to the right profile? The other option I thought about was to fit a strip (pre-shaped to the top of hull line) to the side of the hull about 10mm down the hull and then plank up to that strip. Any thoughts or ideas welcome
Thanks
Wayne
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I'm not sure what you mean Wayne but it may be what is referred to as a Toe Rail, possibly custom designed, but these are usually not part of the planking but are fixed to the deck. If you try Googling toe rail in Google images you'll see what I mean .... Toe rails usually have holes at deck level, known as freeing ports that allow any water that comes on deck to be drained overboard.
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Hi Artistmike, I am pretty sure it is what you call a toe rail, this yacht has a steel hull so the plates were probably just brought up above the height of the deck to form the rail, which is lower near the middle than it is at the bow
Wayne
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Right I have my prints of the plans sorted out. Now to prepare the hull lines into individual bulkheads and get some 4mm ply and we can start - She is a bigg'un
Wayne
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Looking forward to seeing how it goes .... :-))
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Things are progressing, I have hand drawn most of the frames, but I am looking at doing them on CAD and then having the frames cut on a water jet - Will have to see how it goes cost wise. I have some 3mm birch ply that I was going to use to make templates from the hand drawn frames and I may just do this anyway.
Also slowly working through a list of fittings etc needed. One thing I am struggling to find is streamlined aluminium tube about 1" across the long length.
Wayne
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Wayne
You asked "Can anyone suggest where I might be able to buy a yacht wheel like the attached please, with the steering post if possible - needs to be around 60-65mm diameter"
Sorry I am getting to the party a bit late - but for future reference check out the Kyosho Fairwind lll is has a helm station much like the one you show in the photo you posted and it is 60MMs.
Fairwinds have been produced by Kyosho for many years. They come in and go out of production - the most recent version being their Faiwind lll the best version so far. I posted a photo of the helm for you to see. Kyosho just pulled the Fairwind lll of production but there are parts available on line here in the states should you or anyone have an interest.
Boomer
Not able to post the picture I mentioned but you can check out this boat at the Kyosho website http://www.kyosho.com/eng/products/rc/detail.html?product_id=103329
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Hi Boomer
Thanks very much I will have a look out for a wheel off the fairwind, much appreciated - might you have any links to someone selling the wheel please
Wayne
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Hi Boomer
Thanks very much I will have a look out for a wheel off the fairwind, much appreciated - might you have any links to someone selling the wheel please
Wayne
Wayne
Go to Kyosho America at this link. You can order from them directly http://www.kyoshoamerica.com/Rigging-Parts-Set-B-FAIRWIND_p_2643.html
Part number for this item is FW17C it sells for $19.00 USD plus postage.
I was able to compress the picture of the aft end of the Fairwind that shows the helm station I am talking about.
That page has a good picture of the parts that you can enlarge. It comes with a few extra trim parts you may or may not be able to use.
Boomer
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Excellent thanks Boomer, and there are a few extra parts I can use in that lot
Are you Boomer1 across on RC Groups? I have the same name on there as here
Cheers
Wayne
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That would be me. :-))
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Hi Boomer
Thanks very much I will have a look out for a wheel off the fairwind, much appreciated - might you have any links to someone selling the wheel please
Wayne
goBulawayo
http://www.giantshark.co.uk/forum/viewtopic.php?f=132&t=5793 (http://www.giantshark.co.uk/forum/viewtopic.php?f=132&t=5793)
I have just taken two wheels off my Kyosho Seadolphin - see the photos in the GiantCod/Shark forum
I'll dig them out and if they're any good to you, you can have them FOC - I intend to hack off the
mountings for the wheels too, and you can have those as well - they should modify OK for what
you want. Let me know what diameter wheels you are after and I'll measure the seadolphin ones.
Richard
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Thanks Richard, looking for around 60mm diameter please
Regards
Wayne
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Nah - these are only baby ones (40mm) - I'll stick 'em in some
compost and see if they'll grow a bit!
Richard
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Thanks Richard, just had a look at the plan again and they are 51mm so yours are still a bit shy on size, thanks for checking
Wayne
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Kyosho Seawind wheels are 48 mm, so only about 1/8" away from the 2" wheels that the plan calls for.
I'm old enough that going back to inches makes it easier to visualise sometimes. %)
Edward.
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Hi Guys
Started laying out the board that I am going to build the yacht on, I see the frames are quite close together, about 35mm centres, and I was wondering whether I could get away with removing some of the frames, increasing the centres to about 70mm or maybe even 95mm? Any suggestions welcome - I certainly think I have too many.
Thanks
Wayne
(http://i297.photobucket.com/albums/mm223/gubulawayo/Force%208/IMG_9531.jpg)
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I have decided to go with half the frames that I had originally planned on using. Now to get some 4mm ply and get on with the frames
(http://i297.photobucket.com/albums/mm223/gubulawayo/Force%208/IMG_9541.jpg)
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@BulaWayo:
I am not a builder, but it sure did look like a lot of frames for the size of the vessel compared to other build pics I have seen....
Seems a good call to me...
Unless you have something wrong with translating the scale somehow???
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Thanks MrPenguin
No issue translating the scale I have taken them straight off the drawing which is for a full size yacht, so probably needs all the additional frames which at full size are about 53cm apart. Having looked at other builds, I think I will be OK with the wider spacing.
Wayne
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Thanks MrPenguin
No issue translating the scale I have taken them straight off the drawing which is for a full size yacht, so probably needs all the additional frames which at full size are about 53cm apart. Having looked at other builds, I think I will be OK with the wider spacing.
Wayne
Aha!!! That would make sense....
If you are working from the full size plans you may well find othere similar issues that need some "translation"
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Hi GoB... I am just about to restore a 36R yacht, about your size at 36 inches and that has 11 frames including the transom. So you are about right with the photo showing spacers.
regards Roy
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Thanks Roy - It will save on material too!!
Cheers
Wayne
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Hi Gob.. what is the displacement of the model? I ask as the keel is not very deep on the plans I looked at on the full size boat. Have you calculated this?
I would think the keel is not deep enough for a model to sail well.
can exchange thoughts on line now
regards Roy
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Hi Roy
No idea re the displacement, it was suggested by the designer that it would be about 4.5kg but I am not sure, how would I work this out? - I know that I would probably need some sort of add-on keel for sailing and keep the original keel as is for display - Again I have no idea how this keel extension would work. Perhaps I could leave a slot in the underside of the original keel into which a tongue on the add-on would slide and then have bolts to fix them together - I know this would leave holes in the original keel when on display but I think I can live with that.
Wayne
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Hi Wayne, you might just get away with that displacement. When you cut out the frames have you made allowance for the planking?
How thick are the planks to be? I think I read earlier that you were going to use ply.
The side view of the full size boat shows only a small depth of keel. You could go to double that depth and it would not spoil the lines.
Another way to increase the displacement is to thicken up the keel. Not a lot, maybe 1/4 of an inch each side and keep it all in an aerofoil cross section not a bluff round that tapers off.
The amount of keel in side view is going to allow rather a lot of sideways movement when sailing, i.e. she will not point up so well when tacking into wind. If you can increase this all to the good.
You will need to get as much lead as low as possible to balance the wind on the sails.
There are a lot of variables. Which are the ones already decided? I.e. have you already cut out the frames? Decided on the thickness of the planking?
regards Roy
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Hi Roy
Drawings of the frames are full width so no allowance for hull thinkness, would adding 1.5mm to the width (well 3mm for both sides) do anything detrimental to the model shape? If so I am going to have to try re-draw them with 1.5mm less. I did start drawing the frames on AutoCAD and I am thinking it would probably be a good idea to complete them that way as it will be easy to offset them and I could even go for 3mm per side for two layers of planking.
I have not cut out the frames yet, I had thought of using 1.5mm balsa strips to plank the hull, but then again ply strips would probably be stronger? I then planned on adding a cloth layer with resin.
The keel is about 30mm wide at its widest point and roughly around 20 wide for a good portion of its thickness - I was thinking that I could form the two halves of the keel out of lead that is then bolted together and the whole lot cloth & resin coated? I will draw out a double depth keel on the drawing to see how it looks and as you say that might be the way to go, there is always going to be some give or take in making this a working model but as near to original as possible -
Wayne
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Hi Wayne, keep the frames the way you have them as adding the planking will give you a greater displacement and this is a good thing.
I don't like balsa for this job, you do not need the lightness so go for a harder wood. You will see the frames through thin balsa as they simply use the frames as corners.
Ply at worst cut with grain running along hull length, but it works, any knot free straight grained wood.
I would use 3 mm planking to allow for some smoothing down afterwards. Planks can be quite expensive.
I have used 3 mm liteply ( cut 5mm and 8mm wide) lengthwise on one yacht smoothed it to nice fair curves and then 1 mm x 6mm wide diagonal planking. If you cut with a circular or band saw allow for the cutting losses.
Very strong hull this way and with diagonal planking there is very little wastage. But the planking is not cheap, work out the area and add 10 %, you don't have to have long planks so they could be cut from Bass wood or obechi.
You can widen the keel simply by double planking.
I think construction in this way will give you the displacement to carry the extra lead as low down as possible.
Have a think about how you will bolt the lead through to the hull to make it a good mechanical joint.
Are you stepping the mast on the keel or the deck?
I think it should all work for you.
regards Roy
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Thanks Roy, will leave them as is -
The frames are going to be 4mm (or is it 3.6mm??) ply, just the covering was to be balsa. I will look into liteply though - I think the shape will be fairly easy to plank along the length of the hull (long planks though the boat is about 936mm long -
The way I have seen the lead keels bolted was holes right through the lead pieces with a wider hole about half way through (or at least enough to recess the nut and bolt) - washers fitted both sides then nut tightened up. I think the builder may have filled the recesses with resin or epoxy adhesive, then glassed over the lead and painted -
I am going to step the mast on the keel, one idea was the widen the keel at that point as well as make the keel higher, then a hole drilled in about 2/3 down the depth of the keel at that point, then once mast inserted drill a hole through the 'step' and mast and bolt it in. Actually I will have to make the hole a slot so the mast can lean back a bit.
Another idea was to widen as before and use a ring like a washer with a collar to fit the mast foot into
Regards
Wayne
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The frames are going to be 4mm (or is it 3.6mm??) ply, just the covering was to be balsa. I will look into liteply though - I think the shape will be fairly easy to plank along the length of the hull (long planks though the boat is about 936mm long -
I know balsa is easy but it is mainly soft and smoothing down will flex the balsa as you do it and it is difficult to get good curves. Another point is that the adhesive will probably be tougher than the balsa.
The way I have seen the lead keels bolted was holes right through the lead pieces with a wider hole about half way through (or at least enough to recess the nut and bolt) - washers fitted both sides then nut tightened up. I think the builder may have filled the recesses with resin or epoxy adhesive, then glassed over the lead and painted -
Are you going to cut up lead sheet for the keel. A good safe way. Then you can bolt it together in layers. I do not think you can glue lead! You can of course surround it with epoxy and filler etc.
I am going to step the mast on the keel, one idea was the widen the keel at that point as well as make the keel higher, then a hole drilled in about 2/3 down the depth of the keel at that point, then once mast inserted drill a hole through the 'step' and mast and bolt it in. Actually I will have to make the hole a slot so the mast can lean back a bit.
Stepping the mast on the keel will work, it works better if you can secure it as well at deck level too. This helps the mast resist the bending induced by the wind on the sails. May I suggest that you mount the mast in a simple way until you find the right position for it, then fit a tube that the mast can slide into. The tube can be fixed at the keel and deck level. It is best if you can then also fit a tube around the mast base that slides into the tube in the hull. I had experience of a wooden mast in a tube that got wet and took 3 weeks to dry out before it could be removed.
Brace the mast opening at deck level with extra beams between the frames and across the deck. This is where the drive from the sails transmits the power to the hull.
The benefits are a water seal at the deck level. It is very easy to rig the boat at the pond side, wind etc. when you can put the mast in and it stays there. You can also reduce adjustments to the mast stays. These can be fixed wire with a very strong spring in the base of the mast so that the spring tensions the stays.
The mast gooseneck can be a problem, if you can machine items you can make your own but they need to be strong and act like a u/j.
Another idea was to widen as before and use a ring like a washer with a collar to fit the mast foot into
Work out where any strong points (shroud connecting etc.) have to be on the deck and strengthen them before the deck goes on.
Have you worked where you will need access into the hull? for instance adjusting rudder servo connections, if using a sail winch sometimes the string gets tangled.
regards Roy
Please do not use Blue as it is reserved for the moderators
Cheers
Ken
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Thanks very much for your help Roy - I had forgotten about marking up strengthing points for the stays etc.
I see liteply isn't all that expensive so I will get some for the first layer on the hull. I suppose as I am going for an overall smooth finish I could use the liteply for the second layer too? If I do the first in long strips along the length of the hull and the second layer in shorter strips at 45 degrees to the first?
Re the keel, I had planned on shaping the two sides in wood and then cast the pieces in lead. But on thinking about it, thats probably too much for my limited capabilities and budget - Your idea of layering the lead (fixed with epoxy glue?) and then shaping it sounds much better.
I was going to run the mast through a brass ring with collar that could be fixed to the deck. I will remember to strenghten the area around where it comes through the deck. As to the gooseneck I will probably buy one. For my stays I have some fishing trace covered in a plastic tube, I will also be using shroud stays that look similar to the ones used on yachts, expensive I know but I am trying to get as much of a scale look as possible. I have not worked out as yet how to connect them to the mast - One thing I am strugling with is finding a streamlined tube for the mast, the original is that shape and works out to about 1" along the long side, I have found tubing about 3/4" but only in short lengths, I cannot recall off hand but I need about 1800 mm length for the mast - I may have to compromise and use a different shape, I know Sailsetc have a sort of half round tube with a slot up the back, or I just go for round, though a 1" round tube is quite big, so would have to reduce it to say 3/4"
Access to the hull is to be through the cabin and cockpit, its not a huge opening but I can get my hands in. I will have to make sure I place servos etc where the screws are accessible once the deck is on so that I can remove them if need be.
I am thinking of using a servo with a large arm to control the sails.
Regards
Wayne
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Hi Wayne, Sounds like you are thinking through and should do well. I would not use 3 mm for the diagonal planking just use some 1 mm thick wood. The diagonal has to take more bending and will still result in a strong hull, but the liteply along the hull is fine. 45 degrees is good for the angle.
When you plank the diagonal keep the 45 degree angle as long as you can and when it gets greater start again at 45 degrees leaving a triangular gap. This is easy to fill in afterwards as the gaps are all triangles.
I have some of that streamline ally mast 3/4 inch wide for a project I never completed. Don't know who has it now and getting 1.8 metres through the post is difficult.
The large arm servos work well but the ones I have seen are fast in their action. I have one in use with an ACTion servo slow down unit.
Sanwa did a nice slow action servo arm, there are still some around. I have used them myself.
I have a yacht where I have used an aileron hinge for the goose neck, round section, one end is lodged in the main boom and the other end slots into a close fitting tube attached to the mast. Works well and is cheap.
How far have you got now?
regards Roy
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Here is another place you can purchase a helm and helm post with compass in the size you are looking for. Very similar to the one on the Fairwind lll I mentioned in an earlier post.
The part number is PRB 3457 price is $9.99 USD here is the link to the web site http://www.horizonhobby.com/products/PRB3450?cm_mmc=BrandSiteReferral-_-PRB-_-ProductPage-_-PRB3450#t4 (http://www.horizonhobby.com/products/PRB3450?cm_mmc=BrandSiteReferral-_-PRB-_-ProductPage-_-PRB3450#t4)
Boomer
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Cool thanks Boomer
Regards
Wayne
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Thanks Roy, I am no further than the photo earlier showing the supports on the building board. I need to wait for payday to get some timber - I was at the hardware store today and had a look at 3.6mm ply and I think its too thin for the frames so I am going with 6mm.
Thanks for the info about servo arms and the goose neck, I will look at the aileron hinges
Wayne
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Had a look tonight at deepening the keel - See attached pic - Pink shows the original keel , yellow the keel twice the depth - It then looked a bit strange so I changed the angle of the leading edge (hatched area), the new angle is random, I just drew what looked about right - Any thoughts please
Thanks, Wayne
(http://i297.photobucket.com/albums/mm223/gubulawayo/Force%208/Force8-Keelextension.jpg)
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Hi Wayne, I am sure others will want to comment.
My thoughts are that the centre of area of the new + old keel should lie in the same vertical plane as the centre of area of the old keel.
The sails are to some extent fixed and the c of effort of the sails should be 4% ahead of the centre of lateral resistance at the waterline of the under water part of the hull. I have used this successfully in several yachts before.
I would say that the lines you have drawn are pleasing to the eye and maybe a tweak to adjust for the above suggestion would leave them looking much the same.
Do you know how to work out the centre of area of the sails and the centre of lateral resistance for the hull?
You may need to increase the area of the rudder by 40 % or so if you do, take the rudder blade dimensions a bit lower.
It is worth doing some sums early on, including the displacement of the hull with the method of planking you are going to use.
I have used the above to good effect in several sailing boats.
The beauty of doing it this way is that the allowance for scale is just a few % and the designer of your boat would still recognize his child!
Looks good and an interesting thread,
regards Roy
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Wayne,
In addition to calculating your new centre of lateral resistance, don't forget to calculate your new centre of gravity.
After I extended my schooner's keel for all the usual scale factor reasons, I float tested it with the major components in place to determine the ballast's weight and centre of mass.
I gridded by keel to help calculate the volumes.
After the first pass through the math, I realized that my keel didn't have enough volume forward for the required lead. So I added a Dutchmen and recalculated.
Unfortunately, I mis-estimated the weight of the masts and deck so while I nailed the fore and aft, I was heavy overall. Fortunately, since I knew where the centre of mass was, it wasn't "too" painful to drill out some weight (If you have to do this, use spade bits and not twists. The extra friction from the twists will turn the lead greasy and seize and snap the bit -- learned the hard way).
Pictures show the general sequence.
Good luck.
Ken
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Right so there is alot more to this than just making the model - I know nothing about working out centres of gravity, centres of area etc etc - I have a copy of Model racing yacht Construction by R. Griffin - I will have a read through it to see if it can help - I take it a lot of things will only be calculable once the boat is actually built?
Wayne
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Wayne,
While it's a joy to build a scale model of a real boat, the realities of physics will quickly get in the way and the modeler will be challenged to make compromises to accommodate them.
I apologize if this is all known to you but if you don't make adjustments, a model yacht will be at much tippier than the full size yacht.
Stability is an interaction between righting moment (which is a combination of hull shape/weight, ballast weight and location) and centre of effort and size of the sails. Hull size and weight is a factor of its volume/displacement and centre of effort is a factor of the size and shape of the sails.
You indicated that you were building in 1/15th scale. Your sail area will be 1/225th the real boat (H X W) but your displacement will be 1/3375th the weight of the real boat (H X W X D) so the scale modeler must make adjustments.
For the large square rigged models, an extra drop keel is often added that hangs way below the true keel. It is removed for display. The higher square sails will not be set to reduce the sail area.
For scale yachts, slightly deeper keels (as you are planning) are usually used. The "J" class allows 2 extra inches. For sail area, slightly shorter masts and booms will reduce sail area without looking "wrong."
Traplet publishes several books dealing with these challenges. "Historical Sailing Ships -- Remote Controlled" and "An Introduction to Radio Controlled Scale Sailing Models" are two I have.
The fore and aft location of the centre of lateral resistance can reasonably guess-timated by cutting a thin plywood profile of all the underwater portions of the hull and then balancing on a thin dowel. If you have highly detailed copies of the full size plans, you may find a circle divided into quadrants located somewhere in the keel. This is the naval architect's calculation. If you balance your area adds in front of and behind this location, you won't disturb things -- same thing for sail area.
There may also be a similar circle marking for the centre of mass (and buoyancy).
If you have the centre of mass marking, keeping you fore and aft ballast adds/removals will keep you in the ball park but battery, receiver, and servo locations (and lack of engines) and difference between building methods can disturb things. Keeping your internal design options flexible to allow some shifting around after pond testing is desirable (but if strict scale modeling is desired, location choices may be limited.
If you're not a racer, adding some area to the rudder will allow you to make up for small errors in the relationship between centre of lateral resistance and centre of effort (sail area). You'll go a little slower.
With respect to early discussion on frame spacing. Feel free to use only every 5th or so frames. As long as spacing is around 10 cms or less, you should have enough strength. Add some in between frames if needed for strength in key areas (e.g., if your mast step is going to be on deck instead of the keel) or you have a complex shape transition area (not likely looking at your design).
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Oops, somehow I posted before I finished.
Keep asking questions and read through the various build logs, on this forum and others. You'll find a lot of people who are working through similar challenges and lots of usually helpful advice (and if you're working cross the pond, don't be surprised by unfamiliar terms (and spelling) -- took me a while realize what a grub screw was.
Good luck,
Ken
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Eish you guys are speaking a foreign language. I will check the drawings tomorrow for any architects points
I am not looking to race the yacht, I just want something to sail around our boating lake, so it does not have to be perfect.
I had a quick read in the racing yacht book I have and I am even more confused!
I have drawn up the frames with as much open space as possible, so should be able to move things about a bit to help with ballast etc.
You mention slightly shorter mast and smaller sails, what percentage can I look at regarding reducing the size? I have a 1/30 drawing of the sail layouts which I can amend with reduced sizes.
Thanks very much for your help Landlocked and Roy
Wayne
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Hi Wayne, as Landlocked says it is quite technical but a lot of it has been done for you by the guy who did the drawings.
When looking at a full size yacht you can work out the centre of effort on the sails by making a drawing of the 2 sails exactly where they are in relation to each other. Then take one sail triangle draw a line from one corner to the opposite side exactly half way or in the middle of that line. Do it again for another corner and the lines will cross, this is the centre of the triangle. Do it for the other sail as well. Then join these 2 points with a line.
Now you should work out the area of each sail triangle (Half the base times the height of the triangle).
bring these numbers down to a low multiple. i.e. if the jib is 70 sq feet and the main 210 sq feet then it is 70 over 210 = 1 ; 3.
On that basis at the jib area centre point draw a line at right angles to the line you have already and measure off the main sail area, in what ever units you have chosen, and it is in this case 3 inches / centimeters etc.
Now go to the other area centre point and measure again at right angles but the opposite direction the other area you have worked out in this case 1.
You should now have a line (joining the triangle centres) with a line at each end going in opposite directions. At the measured points draw a line between them. This will cross the first line you drew. This is the centre of effort of the sails.
Drop this point down vertically to the keel of the boat. This line will cross the waterline of the hull (at right angles) and this can be assumed to be 4% ahead of the centre of lateral resistance. This will save the cutting out mentioned by landlocked. What landlocked suggests is fine for a new or unknown hull but here we can work from known things.
You now know where the centre of lateral resistance is. Now any alterations you make to include a deeper keel should have the same centre of area.
I don't think you need to worry about the centre of gravity, you can calculate it but I don't think it will influence your build.
landlocked mentions the J class. I have a 1 : 35 scale J class and you do have to reduce the sail area as the full size yachts were grossly over canvassed and only sailed in no more than a Force 4 wind.
For your model the sails and mast height are OK. A rule of thumb for the mast length from deck to tip of mast is 1 1/4 times the length of the yacht. But as I mentioned before a 10 % reduction in sail area will do no harm. This is to accommodate the square and cubed rules mentioned by landlocked.
ALL YOU REALLY NEED TO KNOW IS:-
keep the extended keel centre of area in the same same vertical plane as the existing keel center of area.
What ever you do don't panic, it will all work.
best of luck Roy
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Thanks Roy, I take it the keel centre of area is different to the centre of lateral resistance? If so how do I work out the keel centre of area? Can I just draw lines from opposite corners and where they cross is the centre?
Thanks
Wayne
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Hi Wayne. Take the keel as a 4 sided shape and as you say draw diagonals and get the centre. This is only correct if the 4 sides make a square or oblong. But as it tapers down towards a triangle shape it should not affect what you are trying to do.
Extend the drawing as you have done and draw diagonals for the whole area, old and new keel together. Do the crossing of the diagonals. The new point of crossing should be vertically in line with the original keel centre.
There is another way but try this first.
Even approximately it will work.
regards Roy
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Thanks Roy, I will try that and try the centre of a trapezoid to see how they differ
Wayne
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Hi Wayne, if you are OK with trapezoids then just divide it into 2 triangles and do it that way.
regards Roy
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Will do, I had a look at the plans, the sail and rigging plan has the centres of the sails and a spot called Total MA which looks to be the Centre of Effort of the sails.
The hull plan has a spot quite low down on the keel, you can see it on the drawing above, its in the pink section, a spot with a vertical line through it, could this be the centre of gravity of the keel? The main plan shows a note saying 4500kg at this point. I have just printed out a copy of the above plan and will work out old and new centres of keel based on a trapezoid
Cheers
Wayne
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Wayne,
I'm guessing that dot IS the center of mass/gravity for the boat. If the keel shape is a normal foil/teardrop, you would expect the centre of the weight to be forward of the centre of the trapezoid.
Can't tell whether the 4500 kg is total boat displacement or just the ballast weight.
Going back a few lines, for a fin keel design with fairly symmetrical bow and stern profiles, the centre of lateral resistance will be very close to centre of the keel's area. When you get to the old full keel designs with long overhangs, things start getting complicated. You should be fine.
Ken
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Thanks Ken, I seem to recall the 4500kg is the ballast weight and the boat had a displacement of 14700kg
Wayne
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I have just printed out a copy of the above plan and will work out old and new centres of keel based on a trapezoid
The centre of the new layout is about 6mm behind the centre of the old keel, could I leave it like that?
Wayne
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6 mm out of a model length of 930mm is 0.65% so it should not be a problem. Using Roy's 4% rule would mean you're either 3.3% or 4.7% of the desired value (Roy, isn't the centre of effort supposed to be slightly AFT of the centre of lateral resistance to give you a trace of weather helm?).
Ken
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Hi Landlocked, you are right a slip of the fingers! C of E should be aft of the C of LR. I agree 0.6% either way will make very little difference.
Main thing is to have the boat balanced.
regards Roy
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Hi Guys, would you suggest 4mm or 6mm ply for the frames? Yacht it 936mm long and about 280mm wide at widest point - As the frames will stay insitu I am thinking 4mm will keep the weight down.
Thanks
Wayne
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I'd go with 6mm. Gives you more meat/surface for fasteners and more forgiving of inadvertent bumps.
I only rough cut out the interior of frames so there's more strength while I'm fairing (usually by sanding with strips of sandpaper glued to a flexible batten). the outer edges to the bevel angle for the planks. Once things are fair, I dismount them from the building board and thin them down.
Ken
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Hi Landlocked, good idea re fairing then trimming down the frames, thanks
Wayne
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Just to follow up from landlocked, you can partially cut out the frames before fitting, then just cut through the remaining notches when planking complete.
good luck
regards Roy
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Thanks Roy, My frames are drawn with hollows inside, some are connected all the way across the top (is underside of deck) others have a partial deck beam on the sides and are open in the middle - I will post pics when I get home - I will cut most of them out and leave a few which may be a bit partial to bending when pressure is applied while sanding
Hopefully get some timber on friday and get cutting over the weekend
Wayne
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Cut out most of my frames, another 4 or 5 from the centre of the yacht to go. Still got to tidy these up too
Wayne
(http://i297.photobucket.com/albums/mm223/gubulawayo/IMG_9574.jpg)
(http://i297.photobucket.com/albums/mm223/gubulawayo/IMG_9573.jpg)
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Frames fitted to building board, they still need to be sanded true. I put them up to display at our club display this sunday
Wayne
(http://i297.photobucket.com/albums/mm223/gubulawayo/IMG_9576_zpsc768db6f.jpg)
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Hi, looks good. The slots for the keel look a little narrow. The keel needs to be wide enough to allow the ballast weight to be secured in the hull. You can double up the keel at the top of the keel fin, but imagine that you hold the hull at 90 degrees with the keel ballast straining to break the keel fin. The keel ballast is frequently bolted through (2 bolts) to a strong point in the hull like a well supported platform just inside the hull. I have used studding a bit thicker than M4 and clamped the keel in place using wide washers to spread the load. You only need nuts with the studding, (I think I got mine from B & Q) and cut it to length.
I think this system is easier than using long screws as you drill all the way through, or leave a space for the studding (2 off) to go through.
Sorry if I am teaching you to suck eggs!
Another point that can be done too quickly is locating the deck edge stringers in the bulkheads. Cut the bulkhead corners very carefully allowing for the bend and curving of the wood. It may be easier to laminate two lengths together. Go for a finish where you do not have to sand most of the stringer off to follow the curves of the bulkheads. You can get the wood to follow the curves by immersing in hot water and pinning in position until dry (use a hairdryer to speed things up).
I have used metal clamps on the stringers to shape using the twisting of the weight of the clamp. I tend now to use dress makers pins with the plastic coloured bobble on the end for securing.
You can double up here for the shrouds points as well. Also consider whether you need any extra deck beams to support the deck and where you might wish to fit access hatches, e.g. over the rudder stock.
good luck it looks a very good start.
regards Roy
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Hi Roy, not teaching me to suck eggs as this is my first boat build ever, so any guidance is welcomed.
My keel slots are 6mm, I was going to cut the keel 'stringer' out of 6mm ply, same as the frames - What about if I glued strips each side of the keel 'stringer', between each frame? What is the keel fin? by this do you mean the actual bit that comes out below the boat? If so I still need to deepen this as per my drawing earlier (see the pink and yellow parts increasing the size of this) - I forgot to draw them on when I cut the frames. I am going to cut off the three parts on the frames and make up a new separate keel 'fin' which I will slot into and bolt onto the hull - My plan was to get the basic shape of the keel 'fin' using frames and then fill inbetween them with lead sheet epoxied together. I would then shape the lead to the frames, epoxy and paint. This should give a nice lot of weight low down.
When I drew up the frames I drew up the stringer positions, I noticed the deck edge stringers needed a fair bit of shaping on their bottom edges as they came away from the hull quite a distance (on some frames not all, mostly around the bow). The top of the stringer, ie the bit under the deck is fully within the frame except for one or two near the middle where the hull curves back intowards the centre. I ordered some 5x5mm balsa stringers which should arrive next week, so I can play around then.
Yes must not forget shroud points, thanks
As for access you can see the main hull access in the photo. At the stern the yacht has a drop in cockpit which I can remove to access the rudder. I was toying with the idea of connecting wires to the rudder that will turn the wheel as the rudder moves, but this will get in the way when trying to remove the cockpit.
Thanks for your help
Wayne
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Hi, 6mm keel is fine. just strengthen around where the keel fin joins.
I would not use balsa for the bulwark / deck edges. B & Q sell 6mm square hard wood which puts a lot of strength into the hull. Balsa for me in this context is somewhere for the glue to adhere to. I think I would cut the slots for the hard wood stringers so that they were parallel with the bulkheads. This would leave a small amount to sand off at the deck level. Use the balsa as filler with a good glue.
My experience has been use the best wood you can for the hull, it will be reliable.
I renovated a small yacht built in the early 1950's from nice seasoned wood, it had a sealed deck and I had to cut it open to install RC (owners request!). We have an endoscope in the club and the wood was perfect.
regards Roy
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Thanks Roy. I will strengthen around the keel fin - Now I was going to cut out the keel and keel fin as one, fit the keel fin frames and fill the gaps with the lead sheet - This would do away with the need to bolt the keel fin on - Does this sound OK or would you make the keel fin a separate item?
You mention cutting the stringer slots parallel with the bulkheads - Not sure I follow. I have put in two pics below of two of my frames, one from near the bow, the other near the middle of the yacht - You can see the top of the stringer is drawn inline with the underside of the deck. As you can see in one the stringer juts out from the frame and on the other the stringer is completely within the frame which I assume is wrong - Any suggestions please/
I will pop down to homebase or Jewsons to see what I can get, I don't have a B&Q near me (well its 30m away and we aren't going that way for a while.
(http://i297.photobucket.com/albums/mm223/gubulawayo/EPSON002_zps687ff58c.jpg)
(http://i297.photobucket.com/albums/mm223/gubulawayo/EPSON002-Copy_zpsb3bf0130.jpg)
Cheers
Wayne
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Hi Wayne the way you have drawn it looks fine. There is plenty of meat left in the deck stringers. I think you are doing the right thing. It is easy to lose the mass of the wood in sanding it to fit. You have to have enough left to plank onto, also to retain the shape of the hull.
The model boat I have in construction now (not a yacht) has virtually no wood to sand away as I have twisted and bent the wood to fit. There is tension in there which I have tried to relieve through wet fitting and pinning in place and twisting the stringers into shape by the hanging clamp method. I may have a photo somewhere.
I would favour the keel and ballast as a separate item bolted in, but I expect there are several ways to do this, I try not to have wood very low down, better to have lead.
I expect there are others who would like to comment?
regards Roy
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Cool thanks Roy - I just realized I need stringers along the edge of the deck to line the access hole in the middle of the yacht too.
Wayne
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Progress to date is that most of the slots for stringers are now cut and filed to size, I need to angle some of them so the stringer fits in better. I also seem to have an issue with one or two of the frames being out of alignment along the keel. Photo to follow soon hopefully.
I do have a question re the keel, I had planned on cutting this about 6mm deep based on the plans (out of 6mm ply) but I wonder now whether this may not be deep enough, any thoughts please?
Wayne
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OK so I forgot to photo progress to date, will try tomorrow
Can I get away with 1 layer of 3.2mm lite ply or should I got with two, or even two layers of 2mm liteply, all to be fibreglassed in and out
Wayne
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Progress photo attached, keel loosely fitted as I am still sorting out the slots - Took delivery of a permagrit spar slotter today, boy is that a nice tool, might get some more permagrit bits when I can afford them.
Wayne
(http://i297.photobucket.com/albums/mm223/gubulawayo/IMG_0055.jpg)
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Progressing slowly, two set of stringers fitted, one more set of balsa stringers then the hardwood stringer at the deck edge, also working on beefing up the centre of the keel for the keel fin fitting
Wayne
(http://i297.photobucket.com/albums/mm223/gubulawayo/Yacht20130512.jpg)
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Hi All - Not sure whether I should plank this boat with 1/2 layers of 1.5mm ply or 1 layer of 3mm balsa - Any thoughts please - I will be planking it longitudinally and I will be glassing the hull once planked. - Just got to add the deck level stringers and I am ready to plank
Thanks, Wayne