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Author Topic: swing rig !  (Read 6932 times)

triumphjon

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swing rig !
« on: February 28, 2012, 08:30:23 AM »

having bought an old builders demonstrator hull/ cabin-deck shell last summer ive assembled it with 3 chanel controls , motor assistance , rudder and a sail arm , ive bought a second hand mast / sails , this happened to be a swing rig , which ive fitted through the deck ( into a suitable stainless steel tube glassed to the keel ) at the original makers position , its first outing was interesting as the rudder had little effect when running under sail , but was adequate on the motor . ive increased both the depth and width of the rudder which will now allow directional control . HOWEVER  i still have a problem trying to sail , in the small gusts last sunday the wind would suddenly spin the model around in its own axis and off in the oposite direction , what do i do to correct this please ? ?  jon





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Tiaki

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Re: swing rig !
« Reply #1 on: February 28, 2012, 10:36:25 AM »

It looks like the center of lateral resistance (CLR) of the hull is not aligned with the center of effort (CE) of the sails by a fair amount causing the about face nature. Sails too far forward cause the sail to lead the hull in a blow, by the amount you have there it wouldn't take much wind I'd say. ie; the sails act as a rudder in wind turning the yacht and overcomming the actual rudder input.
If memory serves correct my swing rigs had a jib of about 25% in area of the main and the pivot point of the jib was be back from the leading edge of the jib sail by 25% also.
As I'm guessing with many years of model yachting and a good seat of the pants formulae. From your photos I would have thought that the CLR of that hull is about midships or slightly aft of that and the CE is just behind the mast. It is a guess as the diamensions of the sails and layout of the rig are required to work out the CE properly.
Unless you are able to make new sails to compensate the only way forward would be to move the mast socket aft closer to the correct alignment point, I suspect that new sails ( basically a larger main and smaller jib bringing the CE aft) with the same socket may cause altenate problems as the socket is well forward of the position I would have thought it should be.
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JayDee

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Re: swing rig !
« Reply #2 on: February 28, 2012, 11:36:23 AM »

 Hello Jon,

Wait for a day to sail with a light steady wind, not too many gusts.
Sail the boat with the wind at 90 degrees to the left or the right.

When a gust hits the boat, watch which way the boat turns.

IF, the boat turns INTO the wind, the sails are too far rearward.

IF, the boat turns AWAY from the wind, the sails are too far forward.

To keep the mast in the same position as it is now, new sails should be fitted with the
Centre of the sail areas moved to correct the boat.

A Swing Rig sail setup, is designed for a particular boat, I don't think you will be able to get your boat to sail well with it.
Use the present mast position and make and fit some new sails, a small Jib and a large Mainsail.

As a starting point, find a picture of a boat that looks similar to yours, note how the sails look, do they look like yours?.

John.  :-))  :-))  :-))
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Tiaki

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Re: swing rig !
« Reply #3 on: February 28, 2012, 07:17:22 PM »

While sucking it and see works you will not be able to fit a large enough main sail to your existing rig to alter the CE enough. You would also end up making several rigs and sails to get it right. Then also a sail with a large foot starts to loose drive. I would strongly suggest doing the maths so to speak, at least you will get into the ball park then it would be just some fine tweeking, like trimming off a little of the roach on either sail to move the CE in the direction you require. The pic if it uploads is of two similar sail set-ups and how the CE is effected. The line drawn between the CE of each sail (each sail triangulated to find their respective CE's ) is divided into the percentage relationship of each sail giving the total CE. To find the CLR of the hull take off the rig and have the yacht preped as if to sail. Place into a body of water (bath etc), you can move the battery to trim the water line to what you reguire. Then push against the hull at midships sideways alternately from each side finely moving the finger aft or forward until the yacht moves squarely sideways. This becomes the CLR of that hull form. Now it is a simple matter of placing the mast at the appropriate position allowing the CE to align with the CLR. All of a sudden there is no wasted maerials, trial or error and a better understanding of the mechanics of model yachts that will stay with you for future ref.
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triumphjon

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Re: swing rig !
« Reply #4 on: February 28, 2012, 07:44:51 PM »

ive managed another two hour session on the solent this afternoon , in which the model behaved much better , it appears to sail slightly bow heavey , with her stern slightly up ? the position of the mast is from the original makers , the internal moulded keel has been filled with around 1.5 kgs of lead from a diving weight pouch , above which ive positioned the 540 brushed motor , ive tried to get as much of the operating equipment along the keel line as possible . . the dimensions for the model are ;- 31" long at deck ,33 1/2 " waterline , 9 3/4 " beam . 48 " top of mast to keel , 38 1/2 " from the deck to the tip of the mast  , the main sail 33 1/2 " high x 10 3/4  wide while the fore sail is 23" x 8 1/2 " . would it be benificial to increase the weight towards the stern ?  jon
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JayDee

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Re: swing rig !
« Reply #5 on: February 28, 2012, 07:49:38 PM »

 Hello Tiaki,

I agree with your methods, but there is one point I would like to make.

You say   " Now it is a simple matter of placing the mast at the appropriate position allowing the CE to align with the CLR."

The Mast is already in position, in a finished boat!.

Not as simple as you make out.

John.
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Tiaki

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Re: swing rig !
« Reply #6 on: March 01, 2012, 09:45:01 AM »

Hi John,
As someone who has done both and also designs/ed and built successful model yachts I have to say your only fooling yourself John. Actually there is nothing difficult in model yachts for that matter if you apply yourself and think before you act. It's all fear of the unknown that makes it difficult.
It is a lot simpler to move a socket than muck around trying different sail configs. First you have to build them, try them and maybe you could get lucky on the first, but I doubt that or the yacht would not have been bought in the first place. The yacht and the resulting question indicate inexperience to me. Socket movement is the cheapest and simplest soluton other than using it as a power model.
I don't believe for a minute making new sails will correct the problem as the rig cannot take a bigger main and would require a new rig being made, do you really think that is simpler than cutting a hole and glueing in a new socket John! This is probably why Kiwi's are so good at building yachts!
 Jon, I think I would join the local model club for input as they will be able to see exactly what is being delt with rather than surmising from the pictures we're working from.
In this part of the world most model clubs would sort it out willingly and put the captain straight. I can't imagine it would be any different anywhere else in the world.
Good luck.
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JayDee

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Re: swing rig !
« Reply #7 on: March 01, 2012, 10:53:26 AM »


Tiaki.

In my considered opinion , what you are saying is complete and utter rubbish.

I had no intention of fooling anyone, least of all myself.
I have "no fear of the unknown",  with regard to  model yachts, have a look at my website.

What I proposed was the easiest way out for someone who is probably a beginner at yachting.
Making and fitting a temporary sail, to test the balance of the boat would only take a few minutes.
Digging out the mast would take longer to do and then moving it, would spoil the lines of the boat.

John.
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triumphjon

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Re: swing rig !
« Reply #8 on: March 01, 2012, 08:41:37 PM »

tiaki , as you may or may not have noticed the yacht in question is a scale model , purchased as a hull / deck - superstructure moulding  , it was as im led to beleive by the vendor the factory demonstrator from local full sized yacht builder . ive fitted a socket in the location provided by that builder , moving the socket aft unfortunatly isnt an option , A, the deck is bonded to the hull , B,  the motor sits directly aft of the current mast socket . my mast socket is a 180 mm  length of stainless steel tube 20 mm od with a 2mm wall thickness , its not only glassed into the hull bottom but also has ties to the bow and across the beam .
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MikeK

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Re: swing rig !
« Reply #9 on: March 02, 2012, 09:39:51 AM »

Take a trip over to Gosport on either Thurs or Sun  morning to Walpole Lake, a stones throw from the Portsmouth/Gosport Ferry, I am sure someone there would be able to give some helpful advice


Mike
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malcolmfrary

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Re: swing rig !
« Reply #10 on: March 02, 2012, 10:17:56 AM »

Putting a swing rig designed for one hull onto another hull that was designed with a conventional rig in mind is always going to be a struggle.  To keep the existing mast position, the option most likely to work with the least grief is to fit a conventional rig. 
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MikeK

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Re: swing rig !
« Reply #11 on: March 02, 2012, 10:40:53 AM »

Putting a swing rig designed for one hull onto another hull that was designed with a conventional rig in mind is always going to be a struggle.  To keep the existing mast position, the option most likely to work with the least grief is to fit a conventional rig. 

Totally agree, I thought it had been designed for the swing rig (must read closer !)

Mike
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malcolmfrary

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Re: swing rig !
« Reply #12 on: March 02, 2012, 02:30:32 PM »

Years ago, I did see a picture of a 12" to the foot cruising type yacht with a swing rig.  There is probably a sound reason why they haven't caught on.
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triumphjon

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Re: swing rig !
« Reply #13 on: March 02, 2012, 08:19:46 PM »

changing to a conventional rig is an option , it would at least mean all of my sailing models would be set up in the same manner ! when i rebuilt my last sailing model i tried sending the club over at gosport an email for some advise and guidance , alas 5 months later ive received no reply
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MikeK

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Re: swing rig !
« Reply #14 on: March 03, 2012, 08:46:24 AM »

changing to a conventional rig is an option , it would at least mean all of my sailing models would be set up in the same manner ! when i rebuilt my last sailing model i tried sending the club over at gosport an email for some advise and guidance , alas 5 months later ive received no reply

Hi triumphjon

I apologise on behalf of my club, I am very surprised at the lack of help you received and will look into the matter next time I am down there.
When I put them in the picture that the club's  action or lack of it has been printed on one of, if not the most popular model boat forums on the internet I don't think they will be best pleased  :((

Mike
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xlaorta

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Re: swing rig !
« Reply #15 on: April 04, 2012, 12:37:35 AM »

Putting a swing rig designed for one hull onto another hull that was designed with a conventional rig in mind is always going to be a struggle.  To keep the existing mast position, the option most likely to work with the least grief is to fit a conventional rig. 

If the general concensus and knowledgeable response is not to convert a conventional mast installation to a swing rig set up, what yacht hulls (racer and scale) are out there that are able to take a swing rig set of sails ?

I ask as I am disabled and find it very hard to do all the rigging which spoils the enjoyment for me.

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triumphjon

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Re: swing rig !
« Reply #16 on: April 04, 2012, 07:45:02 AM »

how big a model are you looking at ? my own models are carried along the main road for around 300 yards to the point where i sail , the models are always pre rigged ( i dont de rig them at home either )
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Netleyned

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Re: swing rig !
« Reply #17 on: April 04, 2012, 09:37:05 AM »

My Victoria will fit in most cars fully rigged as will a Micro Magic or a Fiesta.
These three are all good performers.
If you are looking for a hull to suit the sails you already have you will be
disappointed unless you get the hull the sails were designed for.
If you are determined to have a swing rig then take a look at the Lazer.

Ned
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malcolmfrary

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Re: swing rig !
« Reply #18 on: April 04, 2012, 09:48:49 AM »

If the general concensus and knowledgeable response is not to convert a conventional mast installation to a swing rig set up, what yacht hulls (racer and scale) are out there that are able to take a swing rig set of sails ?

I ask as I am disabled and find it very hard to do all the rigging which spoils the enjoyment for me.


Like Ned, my Victoria fits into the back seat area of my car fully rigged.  Again, the Laser,  http://www.rclaser.org.uk/ , while being a una rig rather than a swing rig, is a viable option.  You do need a pole with a hook on the end to get it out of the water, though.  The lack of rigging does mean that you can't lift it from the water by the mast.
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Re: swing rig !
« Reply #19 on: April 04, 2012, 10:07:20 AM »

http://www.modelboatmayhem.co.uk/forum/index.php?topic=36308.0

I thought I had already answered the question on another thread.
As MF says whatever swing rig you use, a handle on deck or a ring for a pole
will be needed to launch and recover.
Depending on your disability it might be easier to have a yacht you can lift in and out by the mast.


Ned
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xlaorta

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Re: swing rig !
« Reply #20 on: April 04, 2012, 08:06:57 PM »

http://www.modelboatmayhem.co.uk/forum/index.php?topic=36308.0

I thought I had already answered the question on another thread.
As MF says whatever swing rig you use, a handle on deck or a ring for a pole
will be needed to launch and recover.
Depending on your disability it might be easier to have a yacht you can lift in and out by the mast.


Ned

Lifting in or out is very simple as i use a double sling & is the a problem. Its all about setting the rigging tension one handed. Plus I wanted to utilise the full set of swing rig sails.
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triumphjon

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Re: swing rig !
« Reply #21 on: May 02, 2012, 09:34:04 PM »

having not had any sucsess with the swing rig , ive put a hacksaw through the jib mounting , ive also opened up the hole through the solid goose neck so it now swivels on the mast . . happily the boat almost behaves itself , ive made a mistake when i placed the ballast in the integral keel as the boat sails very bow heavy , so time to dig it all out & repostion it with a little more towards the stern . jon
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offshore1987

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Re: swing rig !
« Reply #22 on: May 03, 2012, 12:46:48 AM »

The boat sailed really nicely with the stone in the back, i still think you could fit a spinaker on her with a sock  :-))

Dan
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triumphjon

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Re: swing rig !
« Reply #23 on: May 03, 2012, 08:35:48 AM »

the stone ballast had the required effect , it got the bow up more , it had a smallish bag of lead under the stern deck ,which when i got home i found had moved , it was in the bow , i will static test in the home test tank later , see if i can get away with less in the main keel but put some under the radio tray towards the stren . spinnaker sounds interesting , not sure how it could be returned to a "bag " via radio when not required ? need to get it balenced to sail properly  & get the motor controller replaced . as this is the boat id probably use to sail in the harbour cruise next month ! ! at least with motor back up situations of no wind arent a problem . jon
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triumphjon

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Re: swing rig !
« Reply #24 on: May 03, 2012, 09:05:18 PM »

having chipped away the resin holding the ballaast in place , ive now removed 850 grammes of lead shot !
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