Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[tiaki]

Hi, If this is your first build it would pay to float the hull to waterline using blocks of lead to ballast. I guess you would be needing around 2 pounds of ballast, up to around 2.5 pounds. This will give you both an idea of the amount required and the position required to attain the waterline correctly. With this detail you can make a dam to control where the lead is poured. As I said previously pour slowly. This will stop the gel coat from cracking through rapid expansion. If you do get cracks then repair them with resin whipped over by hand. Finally once you have the ballast right seal off  with a coat of resin, this give a second barrier for water tightness. A dam could be from MDF as the molten lead will only scorch the MDF initially. I use it to make quick moulds for lead bulbs on dagger board keels. Smells some in the process though.

[g4yvm]

Thanks for that.

I've already floated the hull in the bath and added blocks of lead just to see.

Waterline checked etcetera etc.

D

[g4yvm]

Right, Ive added lead.




I did the "pour molten lead into the hull" trick and it worked fine.  A bit of a pong of glass fibre but no scorching etc.


The total weight now is 9.5lb, the bear hull was 3lb, thats 6.5 in the fin.  Actually, IN the fin.  If the all up weight is 12.5 - 13 I think thats about right, based on the 60% AUW in the fin idea, perhaps a tad heavy.  Anyway, she floats just about on the waterline.   Actually, Ive just thought about that...the topsides weight will drop her a bit.  Oh well, its done.


I have imagined that the topside will not weigh m ore than 3lb, but I have no real idea.




David

[Netleyned]

Well done !
Top weight can be kept down with carbon fibre mast
and spars.

Ned

[g4yvm]

Thanks Ned.


Is there much to be gained from going shroudless with a carbon mast?  Obviously there's ease of rigging I guess.


D

[Netleyned]

Not gone shroud less.
My Victoria has two shrouds each side
On a carbon fibre mast.

Ned

[g4yvm]

Ah right.  I was thinking of bonding chain plates to the inside of the hull prior to gluing the deck down anyway, so that would work.


D

[g4yvm]

Am I right in thinking about 1.3m mast height for this boat?  My plans are for a iom and they show anything between 1.2 and 1.8m.


D

[tiaki]

Hi, Wow that's a lot of lead for that length hull. The closest yacht I have to that is a J class which manages to comfortable handle a 1.6m high mainsail with a 3/4 height jib. I use a 12mm diameter alloy tube mast and two shrouds, one from the crosstree and the other from the masthead through the crosstree.

[tiaki]

Sorry shroud is not from the masthead it is from the jib fixing point.
Cheers

[g4yvm]

Thanks

How much lead is your j class carrying?
D

[tiaki]

Hi, Around 8.6 pounds. The draft is 8.3 inches and waterline length is 31 inches, beam 8.86 inches. We sail in stronger winds than most and she handles well. I went for a high aspect ratio sail as the longer sail foot of a low aspect sail allows the wind to drop off giving poor performance. This picture is how they are originally set-up. They don't handle very well, I prefer a sweet handling yacht hence some major changes.
Cheers

[mrpenguin]

Hi,
It is possible to pour lead into the keel. To do so mark the desired waterline on the bow and stern, Check that there is no pin holes that water can get into the hull, if it does the lead will explode into your face. If there are no leaks then put the hull into a bath/container of water which takes the heat out of the lead before it can burn the F/glass. Then slowly pour the lead into the keel until you reach the water line. If it looks like the hull is sitting up at one end stop the pour and fit an internal dam into the keel to position the yacht hull at the correct waterline and continue the pour. This is a common way to pour lead into an EC12 yacht hull.
Cheers

This sounds REALLY dangerous to me, sorry. One accidental drip of molten lead into the water the hull is sitting in would create quite a disturbance; you need nerves of steel (or lead..)
 
I am not saying don't do it, just saying that if it were me, I would find a different way....
 
[EDIT] Just read more of the thread and I see you have done it successfully, congratulations!
My comment still stands however...
 

[g4yvm]

Your concerns are valid, but I've poured a lot of lead over the years. I've tought my boys to do it too. Done in the right manner and with care it's not so hard.

David

[g4yvm]

So I'm thinking 11.1mm mast dia and 1.3m tall, keel stepped (slid into a tube I guess).

1/4 scale servo swinging a main sheet arm, rudder from an IOM type boat

Plywood deck.

Simple Bermuda type rig

D

[tiaki]

Hi, I prefer a sailwinch as it is a more gentle sheeting in and out and a lot more grunt for around the same cost. In fact the Hitech sailwinch is cheaper here in NZ than the sailarm, 16 sailwinches and only 1 sailarm that is not being used. Add a little deck camber for a good look.
Cheers

[g4yvm]

Thanks for the comment. I has heard that sail winches are a pain because of "birds nesting" the sheets!   I have no experience though.

I also already have a 1/4 scale servo.

D

[g4yvm]

Ok I actually have a hitec HS700 bb 1/4 scale servo AND a hitec HS785 HB sail winch servo

Which should I use for my yacht?

D

[tiaki]

Hi, For me it's a no brainer, the sail winch every time. I will post a picture of my set up for you which is pretty much bullet proof, bar breakages. I have to catch the America's cup first! If you are worried about the sheeting dropping off the winch it can be mounted on it's side so the sheeting cannot drop off the drum.
Later

[tiaki]

Ok, this is a 36inch hull. The black device attached to the rudder brace is a security pass recoil holder (plastic non rust) this holds tension on the sheeting to the winch which prevents the sheeting dropping off the drum or getting knotted up. I usually fit a close fitting pulley in the bow but on this occasion I couldn't be bothered making one and have used a piece of copper tube to guide the sheeting around. You will see that there are two sheets coming off and through the deck. I use two so I can get the travel I want without cluttering the deck side. The "chain plates" are just loops of stainless wire epoxied into the deck and the sheeting exit is PTFE which is offset as it makes it easier to deal with and away from any potential snags. I have mounted the winch upright so the drum can be accessed when required. All but one of my yachts are setup this way and the one that is not is an early variation on this theme. This system can handle any sail size, my biggest being 2000 square inches.
Cheers

[g4yvm]

Thanks.  Thats clever, using the recoil holder. 


I appreciate the photograph.  Presumable the deck has yet to be glued down? Its not a removable deck??




D

[tiaki]

Hi, Yes the deck is to be epoxied down as my yacht hulls are concidered boyancy aids, monocoque construction. The only parts given great attention are the jib fixing point, the mast mount tube and keel where the stresses are dissapated through these mounts into the hull. The deck is 1.5mm marine ply which is an important part of the monocoque. When I use cedar planked decks I fiberglass the undersides to build up the strength to that of the ply, typically my cedar is 1mm thick plus the glass. I'm working on 5 yachts at present and have had to delay the builds until the spring with warmer temperatures to cure the fiberglass.
Cheers

[mrpenguin]

Ok I actually have a hitec HS700 bb 1/4 scale servo AND a hitec HS785 HB sail winch servo

Which should I use for my yacht?

D

I would think the HS78HB would be the go for a boat this size. From memory, I think it is about 4 turns from one end of travel to the other and is STRONG. There are some other alternatives that are similar specs but not nearly as expensive if you are planning to buy a sailwinch (eg the Vigor ones on HobbyKing).
 
Drum winches are slower than arm winches, but great once you get used to them. Tangles are not an issue if you set up a continuous winch loop and attach your sheeting to the loop. Have a look at this Youtube video of a modified setup on my Surmount, it is a variation on what Tiaki posted. This setup is much modified from the original Surmount arrangement. It works great.
http://www.youtube.com/watch?feature=player_detailpage&v=JWhI3F_MY74

[tiaki]

Be advised, Hobby King sail winches are junk, They are a glorified 1/4 servo that only creep to the correct end position. Read the feed back on the HK site for the winches. It is a symptom of changing the pot in a standard servo to a multi turn pot. A conversion I used to do before proper winches became more obtainable and cheaper. Unless there is a specific need for a winch that slows down as it gets to the end of desired position, move on. I think the number of turns is depend on the brand of radio being used and will vary, I get 3.6 turns running Futaba radios and 4 with Hitech radios. I have discovered a use for the HK winches but am not sure which end of the anchor chain I should put them!
Cheers