Kick up Rudder - downhull?

Hey guys,

I'm working on building my first boat, a Jim Michalak Piccup Pram.



I'm doing pretty good right now, over the winter i've build what i could given the weather.
- spars
- mast
- boom
- leeboard guard and guide
- tiller
- working on completing the sail right now.

I've been looking over the rudder construction and i like Jim's simple concept


but i dont really want to do the lead counter weight, im not setup to do lead melting. I've read about others using bungie chord or springs but i've also heard of others using a downhaul and the uphaul method.

The current method has the pull up which i understand but i'm trying to understand how to ropes can hold it down under sail. When i see the photo below, it makes me think that when lowered the two lines help each other out in tension and not allow the rudder to kickup when under sail but then how does it do it when in an emergency if hit with sandbanks or shallow waters. It seems this version below may be using a breakaway cam cleat for that emergency scenario, correct?



Can anyone help explain to me how i can make this happen without the use of lead counter weight?

It seems with the photo above it would be possible, does this make sense?

Patrick

 

In the photo, the sailor will have to snatch the downhaul out of the block to allow the rudder to kick up. A light bungee cord in place of the downhaul would do what you want. I would move the fairlead eye forward more to give a more advantageous angle to the beginning of the pull.

You might also consider putting a long groove in the leading edge of the blade and laying a heavy steel wire into it. Match the commercial wire size, no smelting lead. It will add a little weight to the board and provide an easily replaceable rock fender to a vulnerable area of the rudder. Then, maybe you don't need the added complexity of another line and block.

‐Will

 

One might also consider using lead shot embedded in epoxy, or lead flashing/sheets, if the objection is melting lead more than using lead.
https://forum.woodenboat.com/forum/building-repair/207538-

 

thanks Will, this is a good idea, i have not heard of this idea of putting steel wire. from experience how much weight is needed when using lead?

 

Hey Tops!

funny i just came about another post mentioning the same thing with the lead shots and then epoxy, i have put this on the option list for sure. its just the amount of weight im trying to figure out if i went that route.

 

Do the Piccup plans mention the amount of weight, either as weight, or a size of the pocket to be filled with lead? 11.34 g/cm^3 or 6.55 oz/in^3
Otherwise it is just doing math or experiments to determine how much weight would make the blade negatively buoyant.
A discussion where 2.5# is deemed good for a Scamp rudder:
Lead for Centerboard and Rudder - SmallCraftAdvisor.com https://forum.smallcraftadvisor.com/message-board2/viewtopic.php?f=3&t=1362

 

Working with small amounts of lead is simple and easy. Scrounge whatever lead you can get your hands on. One source is wheel balance lead. Your friendly tire dealer may give you enough used ones for your rudder slug. One pound of lead occupies 2.4 cubic inches. Melt the scrap lead in a discarded sauce pan or frying pan. You can even use a tin can but I advise against that method. The lead will melt quite satisfactorily with a simple electric hotplate. A camp stove like a Coleman will also do the job. You do not need a forge, just an ordinary heat source.

Here is the downside of messing with lead. Be very careful that you do not let water or any kind of moisture become splashed or dribbled onto molten lead. Be certain that when you pour the lead into the rudder hole or into whatever mold you might use, that the mold is NOT Moist. Of course molten lead is dangerous but in small quantities it is not difficult to handle and is to be used with a good measure of caution. Do the melt in an open area. There may be nasty fumes during the melt process. The surface of the melt will have a skim of dross on top of the melt. Skim it off with a flat stick or other sacrificial paddle like tool. Try not to burn down the workshop.

After all that....I do not see any need for a weighted rudder blade. So ignore the lead. The down haul or Bungee will hold the blade down. If your boat goes really fast, the rudder would tend to raise part way, lead or no lead.

 

No experience with weighted rudder at all. It will depend on the type of material the rudder is made from and the tightness or resistance in the pin that it rotates around. Spruce floats more than mahogany, so requires more counter flotation.

-Will

 

That is a rather crude rudder,but easy to make.I don't think it is ideal for using a rope downhaul as there is nothing substantial to prevent the rope jumping off the side of the rudder blade.You wouldn't expect a line to remain in place on a block with that type of construction,so why would it do so with this installation?There is also the wear factor of having a bolt cantilevered form the side of the single cheek.

It is much more satisfactory to have a pair of cheeks to the rudder stock and thus reduce the horrible conditions that the bolt has to endure and at the same time,reduce the risk of the rudder blade fracturing at the bolt by giving greater support.The rudder can be held down by a line very nicely but if the cleat is of the type in the image shown in post #1 there is a high probability of damage if you hit the bottom.You might pull the pintle off the transom or break the rudder assembly as the cleats are secure and modern rope is strong stuff.There is a cleat made specifically for the function and it is the Clamcleat CL257 which releases under shock loads and can be adjusted to arrive at a release force that is safe for normal sailing but lets go when a hefty enough impact triggers the system. CL257 Auto-Release Cleat 4-6mm(3/16-1/4") Rope |Clamcleat® https://www.clamcleat.com/auto-release-racing-mini.html


If you combine it with a rudder stock that looks similar to this,you will have a much better rudder assembly.You will see the gap between the spacers that hold the cheeks apart and through which the downhaul line can be led.


I would also suggest that you forget about rigging a fairlead for the mainsheet from any part of the rudder assembly as the forces will tend to lift the rudder off the boat.It would be safer to rig a pair of rope strops from the quarters of the boat to a ring that centres above the tiller,both for an improved lead and to lose any additional loads on the rudder assembly.

 

Hi Patrick, WetFeet's rudder assembly example with double cheeks is the best home build style unit to use, but your rudder setup can be improved with minimal extra work. Use thick strong bungee on the blade downhaul as mentioned earlier; and with the blade fully down, place an extra block of something at the 1 O'clock or 2 O'clock position near the edge of the radius, for the bungy to be held away from the pivot, for better downhaul leverage when rudder is already up. Grooving the top edge of the blade isn't necessary since your control line runs offset at the side, from that lower, side lug; you could / should groove the extra lug. Use bungy vertically up (around the outside of your extra lug), and through the tiller loop, (I'd screw a pulley on the tiller's side, just forward of that inadequate tiller loop, so the bungy can roll through), then a loop or knot making an eye in the end of the bungy, (whipping works well there), with plain cordage going horizontally the rest of the way along the tiller to the cleat. Cleats eat bungy, but not cordage so easily. There will be an ideal length of bungy; shorter is better since it will slowly weaken and stretch; and you can hold it up with the uphaul cord in a cleat, when it is new and tight.
I always drill a small cross hole near the top of the top rudder pintle, about 2 - 2.5mm diameter, and fit a stainless steel 'R' clip in there to stop the rudder assembly coming up off the pins, leaving you out of control, (I've been there), not fun; R clip held with 150mm cordage secured nearby, so you never loose it.
Have small levers welded to the rudder pivot nut and bolt head, to easily adjust friction at sea; lube between the faces with wax to avoid the paint / varnish galling after a bit of use.
Going all out, a small pulley system can work on the uphaul part, to easily pull it up out of mud. Not essential, but helpful.
Have good comfortable long grip on the tiller extension, to a comfortable diameter. Aluminium tiller extensions get cold.
Please show us a picture of the whole boat in sail, just to look at.

 

Piccup Pram Plans PDF https://duckworks.com/piccup-pram-plans/
There's a multi-image gallery at Duckworks. One of the Piccups is rigged with a modern Sunfish bracket/cheek with springs/rudder.

I built a small boat 8'/2.3m with the Michalak rudder shown above in post#1. My bigger fiberglass boat 21'/6.4m came with a double cheek and retention clip as described by @wet feet and @seasquirt. Neither has lead but I would not be opposed to adding it as I do some metal casting.

 

You only need a propane torch to melt a small volume of lead. Make a plaster mold and melt it right in place.

 

The lead can also be poured in place, in a cavity in the rudder backed with a metal or even a wooden plate.
If molding separately: a wooden box, a dry empty tuna can...
Here is a video. He is working on a centerboard and mentions an upcoming keel. He also shows how to do the 'math' for lead as well.
The pouring part starts at 17:50

There are other YouTube videos of people pouring lead into rudders but with less safety and production quality.

 

Thanks everyone, this is very helpful information.

based on what i gather its best to build a complete cassette for the rudder blade, agreed also will look nicer.

take a look at this video i just found, i think this is what you guys were talking about. with having an eyelet at the cassette i can use a bungee at blade to keep tension.



Is this somewhat what you were referring too?

 

That looks like a better solution,but if you use that design you need to be aware of the risk of splitting the tiller.The usual cure was to drill a transverse hole a little way ahead of the end of the slot and to use a length of copper rod,rivetted over a washer on each side to resist splitting.My own preference with wooden tillers is to use the more common tapered end and insert it into a matching mortise in the rudder assembly.The wooden rudder stock I posted earlier would have a stainless steel channel section installed at a slight angle to provide the taper and a through bolt at either end will deal with any tendency to lever the sides apart.