Gaff rig with jib?

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I sure didn't compare a VOR to a pd racer on any level. I made the point twice that I was not recommending the square top rig for the cardboard boat.
However, there is no limit to the size boat that could benefit from the improved planform of a square top main or jib. They are used on radio controlled models on up to Banque Populaire V. This type of rig may or may not be more expensive than other rig types. References had been made to gaff, sprit, triangular rigs and others. I thought the square top planform should be mentioned.
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A note on square tops: One can look at a square top as a sail with extra sail on top but it is probably more accurate to refer to the square top having a lower center of effort than a triangular sail with the same area and same length boom. For instance, as an exaggerated example, a rectangular planform with a 6' boom ,
6' head(close to some 18s) and 14' luff would have 84 sq.ft. SA with a center of effort at 7' above the boom. A triangular sail would have 84 sq.ft, a 6' boom,28' luff and a CE at 9'3" above the boom. Practically, you can convert a "normal" triangular main to a square top of the same SA with a lower CE.

 

Sharpie2 that rig is standard fare on many RC sailboats. It works quite well and the club on the jib makes it self tending. The RC boats usually have shrouds but it can be done "wireless". As long as we are having trick rigs, how about a swing rig where jib luff tension is tied directly toward vanging the main. Well maybe not. We'd better let CK choose his own poison.

And your sketch shows an eleven foot by three foot punt or scow type. You have let it weigh 150 pounds....Why so brutally heavy?

 

Because it is made of cheap 1/4 inch plywood, has a false bottom, and Comes apart in three segments. The bow and stern segments are decked over and each has a watertight bulkhead. I designed every part of this boat, so I could find its weight. This weight includes the rig and all appendages.

There are no curves at all on this design. The bow is a triangle and the stern is a rectangle.

Here, I'll show you.

 

The choice of rig should be governed by what you want and what you have. Clearly, this boat will prefer a modest rig, low aspect and preferably one that doesn't have a high percentage of it's area, near the top of a stick. The merits of a rig choice can be debated continuously, with each having good and bad things to consider. Given the build type and the owner's experience level, a low aspect uni rig is an obvious call. It'll get to windward better then any of the other logical small boat choices (within the limitations of the boat), with minimal strain on the boat or novice sailor, trying to remember which string to pull and a minimum number of spars.

In small, novice sailed, flimsily built, experimental craft, simple is always going to be better.

 

Here's a classic working gaff rig. Examine each part carefully and you will learn a lot.

 

Well, I found a web site that actually goes into considerable detail about how to set up a gaff rig, and I have to admit it didn't do anything to dissuade me. I am a Physics teacher, and one of my favorite lessons is Mechanical Advantage because it gives me an excuse to set up a block-and-tackle that will lift a 1 kilogram mass using only 110 grams of mass on the other side. Yes, it's complicated, but just setting it up is fun, and then seeing how this miniscule amount of weight can lift this huge chunk of metal is amazing. A gaff rig, with all of its pulleys (blocks..sheaves..whatever their proper name is in this context) is exactly the kind of thing that everyone who knows me would expect to see on a boat that I built.

Also, in this month's Sail Magazine, I read an article about the Beetle Cat. It is a class racer built uniformly by a 90-plus-year-old company, and even though it's only a slight bit bigger than my PD Racer, it features a colossal gaff rig. Yes, I understand that my cardboard construction might not be able to withstand the same forces that a full wooden boat would, but nor did I say that I intend to win any races with it. Although I do intend to register my hull with the class, I doubt very much if I'll actually ever race it at all.

Since I don't need speed, I'm sure I can get away with a much smaller sail, which would avoid making my gaff rig heavy and useless. And then there's the fun factor. I think I would much rather have the classic look of the gaff rig, with its added complexity, than to just throw something together for the sake of getting out on the water sooner.

Plus, I think I'm going to learn more this way. It's like playing a video game on the "Easy" setting. Yeah, you can play the game, get through all the levels and defeat it, but then if you adjust the difficulty up, you end up failing because you are used to it being much easier. If I start my sailing life with a more complex rig, I think it'll be much easier to adjust to a simpler rig later than it would be to try and figure out a complex rig after I've gotten used to everything being so simple.

 

The first boat I learned to race was the 19' Fish Class at the Pensacola Yacht Club. In fact, the Fish was used as the youth training boat on the whole Gulf Yachting Association while most other regional associations used much more "advanced" boats. I enjoyed my few years with the Fish class and learned a lot-just not how to race with a spinnaker!

Fish Class fleet-click-

 

The problem with a gaff rig, even a small one is the attachment point loads. Sure, you can lift a 100 pounds with a 20 pound pull on a 4:1 tackle, but the attachment points on a cardboard boat will see otherwise, testing their pullout abilities and you'll have a quite a few of these attachment points, which isn't so on other rig choices. Secondly, placing a high percentage of area high up in the rig, generates a significant leverage moment, so cardboard "partners" will get pissed pretty quickly. Then of course there's the weight and windage thing. This is why many have suggested a sprit rig or a sprit boomed rig. These place the loads low on the stick, often right near the partners, so load paths are short and into the hull shell quickly (where they need to get to). A sprit boom low aspect Bermudian, will not have vanging and sheeting loads anywhere near what the other rigs will require. On a 100 sq. ft. sail, you can live with just a single line dangling from the end of the boom, maybe just a whip tackle through a bee hole. No tackle, no loads, just a single string to pull. After you get some experience, you can consider making up some new rigs, or likely a different boat, intended for a specific rig. I too learned with a gaffer, but is was a 1,100 pound 15' boat and an old fart was showing me why not to over sheet in a stiff breeze (etc.). The best way to learn about sailing is with a rig that is uncomplicated, so you can focus on sailing, not tweaking a lot of strings as you must in more complex rigs.

 

It seems like I'm hearing a lot of prejudice here. Very low aspect ratio gaff rigs are just as possible as very low aspect ratio rigs of other kinds. A gaff rig can also be boomless.

The vang loads are usually taken by the mast, not the hull.

The loads that are taken by the hull are the heeling loads, the sheet loads, and the driving loads.

This is true for just about any kind of rig usually used, including the alternatives mentioned.

Luff tension loads are also taken by the hull, if a jib is used. These are the most extreme. This is one reason why the jib is usually the last sail raised and the first sail set. The jib will, as a consequence of the stay tensions needed to make it stand well, impart a great deal of compression on the mast step.

The rig I would use in this situation would be a Boomed Latin, with a dead flat cut sail. I would use this sail because it can be feathered to almost zero drive, without flogging itself to pieces.

I find the notion that it is best to learn how to sail on a boat, with just one sail, a bit silly.

I taught myself how to sail on a sloop rigged sailboard, which I built myself.

I had nobody around to teach me and had books that were all but useless.

I did learn how to sail on that boat, as poorly constructed and dysfunctional as it was. Not only did I learn on that boat, so too, did my brothers and one of their best friends. And they did it, without me around to call balls and strikes.

Perhaps, instead of trying to dissuade CK, we should find ways to help him meet his goals.

I'll start by suggesting that the jib be used as a down wind sail only. This way, it will be relieving some steering loads, as well as creating compression ones. As a down wind sail, luff tension is far less important, maybe allowing you to get away with an un-stayed mast.

Using a spreadsheet I set up for this purpose, I have come up with a possible rig which has just over 60 sf of sail.

It has 45 sf for the main and 15 sf for the jib. The mast is just 10.5 tall; the boom is 8.0 ft long; the gaff is 5.0 ft long; and the jib boom is 4.0 ft long. The sail hoist is 5.5 ft and the gaff sets at a 45 deg. angle.

The Horizontal Center of Area (HCA), for the main alone, is 39.5 inches aft the mast.

The Vertical Center of Area (VCA), for the main alone, is 72 inches above the mast step, or 36 inches above the Boom.

With the Jib, the combined HCA is 26 inches aft the mast, and the combined VCA is 26 inches above the Boom.

 

How about this ?

 

Did you, by any chance, sketch a diagram of this rig? I looked at the picture you posted earlier of the rig with the boomed jib, but I don't know how all of the stuff in the picture actually connects together or how it moves.

I don't have a problem with stays or shrouds. I'm thinking it might actually be better to use them because it would help distribute the force around the boat, rather than concentrating it in one area.

In regard to this, is it possible to have a stay led directly aft? It seems like it would be awfully in the way. I'm thinking the solution to this would be to have two aft-leading stays, each one tied to one of the corners of the stern.

 

CK you can have a stay running aft, (called a backstay) if it does not interfere with the leech (trailing edge) of the sail. If the sail and the backstay interfere with one another, you can have "running backstays" that are usually attached near the outer corners of the stern structure. They will keep you busy because one stay must be released while the other is reattached and cinched up during a tack.

The whole idea of stays or shrouds bring structural implications. The stays will cause the mast to go into compression mode. That means that the bottom of the mast will do its best to punch a hole in your boat bottom. As a physics teacher you can easily do the math. It might be fun to let your students do the calculations for various sail loading and shroud tensions.......That is not all. Free standing masts can be allowed, even encouraged, to rotate. There are advantages in sail performance on many types of rigs when the leading edge of the sail can be aligned, or partly aligned, with the apparent wind.

 

Thanks for the recommendations, but I really can't see my boat having a rotating mast.

And I do understand what the forces would be on a stayed mast. What I am envisioning, though, is to create a force-bearing network of structural pieces that effectively make the whole mast system - complete with its step, stays and shrouds - a unit that would be structurally sound independent of the boat. For example, shrouds would not connect to the deck or sides of the boat, but to some structural piece that causes their force to pull up on the step. So, yes, the mast would be in compression mode, but it would be compressed from both sides, and the whole apparatus would just be connected to the boat, similar to the way a car engine is connected to a car.

I have no idea how it would ultimately work out, but I think it could be done. Maybe.

 

What the heck. The guy's building a boat out of cardboard, for cryin' out loud. And you folks are trying to talk sense to him now, about what rigs would be the most practical?

If you want a gaff rig with a jib, CbK, go for it. Be sure you keep us informed and up to date, and remember we like lots of pictures.

 

I once made such a device for a four man Vinyl raft. I did it when I was 17. It did work.

I can see your motives for going this route.

The cardboard boat can be seen as nothing more than expendable, so it would be nice to have a permanent rig structure that can just be added on to a new cardboard hull.

Such a device would resemble a bed frame, with deep side rails, which would fit just over the sides of the hull and be attached there with large diameter wooden dowels (broom stick diameter), through re enforcement patches on the inside of the hull.

This device would have three cross beams.

The first would go across the bow at that end of the deck, and it would be much wider than it is deep.

The 2nd would go about one foot aft the front edge of the front one. This one would be deeper than it is wide, for the mast will step on top of it.

The third would resemble the first and fit over the forward end of the aft deck, or the transom.

A three foot long bowsprit would be fastened to the first and 2nd cross pieces.

Two pair of shrouds would hold up the mast.

the first pair would attach to the front ends of the side rails and the 2nd pair would attach to the side rails about one and a half feet aft of the 2nd cross beam.

This structure would take care of the majority of the high stress loads, but the jib might need a little help.

I suggest a bob stay that attaches to the bottom of the bowsprit, one one end, and to the bottom of the boat, at the bow, at the other. A plywood attachment plate could be made that is triangular in shape. A large number of dowels and bolts, through the hull and re enforcement patches in the hull, can distribute the loads there.

Although the hull will not be able to handle concentrated loads very well, it should have a considerable amount of structural stiffness, especially if there is any depth to the sides.

I suggest making the sides 18 inches deep for this reason. The depth of the sides can be subtracted from the length of the mast, which I described in an earlier post. So, with 18 inch deep sides, you can have a 9.0 foot mast

You will need a dagger board rack as well as a rudder rack, to make this into a real sailboat. I suggest making these separate from the rig rack, as making them a part of it will be both heavy and complicated.