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spray dodgers – why collapsable?

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Question:

….Racers tend to fold them down when going to windward, in the belief that there will be some undesirable windage effect. Of course, there’s no evidence for this….. Except for the last 100 years or so of aerodynmamic research…

Oh, c’mon, give me a break. Any windage from a dodger is miniscule compared to the topside, the cabin trunk, all those guys setting along the windward rail, the ones in the cockpit, etc, etc. Aerodynmamics, indeed. — Pete

Response:

Perhaps he’s suggesting that the dodger would divert air around the crew, and therefore decrease the windage that the crew would otherwise create…. Hard to visualize a dodger that somehow protects crew on the windward rail. — http://www.well.com/~pk/fishmeal.html -"Call me Fishmeal"-

Response:

Remember that some of the functions of a dodger are done better by one of those hemispherical polycarbonate domes, especially for shorthanded sailing. I had one on my Merit 25 for the ‘86 Singlhanded Transpac, and it turned out to be one of the most important upgrades to the boat. — http://www.well.com/~pk/fishmeal.html -"Call me Fishmeal"-

Response:

I’m not too sure that will stand up under scrutiny. I’ve got a dodger – about 2.5 foot above the cabin top and width of the cabin top – say 6 feet. That is a flat plate area of 15 sq. feet with me hiding behind. You got those eight or nine 250 lb gorilla’s on the windward rail. I might have less windage then you, unless you make them scrooch way down there. :-) Wait a minute, are you saying the dodger somehow *replaces* the crew on the rail? Seems to me we were just interested in the effect of the dodger, independent of crew disposition. But – since no-one brought up the one *possible* way that a dodger could improve aerodynamics, I’ll mention (for completeness) that a dodger might improve the performance of the mainsail by providing a good "end plate" seal along part of the bottom of the boom. In fact I’ve experimented with similar root sealing devices on my boat, following the lead of physicist John Clauser who installed a "Clauser curtain" on his modified Ranger 37 some years ago. The improvement in pointing angle was small, but detectable. On my boat the "Clauser curtain" took the form of a dorsal fin from the mast to the companionway hatch, with a foam tube on top that the boom could seal against. Naturally the crew hated the thing – and I couldn’t use a fixed boom vang or slide the hatch open – and it came off for the one-design season. In the case of a real dodger, I’m pretty sure that any gain from root sealing would be more than lost to parasitic drag, but I don’t have the numbers to prove it. — http://www.well.com/~pk/fishmeal.html -"Call me Fishmeal"-

Response:

- Hide quoted text — Show quoted text – I’m not too sure that will stand up under scrutiny. I’ve got a dodger – about 2.5 foot above the cabin top and width of the cabin top – say 6 feet. That is a flat plate area of 15 sq. feet with me hiding behind. You got those eight or nine 250 lb gorilla’s on the windward rail. I might have less windage then you, unless you make them scrooch way down there. :-) Wait a minute, are you saying the dodger somehow *replaces* the crew on the rail? Seems to me we were just interested in the effect of the dodger, independent of crew disposition. Perhaps he’s suggesting that the dodger would divert air around the crew, and therefore decrease the windage that the crew would otherwise create. Like the air ramps thingies that they put on the cabs of semis. Would it?

If that were the suggesting, he should not be comparing crew and the rail vs crew behind dodger. In the former case the increased RM ofsets any aero problems. If he is suggesting that the dodger makes a net improvment because it makes the people behind it more aerodynamic… he has to explain how my head and shoulders could have 15 ft^2 of FPA. Sincerely, Terry "even-my-head-is-not-that-big" Schell

Response:

<snip – Hide quoted text — Show quoted text -But – since no-one brought up the one *possible* way that a dodger could improve aerodynamics, I’ll mention (for completeness) that a dodger might improve the performance of the mainsail by providing a good "end plate" seal along part of the bottom of the boom. In fact I’ve experimented with similar root sealing devices on my boat, following the lead of physicist John Clauser who installed a "Clauser curtain" on his modified Ranger 37 some years ago. The improvement in pointing angle was small, but detectable. On my boat the "Clauser curtain" took the form of a dorsal fin from the mast to the companionway hatch, with a foam tube on top that the boom could seal against. Naturally the crew hated the thing – and I couldn’t use a fixed boom vang or slide the hatch open – and it came off for the one-design season. In the case of a real dodger, I’m pretty sure that any gain from root sealing would be more than lost to parasitic drag, but I don’t have the numbers to prove it.

I am pretty sure it would make a shitty root seal (somebody *flame* me), primarly because it covers so little of the root area. Perhaps if you had 6 ft long dodger you would start to see some advantages. As far as a root sealant… have you considered a small, clear sail that mounts on the bottom of the boom? (short luff between the gooseneck and the deck, long foot out to mid-boom). The leach could contain a line that is used as a vang, particularly if the sail was not the full length of the boom. It would have a non-optimal aerodynamic profile… but would make your mainsail more efficient so it would still provide a net benefit in efficiency as well as a increasing the total power of the rig. It would not be race legal, but it might be nice for cruising in a boat that is a bit slow to windward. Sincerely, Terry "windward-performance-isn’t-just-for-racers-anymore" Schell

Response:

Perhaps he’s suggesting that the dodger would divert air around the crew, and therefore decrease the windage that the crew would otherwise create. Like the air ramps thingies that they put on the cabs of semis. Would it? –Steve

Response:

why do you install spray dodgers (over the companionway) that are collapsable? and the supplementary question is…. How often and in what circumstances do you fold down the spray dodger?

Some years ago I wanted something to keep water out of my face, and also cold wind on those late-season, last couple of hours motoring dead to wind, done-sailing-just-want-to-go-home evenings. I have a Catalina 27. The dodgers I saw were either too narrow to be worth much, or if wide enough, impossible to get around to go forward. (It’s hard enough to clamber forward on the C-27 as it is.) Sure, the cloth part folds, but the metal doesn’t, and where do you PUT the thing when you don’t want it? Besides, a big dodger on a smallish boat is ugly, not to mention expensive. The answer to that dilema was a windshield. I made it out of aluminum stock and plexiglass. It sits atop the cabin, and is about as wide. I’m completely satsified with it, and wonder why it isn’t standard equipment on cruising boats, at least. It keeps the spray out of the cockpit so effectively that if you don’t need foul weather gear or an umbrella while sitting at anchor, then you hardly need it under way. Many are the times I’m comfortable in regular clothes while the crews of all the other boats I see are all bundled up in foulies. The windshield deflects cold wind from ahead, making that last leg of a day trip far more bearable. It is unobtrusive the rest of the time; you hardly notice it except when it’s doing something useful for you. It doesn’t fold down, though I suppose that could be arranged with some more professional design and fabrication. With some attention to lines and angles, it complements the appearance of the boat. While I caution guests not to step on it or grab hold of it for support, it is robust enough to stand to 60+kt of wind durring thunderstorms – I wouldn’t dare leave a dodger up in a storm like that. I doubt the added windage amounts to much. I’ve always wondered why sailors have to be either enclosed in a dodger or wheelhouse, or totaly exposed – either of which seems extreme in most conditions most of us sail in. Andy Lubenow.

Response:

why do you install spray dodgers (over the companionway) that are collapsable? They are cheaper than hard dodgers and collapsible so the cloth

can be taken to an oversize washing maching and cleaned.

Response:

<snip shelter). Everyone has some form of bimini or sunshade or dodger since without it you are either par-broiled or drenched. After having fought those collapsible binimis/dodgers for a while I decided that looks "be-damned" and now have a perminant steering shelter with an fabric extension to cover the cockpit. Big window/hatch in the front to get airflow. Now, while all the others are scrambling about in their foulies I’m setting there in my shorts and singlet.

I agree with Bruce. Seems that many of the more experienced voyagers in the South Pacific have permanent doghouses. I wish our mainsheet allowed more than a pram hood (little dodger) over the companionway. We also have a Bimini with deep removable side curtains that will stand up in forty knots. The reason some dodgers are collapsible is to allow you to get below easily without ducking — you just push the dodger forward as you go down. A dodger high enough to avoid this is often hard to see over, looks ugly, or both. Jim

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And yet another reason for a removable dodger is trucking. Big discount for boats under 13 feet 4 inches keel to coachroof.

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A relatively simple question to all you good cruising folk: why do you install spray dodgers (over the companionway) that are collapsable?

Here are some reasons I can think of for lowering the dodger: – Racing – to gain performance during the occasional club race – Cleaning – Assuming you don’t have a permanent dodger, lowering it makes it easier to clean the boat. – Winter layup – makes it easier to cover the boat – Ease of entry – especially for older or impared visitors Reasons not to install a permanent dodger: – Preserve the original appearance and value of the boat. Permanent modifications may not suit future buyers. – Cost – Many owners add a dodger as a luxury, after they can afford it. A permanent dodger is probably more expensive. – Inability to lower it. Bill Spencer LIONHEART

Response:

Some have written that one’s view of Dodgers is related to where one does ones’s boating. I disagree. I grew up in Los Angeles and was a big Dodger fan in my youth. I now live in northern California and am a Giants man, with a secondary feeling for the A’s. I hate Dodgers, except for Sandy Koufax, my childhood hero. Don’t have an opinion about these Giant Dodgers, as discussed earlier on this thread, but do have an extraordinary respect and admiration for Dusty Baker, who was both a Dodger in his playing days and is a Giant as a manager. Go Giants, beat those Dodgers into collapsible unbattented pulp. Best Regards, Rex Malott Rex Malott

Response:

- Hide quoted text — Show quoted text – I firmly believe that ones view of dodgers is based entirely on where you do your boating. Here in Florida and further south or east boats are invariably fitted with some form of bimini top to help keep the evils of sun induced skin cancer at bay. A permanently installed dodger cuts down on air flow through the cockpit such that the occupants would be medium rare in no time. Both Halberg Rassy and Amel install permanent hard dodgers on their boats and they can be really miserable in tropical areas. However in our colder climes we need every bit of warm sun we can get, hence no bimini top but a dodger to hide behind "in case of a change in the weather".(apologies to Rodgers and Hammerstein). Why have a dodger at all in the tropics? The main use I make of mine is to put it up when I go ashore so that I can leave the companionway hatch open and yet still get protection from the common afternoon tropical showers. ….. I decided that looks "be-damned" and now have a perminant steering shelter with an fabric extension to cover the cockpit. Big window/hatch in the front to get airflow.

Exactly what I plan for Kihoe. How did you approach the project? design? construction? Tim Wight KIHOE

Response:

Hell… you don’t even need the theoretical research, just *observe* the thing as you sail into the wind. As you beat into 35 knots of wind you can see each little snap attaching the dodger to the boat *strain* to pull your boat to a stop. :-) Of course it does not succeed in stopping your boat, but the drag is obvious. You might argue that the effect will be small, but I don’t see people dragging tires behind their boats while racing just because they "won’t slow ya down too much." For cruising, they are great. No question about it. BTW has anyone considered installing a *really* big dodger to be used as unrated sail area for going downwind. :-) The kind of thing you need to drop down in order to jibe the boom. Sincerely, Terry "at-25-knots-I-switch-to-the-.75-poly-dodger" Schell

Response:

why do you install spray dodgers (over the companionway) that are collapsable? and the supplementary question is…. How often and in what circumstances do you fold down the spray dodger? At first thought it would seem cheaper, stronger and generally more sensible to make a permanent structure (not quite a doghouse/wheelhouse, but part way towards it).

Well, if a big storm (typhoon or huricane) is bearing down, it’d be nice to eliminate the windage completely. Nice to take them down in the winter so ice and snow don’t damage them. Don’t really want to race with them up. Might want to fold it down in light air to allow full ventilation to the cockpit. A quick look round the boat harbours and anchorages shows a complete absence of folded-down spray dodgers.

Laziness. See lots of biminis up, too, though fewer around here. — Jere Lull Xan-a-Deux ‘73 Tanzer 28 #4 out of Georgetown, MD Xan-a-Deux’s Pics & Specs: http://www.castle.net/~jerelull/X-Main.html Our British Virgin Island pics: http://www.castle.net/~jerelull/BVI.html

Response:

I firmly believe that ones view of dodgers is based entirely on where you do your boating. Here in Florida and further south or east boats are invariably fitted with some form of bimini top to help keep the evils of sun induced skin cancer at bay. A permanently installed dodger cuts down on air flow through the cockpit such that the occupants would be medium rare in no time. Both Halberg Rassy and Amel install permanent hard dodgers on their boats and they can be really miserable in tropical areas. However in our colder climes we need every bit of warm sun we can get, hence no bimini top but a dodger to hide behind "in case of a change in the weather".(apologies to Rodgers and Hammerstein). Why have a dodger at all in the tropics? The main use I make of mine is to put it up when I go ashore so that I can leave the companionway hatch open and yet still get protection from the common afternoon tropical showers.

My experience sailing in Asia is directly opposite to yours. Over here it is either boiling hot (in which case you need shelter) or pouring down rain (in which case you need shelter). Everyone has some form of bimini or sunshade or dodger since without it you are either par-broiled or drenched. After having fought those collapsible binimis/dodgers for a while I decided that looks "be-damned" and now have a perminant steering shelter with an fabric extension to cover the cockpit. Big window/hatch in the front to get airflow. Now, while all the others are scrambling about in their foulies I’m setting there in my shorts and singlet. — Bruce P. Barden Bangkok, Thailand

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Well my answer would be that cruising boats are likely to spend time at sea in bad weather, those at the yacht club are less likely. If green water comes on board it is quite capable of demolishing a rigid spray dodger. If that happened then I would hate to be standing (cringing) behind it. As for the second question, the answer is "right before the green water comes on board! <grin" Steve — Steve Cork | Ph: 61-9-429-6047 | "Beware the Jubjub bird AlphaWest P/L | http://www.alphawest.com.au | and shun the frumious Consultant | Fax: 61-9-429-6030 | Bandersnatch"

Response:

A relatively simple question to all you good cruising folk: why do you install spray dodgers (over the companionway) that are collapsable? and the supplementary question is…. How often and in what circumstances do you fold down the spray dodger? At first thought it would seem cheaper, stronger and generally more sensible to make a permanent structure (not quite a doghouse/wheelhouse, but part way towards it). A quick look round the boat harbours and anchorages shows a complete absence of folded-down spray dodgers. — Kim Klaka Regional Manager Australian Maritime Engineering Cooperative Research Centre (AMECRC) Curtin University GPO Box U1987 Perth Western Australia 6845 phone: 61 9 351 7380 fax: 61 9 351 2377

Response:

I do not fold my dodger down at all. I remove it when it is not needed. I found that folding it down causes creases and tears in the window material. It takes only about three minutes to remove or install it, that is, zipping it or unzipping it from the metal supporting frame. I do fold down the frame. The dodger gets most use in spring and fall when cold spray is more likely to come back over the cockpit. In warm weather I remove it because it blocks the flow of air across the cockpit occupants. Warm weather usage is limited to rainy days, to keep water out of the companionway. Ken Thorn Second Encounter Solomons, MD

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At least here in Florida in the subtropics, the doger makes the cockpit too hot about 6 months of the year, even with the opening sections rolled up, flattening it is the only answer (actually we remove the dodger entirely and only put it back on in winter if needed), we use the bimini top all the time. A hard bimini top with removable panels all around is really nice, but a lot of work or big $$$, it can also have a boom crutch/gallows as part of the structure. But not being removable, it’s also windage. During hurricane season, we strip everything if there is one coming our way. Steve

Response:

First of all, there’s no way that a permanent structure would be cheaper. Folding dodgers are quick and simple to make in quantity, and even simpler to install. Racers tend to fold them down when going to windward, in the belief that there will be some undesirable windage effect. Of course, there’s no evidence for this. Most people leave them up because they provide shade from the sun (something most sailors will benefit from), and also from wind, rain, etc. — Pete

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