Boom Advice Please!

[CharlieJ]

I'm definitely keeping it end sheeted since the traveler is at the transom. Mid-boom would get in the way.  :)

You told me center sheeted.

"Depending on if the PO used sails from the Nomad or the W22, sail area is between 111 and 115 sq ft.
Sheeted at the center."

That's why I suggested the deeper boom.. If it's end boom, then the smaller should do fine

[Travelnik]

OK, I feel stupid! I meant end and typed center!  :-[

It is definitely sheeted at the end. The traveler is at the transom.

I still like the beefier size though. I would feel better with something larger than 2.2 x 3.6. The mast is 5 x 3, and the smaller boom would feel skimpy to me.

Maybe I'm just paranoid about strength.

[Jim_ME]

Here's a photo from the Nomad brochure to give a visual sense of the size of the original boom compared to the mast.

[Travelnik]

It doesn't look too skimpy in the picture.  :D
Maybe 4" +/- ?

Thanks for posting the picture.

[Captain Smollett]

Don't know if this is something to consider or not, but ...

Going larger to gain strength is one thing, but you are also adding weight.  Getting too heavy a boom could (in my theoretical mind, anyway) adversely effect light air performance by holding the sail down too much.

We all like to put a tremendous effort into beefing things up and thinking about the bigger winds, but (in my opinion) too often ignore the other end of the spectrum.

You asked about sailing on the ICW.  I think being set up for light air to be important in that case.

The question is not is the smaller boom as strong as possible, but is it strong enough.  It only has to not be the weak link in the system.  You have a 115 sq ft sail and a boat whose displacement and righting moments are "known" quantities.  The boom only has to be "strong enough."  If a 3" or 4" section meets that criterion, the 5" does not really give you anything but may cause other problems.

I do not know the answer, of course.  I'm just throwing it out there as something to consider.  How likely are you really to bend/break a 3" section boom?  If the 3 is too weak but a 4 meets the need, I'd go that route (even if it costs more, but that's just me) rather than the 5.

Everything is a trade off.  If you make something as strong as possible but stronger than it really needs to be, something else is likely getting traded off in an adverse way.

There really should be a chart somewhere showing recommended minimum boom sections as a function of boat size + sail area.  Short of that...contact a designer/naval architect and ask them.  I would not guess, but nor would I just go as big as I could find blindly either.

Hope that makes sense....

PS: In that picture, the boom is very clearly smaller than the mast.  If the mast is 5" section, the boom is 4 or smaller, maybe even 3.

And man, I LOVE the lines on that hull.  That boat screams "seaworthy shape" to me. 

[Travelnik]

I'll have to research the weight issue.

The Nomad isn't famous for being a racer, but I don't want to upset the balance bu making her too top heavy either.

Thanks for bringing that up.

I love the lines too. I think Denys Rayner was really on to something there.  ;D

[Godot]

If you want to save a few dollars, you could always build a wood boom. There is something to say for do it yourself.

[Travelnik]

If you want to save a few dollars, you could always build a wood boom. There is something to say for do it yourself.

I have seriously considered it, but I don't know anything about spar making, even though I have done some construction work in the past.
Plus, I don't really have much in the way of woodworking tools anymore. I had to sell most of them before we moved to Texas.

[Godot]

I don't think there is a real need to do anything fancy like building a birdsmouth spar or anything. I'm not sure of the best size wood to use; but I would start with a couple two by fours (or I think I'd be reasonably comfortable with maybe three 1-by boards) of the appropriate length, glued and screwed together, and tapered an inch or two at the end. I would use something clear and reasonably durable, maybe douglas-fir or the equivelant. You can lash the foot of the sail on the boom. Grab some blocks to manage outhauls, and some cleats the tie them off. I would think the gooseneck would be the only difficult to source part.

I'm not sure of the strength required and I'm not qualified to do the engineering math. For something like this I usually just eye-ball it and see how it works. I bet you could build several booms locally (including buying a few tools) for the price of buying one commercial aluminum spar.

[Captain Smollett]

The Nomad isn't famous for being a racer, but I don't want to upset the balance bu making her too top heavy either.

I'm not talking about weight from a racing or a weight above waterline standpoint.  I simply mean that in light air, a too-heavy boom will pull the sail down when there is insufficient wind to blow the sail into proper shape.  Imagine trying to sail with a flat sheet of plywood rather than an airfoil...in light air, even very small imperfections in shape mean a lot of lost efficiency.

This is the reason light air sails are made of lighter weight nylon than dacron...it's easier to blow out into airfoil shape.  I'd love to have a lightweight nylon mainsail for those light air days around here. 

On protected areas of the ICW (and even some open ones) you will have a lot of light air days...in summer, far more light air days than heavy air days.  Summers can be hot and still; being able to catch the slightest breath may mean the difference between moving some each day and sitting still for days (weeks) at a time.

Heavy weather gets all the attention, but light air requires some serious thought, too, especially if you plan to mostly move the boat under sail.  That's why I say make it just heavy enough to withstand what it needs to withstand, but no more.  There should be some engineering chart somewhere that shows what size boom is NEEDED to hold up to the forces on a 115 sq ft sail with boom-end sheeting.  I'll bet it is smaller than one might expect.

The general rule of thumb around here seems to be if the wind is light enough that boat speed is less than about 3 knots, they fire up the engine.

Think about that, though.  2 knots for free vs burning fuel.  2 knots with nice, peaceful quiet vs the droning of internal combustion.

Light air makes the sailor.   ;)

[Travelnik]

Boy! Things would have been a lot easier if I still had the original!  ;D

OK, not to be argumentative here, I'm just trying to get the best for my all around use, both ICW and open water. That's why I'm asking so many questions before I lay out the cash. The more I can save, and still do the job right, the more can go into cruising!

I checked the weights on Rig-Rite, and the smaller weighs in at about 1.3# per foot, the larger at about 1.42#.
Over a 10-11 foot span, that's under 2# total difference.

Will that severely affect the light air performance?

I would rather sail than drive as much as possible (now that I know I can). If I wanted to drive to Maine, I could just take the Cougar!  ;D

[Captain Smollett]

Ok, by my (ultra simplistic) calculation, the effective windspeed force loss to boom weight at 5 mph differs by 2% for the two booms and at 3 mph it is about 1%.

In my experience in light air, I think 1-2% in some metric of efficiency is huge.

IF the 3" is "strong enough," I'd opt for lighter. That's just me I guess.

I welcome others' thoughts on this, though.

[CharlieJ]

IF the 3" is "strong enough," I'd opt for lighter. That's just me I guess.

I welcome others' thoughts on this, though.

Agree. Only reason I even suggested the larger was because I thought it was mid boom sheeted.

Tehani carries a wooden boom that I built. Fir, box section, 12 feet long, end boom sheeting and it's 2 inches by 3 1/2.

And it's heavier than I'd like, but in light air, I just take the load of it on the topping lift, which is after all, what's it's there for.

[Travelnik]

Thanks guys!

I'll go with the lighter one. I'd rather pay more for the right thing, than go cheap and regret it later.

[Travelnik]

OK, I just bit the bullet and ordered a Dwyer DM-5 Boom!  ;D

Shipping is almost half again the cost of the boom, but at least it's new.

Thanks again everyone for all your help!

Have you checked with Dwyer's?

https://www.dwyermast.com/families.asp?cat1ID=30&cat1Name=Booms

For example, if you want to split the difference between the two you are considering, they have one that is 2.75" x 4.50"

Don't know if it's in your price range at $25.55 / ft boom only (and you'd have to install hardware, etc).

Anyway, you might want to call them and see what they recommend for your boat.

Are you married to the idea of mid boom sheeting?  Not trying to talk you out of it...just there are pros and cons either way.

[Godot]

Good luck!

[Travelnik]

Well, I got the boom 3 working days after they shipped it, and it looks like it should work. I may need to cut it down a little to clear the backstay. I will know for sure once I get it all set up.

The only problem so far is that the 2 little tangs (?) that hold the sail tack on the gooseneck broke off in shipping. The cast aluminum seems very fragile, and I don't know if I should get a couple more from Dwyer (1 to use, 1 for a spare), or if I should take the cast piece to a machine shop and have the whole thing made from 316 stainless, or billet aluminum.  ???

I didn't think the parts were so fragile.

[s/v Faith]

Well, I guess the stresses on the tabs are very different in shipping then in use (lateral loads, likely impact with sheer and irregular compression).

Any recourse with the seller or shipper? 

[Travelnik]

Well, I guess the stresses on the tabs are very different in shipping then in use (lateral loads, likely impact with sheer and irregular compression).

Any recourse with the seller or shipper? 

I mentioned it to the seller, and he said that he would see if he had any that would fit. No further response.

The piece is only 30 something dollars, so that isn't really a big deal. I just don't know about trusting a replacement made from the same quality cast aluminum.  :-\

Billet may be too expensive to have made, so I was seriously considering having it made from stainless.

[sharkbait]

Just make your own.When mine snapped off Berkeley I looked for 2 months for a suitable aluminum extrusion.One morning I woke up and remembered that wooden spars worked for for all the old boats.So I went down to the lumber yard and ordered 4 spruce 12' 1x4.
Made some calls and borrowed a bunch of clamps then epoxied them together,cut to  length,chamfered with a skillsaw and rounded with a belt sander. Worked great and lasted through some heavy weather 65kts.
Ericson 27 mid boom sheeting.