Nacra 5.8; adding a boom, losing a boomlet

Just picked up a Nacra 5.8.

I plan on doing some modding this fall/winter.

I am planning on getting a square-top main via whirlwind, as the main it came with is in pretty marginal shape.

Here's my question:

Does anyone have experience with converting a boomless rig to a boomed rig? I would imagine it is a relatively simple operation, especially considering the main i'm having made is all custom anyways.

I am coming to this nacra after around a decade of skippering E-scows, and, though i am happy with my purchase (a great deal, and the boat flies) the boomless rig just gives me the heebee jeebees.

Would this conversion to a boomed rig gain an appreciable increase in performance? especially with the use of a squaretop? or does keeping on the sheet and dropping the traveler produce the same results in a boomless cat? Finally, if i do throw a boom on it, i take it my traveler and sheet are my vang? i dont see vangs on these boats....

-the safety issue of boomless is a non-issue for me.

Traveler and sheet are your vang - yes. The traveler is long enough (and you don't sheet out so far as on a monohull) that you don't need a vang.

If you are going with a square top, upgrading to a boom would be worthwhile. The boomless setups were driven largely from safety - removing one hard thing that can significantly hit you. In order for them to control sail shape well, they need to pull a significant angle to toward the mast to control the draft of the sail. However, with the square top, you will need much more leech tension to bring the square top into play. Having a boom and good geometry between the traveler and the boom/sail connection point is important.

Make sure your sailmaker knows what the foot dimension of the sail needs to be for the boom geometry to be correct. You need the sheet to angle off the back of the boat enough so that it pushes the boom forward with enough pressure to induce mast rotation but not so far that it unnecessarily loads the boom and gives up leach pressure. You will also be able to simplify your mast rotation controls since the boom will help take care of this now. Also consider connecting the sheet directly to the sail clew with a strop around the boom. This will help reduce the structural requirements of the boom since the majority of the sheet loads will now go straight to the sail and the boom just carries the inward rotational forces to the mast.

If you can get a chance, look at an F18 rigged and take some measurements from the sheet/boom geometry. That should get you started.

I did not think about the angle of the sheet coming off the traveler as it pertains to the degree to which the boom induces mast rotation. Interesting.

One thing which comes to mind immediately: My 5.8 has a straight traveler track, meaning that the angle of the sheet loads, and thus the fore-aft boom pressure, will change as i drop the traveler, tending to induce less forward boom pressure the further i drop the track. Is this problematic? How do other boats get around this?

One solution which comes to mind; would it be stupid, nonsensical, and otherwise idiotic to take the boomlet track system i have currently and place it on the end of the boom, thereby making the sheet-angle geometry adjustable? or am i over thinking/engineering now?

And that all being said, i thought mast rotation was induced by sail loads, not sheet loads; but i am not well-versed in this type of rig.

Glad to hear my thoughts on square-tops requiring a boom echoed. thanks!

Your sheet loads do increase if you travel out without easing the main. However it's pretty rare that you travel out this way. Normally when bearing away the mainsheet is the easiest to use to control power and it gets eased before the traveler is moved. In rare circumstances (death reaching), it pays to play the traveler before easing the main. It both reduces the angle of the sail and sheets it in harder (flattening/bending off the square head).

You are over-thinking...18squares used to employ such a track - but they are 11 feet wide and single handed (light) so they sheet in pretty hard when going downwind. A-cats used to use a similar setup for the same reasons before they went to curved tracks. For modern narrow/heavier boats, it's overkill to try and accommodate the slight angle change made by traveling out. You would lose as much time/distance while trying to make that adjustment than by just leaving it alone. You will normally have a little twist in the main when sailing downwind...so this really doesn't matter.

You will still need positive rotator for downwind tuning but you will no longer need the positive rotator for upwind use like you did with the boomless rig. You will need a rotation limiter, however, to keep the mast from over-rotating. Again, take a look at an F18 for a better reference.

Find a sailmaker with lots of Nacra experience and most of your questions will get answered. Glasser comes to mind along with Skip Elliot and the other sailmaker out of Florida (can't recall his name but he always advertizes in Catsailor)

Upwind on my 5.5 Uni mast rotation with the boomless rig is easily controlled via the boomless traveler. Readily adjusts the mast out of rotation if needed to fit wind conditions. Downwind, boomless traveler is released all the way and rotation is controlled via a front crossbeam mast rotator. No big deal for me.

Jake is right though, make damn certain the sailmaker understands the sailcut differences between boomed and non-boom rigged sail geometry. Ask for references and then call them.

Good luck, Tom G

You are thinking of Calvert. Whirlwind should be good too. If I'm leaving the foot dimension up to the sailmaker, I would at least want to feel confident that they understood what you were trying to do and the parameters involved.

One more thing; If i use a strop so loads are transferred directly to the sail, won't i use the ability to adjust the outhaul? Don't tell me you guys don't have vangs AND you don't adjust your outhauls either?!

Thanks for the replies; huge help.

No - your outhaul still connects the end of the boom to the sail/strop/sheet. It's what outhuals the sail (obviously) and that force makes the mast rotate....but, we rarely mess with that anymore with the spinnakers. It's usually a set and forget thing.

You are ripping a decent boat apart without any reason.
Just sail it how it is and you will realise that there is much more to it than you think and you will trust the guy that designed it and get a replica sail

seems like a very reversible upgrade to me... nothing lost but time and money

Adding a boom and new sail is a fantastic upgrade to that platform. I think you're making a wise choice to do so.

Sail it as is. Get a new aftermarket 5.8 sail when you want, but the rest is time and money that could go towards a boat that is already set up the way you want IMO.

It is a hull flying beast as it is.

you know what opinions are like?

It's an interesting project that would make the boat look more modern so I'm not knocking it.
I had a Taipan 5.7 with the new rig on it that your changing to before my Nacra 5.8, couple of personal concerns I have are the hull shapes between the 5.8 and the square top cats are very different. The 5.8 mast is strong but not really a wing mast, is it strong enough to hold the big square top leach up? I had a cat before that the mast used to hook over at the top laying off the leach unless the mast was aligned with the main sheet direction. Personally I think the 5.8 was built for raw power that just shoves through waves while most of the square top cats are designed to harness the wind more efficiently and use it more elegantly and I think that starts with the hull shape.

I realize that there will be some that say "leave the poor thing alone" but i think that the differences in design between the 5.8 and more modern designs are primarily in the rig, and while the hulls certainly do have some differing profiles, i am not convinced they are so great (especially when planing) that they would inhibit the ability to see some major performance gains with the installation of a modernized rig. If anything, the more robust hulls give me a great margin of error; i won't need to worry about over canvassing the platform.

As for the stick. I wonder if structural concerns may be valid, especially in a blow, since we're talking about doubling the sail are adjacent to the part of the mast which the current diamonds do not extend to. I have in my possession a masthead (as in top to bottom) diamond-stay kit for a 30 foot mast. (leftovers from an e-scow rig i bought) It would fit the 5.8 mast perfectly. Spreaders are adjustable, both in length and angle. Throw them on? necessary? not necessary?

Finally, since we're on the topic, and while i have your attention, what about adding a "blade" jib in the mix too. Namely, one that is self-tacking, and non overlapping. Will this cause "balance" problems? I've heard i can actually obtain roughly the same sq. ft. of area by extending the leech, which would be in keeping with the high-aspect theme of these potential rig changes. thoughts?

For the money you are looking to invest in your 5.8, you could also do this:

http://www.thebeachcats.com/classifieds/catamarans-for-sale/p12903-2003-hobie-tiger-f18.html

With the Tiger, you'll have a proven platform that works together, plus a spinnaker, and a class to race in (if you desire to that).

i got the 5.8 for 2600 and it's in immaculate shape. i don't think these mods will exceed 3600 dollars. Plus the lower priced f-18s have usually been beat to heck from racing...

besides the mods are their own source of fun. (gotta find SOMETHING to do during the snowy month.

i'm more interested in feasibility than practicality. We are talking about boats here.

even with all the mods you want ... you are talking about going 1-2 mph faster ....


(IMHO)
I would just sail the boat, learn how to sail the snot out of it .. then buy a newer design when ready. IF you MUST upgrade .. get a new (stock) main sail and stock jib. they will be a great boost to the cat...

I did all of the mods that you are talking about to a N6.0, oops, not the addition of the Boom. I worked with the boomlet and never had a problem flattening out the main or getting the sail shape i wanted, or close enough for my skill level.
That being said, I just threw a boom on my N5.0 to get a little more control of the foot of the sail and for easier mast rotation control.
As far as the Sq Top Main and self tacking Jib, Awesome! No helm problems but much better control of the power in the sail. A very small amount of weather helm upwind.
The problem that you will run into is when you add the Kite. The boat will have way too much power up front. I was always pushing on the stick. On a lake with fairly smooth water, not too bad. But in the ocean, with big waves that you are constantly climbing and surfing, and the apparent wind swinging for and aft, it was a lot of work! Also, the boat wanted to dive the bows unless the mast was raked waaay back.
I now have an I20(ie, more modern hull shape) and the things that I notice other than the buoyancy in the bows are, Balance under Kite, and it seems that the wide hulls allow the boat to pick up speed much faster than the 6.0. The 6.0 had a much smoother ride, and went through waves like a hot knife through butter(intermittently more whetted surface). The I20 (more modern hull shape) sits on top,(less whetted surface). The I20 will turn on a dime, losing very little energy, whereas the 6.0 had to push her rounded hulls sideways through the water, losing a lot of energy. Not a huge deal until the top of your boat tries to accelerate much faster than the bottom of your boat wants to go!
A good friend had a 5.8 with the same mods, we were always very close. In fact, he got GPS readings of over 28 mph for about 10 seconds on his 5.8 under Hooter, double trapped, (he was pushing 270lb, his crew 160lb), and then an incredibly quick and spectacular pitch pole. I think winds at the time were around 25-30mph. I know, GPS reliability. But that's what it said.
On both boats, Upwind, the mast would keep its shape pretty good. The 6.0 had double diamonds. (after I got caught in winds clocked at the ranger station 1/4 mile away at 56mph. We were triple handed and double trapped. Snapped a Single diamond wire and of course, the mast. Insurance bought me a NA mast with double diamond wire.NICE!). The double diamond handled the Kite, no problem. I could have hung the kite off the mast head with no problems.
The 5.8 mast( and also my earlier N5.7 with the same setup) on the other hand, would take a hard left turn at the Hound. Neither ever snapped, but it was uuuugly! I would estimate that I had seen the 5.8 mast bend off +5-6 feet under kite and double trapped. When they finally looked up and saw what the mast was doing, they backed off.

I guess what im getting at is, congratulations on the new boat! You will have a blast! Do all the mods you want and do them well and well thought out. Have a blast on your new 5.8. Its an awesome boat. You will come out of it with a greater understanding of what makes these boats tick, and what doesn't.
But do it with the understanding that you could more easily sell the boat and for the money you would have put into it, grab a newer F18 with three sets of sails and a faster design and a clean tramp.

Holy..

My thoughts on the jib are that all the bighead sails have a relatively small jib that just shapes the wind into the slot so you really just need to match your sail shape with your jib shape, the Taipan 5.7's went to self tackers by dropping the tack to the top of the spin pole using a stainless steel rod to give them a longer jib with roughly the same area, I'm not sure about lifting your hounds or putting your jib higher than the hounds. The F18 mast is only 20cm shorter than the 5.8 so you could try some F18 sails as a starting point and see how they feel and see if the mast holds the leach up.
Couple of other things to consider, the 5.8 mast is designed to loosten your diamonds as the wind gets higher allowing the mast to depower the rig by bending into the slot in gusts.
On a reach the 5.8 is the most fantastic boat I've been on, I've got video of me on a reach jumping over and through waves in over 20 knots on the 5.8 and it's totally controlled, I've never pitchpoled it on a reach but on downwind course's I've gone in big time. I run a F18 spin on my 5.8

-____
Yea, an abrupt turn above the hounds. Maybe pushing 30*.
Jeff, you have to see some stuff up there that looks pretty scary once in a while when you run spin, right?
I had a spin and sq top on a 5.7 also. I think it was a lighter mast section than the 5.8 & 6.0. Saw that thing bend off pretty bad also. Close to the 5.8, but I usually ran less weight on the trapeze and couldn't push as hard as Manny with his 5.8.

I mainly saw the wild mast with my old style fat spin that fluffed around as soon as I got going properly. The F18 spin behaves nicely and doesn't do such dramatic pulling to the side. My Taipan 5.7 was set up beautifully when I got it and I just pulled the spin up and went double trapped at 185kg crew weight, I haven't got to that stage yet with the 5.8

20 CM?!? Well, shoot. Sounds like my best route is buy a used F18 main and chute. That way i could save $$$$ by buying used as opposed to new/custom. the only question is will it look like hell, e.g. boom is way too high. I can't get the thing lengthened either because it's tri-radial construction right?


As for the chute, i have to add a pole and halyard anyways, i'll just place them wherever i have to in order to make the chute work.

bada bing bada boom!


The jib, i'm afraid WILL need to be custom however...

Am i on the right track here? this way i'm not spending the same money as a used F18, but still getting a major modernization of the rig..... or will this route yield a frankensteined POS?

I wouldn't plan on keeping up with a real F18. I think your underestimating the difference the hull and foil shapes make.

I may have missed it, but are you planning to race or just tear up the water by yourself?

no, i don't plan on keeping up with an f-18, i just want to get as close to them as possible, while spending as little as possible....

I am just going to be ripping it up by myself, with the occasional portsmouth event.

It won't be a POS but will be a frankenboat, if you sail your boat as is around 20kts you will feel the controllable power in it, I don't know how the boat will react to having a third more drive up high with a square top but I can guess. A Tornado main is only slightly longer so perhaps have a go with the rig of one of those