i550class.org

Hey Everyone,

What have you used for mast through blocks for jib and spinnaker halyards? Any info on halyard selection is beneficial too. This is my next stumbling block that I'm having trouble getting passed. 'Thanks' in advance!

Jib halyard can be a simple through-deck block such as:
http://www.apsltd.com/wire-bullet-thru-deck.html


Spin block depends on your masthead configuration- could be a sheave between two plates, could be another exit block like above, could be an external bullet block on a shackle to a crane-type masthead, with a halyard entry hole ~18" below.

For a jib halyard, some kind of 1/4" line with some spectra in it (core, or blend) is ideal. For the spin: a knobby, textured, stiff (non-hockling and low-stretch) polyester single braid in 3/16-1/4" size range is cheap and works well.

Hi Chad,

The photo shows may masthead. It's a complicated story but I don't think I should attach my spin halyard to this head. Basically the main halyard sheaves may interfere with the spin halyard. So, I think I need to go with a through block. Do you think the Harken 302 is a good choice, 11mm x 39mm cutout, 1000 lb working load / 2000 lb breaking, max line size is 4 mm?

Also, the distance between the forestay connection the max hoist of the jib is 8.5 inches. How close to the forestay connection do I put the jib halyard block? My forestay connection is a size 4 tee-ball fitting with backing plate. this fitting will be pretty loaded in a breeze. The mast is a Dwyer DM-5 section. I gave up on the M-20 carbon mast, it's too stout. Anybody want to buy it?

Thanks again!

The 302 is a very high load block, and 4mm is just too small for a kite halyard.

I'd do something like this:

...and cut a line entrance slot in the forward face of the mast, about 18" below the block.

If you want to use a through block, the same model as the jib would work just fine.

As for distance below the forestay, anything from a couple inches to as much as 8-9 inches is fine. The higher you go, the more parallel your halyard is to the stay, and the less it will "sheet" the stiff part at the top of the sail. I don't think you need to worry about getting too close from a structure point of view- just getting the fittings far enough apart so their fasteners don't interfere should be plenty of cutout separation.

Hey! Hey!, I like the additional option. I'll brainstorm on that. Thanks for the help. This is the first rig I've assembled. -Tim

I used a Dwyer DM4 for my mast. The 5 is pretty much the same but heavier. I used the Dwyer masthead (https://www.dwyermast.com/itemdetails.asp?itemID=424 for the DM5). This masthead is plenty strong enough for this application, but unfortunately comes with a solid base plate which covers the top of the mast. I drilled a couple of holes in the base-plate and made a slot that allowed the main and spin halyard to reach the sheaves. I used a block much like the one that Chad showed for the jib halyard.

Phil

yes FWIW, I to used that h288 block as my jib exit...can't help you with the kite set up as I have the C-tech carbo rig.

Hey Folks,

Thanks for the ideas and assistance. I'll make more progress on this soon, parts are ordered.

Phil, The DM-5 masthead from Dwyer is of a simular design you descrbed but, the sheave is too small to allow the forward side of the main halyard to miss the transverse stiffener inside the mast. That stiffener would cause great chafing of the halyard.

Tim, I too selected the h288 block for the jib.

hmmm... I just put a pair of calipers on both a DM4 and DM5 section (I use a DM5 for my boom). There is only 1/8th of an inch difference between the location of the front of the transverse stiffeners on the two sections. I have not noticed even the tiniest bit of chafing on my main halyard. I did file that edge and of course the two mastheads could be slightly different. I think that you will get far more potential for chafing where the halyard leaves the mast base, even with an exit plate. In any case, there are many solutions to any problem in building an i550.

Phil

Hey Phil, It just looked too close for my comfort. I'm on to plan 'C' now. I think it's rigid enough to last awhile. My delivery hasn't arrived yet so install of jib halyard is delayed.

I’m desperate for a bigger shop, yet thankful the window in my side door broke last fall. I drilled a 5” hole in my makeshift plywood window. Eureka! A bigger garage! Checkout photos, first the inside then the outside.

Hey Folks,
What are your thought about whether the Harken vang kit #447 is stout enough for the i550? It's rated at 450 pounds. I haven’t looked into vang loads yet, thought I’d ask the authorities.

That's a nice looking masthead. How did you fabricate it?

I just made my own vang (8 to 1) out of parts that are about the same weight as the one used on that Harken kit. I route the tail to one of my spinlock clutches. It seems to work fine.

Phil

Phil,
Had I been smart I would have welded two aluminum plates on either side of the slot I cut into the mast and went on from there. I don’t have access to a welder for AL. Transportation and handling of the mast is still a problem for me. So I went to work with ¼” G-10 plate that I had on hand. I think it turned out kind a stout and heavy. If I do it again I’d use 3/16” thk mat’l. The masthead plate is long enough to accommodate a two-to-one main halyard to reduce loads on the deck hardware cleat.

I started by selecting the sheave to determine the width of the internal slot. Once, the width of the slot is known I cut, with a router, two recessed grooves into the bottom of the masthead plate. The distance between the grooves is the same as the width of the sheave. The groove width was ¼” to accommodate the side plates. The recessed grooves substantially increase the strength of the joint between the masthead plate and two side plates. It’s important to route the grooves in the top plate when it’s still rectangular, before shaping it to match the teardrop profile of the mast. When routing the groove in the plate I cut it long enough to fabricate the bottom plate to. Epoxy the two side plates to the top and bottom plates to form the box like structure. Use caution to assure is stays square.

Once the epoxy is cure it’s a matter of cleaning the assembly up by sanding and then laying out pin placement for the sheaves and slot to cut in the mast. It works out that the sheave’s pins placement lines up with where the mast intersects the side plates. Therefore, I need to fabricate two pins the width of the inside of the mast.

Blah, blah, blah … I’ll post some more pictures tonight to help explain.

Is that sheave for the spin at the forward edge of the masthead then? From the pics, it looks like plenty of room for a sheave each for the main and spin. Maybe I'm not understanding the earlier comment?

Chad,

Correct, I changed directions a little bit. The forward sheave is for the spin and the aft is for the main.

Aah, got it. Round those cheeks a little in front of the sheave so the halyard doesn't chafe too much when pulled sideways on a reach -G10 is pretty abrasive.
The part looks nice, good job.

Chad,

Your right again on champhering the cheeks. I was waiting for my jib through block to arrive so I can match that, good catch.

Tim, I love the door solution! Your wife must be a saint, though...mine would shoot me if I McGyvered that!

With regard to the vang, might want to consider this: run the control line aft to where someone can blow the thing whilst running off in a big breeze. Here are some shots of mine, including one that was taken while trying out where to belay the tie-off and drill holes for the lead. This wasn't a lot of fun to install (I wouldn't do it on a 95 degree summer day) but if you can stand a bit of claustrophobia, then it's not too bad.

TF,

Oh Boy! Good point, one wants to be able to reach it. I see it's not as easy as slapping $200 Harken vang kit on the boat. Thanks for the info/photos. I'll brainstorm on your vang arrangement for a while. Thanks again!

OK, I haven't figured out a vang idea yet. My pressing decision is which side of the mast should each halyard exit from? I know there are advantages for either side but I can't recall them. Please pass along your thoughts.

The thinking for a standard port-rounding, bear-away set at the windward mark is to have the person on the starboard side of the boat, so spin hal should exit on the starboard side, where you want the weight, up to the mark and thru the spin set.

We've been leaving the jib up downwind, but for the same reason we wanted the jib halyard on the same side as the spin halyard (as it on the J24, most other boats, etc)

Main you set, cleat and leave so it's less important to have to fuss with, leave it on the port side and forgeddaboutit.

Is this what you were thinking?

Exactly the info I needed. Thank you!