O'Day 20 Mast Rake

[CHris F]

I am (finally) getting our 1976 O'Day 20 ready for launch this season here in Southern New Hampshire. I purchased a new forestay, and am wondering if there is any specific amount the mast should be raked back. Based on what I am seeing with the new forestay, and was also the case with the old one, it will not be vertical. Thanks.

 

[Sunbird22358]

I would think the mast should be near vertical when stepped, with maybe the top being about 2-3" max aft of the foot. Owners Manual is not specific, but mentions having the mast "plumb".

 

[Brian S]

Since these aren't 1 design race boats, nobody will have a mast rake measurement. What I do is get it looking ok at the dock, then go out sailing on a 10-12 knot day. I'll sail close hauled, and check for about 3-6º of weather helm. 3º is better, with that little bit of the rudder aiding lift to windward. If I've got too much weather helm, then I loosen forestay and take up on uppers. (On my boat, fractional rigged, with swept spreaders.) I once had the boat so balanced, the next weekend in higher winds I learned I had lee helm. Nope! You can make sure your mast is level side to side by bringing the main halyard down to each chainplate. Also, you should have about .5-.75" of mast pre-bend, which you can kinda sight by holding the main halyard along the mast. Lowers are used to keep the mast in column, and if over tight can pull pre-bend out of the mast. Taking out cotter pins is a PITA, especially when you're out on the water tuning and don't want to lose them overboard, so this year I've got some velcro pins like the racers use. Overkill, yes, but I've got too much racer in me to stop now.

 

[CHris F]

It occurs to me that the problem might be compression under the mast step, since the forestay is tightened as much as possible, the side stays that go half way up the mast are also as tight as possible, and the ones that go to the top of the mast are almost as tight as possible. I have seen pictures of the interiors of some O'Day 20's and they seem to have a half bulkhead in the cabin in front of the sink that might give some support to the mast, mine does not have that. Perhaps wedging a 4 x 4 vertically under the cabin roof right below th mast step might eliminate this compression? I don't want to force anything too much though...............

 

[Sunbird22358]

The 1976 O'DAY 20 must have had a beam built into the cabin top, there never was a factory bulkhead on the 1976-78 models. only the earlier 1973-75 models had that (and masthead rig). You could add some kind of compression post under the mas step, but would need to clear the head space if you have one. Maybe 2 posts with a beam between them?

 

[CHris F]

Here is what the mast step looks like on the top of the cabin. As you can see, the entire mast is supported by a relatively thin tabernacle "rod", which I replaced this year. Is there any hardware missing here? I am aware that the more recent mast steps are "beefier".

 

[Sunbird22358]

Your tabernacle is setup fine, as built. That pin is the right one as far as I can tell. If you look closely, you should see that the forward edge of the bottom of the mast is (or should be!) resting on the base of the tabernacle, this takes some of the vertical downward load (actually most of the load) off the pin and concentrates it on the bottom of the tabernacle. I have seen other examples of this same tabernacle (on a 22 I think?) that had a little ridge that interlocks with the mast butt to prevent the mast pin from sliding aft and out of the tabernacle slot.. I'll try to post a pic.

 

[CHris F]

Yes, the mast step attached to the cabin has that ridge similar to what you have pictured on which the forward edge of the mast rests. I also looked carefully at the cabin yesterday evening and don't see any indication of sagging under the mast step, and the cabin roof appears to be firm. I think I will just have the forestay shortened by an inch or two, that should straighten the mast, and allow the side stays to be a bit tighter. Of course the other possibility is that I am over=thinking this whole thing a bit.....thank you for all of your help.

 

[Will Gilmore]

The O'Day 20 looks like a masthead version of my Mariner 19, in terms of rig. I have the same tabernacle. The 19 also has a single backstay. Without rake, some Mariner owners catch the boom on the backstay when jibing. Adjust your rig on the water so you know she's level. Mariners have 3-4" of rake measured by the halyard at the gooseneck. On a windless day, take a look at how your sail is cut as it holds the boom up. Ideally, your foot should not let the boom drop at the stern. Level is best. If that is not the case, take some of the rake out. I prefer a generous amount of rake, I think it performs better, but that's just personal preference.

- Will (Dragonfly)

 

[CHris F]

I took the measurement as you suggested from the halyard to the goose neck, it is 16 inches!! I looked carefully at the mast and it is not bent, and I really don;t see evidence of the cabin roof having compressed under the mast step. I think I will need to try to remember my high-school geometry and shorten the forestay.

 

[Will Gilmore]

I took the measurement as you suggested from the halyard to the goose neck, it is 16 inches

That is a lot of rake.
Just to be sure I understand, you let the halyard hang freely while the boat's waterline was level and it measured 16" aft of the gooseneck? That's a lot of rake. Have you hoisted the sail like that and looked at the hang of the boom?

- Will (Dragonfly)

 

[CHris F]

I am going to measure again with the boat at the dock and me measuring from the dock, not standing on the boat like I did this morning when it was on a mooring ball. With the main sail up the boom is level, and clears the back stay just fine. Looking at the boat from afar, while there is definitely rake aft, it does not really look too bad. My concern is really that the turnbuckles for the forestay and side stays (two on each side, one to the top of the mast and one just below the spreader), are as tight as possible, yet there is still a bit of play in them.

 

[Will Gilmore]

My concern is really that the turnbuckles for the forestay and side stays (two on each side, one to the top of the mast and one just below the spreader), are as tight as possible

Not as tight as possible. As loose as possible and still do the job of holding your mast steady.
Set your rake by your forestay. Tighten the backstay to introduce a small amount of compression in the mast for just a little prebend.
Your lower shrouds hold you're mast steady and should be tight so it is some effort to deflect them when you pluck at them. The upper shrouds are a bit tighter still. Take her out sailing in 15 knots of wind and set her on a beam reach. If your leeward turnbuckles loosen just a little, it's ok. If they actually start to fall out off line with the cable, tighten both sides equally until they are straight again. That is just enough. No reason to over tighten. You don't want your stays too loose or a jibe will really snap hard against them. Too right and they stretch out prematurely.

-Will (Dragonfly)

 

[SUMB44]

Our o'day 20 has a bit of rake to her mast as well, not quite perpendicular. Last time we had her out we adjusted the stats (for a and aft) and it helped a bit, but she still sports a roguish rake.