Thread: Oklahoma OZ PDR

Originally Posted by BradLH

Hello All,

I'm new to the forum and starting the OZ PDR in Oklahoma USA. My plan is to periodically post progress reports on the forum and I'll probably have a few questions as I go along.

Brad

Welcome! Feel free to ask lots of questions. I know I've made lots of dumb mistakes that many people can learn from. Good luck with your build!

Welcome Brad!

MIK

Thanks for the welcomes.

Progress report:
I lack framing one bulkhead and one bow transom to be ready to go 3D with the two boats.

Observations:
If I were doing it over I would use the stitch and glue method. I don't want to fill any more screw holes than absolutely necessary so I'm using clamps to glue the frames. I only have about thirty clamps so I've spent a lot of time waiting on epoxy to dry.

The only clear relatively straight grain wood I could find for the masts was yellow pine in 8' lengths. I sawed and milled all the staves then weighed them, they were heavy. That along with the thought of all the scarf joints I would have to make to stagger the splices, and the labor to put the thing together gave me reason to look at other options.

I would have liked to have 2.5" OD x 0.065 wall 6061 T6 aluminum at 14' length, which would have made a 9 pound mast, but to get it to me would cost a small fortune with the crating and shipping. I've decided to go with 2.5" OD x 0.125" wall and 2.25" OD x 0.125" fiberglass tube to make a tapered mast. It will weigh about 11 pounds and I'm satisfied with that since there will be very little labor involved in getting it together compared to the wood mast.

Thoughts and questions:
I'm building my boat with a different bow angle than what the plans call for and the mast location measurements in the plans are from the bow aft. I'm going to need to draw the original plan out on cardboard and get a measurement from the bulkhead forward. I'm wondering how sensitive the OZ MKII with the balanced lug rig is to COE position. I've thought about making an elongated slot at the mast partner so I can use chocks to change mast rake but I'm also wondering if the sail can be moved fore and aft in relation to the mast.

I've looked at photos of Mik doing his speed runs. The boat is healed quite a bit and the bow is up. On the boat I race heel causes weather helm and with the bow up and mast raked back I would think the COE would move far enough back to cause weather helm but it looks like the tiller is centered in the photos. Is it possible that the board and rudder being close together lessens the effect of weather helm?

Well that's probably enough for now. I'll post some photos soon.

Thanks,
Brad

Not a very good photo but here's one boat with transoms and bulkhead glued & screwed with sides for second boat in the background. It has taken two weeks to get to this point.

Originally Posted by BradLH

Not a very good photo but here's one boat with transoms and bulkhead glued & screwed with sides for second boat in the background. It has taken two weeks to get to this point.

She looks really great!

Originally Posted by robhosailor

She looks really great!

Thanks.

I screwed the bottoms on both boats and took a photo for the registration process. I'll need to take them back off to get the mast steps in. I'm also going to mark the center case and frames so I can cut a slot for the center board while the bottom is off.

I received the fiberglass tubing I had mentioned earlier and it isn't going to work. The salesman led me to believe the tubing would be much stiffer than it is. It may work for a sprit sail but not for the balanced lug so I'm looking for aluminum again.

Here's the latest photo of the boats.

Originally Posted by BradLH

I received the fiberglass tubing I had mentioned earlier and it isn't going to work. The salesman led me to believe the tubing would be much stiffer than it is. It may work for a sprit sail but not for the balanced lug so I'm looking for aluminum again.

You could apply some unidirectional carbon to the tubing. It will stiffen up considerably.

Originally Posted by BradLH

Thanks for the welcomes.

Thoughts and questions:
I'm building my boat with a different bow angle than what the plans call for and the mast location measurements in the plans are from the bow aft. I'm going to need to draw the original plan out on cardboard and get a measurement from the bulkhead forward. I'm wondering how sensitive the OZ MKII with the balanced lug rig is to COE position. I've thought about making an elongated slot at the mast partner so I can use chocks to change mast rake but I'm also wondering if the sail can be moved fore and aft in relation to the mast.

I've looked at photos of Mik doing his speed runs. The boat is healed quite a bit and the bow is up. On the boat I race heel causes weather helm and with the bow up and mast raked back I would think the COE would move far enough back to cause weather helm but it looks like the tiller is centered in the photos. Is it possible that the board and rudder being close together lessens the effect of weather helm?

Well that's probably enough for now. I'll post some photos soon.

Thanks,
Brad

IMHO Brad build your mast partner and support as per plan the good thing about a lug is it is possible to move the COE a bit just by the halyard and downhaul position.

As for weather helm it will be negligible, I have found with the full sail up in a breeze that requires hiking it is fairly neutral then as you pay off a fraction it begins to plane so your more worried about other things than weather helm. It can be a bit disconcerting when the breeze is puffy as the hull rocks forward on the initial gust a bit like a rocking horse.

Come to think of it if anything in light to moderate breeze mine has a touch of lee helm, again it depends on how the yard and boom are set up in relation to the mast.

Hope that helps

Cheers
Mike

Woodeneye,

I could make the fiberglass tubes work but I'm not really satisfied with the overall quality. They appear to have been sprayed over a mandrel with a chopper gun.

I could just get a carbon tube mast, then I could rig up trap wires, but that would probably lead to a carbon bow sprit and asym spinnaker and I would have to design a launch/retrieve system or furler. The beginning of a never ending deal LOL.

I did look at prices for carbon tube and the cost for a mast would be about $500 US. Sounds like a lot of money but I figure a person could build two first class PDR's with carbon masts, dacron racing sails, nice Harken ball bearing blocks, and top quality lines for much less than one new Laser, so if I worked at it I could find a way to rationalize the expense

M2c1Iw,

Never having sailed anything with a balanced lug rig or anything shorter than a Sunfish I know there is going to be a steep learning curve in the beginning. Getting used to the pitching moment is of some concern, I'm sure there is a lot of fore and aft weight shifting going on in heavy weather.

My concern with weather helm is most likely unjustified as I'm sure the helm on the PDR is going to be lighter than what I'm used to.

We get some wind here, this is a link to our weather forecast later this week,
Hourly Weather Forecast for 35.48N 97.54W

The help is much appreciated,
Brad

Brad, Brad, Brad you have lost sight of the guiding principle of Puddle Ducking.............low cost. Please refer to rules OK they are the OZ subset but still applicable.

Repeat after me "I do not need Harken nor anything dacron or carbon"

You may be right, the carbon mast is probably a bit much but I've always wanted one. Too late on the Harken blocks, I've already ordered them. The Harken small boat blocks aren't cheap but I don't consider them expensive. I'm going to use polysails but I would like to try a nice dacron sail when the GIS guys get the spar, sail, and control combination figured out.

My goals are to build an inexpensive boat, not a cheap boat and build a fast boat, not build a boat fast. That does seem to conflict with some PD folks idea of what PDing is all about. .

I doubt I'll ever ship my PDR halfway around the world to race so the OZ rules won't apply. The rules here in the US are changing so I don't know what we'll end up with.

Brad

Hoop pine and polytarp... hmmm

Originally Posted by BradLH

My goals are to build an inexpensive boat, not a cheap boat and build a fast boat, not build a boat fast. That does seem to conflict with some PD folks idea of what PDing is all about. .

Not at all, my thoughts exactly. Perhaps I should have added a in my last post.

Have fun

Cheers
Mike

Originally Posted by BradLH

Thanks for the welcomes.

Thoughts and questions:
I'm building my boat with a different bow angle than what the plans call for and the mast location measurements in the plans are from the bow aft. I'm going to need to draw the original plan out on cardboard and get a measurement from the bulkhead forward. I'm wondering how sensitive the OZ MKII with the balanced lug rig is to COE position. I've thought about making an elongated slot at the mast partner so I can use chocks to change mast rake but I'm also wondering if the sail can be moved fore and aft in relation to the mast.

Not very sensitive. I would still try to get it right and the lug rig does allow you to move the sail relative to the mast a bit.

I've looked at photos of Mik doing his speed runs. The boat is healed quite a bit and the bow is up. On the boat I race heel causes weather helm and with the bow up and mast raked back I would think the COE would move far enough back to cause weather helm but it looks like the tiller is centered in the photos. Is it possible that the board and rudder being close together lessens the effect of weather helm?

The thing that gives you weather helm or lee helm in a breeze downwind (eg speed run) is heeling - at least in a conventionally shaped racing boat but particularly ones with a wide transom and fine bow (the trend in most racing boats in the last 40 years - except for particular ones like the Moths (before the foils) and 18ft skiffs in the last 20 - they have departed completely from that old way of thinking, so are much more stable downwind in terms of heeling - they can do it without wandering around too much.

Whichever way a lightish hull with a wide stern and narrow bow is heeling towards it will want to head in the other. The more it heels, the more it wants to. The leeward side of the boat creates a big triangle shape to leeward and that overpowers the rudder which is halfway out of the water by that point.

But sailing canoes and other boats with more balanced fore and aft volume don't get this affect so badly. My Beth has a tiny rudder - less than a foot deep and about 6 inches wide (300mm x 150mm). It can let go if the mizzen is oversheeted. However the boat will keep going straight despite the stalled rudder - this is total round up lie down death in a regularly shaped dinghy.

The PDR also has close to an equal volume distribution fore and aft. I was about to say "when the rudder loses its grip ..." but it never has. Because the rudder is deep enough, wide enough and very nicely shaped.

Same with the Goat - you can lie it over a long way because of the high topsides and still steer because of the balanced volume distribution of the hull and the nice rudder.

In the World titles in the USA last year I had a borrowed boat #23. Paul Helbert had made a slightly smaller than Oz lugsail for it and had been for several sails taking photos and reporting how it went. By the time I got the boat at the worlds the rig was very well sorted indeed.

In the last race we had a bit more wind coming through - maybe about 13 to 15 knots. The big downfall of #23 was the foils - they were very badly shaped - little more than rounded edge ply and the rudder was quite a bit smaller than the OZ.

Coming down to the gybe mark I couldn't turn the boat at all against the pressure of the sail - turning to port with the sail also to port. I had to get to the mark then force the sail over even though the angle was not right for a gybe and then the sail would bring the boat around the mark.

Compared to that - never a whisper of a heavy helm or a stalled rudder from any of the OZes so far.

Good rudder size and design and balanced fore and aft volume. And the skipper weight is so effective in the fat little boat that there is no reason to be heeling much.

The most problematic bit of steering you will find is when you are sitting too far forward going downwind and the bottom edge of the bow transom digs in. The bow drops (no water over the top though) about half the rudder blade comes out of the water, but I was able to steer just fine with 25 knots of breeze from behind. It FEELS precarious but you can still send the boat in any direction you want.

Moving back a foot means the bow suddenly pops out of the water and the boat accelerates and the stern squats suddenly and the bow is a mile high and you are way out of trouble.

Hope this paints a happy picture.

MIK