MacGregorSailors.com

How do I do the PM thingie?

Just look to the right of anyones post for the (ahem) PM button

PM = private message

The little envelope next to it is for EM= email of course....that wont show if the person has chosen not to make themselves available by email on the forum, as some choose to do.

Mike happens to accept both - click the link below, then use the JUMP to POST link on the far right to see these...

Link to a couple of Mikes posts

SkiDeep2001 wrote:Jeez J1234, TMI, made my head hurt, just go sailing, learn as you go and stay out of the nasty weather. Rob

Hello Rob,

I'm sorry. You are of course correct and I am not timid in that sense, well, outside of my usual caution, but it's a little more than that. I just got her and I have no idea whether to trust any part of a systems which is curently on board or not and I don't have anyone to scream at me to "release the sheets and pull away from the wind" like my grandfather would scream at me while he shot out of the cabin to whack me on the head.

Catigale wrote:

How do I do the PM thingie?

Just look to the right of anyones post for the (ahem) PM button
PM = private message
The little envelope next to it is for EM= email of course....that wont show if the person has chosen not to make themselves available by email on the forum, as some choose to do.
Mike happens to accept both - click the link below, then use the JUMP to POST link on the far right to see these...

Link to a couple of Mikes posts

I see said the blind man. I thank you once again.

Its' like riding a bike - crash a few times, then never look back....

J1234, I understand, also FYI, on this board you have to look at the emoticons to know that you are being ribbed razzed, laughed with or laughed at. And on rare occaision, yelled at . Welcome aboard and good luck. You can't beat the Macgregor Sailors website for help from others across a broad spectrum. Rob

I have had a Mac 36 cat for just over a year . Only sailed her once for three event filled days with this group.http://www.beercruise.info/
I customized the trailer so you can assemble the boat on it. It takes about 4 hours to put her together. I hope to get that down to around two hours. A few more mods.


The ladder is the rear mast support for trailering and also raises the mast high enough to pull it the rest of the way up with the trailer winch. No gin poll needed. I raise the mast opposite what the book says. This lets me keep all 4 back stays connected.





The one 29hp out board is a real pain when maneuvering. From a stop if you want to go straight forward or to the right, you can forget it. Also if there is any waves say 3 feet or so the motor will go under and quit.

Try these.
http://joemaletz.com/wavemagic/wavemagic.html
http://www.ne-ts.com/mac/bb/76brop7.html
http://www.youtube.com/watch?v=O5wPt3xz1K4
I bought some parts from this guy, and this boat is for sale around 250k when I seen it.
http://picasaweb.google.de/groupwareinc ... irectlink#

Hello to all,


I dont feel alone anymore.
Lots and lots of questions will be made to ahem...Steve.
Steve, thank you for your kind contributions. I am ever grateful.

SkiDeep2001 wrote:J1234, I understand, also FYI, on this board you have to look at the emoticons to know that you are being ribbed razzed, laughed with or laughed at. And on rare occaision, yelled at . Welcome aboard and good luck. You can't beat the Macgregor Sailors website for help from others across a broad spectrum. Rob

Rob, It's true. I think that there are many times when misunderstandings may take place because it is extremely difficult to get a message across by way of an internet communication. I'm not the kind of person to just blatanly offend someone or make an effort to be sarcastic in getting my point accross (if I did want to offend or be sarcastic, it would be so obvious you would definitely know it). So if it ever appears that way, just bring it to my attention and I will clarify my position and if need be apologize. Conversely, I don't mind a good laugh even when the joke is on me and don't consider myself thin skinned so I don't take offense to what may appear to be at first site offensive, unless it is crystal clear that an offensive gesture has been made. I don't believe in censoring opinion and take a strong position that we can all agree to disagree as long as we do it espectfully. I will never take offense for being yelled at if the sreaming will set me straight or keep me from killing myself, that's for sure.

Thank you for the kind welcome.

Okay, I did some more calculating and estimating based on some more dimensions received I worked on the motoring potential and requirements.

Power-plant. Actually, mine is overpowered for the dimensions and weights calculated. For motoring, I calculated 10.25 HP at a displacement of 4400#'s. This is incredible but it shouldn’t be surprising because she has long narrow hulls with little hydrodynamic drag and very light displacement. So what does this mean? It means that she requires 1 HP to move 429 pounds of weight at a hull speed of 1.9(LWL^.5) or a whopping speed of 10.9 knots or 12.9 mph. That's much faster than 1.34(LWL^.5) for the same consumption of fuel translating into faster passages and longer distances for the same weight. Double up on the motors to have a back-up in case of failure or really dig in when steaming off a lee shore or strong head current and life is good for a couple of dollars more. This appears to agree with the recommendations in the manual.

I would like to expand on this a little further to explain a bit more of my findings. I want to discuss the importance of motoring speed and motoring range and by what measures they should be designed. Do we just say lets add 500 gallons of fuel and hopefully we will get across the Atlantic at a certain speed while consuming fuel at a certain rate? If we did, where does it stop? Why not just add enough fuel to circumnavigate (fuel might need to be nuclear) and call it at that? Nope. Here is my thinking and yes, there are as many ways to calculate this as there are calculators.

Knowing your design (the 36 in my case) can lead to good decisions. So what do we use as the goal for establishing distance to be covered under power for a sailboat? A race? No, because we can empty the tanks. An ocean? No, because we are not a powerboat.

Enter the doldrums, or better known as the South Pacific Convergence Zone. This zone to us navigators is a brutal place for passage making. The closer one gets to N/S 10 degrees, the less one eats and the more water one conserves in anticipation of the doldrums. Although it varies in width, it is at its worst +/- 7 degrees N/S. A degree in that zone equals approximately 69 miles for a total of 483 nautical miles. Knowing that distance and your hull speed you can calculate range. Once you have range, you can calculate consumption and time and finally, calculate tank capacity.

In the case of the MAC 36, it would require 1.84 days (44.16hrs) motoring to get across the zone requiring 49.6 gallons of petrol and 37.25 gallons of diesel. Would I carry that much in this design? I probably wouldn't but at least I know that I'm going to need at least half that much plus another 1.5 hours worth to make an equatorial crossing tolerable since the Mac 36 can only provision so much in consumable stores and one could be becalmed for an insane and unbelievably long amount of time.

Worse case and in my thinking the best case, install dual 25 gallon tanks for those "maybe" moments and keep them empty (flotation) or with just enough fuel (1gal) to get you berthed if you want to kick an a** while you round up the buoy in a race. This addition would fare well toward attaining Offshore Category A status and it would help make things a bit more comfortable for those that like to stay on the hook for long periods of time.

More later.

Thanks

steve-nacra58-MAC36 wrote:I have had a Mac 36 cat for just over a year .

Hello Steve and ahoy to all,
Well good for you. I just got mine. I was awe struck when I first saw her there at the dock. She needs some help, but I love her. I do a lot of crying because she is all the way down in Florida and I'm all the way the hull up here in NY, but time cures everything and my time to hug her is almost here. I got her for about 65% of market so you know that some work will be required, but I want to bring her back to her old glory again so I don't care. I already got quotes on new netting, boy that's expensive, and I'm waiting for a quote for a new suit of sails and I suspect that isn't going to be cheap either. I may have to learn to sew and weave. I may consider replacing the standing rigging and cross beams, but I have little information about them and what I have I can’t in good faith trust my life with, so I'm reverse engineering the design to see if what I have is effective or if her structural integrity is compromised by owners that "downsized" her engineering for financial reasons.

So, I see that you are devout. I hope that I can pick your brain. I'm not trying to take the easy way out and intend to calculate her scantlings anyway, but I would just like to corroborate some of the information.

1. Did you design make the trailer yourself? Cost? Time to make? Would you consider making another? Was the job shopped out? I started to put together a little design of my own and I'll attach it later for everyone to peruse since I'm not home, but I like the simplicity of your design much better and it definitely appears to be much lighter. What is her empty weight?
2. How do you splash her? Crane? Roll off? How do you retrieve her? Do you deploy her already telescoped or do you open her up on the water?
3. Does she handle highway speeds well or is it advised to keep to 80% of speed limit?
4. What wire thicknesses do you have? Did you just use the largest required for all shrouds and stays? Can you share all of them if different?
5. What is the wall thickness for your fore, aft cross beams and mast compression tubes?
6. What is the x and y dimension for your mast and what is the wall thickness? What is the section?
7. What is the same x,y dimensions and wall thickness for the spreaders and dolphin striker? Section?
8. what is the same x,y dimension and wall thickness for the boom? Section?
9. What is the foil section for the rudders? What is their span and chord? Does it kick up?
10. What is the same for the dagger board? Foil section? Is it designed to shear at the hull junction?
11. What size winches do you use for main, jib, genoa, spinnaker, gennaker?
12. What size blocks, cleats, etc?
13. What diameter mainsheet and length is used and what diameter sheet for jib, genoa, spinnaker, gennaker sheets?
14. What is the size of your turnbuckles, tangs etc?

Okay. I don’t want to impose so much at one time…need to calculate some more.
Thanks, thanks.thanks.

Gotta run.

Do I get paid for all this home work. There was a Mac36 for sale in Florida for around $8000.00. I thought about buying it for spare parts. Is that the boat you bought?
1 I started with the trailer that came with the boat. The boat had to be compressed and rudders removed in the water before loading onto the trailer. To compress the boat the mast has to come down and be carried of the boat. Two semi strong people can carry the mast but it aint easy. Following the owners manual, compressing the boat is no problem if the cross beams have not been modified. Getting the rudders out requires about 7 feet of water under the boat. They do not kick up. We rigged a sail bag around a rudder so we would not drop it to the bottom. Remove the tiller handle and the rudder will slide down out of the bottom of the boat. I had to get in the water and stand on the top of the rudder to push it down far enough. After the rudder post came out of the bottom of the boat we discovered that they FLOAT!!

This trailer If you lined the sterns up with the rear of the trailer had way to much tongue weight. We had to slide the boat about 10 feet back. This made about 55 feet of total length.


I wanted to be able to totally assemble the boat on land. This limits launching to 19 feet wide boat ramps, but so far is worth it. Now I can totally assemble the boat , raise the mast and ramp launch by my self. If I have to.



This is the same trailer with the fixed bunks removed and sliding roller bunks in stalled. The brown primer painted pieces remove for trailering. There are three cross bars that hold the hulls. Each cross bar is under a bulkhead. The cradles ride on Duraslide. I can push by hand on the boat and it will slide on the cross bar. That's not to easy going from one end and pushing about 6inchs then to the other end and pushing 6inches. I have a 12 volt power winch that should make it easier.

3. Does she handle highway speeds well or is it advised to keep to 80% of speed limit?

She pulls great, but 70mph was to much for the 10inch trailer tires. We had two blow outs on the way to Florida. Slowing down to 60 got us there and back with no more blowouts.
The trailer and the boat empty, the weight on the trailer wheels is 5500lbs. Since this photo I have added a third axle to the trailer. I also am going to 15" wheels.

ENOUGH for NOW

steve-nacra58-MAC36 wrote:Do I get paid for all this home work. There was a Mac36 for sale in Florida for around $8000.00. I thought about buying it for spare parts. Is that the boat you bought? ENOUGH for NOW

Well, information is paid in kind so I will endeavour to provide as much as I possibly can and I wil always thank you for your contribution and effort. Great info and thanks. I don't know if the one that you were looking at for spare parts is the same one or not, but, I didn't pay $8000, and I don't think it's worth can be defined strictly as "spare parts" if it is the same boat. She does however require work, and that was the attraction so I can make her my own.

Hello to all,

Are we able to attach drawings or word documents or excell spreadsheets? If yes... ahem...

Okay, I did some more calculating and estimating. Maybe I should put all of this in a PDF book for future use by Mac 36 owners that are also looking for information? Also, I have my own little sketch of my idea of a custom trailer I was planning to have built, but I like Steve's better.

SA/Wetted Area: This figure is 2.6 as of right now because I haven't had the chance to calculate exact areas for the dagger board and rudders but anything above 2.5 is usually indicative of excellent performance in light wind speeds.

BN: The Bruce number is 1.52 and it is a sort of power to weight ratio much like the SA/D ratio and it means that the possibility that a vessel's speed will exceed wind speed increases with numbers above 1. Formula 40 racers are in the 1.8 range.

MAR: The mainsail aspect ratio is 4.9, which is actually high.

Capsize Velocities:
Storm Reef is 101.11 knots
Main and Jib Reef is 34.73 knots
Main and Genoa Reef is 21.71 knots

Capsize Stability Speed: It calculates to 21.51 knots and an offshore minimum is 20, with 28 to reef the main/jib combination much better, but this is not a cruiser. Except for being reefed in a storm suit of 63 square feet, velocities to capsize are low and it is imperative that the skipper understand that reefing should never be second guessed while witnessing the boat go over on her ear and instead reefing should be executed the minute that one "thinks" that the vessel feels overpowered.

Base Speed: Her base speed is 10.89 knots.

K Factor: The potential K speed is 18 knots. This is yet another method to establish the V/L ratio for the design and in this case, it turns out to be 3.08times LWL^0.5. I know it is mind boggling, but reliable disinterested sources and electronic instruments have confirmed speeds greater that 18 knots. I suspect that those speeds can be attained consistently only with the perfect environment while an experienced skipper works every lull and puff like a synchronized machine. I know that any vessel large or small will surf at the speed of the wave, but dammmmmm, 18 knots!! To put that speed in perspective, 18 knots equals 20.7 mph on the water which equals 207 mph on the road!!! It would be like having your head in a wind tunnel.

Average Speed with Jib: Her average expected speed over a 24 hour period is 10.7 knots at 15.7 knots. Here she is well over 65% of wind speed.

Average Speed with Genoa: Her average expected over a 24 hour period is 15.5 knots at 15.7 knots. Clearly it can be seen that she will exceed wind speed. With this speed and a deep board, she will turn 180 degrees through the wind with little effort despite her lightship disposition and low momentum.

TX Up: Her upwind texel is 107.

TX R.: Her reaching texel is 75.09.

P.I.: Her performance index is 1.15.

Those that know about the Texel know that nothing else needs to be said about that! Competitors will always find their way home by following the rooster tail wake that the Mac 36 leaves behind for them to follow. I think those approximations may be a bit low, but even at 110 or 112, she is a speed demon. I have a spreadsheet with over 100 design texel's for other designs. There are actually good reasons why a low texel is bad, but that's a subject for another thread.

I: Her moment of inertia is 6.16E+04

RP: Her roll period is .42 seconds making her extremely stiff.

RA: Her roll acceleration of 0.056 g's was calculated at her maximum heeling angle of more than 7 degrees when she flies a hull!
G levels above 0.06 are undesirable for offshore work.
Malaise begins at 0.1 g's, Intolerable at 0.18 g's and intolerable for any period of time is 0.4 g's.
Calculating her roll acceleration for a more reasonable heeling angle of 4 degrees produces a force of 0.032 g's which is more closely defined as imperceptible.

Okay, enjoy the read. Will put together some more later. I couldn't figure out the attachment procedure, so if anyone would like to see the trailer sketch or the texel sheet, let me know and I'll send it.

Thanks

7. What is the same x,y dimensions and wall thickness for the spreaders and dolphin striker? Section?
8. what is the same x,y dimension and wall thickness for the boom? Section?
9. What is the foil section for the rudders? What is their span and chord? Does it kick up?
10. What is the same for the dagger board? Foil section? Is it designed to shear at the hull junction?

Some of these questions make me wonder if you have seen the boat. If you haven't I can load more photos of mine.
The rudders are post mounted under the boat, the mast section is oval, my boom section is tear drop , I don't think the dagger boards are not designed to shear.

steve-nacra58-MAC36 wrote:

Some of these questions make me wonder if you have seen the boat. If you haven't I can load more photos of mine. The rudders are post mounted under the boat, the mast section is oval, my boom section is tear drop , I don't think the dagger boards are not designed to shear.

Ahoy mate,

These questions were not meant to cause you any disbelief. I did see the boat, but, I did not measure it out nor do I trust that what is on there is as "designed" after 30 years, she is a 1979. So I ask, and calculate, so that I can try to corroborate what I do have. Even if I were to take the trip to Florida again and measure out all her lines, I would ask the same questions, of more than one person if possible. Care to provide some answers?

The mast section is oval. Good because so is mine. The boom section did not look like it was tear drop. This may or may not be good or bad, but now we have 2 which are different. The rudders are not post mounted and are kick-up rudders instead. Again, this may or may not be good or bad, but again it is different. Actually, it isn't good for pure performance because they cavitate at a certain angles of attack once a specific velocity is reached and once the bubbles are introduced, the foil will stall. If you're messin about, it is only an inconvenience, if you are crossing a shipping lane and you are evading a million pound tanker doing 30 knots, well, that is your a**, because you won't even survive the bow wave a mile away even if you do avoid the impact of the freighter itself. Ever see a million pound wave traveling at 20 knots? Ever feel its evergy?

Yes! More photos! The more I can see the better.

Fair winds to all, gotta get a little rest now. I just received news that I will be a grandfather for the 5th time, so I'm not exactly sure how to handle having an uneven keel from having three hanging on one side and two on the other. Things used to be even and now...back to feeling like a monohull in the trades...

My boat when I bought it.http://www.sailingtexas.com/smacgregor36101.html
Here is an older one http://www.sailingtexas.com/smacgregor36a.html
An old threadhttp://www.sailnet.com/forums/general-d ... maran.html Some 36 owners.

Here you can see the rudders and more of the trailer.

steve-nacra58-MAC36 wrote:My boat when I bought it.http://www.sailingtexas.com/smacgregor36101.html
Here is an older one http://www.sailingtexas.com/smacgregor36a.html
An old threadhttp://www.sailnet.com/forums/general-d ... maran.html Some 36 owners.

Beautiful! Very very nice.
I'm hopeful mine will be like your's one day. Maybe better!
Can you tell me about your choice of netting and wny the combination you chose? Have you heard of dayeneema or dyneema or something like that?

Anyway, there is another difference I found among those photos. Mine has a port dagger only. Believe it or not, this was genius for its time. Not only does 2 foils intrude into both cabins, but you have the additional drag of one whole board because you only need one. Beter even would to have canted the boards in (tip inboard) at better than 25 degrees, the bunks would be clear and additional lift would be realized from the foil.

I really love my boat the more I see her sisters and I really love this place! GOD bless America and (insert your country here)and this forum and all its members and families and all our boats.

I forgot and had to edit. I also don't have the masthead float. I want one. Does anyone know a source or have dimensions and materials used?

Until tomorrow.

Mast head floathttp://www.thebeachcats.com/index.php?m ... emId=11941