Jump to content

Alan Stewart

Members
  • Content Count

    430
  • Joined

  • Last visited

  • Days Won

    45

Alan Stewart last won the day on June 7

Alan Stewart had the most liked content!

Community Reputation

102 Excellent

About Alan Stewart

  • Rank
    Advanced Member
  • Birthday January 1

Contact Methods

Profile Information

  • Gender
    Not Telling
  • Location
    North Carolina, Raleigh

Recent Profile Visitors

The recent visitors block is disabled and is not being shown to other users.

  1. I never have. Sounds like a lot of work but i havent used brightsides just 2 part poly devoe and awlgrip.
  2. I think that is a typo in the drawing, at one point we were playing with putting a block on the cb itself but decided against. There should just be the one block which is labeled.
  3. I am jealous. what a sweet boat.
  4. I also like the chair, need to get one of those in my shop. And the boat looks great too!
  5. Whatever the longest piece is is what i was going to make. I think its about 36"
  6. Hi Bob, Well i think you are very wise to consider building one in the first place! Know that you'll have plenty of support from us here on the forum. I would checkout the dutch OB 20 build thread for a step by step guide on best practices. -Alan
  7. The main problem we had with this year in the EC on Southern Skimmer was with the torque line. We were just using a twisted pair of 3/8" double braid line to transmit the torque to the top of the luff the problems come with furling in higher winds it takes a lot of torque to get the sail to start wrapping and then when the sail is half furled the torque required is much less so a lot of twists are built up in the torque line and then they are relieved inside the rolled up sail which causes a bunch of wraps in the wrong direction at the top so then when you go to unfurl it gets all fouled at the top until you can shake the twists out. Part of the problem is that the free standing mast can't generate as much tension in the torque line as a stayed rig can so the torque line is never really super taught even with the backstays full on. So if the torque line doesn't have enough tension it can more easily twist leading to the above scenario or even worse it could pigtail. I don't know what it would cost to have a piece of proper top down furling torque line made up for the boat but I think it might be worth it. They make fancy braided and wrapped torque line exactly for this.
  8. Finally got a quote back on the fiberglass epoxy bonding angle mentioned above https://photos.app.goo.gl/WRCfHXduXu3szT4Q6 It came out about $6 per foot so at this point I think were going to pass on it.
  9. Hahaha, it's something we've been thinking hard about. Steve, I agree it would be nice to have some kind of prevention line on the centerboard but on the flip side it's a rare enough event for a regular Core Sound to capsize let alone a Mark 3 Core Sound so it wasn't a top concern in the design process and Graham I think still isn't convinced it's necessary.
  10. I repeated myself a little bit but it's worth repeating since this is an area that you will not be able to ever work on again without much difficulty!
  11. Correct, not necessary for strength. If you want the lightest boat possible then don't sheath in glass just tape the seams. Every ounce counts on a small tender. It'll make it easier to carry and haul on board. That is what I personally would do. On a small boat it's easy to do little repairs to the bottom if it gets scratched or dinged. You can just flip it over, do the repair and your good to go.
  12. Looking real good Todd! A while back I looked at many cases for the 20mk3. You can see some of the results in the form of stability curves here. https://docs.google.com/spreadsheets/d/1rqaVj7Ncj45HQtIq8PMWILgZhQCXYuGpHj3qkUgu6DU/edit?usp=sharing Sealing the cockpit comings entirely would certainly add some positive buoyancy to the boat in a capsize. The stability curves we calculated assumed the coamings were flooded. Basically you would be increasing the angle of vanishing stability. The water ballast however is by far the largest determinant factor. We think the boat should always be sailed with the water ballast filled unless you are motoring in a dead calm or sailing in drifting conditions. The numbers don't lie and I am confident that the 20-mark 3 WOULD turn turtle without the water ballast in even if the cockpit comings were completely sealed. A small mast had float on the 17 mark 3 and 20 mark 3 can be added to prevent the boat going turtle in all scenarios which would be a good idea if you like to sail the boat without the ballast of if you plan to participate in say the Everglades Challenge for example. I plan to have a mast head float on my CS-20 Mark 3 because I like to sail without the ballast because it's faster! and I don't want to worry about turning turtle when I don't have the ballast in. If you always have the ballast in then no need. With the water ballast filled the boat should not be able to turtle even if the centerboard is up on the 20 mark 3. (maybe not true for the 17 mk3...see below) This is I think attributed to the taller masts which (once partially underwater) provide the missing righting moment lost from the CB which is good because it remains to be seen if the centerboard could be reached from the water if the boat capsizes to starboard (putting the offset board higher up in the air). I intend to test this extensively with my boat. We have only been able so far to test capsizing a CS-17 Mk3. Based on these few tests, the 17mk3 was easily righted by one person with the tank full and the board down and even while at the same time scooping the crew into the cockpit. The one test we did with the board UP it looked like she wanted to turtle even with the ballast tank filled. The boat tested did not have sealed cockpit coamings. There were a few extra variables in this test though such as the mizzen being flipped over and could have been scooping water as they tried to right the boat with no CB. Also this test pointed out the possible usefulness of a line tied to the trailing edge of the CB that could be pulled on from the water to re-lower the centerboard. The 17mk3 is still quite stable without the ballast with an angle of vanishing stability of around 70-80 deg or so. We tested the angle of vanishing stabilty of Grahams 17mk3 here but with no sails at the time and got 85 deg w/o ballast. And we did a similar test of the first CS-20 Mark 3 with the ballast in only here. Only because it is pertinent to the above we are also working on a new design...(spilling the beans here) we are currently calling the Core Sound 17/20 SR. (SR stands for self righting). We're pushing the limits of the water ballast in a remake of the original CS-17 and 20. The boat below has almost the same hull shape as the CS-20 mk3 but with added sheer height to gain the maximum righting moment from the cockpit coamings which are now completely sealed. The water ballast tank is a full 550lbs in the CS-20 SR and there is 4 inches of blue closed cell foam blocking between the underside of the cockpit sole and the top of the water in the ballast tank. The purpose of this is to push the center of volume of the water ballast lower in the boat thus reducing the vertical center of gravity. It has the added benefit of being able to fill the tank without topping off with buckets or pumps since the entire tank is below the waterline. It is very hard to get a shallow draft boat to self right and it's impossible to do it without sealing the cockpit coamings. That also makes the boat very stable in the inverted position. To solve that problem. One of the coamings is flooded automatically if the boat turns turtle allowing the boat to be rotated back on her side and then righted. If I had this boat, I would also have a mast head float on it for the same reasons as above. I like to sail w/o the ballast (because it's fast) and don't want to worry about turtling. The 17 and 20 SR will also have an integral outboard well in the stern of the cockpit, a longer forward cockpit seating area for camping under a dodger and we're shrinking the weighted CB down so just the top of the trunk sticks up above the sole.
  13. Ben, The angle between the sheer and the top of the bow transom is approximately 115 deg. That would be the angle of the forward quarter knee (or very close to it). The bevel angle of the stiffener on the bow transom will not be this angle because the bow transom has a lot of rake compared to the stern transom. Measuring the angle at 90 degrees to where the side and bow transom come together (shown with a disk below) is much closer to the given angle of 127 deg. I can see how that would be confusing but that is the angle you would set your bevel gauge to in order to cut a bevel on the end of the bow transom stiffener. Let me know if that make sense. -Alan
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.