Core Sound 20 mk 2, Hull #2

[Tom the rower]

Started on Sunday 3/17. Got the sides glued, part of the bottom, and the transom done. Rain here Monday and Tuesday. Fun build so far. Will cut the side stringers and inwales out of a 24 ft 2x6 yellow pine soon. Nice to not have to scarf the stringers and inwales. A CNC kit is really the way to go.

[Chick Ludwig]

Good to see #2 started! Look forward to pictures. Have fun!

[kaeptnr]

Hi together, is #2 a second prototype or the first of the final plan?

The MKII ist still not available on the website?

[Tom the rower]

I would guess that one could contact the designer for plans. Seems like a normal core sound hull with some changes. I will try to figure out the adding photos thing.

[kaeptnr]

I contact the designer regarding availability CS20MKII but I get no answer......

[Tom the rower]

He just had surgery and may not be near a computer right now.  It might be easier to call the phone number listed on the website and either ask for Carla, or leave a message about the email.  Obviously, being in Germany, you won't be able to pick up a cnc cut kit boat like I did, so you will have to get the plans only and cut yourself, or maybe, you can get the cnc cut file and have someone over there cut it for you.  I can't believe how nicely these pieces fit together.  Someone on this very site suggested that I go ahead and get a kit for this build and all I can say is "what a great suggestion"

[Tom the rower]

Things I have learned.....on a kit cut boat, when you join the sides scarfs , you pre wet the finger joints and add thickened epoxy, but you don't fiberglass tape those same seams.  That is for the folks who are just doing butt joints.  Darn, darn, darn..... Read everything twice, and then twice again....  I hope that thru the fairing process I will be able to make those taped seams less noticable.  Glad I don't know how to post pictures yet.  Functional not pretty.

[Dnjost]

two words.  fairing compound.  I'm sure it will be fine in the long run. everything can be fixed with the grinder, epoxy, and filler. 

[olp4835]

Tom,

 

What the cost of the plans and the kit? I take it that the kit is ocume?

 

Otto

[Miyot]

Wouldn't it be nice if we could learn from an experienced boat builder.  Even then we would continue to make mistakes.  Problem is we are human.  I have suffered over a problem, sometimes for days.  Making a part that doesn't fit, doing it again and it still doesn't work.  Then some grumpy old wood worker comes along and says "try this".  It was  so easy, NOW WHY DIDN'T I THINK OF THAT.  That's boat building.  FUN

[Nacrajon]

Can you please post some photos of the Core Sound 20, Mk 2. There is little available on the Internet. I am interested in the water ballast set up and if the cockpit is self bailing. I have contacted the designer but I haven't yet recieved a reply.

[Chick Ludwig]

Here is the building thread on CS-20 Mk2 - #1. http://messing-about.com/forums/topic/8080-cs20-mk2/

[Nacrajon]

Thanks Chuck, I missed that thread, do you know if an open cockpit version will be offered as well for the Mk2?

Jon

[Tom the rower]

Hello....it has been a while since I last worked on my boat.  The "unfolding" process has been more than a one person job, and life got in the way.  I just unfolded the boat, and during that process, part of the stbd side bottom came unseemed.  That is to say, all the bottom panels were put together per the plans, starboard bottom forward, attached to starboard bottom middle to starboard bottom aft, then same for port side bottom, then side panels, same.   Then, the side panels were partially attached to the bottom panes, at the nose of the boat, then the bottoms wired together, tighter at the front, but a little looser at the stern.  

 

Well during the unfolding, the bottom stbd, at the first seem between front and middle section seem of bottom panel, came apart, halfway.  I now have the plywood supports under the boat, on top of the build cart I made.  The sides and bottoms are lined up and ready to be wired and the boat is now stable, kind of ....  Now, I need to figure out how to fix the starboard bottom panel were in tore.

 

Any thoughts before I screw this thing up even more?

 

 

Thanks

 

 

Tom

[Chick Ludwig]

If I understand you correctly, the wires tore through? Try re-drilling new holes to wire the side and bottom. Maybe closer together and/or double wires in each hole. Is the wire fairly large in diameter, or "skinny". A skinny wire will rip right through. Keep working between the wires gradually twisting them together so the strain is spread between several wires, not at only one wire.

 

About the time you get all this stuff figured out, the boat will be done. You'll have to build another to see how "easy" it can be.

[Designer]

Tom,

 

I am sorry that you have had a problem. I note that you said that you left the aft wires loose. The instructions said that the entire centerline ties must be loose. Think of a spiral bound book, imagine if the binding was tight except for the bottom half and you opened it up. Some of the pages where the binding was tight would be torn.

 

All is not lost, this building method is very forgiving. As Chick said, drill some more holes midway between the torn holes and retie the affected area. By the time you get the centerline taped you will never know that this problem existed.

 

You can add extra holes wherever you need them. We are not looking for perfect wire spacing or symmetry with the ties. What we are looking for is a fair hull. In high stress areas where the panels do not want to come together, you can drill more holes and even double up on wires through the same hole. One such high stress area is the last tie at the back of the keel, I always put two wires through the same hole and if necessary I will put in another hole 1" forward to draw the seam together.

 

When the boat is all wired up, take some time to inspect the boat all over. She might need some massaging here and there to make her just right. Do not be in a hurry to glue, once glued you will own any flaws in your wiring. We are looking for a fair hull. look at her critically from every angle that your shop will allow and fine tune her.

 

Good luck.

[Tom the rower]

Actually, this is not a case of torn holes.  As a CNC cut kit, the bottom pieces have cool puzzle joints to join the front bottom to the middle bottom to the aft bottom, done with thickened epoxy and no fiberglass tape (actually, those same pieces on the sides were joined using thickened epoxy and fiberglass tape, the way you would do if you did not have a cnc kit boat, and had actually scarfed your plywood, but I didn't read the directions enough and did the tape in addition to the thickened epoxy)

 

Again, those bottom pieces were done without the benefit of tape.  So, it appears that the finger joint actually tore.  Center line of the two bottoms is fine where the wire ties are. It is the starboard bottom between the front stbd bottom and middle stbd bottom.  It only tore halfway, from center keel line (where the two bottoms are wired together) halfway up that bottom join.  So that means where the stbd bottom and stbd side meet is fine, because that part of the bottom join is still together.

[Mike Vacanti]

Did you glue the center seam before the entire boat was wired together?

[Tom the rower]

No....I pretty much did the standard thing.  Got the port side bottoms all joined together at the finger joints, till the port bottom was 20 ft long, same for starboard bottom, then same for port and starboard sides, making each 20 ft long and did them at the same time so that the bottom 20 footers were identical and the sides 20 footers were identical.

 

 

Then, I cut four 14 inch strips of fiberglass tape and joined on each side the bottom to a side and let that cure.  When that was done, I added square blocks to each side of the bottom/side fiberglass join to make sure that when I unfolded the boat that it wouldn't stress that 14 inch fiberglass join of bottom and side.  Then , I turned over each bottom side join and added the seat stringer to the inside side of 20 side piece.

 

Only then  did I put everything back on top of each other, making sure that the 2 bottoms, port and starboard exactly lined up (same for the now partially joined sides---(20 ft sides joined to each half of bottom by a 14 inch strip of fiberglass at the nose of the boat).  Then I wired to bottom together from stem to stern and unfolded.

 

Upon unfolding, I saw that part of the finger joint located at starboard bottom between the front section of bottom and middle section of bottom had torn halfway.

 

I would actually drill holes in this tear,and try to wire, or I could unwire the bottom join and lay the stbd bottom 20 ft section that still has the stbd 20 ft side piece still attached at the nose by a 14 inch strip of fiberglass tape flat on the ground and try to go over the torn area with a larger piece of fiberglass , both sides.  Seems like alot to do, especially now that the bottom and side are joined at the nose by that 14 inch strip of tape, now well cured.  It is a big floppy messy thing to move about.

[Designer]

Tom,

 

There have been close to 500 Core Sounds of all sizes folded without major issues.  We have to figure out what went wrong. Did I interpret correctly that the scarf in the bottom failed?

 

When a glue joint fails, I try to figure out why. Did the glue pull wood fibers with it on all of the surface that failed? Was the joint glue starved? Did the glue cure properly? Did the joint debond? Did the ply tear near the scarf?

 

I folded Chicks boat with him and it went pretty slick. You may have to separate the two halves and rejoin the failed scarfs and glass tape both sides of the failed joint to get back to full strength and fold her up again.