Here I go again.....

Topics primarily or specifically about the DS1. Many topics are of general interest, so please use forum sections on Rigging, Sails, etc. where appropriate.

Moderator: GreenLake

Postby GreenLake » Mon Feb 20, 2012 11:14 pm

I think the forum software doesn't like any image links that aren't to the actual image (ending in .jpg or .png). I've edited yours so that they use "URL" command so one can klick on them.
~ green ~ lake ~ ~
GreenLake
 
Posts: 7137
Joined: Mon Jun 18, 2007 3:54 am

Postby GreenLake » Mon Feb 20, 2012 11:42 pm

On epoxy.

SystemThree sells T-88 (a structural epoxy adhesive) which has the following properties:
Pot life of the mixed
adhesive is approximately 45 minutes at 70°F. However, a
coated joint may still be pulled up tight for two hours. Cap containers
promptly after use. Mixing in small lots or with large
surface area exposure will extend pot life.

The interesting thing is that they sell this in a cartridge that goes into a regular caulking gun. The cartridge has a self-mixing tip which means that only as much epoxy is mixed as you squeeze out. As long as you keep squeezing more of it out at regular intervals, you will experience no "pot life" limitation.

I have also found that using the cartridge gives a much better way of getting the glue to where you need it, so application is less messy. By not having an actual "pot" the epoxy doesn't sit around in a large volume, so the heat that it releases after mixing doesn't get trapped (see the remark about "small lots").

I read these specifications as follows: If you were to prepare your joint with narrow spacers, had holes drilled for copper wires and the wires ready to cinch down, then you could put a nice bead between two spacers, remove the spacer and give the wire a twist. In 45min you should easily make the circuit of the hull. Then you have another two hours to twist things down / clamp to final tightness.

If you do want to mix up your own, you'd pick something with a "slow hardener" and that should help you with your working time as well.

(I use the SystemThree stuff myself, and I have used T-88 in the past. I've not used it with a cartridge yet, but I've used GelMagic from a cartridge and that works well - from the literature, you can get that with a working time of 120min at 77F if you can get the slow hardener. Other makers, like WestSystem sell similar stuff, e.g. 6-10 in the cartridge, but I have no personal experience)

Usually, the stated times, like curing times, change by a factor of 2 for every 10°C or 18F.

So, I don't think you need to necessarily rule this out as possible alternative - and if you have a helper or two you should be able to stay inside any reasonable time window.
~ green ~ lake ~ ~
GreenLake
 
Posts: 7137
Joined: Mon Jun 18, 2007 3:54 am

Postby JACK FLASH » Tue Feb 21, 2012 8:49 pm

That is an interesting product. I will definately look into that some more. I know from experience the West system, even with the slow hardner will kick before the deck is mated. The plan is to have every thing ready to go including a few helpers. I was going to make the trip around the boat, calk gun in hand with what ever I end up using. I was then going to lay the deck on the hull. I will use a multitude of mini c clamps only for the purpose of keeping the deck and hull aligned. With the deck off the sides of the hull tend to want to fall out about a half inch or so. The weight of the deck will probably be more than sufficient to for the curing process. Once cured I will then go back and make the second mechanical attachment with wires, screws, or what ever. The reason for the delay is that I will want this secondary fastner to be tight. Tightening during the cure may squeeze out too much epoxy and cause a poor bond.

On the picture note my wife says I am an idiot and that she can make the pictures post. We will do that once the deck is off as I may be the first to do this to a daysailer and I am sure other will be curious to see how smart/stupid/crazy I am.
JACK FLASH
 
Posts: 33
Joined: Mon Jan 30, 2012 3:11 pm

Postby GreenLake » Wed Feb 22, 2012 2:19 am

Because of what you write about the deck and hull not mating up naturally, I was suggesting that you dry-fit these. This is how I would imagine the procedure in detail:
  1. Lay the deck on the hull
  2. Align one spot
  3. Drill a hole through the joint at that spot
  4. Insert a bit of wire(copper)
  5. Twist the two ends together
  6. But leave a spacer to maintain a small gap
  7. Do same every six inches or so until hull and deck are joined everywhere, but kept apart just a bit by spacers
  8. Then go around apply your joint compound (or epoxy) in the gap
  9. Pull spacers and tighten wires (as you go along)
  10. Give a final pass of tightening and perhaps clamping as needed
  11. let cure
  12. Remove clamps and snip wires (file flush if needed)

The way I imagine this, the advantage of using the wires and spacers would be to allow complete "dry fitting" of the joint, while preserving a small gap to get your caulk-gun in. You wouldn't be trying to wrestle the joint into position with epoxy or caulk applied, instead, you'd fill one gap, pull the spacer, fill where it sat, and have your helper give the wire some twist while you move to the next part.

That should make step #8 nearly as fast as laying on a bead on one side, but you'd actually mate the deck pretty much immediately (well within pot life). This allows you time for additional tightening/clamping in step #10, which for T-88, for example, the literature says you may do for a much longer time than basic pot-life.

One more note: if your chill the epoxy in a water bath to about 65F or 70F (not lower, or it won't squeeze out the gun) then this will extend your pot-life as well.

(Laminating epoxy, which is mixed in batches, I imagine could be chilled to the lowest range of the curing temperature given in the specs, because it will heat up as the batch is mixed - and it helps to work in the morning when air and boat are as cool as you'll get them in a warm climate. There's really no reason for stuff to go off in minutes).

Final note: by dry fitting, if you discover at step #7 that you need to brace the hull to bring in the sides for better mating, you'd have all the time in the world to do that.
~ green ~ lake ~ ~
GreenLake
 
Posts: 7137
Joined: Mon Jun 18, 2007 3:54 am

Who knew these things came in convertible models

Postby JACK FLASH » Wed Feb 22, 2012 10:27 pm

Well the deck is now in the garage. Here are a couple of pics of the hull with out the deck. If any of you crazy people want pictures of a detailed area let me know and I will snap one.
My wife showed me how to resize and upload photos to the site so hopefully these two will appear here. Really not that hard actually, just needed someone to show me the way.

1220
1219
JACK FLASH
 
Posts: 33
Joined: Mon Jan 30, 2012 3:11 pm

Postby GreenLake » Thu Feb 23, 2012 2:03 am

Nice pictures. Good to have expert advice at home.

Question: how wide is the "lip" that froms the hull part of the hull-deck joint. Is it a full 1", or less? I'm just curious and can't see that on my boat, for obvious reasons.

Also, I notice that your hull already has stringers. I missed that before. What shape are they in? They may have balsa cores.

For stringers like that, the strength comes from having a second layer of glass, separated by the core, the balsa only provides the separation, not bending stiffness.

If moisture did get in, the balsa would, of course, rot, losing compression strength. In a northern climate, you could even get frost damage, but I assume that's not a concern where you are.

If you don't have moisture problems, then perhaps you can save yourself the trouble of entirely new stringers. I might throw in this suggestion: drill a few holes to check the condition. If good everywhere, add a layer of glass, biaxial perhaps, along the entire length of the stringer, going, say 1-2" out to the side. (Use epoxy for better water seal). That should add a little to the stiffness and do a lot to prevent future cracks and rot.

If you have localized problems, you might fix those by removing bad balsa and replacing it by same, or foam. Continue as per above.

If you have waterlogged, rotted stringers for the entire length, then I'd imagine you'd want to cut the top off, pull the wood and replace with a foam strip of same profile. Then laminate over that, but you'd need more than one layer of glass. K.C., can probably suggest a layup schedule, but he might try to talk you into foam coring the whole hull :wink:

Seriously, I'm not sure I would go with that PVC tube idea that you had mentioned. I had thought you had a DS1 like mine, which does not have any stringers. My hull was/is not as soft as K.C. described his, when he started with his "core" project. I don't know whether hulls with stringers had thinner laminate, or whether it's simply a matter how hard hist boat was sailed (waves) or whether it was pounded on a trailer.

My thinking would be this: If you make a narrow, tall stringer, you create more of a "hard" line on the hull, and a tall stringer gets in the way underfoot. The PVC as such won't really add a lot of stiffness, it's job, as with the foam, is to provide compression support to keep the top layer of glass separated from the bottom (think "I" beam). The stiffness comes essentially from the top layer of glass and the separation from the bottom layer (hull). For a fully cored hull, the effect is less of a beam than of a "plate" and that changes some details, but probably not enough to matter. Whatever, the material in the middle does not direclty contribute to the stiffness.

If you need to replace your stringers but you want to make your boat stiffer than it is now, I would tend to suggest a slightly wider stringer (the widest stringer would be a full hull core, but I'm not going there).

If your stringers are fine, you could add some foam strips left/right and then glass over the whole to get wider stringers. Would be less work than having to remove the old ones. (Use epoxy for superior bonding and waterresitance, but you must paint it).

Anyway, enough about stringers.
~ green ~ lake ~ ~
GreenLake
 
Posts: 7137
Joined: Mon Jun 18, 2007 3:54 am

Postby JACK FLASH » Thu Feb 23, 2012 12:59 pm

The lip on the deck portion is roughly 3/4 of an inch. On the hull section is maybe slightly less than this except in the curved portion just in front of the seats to about 1 foot from the bow. Here the lip on the hull section is only about 1/2 inch.
The stringers on the cockpit floor are rectangular and I have no intention to replace/remove these. Where I was talking about adding stringers was more on the side of the hull between the cockpit seats and the forward bulkhead. I have heard people say the hulls can oil can up in this area. My last Daysailer was a II so some of the Daysailer specific stuff is uncharted territory for me.
Your analysis of stringers and how they work is correct. The core is not what gives it the strength. In the automotive world they put bends kind of like a channel in flat sheet metal to make the panel stiffer. The reason I would use the half pipe is because it is easy to mold to the hull curve, its cheap, and its long enough to go the distance. One thing to correct you on regarding stringers is the need to have a core at all. Sometimes in production they use card board, even poster board to form a shape for the glass to contour to. I can assure you this core doesn't last long in a marine enviroment. Having said that, the shape of the stringer is very important. For example on rectangular stringers currently on the cockpit sole of my daysailer, they need the core to maintain the seperation between panel and stringer. If the string profile was oval or triangular it would not need the core, only something to make the profile during the layup. Short version, an effective stringer cannot be flat and parallel to the panel it is giving strength too with out a core to maintain seperation.
The next structural area of concern is with the deck it self. There are some early rot signs in the wood behind the coamings. Also the glass used to attach said wood is thin and only bonded to the two sides of the wood and to the underside of the deck. It almsot appears the wood was put there solely for the purpose of screwing the brightwork to the cock pit sides and not for structural reasons. This will probably be an overkill step I intend to remove the wood and replace with a foam or pvc core. This should give the boat some additional longitudnal stiffness. The bright work fasteners can be changed from wood screws to machine screws with fenderwasher on the hidden back side. This is also an oportunistic time to devise how my traveler and spin lines will run underneath the deck so a little for thought will be going into it before I start cutting. The weekend I hope to at least get all of the paint off of the underside of the deck and the interior of the hull. I will be thinking about the before mentioned under deck lines while doing this. Believe me, you have a lot of time to think while running a sander.
One last note about KC's project. I had read his post with utmost interest before I had even bought this boat. Its a big project and would probably have been easier if he had removed his deck. My only concern would be the added weight. My plan is to make the boat as light as I can get it. Any shortage in weight to meet the class rules can be made up with corrector weights, which when placed in accordance with the rules are low and centered in the boat which would be better than if it were up high say in the coamings in the form of wood or in the foam under the seats. I haven't cut the holes yet for the seat foam removal. So that is still on the list of to-do's.
Speaking of seats I was thinking about cutting the big hole in the front and leaving it open for the foam removal and then cutting small drain holes along the bottom of the seat where it meets the floor effectively making the seat tanks self draining. I was planning on using bouyancy bags (not soda bottles as suggested in other threads) for posotive flotation which would not be dependant on the seat tanks being sealed to function. I am not sure why everyone is using soda bottles. Bouyancy bags cost a lot less than the amount of 2 liter sodas to do the same thing, weighs less, and is certainly alot healthier than drinking all of that soda.
JACK FLASH
 
Posts: 33
Joined: Mon Jan 30, 2012 3:11 pm

Uh oh, more fun to be had

Postby JACK FLASH » Mon Feb 27, 2012 1:14 am

So I took the pressure washer to the hull this weekend. While picking up the transom of the boat off of the trailer I noticed the floor has quite a bit of movement. Laying under the boat I can see the bottom has some deformation. So even though there are stringers I have to assume at this point they are toast. I will be replaceing them with my half pipe pvc pipe method glassed in with epoxy and biaxle cloth.
I have decided with the decided on Red Cedar for the core behind the cockpit coamings. My reasons for the Red Cedar are rot resistance, lightweight, readily available at the local hardware store. The down side to the cedar in this application is that it does not tend to hold fasteners well so I will be running the fasteners all the way through. The core will be compromised of two layers of the cedar epoxied together with a layer of biaxle tape between them. Once cured in the curved shape I will encase with biaxle and vacuum bagging. The plan is to have every thing ground out and sanded by the end of next weekend.
JACK FLASH
 
Posts: 33
Joined: Mon Jan 30, 2012 3:11 pm

Postby GreenLake » Mon Feb 27, 2012 2:06 am

On carlins (the wood behind the coamings):

Since you have the deck off, replacement is much easier. Otherwise, "slight, beginning rot" would be a good application for a rot-restoring treatment.

The structural importance of these carlins is indeed in anchoring the coamings. The coamings are tall (top to bottom) and will easily take all the bending forces (what you call longitudinal).

I predict that making the carlins stiffer will have little effect, because the coamings are so strong in resisting bending in the vertical plane.

In the horizontal plane, the deck laminate will transfer any loads from any tendency of bowing out at the rubrail into compression loads for the coamings, and they are plenty strong for the purpose.

So, all the carlins need to provide is a solid attachment between deck and coaming. Your idea with the red cedar looks promising, with the fasteners run through. I assume that splitting the wood and inserting a ply of fiberglass tape is done with an eye towards preventing splits.

You don't appear to state this anywhere, but I assume the tape would need to lie vertically for best effect. Correct?
~ green ~ lake ~ ~
GreenLake
 
Posts: 7137
Joined: Mon Jun 18, 2007 3:54 am

Postby GreenLake » Mon Feb 27, 2012 2:17 am

On weight:

The DS is a rather heavy hull. Around 600 lbs. You would need to save 30 lbs to make a 5% difference in overall weight. I suspect that 5% is about the limit where you can observe differences in actual sailing --- except, at the ends of the boat or up along the mast, where you have large lever arms.

That's why K.C. wasn't worried about the weight penalty of his core, and I think he's right. (I'm still not prepared to go to that much effort myself, though).

If you have a stock rudder, you can save 4-5 lbs by building your own, and making it nicely profiled to boot, so it's more efficient. That will help to counteract a tendency of the DS to squat and should have much more of an effect than the same 5 lbs saved near the center of gravity.
~ green ~ lake ~ ~
GreenLake
 
Posts: 7137
Joined: Mon Jun 18, 2007 3:54 am

Postby GreenLake » Mon Feb 27, 2012 2:19 am

On drinking soda:

Where you're right, you're right.
~ green ~ lake ~ ~
GreenLake
 
Posts: 7137
Joined: Mon Jun 18, 2007 3:54 am

Postby GreenLake » Mon Feb 27, 2012 2:23 am

On inspection ports, drain holes in seat:

From a safety point of view, the bladder version looks like it would serve. With the big hole open, it would be easy to test the bladder on every trip.

From the class rules, though, this might not be legal. You might need to be able to close any holes if you ever want to race the boat under class rules.

Sizing the drain holes such that they can accept a rubber stopper would possibly be enough - my DS1 came with 1" holes that had corks in them. (Unfortunately, they are not at the lowest point, so they are useless for draining purposes.)

For the big holes you could fit deck plates (inspection ports).
~ green ~ lake ~ ~
GreenLake
 
Posts: 7137
Joined: Mon Jun 18, 2007 3:54 am

random Monday thoughts

Postby K.C. Walker » Mon Feb 27, 2012 9:34 am

It's amazing how projects like this can suck you in. Doing the core on my boat was as you say was, "a big project". Your observation that it might have been easier with the deck off may be true for part of it. My concern would be that it would be difficult to keep the hull in shape. Once I put the core in that shape is not changing!

I think that adding multiple stringers will make a huge difference in the stiffness of the bilge. This is what four-time national champion Dave Keran did with his #316 Vieja. I believe that #316 is a bit overweight but they felt the added stiffness was more of an advantage as did four-time national champion Phill Root when doing the core on his boat. It all depends on how soft your hull is now and how stiff you want it to be.

The de-formation or hogging of the bottom of your boat sounds like what I had. When I removed my stringers some of that hogging was relieved. Of course I was suspending my boat from the gunwales so there was no weight on it in the bilge area. After coring, I still had to do a lot of fairing and filling on the bottom with lightweight filler especially forward of the transom. I think the boat is most susceptible to softening in the "planing surface", that is the flat hull section between the seats. That's where the boat rides on trailers and it is also the flattest and least supported part of the hull. Judging by the condition of your boat I would have to guess that the bottom is pretty soft.

I'm going to suggest that cedar is not a good wood for the purpose of carlins. The purpose of these is structural, i.e. to hold fasteners and to stiffen the side deck. Being that cedar is only a little better than balsa wood as a core for compressive strength even going with the through fasteners, fender washers, and nuts on the backside, it's still not going to be as good as something like plywood or hardwood. You would need to be very careful not to over torque your fasteners or you would risk de-laminating your glass on the backside. If you went with a three-quarter inch plywood and totally encapsulated it with epoxy you wouldn't need glass laminate on the outside, therefore saving that weight. I would guess that you would come out stronger and lighter (possibly the same weight), and it would hold fasteners much better. You would eliminate the need for through bolting.

Just some random Monday thoughts.
KC Walker, DS 1 #7002
K.C. Walker
 
Posts: 1335
Joined: Sun Jul 06, 2008 10:50 pm
Location: North Stonington, Connecticut

Postby JACK FLASH » Mon Feb 27, 2012 12:39 pm

GreenLake wrote:On carlins (the wood behind the coamings):

Since you have the deck off, replacement is much easier. Otherwise, "slight, beginning rot" would be a good application for a rot-restoring treatment.

The structural importance of these carlins is indeed in anchoring the coamings. The coamings are tall (top to bottom) and will easily take all the bending forces (what you call longitudinal).

I predict that making the carlins stiffer will have little effect, because the coamings are so strong in resisting bending in the vertical plane.

In the horizontal plane, the deck laminate will transfer any loads from any tendency of bowing out at the rubrail into compression loads for the coamings, and they are plenty strong for the purpose.

So, all the carlins need to provide is a solid attachment between deck and coaming. Your idea with the red cedar looks promising, with the fasteners run through. I assume that splitting the wood and inserting a ply of fiberglass tape is done with an eye towards preventing splits.

You don't appear to state this anywhere, but I assume the tape would need to lie vertically for best effect. Correct?


Splitting should not be an issue as the holes will be predrilled and through bolted with machine screws versus wood screws as originally equiped. The biaxel will be vertical sandwiched between the coaming and the first board, and between the first and second board. I will then encase the entire piece in biaxel.
JACK FLASH
 
Posts: 33
Joined: Mon Jan 30, 2012 3:11 pm

Postby JACK FLASH » Mon Feb 27, 2012 12:44 pm

GreenLake wrote:On inspection ports, drain holes in seat:

From a safety point of view, the bladder version looks like it would serve. With the big hole open, it would be easy to test the bladder on every trip.

From the class rules, though, this might not be legal. You might need to be able to close any holes if you ever want to race the boat under class rules.

Sizing the drain holes such that they can accept a rubber stopper would possibly be enough - my DS1 came with 1" holes that had corks in them. (Unfortunately, they are not at the lowest point, so they are useless for draining purposes.)

For the big holes you could fit deck plates (inspection ports).


You are right. I reread through the rules and the seat tanks must be sealed. I do plan to race so I will have to forgo my previous plan. I will still use the bladder however to know that I have positive flotation. Do you know if there is foam in the front tank too?
Last edited by JACK FLASH on Mon Feb 27, 2012 1:36 pm, edited 1 time in total.
JACK FLASH
 
Posts: 33
Joined: Mon Jan 30, 2012 3:11 pm

PreviousNext

Return to Day Sailer I Only

Who is online

Users browsing this forum: No registered users and 20 guests