Thread: Detroit GIS build log

Originally Posted by phoran

Will I want to epoxy coat the bulkheads before I glue the frames on them? It looks like some guys mask the gluing surfaces. Is that necessary for better adhesion, or not?

In theory you get a stronger bond when gluing bare wood to bare wood. The secondary bond to cured epoxy is generally considered weaker however all big glass-epoxy boats have tons of secondary bonds and they do just fine. As long as you abrade the cured epoxy and make sure it's free of blush you should be fine bonding to cured epoxy. There's a lot of internet chatter on both sides of this argument so as an experiment one side of my boat is wood to wood joints and the other is cured epoxy joints. So far no hint of failures.

What he said. Either mask the to-be-glued areas or coat the assembly with the cleats epoxied in place. I did not mask so I must have done the latter (memory is pretty bad ).

Once the bulkheads are coated some guys dry-fit everything, disassemble and mask, then coat with epoxy. Then they do the assembly again for the final time. I just assembled with the sides uncoated then put the boat on its side for sealing with epoxy, one side at a time. Epoxy runs terribly so anytime you can do it "down-hand" you're ahead of the game.

If you haven't purchased your epoxy yet, there are a number of places you can pay 1/2 to 1/3rd of West System prices, for a goo of the same quality, some without blushing.

As far as chemical or mechanical bonds, don't worry about them. All boats will have both and both bond types will exceed the substrate shear strength if done properly. A GIS isn't highly loaded enough to get too concerned over this issue.

Most boat builders avoid finger jointed pieces. In reality, of course depending on the type of finger joint and the adhesive used, it too will exceed the strength of the surrounding wood, so not a problem. It should be check, that the adhesive is a real WBP one, so you don't end up cussing a lot when it gets wet and lets go.

Fillet and joint mixtures should be multiple materials in most cases. Silica is used to control viscosity and some is usually in every mixture, at varying percentages. Wood flour should be combined with milled fibers or cotton flock, to improve modulus of elasticity. Again, a GIS isn't so loaded up that aunt Millie's mashed potato salad couldn't be used as a fillet mixture, but well made fillets and joints hold better and longer.

As to pre-coating or not, I dry fit everything a few times to get fits right, then I coat places I will have difficult or no access to after assembly. It's often wise to pre-coat a sealing coat, while the pieces are on the flat (work bench). This first coat just seals the grain and much could be said about pre-coating each piece of plywood before it's cut. It cuts down saw "tear out" and splinters too. Maybe drawing out the parts on the plywood first, then coating the areas you need to, which will save some goo. You'll still need another 2 coats, but spilled coffee will not cause a problem if things are pre-coated, which can be especially important on brightly finished surfaces.

I actually found a great fiberglass wholesaler very near me who offers a different brand of epoxy at a great price.Michigan Fiberglass Sales - 48080 - Resins : Polyester : Epoxy : Gel Coat : Vacuum Bagging : Carbon Fiber : Kevlar : Fiberglass Michigan since it's 23 degrees out, i'm gonna wait to do much bonding until it warms a bit.

So the big box stores stock red oak and poplar for hardwood. what would be ideal for the leading edges of the rudder and daggerboard? also, since these parts are 1" true dimension, i'm probably gonna have to rip some 2" stock to size. what do the GIS experts suggest?

I don't know what the experts will say, but I'll tell you that I used HD Red Oak. Red Oak doesn't get great reviews for boatbuilding in general, but I believe that has more to do with its low resistance to rot. In this application it will be entirely sealed in epoxy and two layers of 'glass.

I did both the leading edge and the trailing edge. Lately, Mik has advised that the trailing edge does not really need hardwood. I look at some of the hard hits that others have reported (callsign222 and Bobwes come to mind) and feel like hardwood won't hurt. I also used the same stock of oak in the center case framing that will contact the daggerboard. It might be smart to go softer in the daggerboard so that it will lose the fight versus the centercase. Make sense?

The only other oak in my boat (because I had enough extra) is the cap at the point of the bow, or false stem. The plans describe an option or a choice of capping of the point where the two hull sides meet. I also wrapped this in 'glass so I ain't skeered.

your bow could slice through the pt-109 like the amagiri! i thought the fiberglass eoxy would offer more protection than the choice of wood.

So i met with my local sailmaker, and he gave a very competitive quote. he suggested only one reef point, and that makes sense for the coastal sailing (and 250# skipper) i'll be doing. But what about battens? i notice the duckworks sail is no longer battened. what do the GIS experten suggest?

This was the discussion on the Goat Island Skiff Facebook Group for reference.

• 
  
  Patrick Horan my sailmaker suggested only one reef point. freshwater, coastal sailing with a 250# skipper, that should be sufficient, right?
  Saturday at 00:30 · Like
  
  
  
  
  
  
• 
  
  Andrew Softley How do you look at the design? If I open the file, it is just text of the sail specifications. Need the software huh?
  Saturday at 00:41 · Like
  
  
  
  
  
  
• 
  
  David R LaFontaine Tibor Rumpler, I sent you a separate message; look for it in "Other" mailbox. Maybe a little more depth in the lower third? Andrew Softley, the file opens in SailCut.
  Saturday at 03:05 · Like
  
  
  
  
  
  
• 
  
  Michael Storer Hi Patrick Horan, sail makers have little experience with reefing small boats that may be used for cruising and racing.
  
  The sail on the goat is VERY big compared to other boats of this size to give lots if speed in light ans moderate winds. But can be made very small when the wind is howling. It increases the sailing range of the boat.
  
  I originally drew two reefs that were equal as on the sailplan drawing.
  
  But users have found making the first reef less far from the boom is better because the first reef took away too much power in one go.
  
  Other thing is you only need two small intermediate holes between the main reef points. Use one piece of light shockcord/bungee wrapped along the boom in a spiral going through these two holes.
  
  Sail maker thinks reef is for survival. But really it is for efficient sailing in different windapeeds and sea conditions
  Saturday at 07:10 via mobile · Like
  
  
  
  
  
  
• 
  
  Michael Storer In Texas 200 John Goodman taught me a lot about choosing the right reef for the day. He had three. Sailing with second reef most days was excellent for speed and safety. Once or twice we went still fast but safer in third reef if the waves got big.
  Saturday at 07:15 via mobile · Like
  
  
  
  
  

so tonight i glued up the rudder blank, and it went pretty much like i though it would. messy! i tried the "ziploc pastry frosting bag" method, and it didn't work very well. i found it was very difficult to mix the thickener in the bag, so i abandoned that method and mixed the pox up in a disposable pot. then i just spread it like honey on each stave, rolling them over as i went. i screwed and clamped some scrap staves across the blank, to keep them level, then clamped them together. i'll give them a couple days to cure, then unassemble everything and check them out. my neighbor has a thickness planer, so i should be able to get them to the required mm before shaping.

The zip-lock baggie method works okay if you mix the resin/hardener in a container before putting it in the baggie. Yeah, there is an extra step but the method has its moments.

Very good phoran. I think you need to do a bit of baggie glueing to get the hang of it. I have a bit of experience with fiberglass and it is messy business for sure. I have a box of disposable gloves I'm sure will get used up. Either that or I will not be able to seperate my fingers.

here is the glued up rudder blank:

Good for you. My epoxy has not arrived yet so you are ahead of me. I should be where you are now next week.