Another BFN Rebuild

Waterdog wrote: Tim, I think when you say glass bubbles you mean glass beads.

Andy, actually its 3M glass bubbles: US Composites Fillers

So youre a proponent of the milled fiber vs. cabosil, huh? I wish it wasnt 4 times the price! Of course, thats by volume- maybe it goes farther? The note on the site says, "1 quart of resin will need about 1 quart of Aerosil to make a mayonnaise like viscosity." Does that ratio seem about right for the milled fiber? Or maybe it goes further?

Tim,
The rule of thumb is the stronger the filler is the harder it is to sand. I wouldn't worry too much about sanding the bilge glass much. Of course I do have a feeling Greg did!!

I sure wish you were working on your 67SN at the moment.

I forgot to add that Im going to coat the entire hull with epoxy resin, and add some layers of glass in a few places... Notably the keel and in the area where the original starboard main stringer was. We took out a little too much glass when we removed it!

So maybe we'll use epoxy mat and either mill fiber or cabisil for the bedding. Looks like cabosil is much cheaper!

Ill grab some glass bubbles... sanding would imply a finished surface- I assume you used it either in the bilge or on the floor (or both)?

Fillets... is it important to have a strong material for this, or not? (I assume not, but please confirm.) I guess that would determine what I use.

Any thoughts on the proposed layup schedule?

Greg, I dont- no time. If I could find a deal like that, I might grab one- that is, if I had a place to put it!

Many thanks again to Joe for letting me pick his brain on his entire approach- from material selection to methods and layup schedules. Many of the ideas below are stolen directly from him- others are a slight deviation.

I just laid out all the cross sections, and I was very close to being able to get away with only 4 sheets of Coosa. For those curious, Im using 3/4" Bluewater 26 for the floor in front of the engine box, 1/2" Bluewater 26 for all the stringers, bulkheads and ribs, and 1/2" Bluewater 20 for the rear and front floor areas. Im close enough to needing a 5th sheet that it probably makes sense to order it in case my dimensions are slightly off or we make a cutting mistake (I'll get another sheet of 1/2" 26 since thats what's used the most). Still, with the pricing I'm seeing, we'll be looking at right around $1.5k for the Coosa... right about what I ballparked.

Next up, fiberglass supplies. Greg, you used more than 10 gallons of resin, right? I wont have as many layers of glass on the floor as you did, but I've got a whole bunch of ribs... my guess is we'll end up pretty close to the same. The trick will be getting the right thickness(es)... the stringer lamination will be done in the basement (80+ deg), while the boat is in the garage (insulated but not heated- figure 50 or so while working). I believe Ill want US Composites 635 resin and 3:1 (medium) hardener for the basement, and 4:1 (fast) hardener for the garage. Sound right? I wonder if they'll let me mix and match on a 10 gallon kit...

Concerning the glass, here are some initial thoughts. Please let me know what you think!

Before installation:
- Main stringers (3 layers of ½”) will be laminated together with mat
- Front bulkheads will get a layer of cloth on both sides (to prevent buckling)
- Floor panels will get 2 layers of cloth on the underside (for screw retention)

Stringer Installation:
- Mains will go in first, followed by secondaries, bulkheads and ribs.
- All structure will be bedded with a combination of epoxy mat and some sort of filler (to take up the gaps)
- Main stringer layup: 2 layers of 2" cloth, 1 layer of 4" mat, 2 layers of 8" cloth, 1 layer of 12" biaxial. Top will be wrapped with the biax.
- Secondaries: : 1 layer of 2" cloth, 1 layer of 4" mat, 1 layers of 8" cloth, 1 layer of 12" biaxial. Not wrapped.
- Ribs: Same as the secondary stringer- though Im considering not adding the biax (to be replaced by an extra layer of cloth?).
Front bulkheads: Same schedule as the main stringers (but not wrapped).

Floor Installation:
- Each panel will be bedded with epoxy mat or thickened epoxy. Undecided on the filler. Also undecided on whether or not to use screws as well.
- Taped to the wall with 2" cloth, 4" mat and 8" cloth.
- Taped to the secondaries with 2” cloth, 4” mat, 8” cloth... not sure if Ill use the mat or replace with another layer of cloth.
- The top of the floor will get 2 layers of cloth and one of mat, except up front where its foamed- which will get an extra layer of mat for thickness.

Any input on this approach would be appreciated!

Fillers... I need some help here as well. I will need fillers for bedding the entire structure (stringers, ribs/bulkheads, and floor), as well as creating fillets before laying glass. Maybe some final fairing as well. I believe I used Phenolic Microballoons and Talc on the Tique. Would it be recommended to use Aerosil-Cabosil, Glass Bubbles, Milled Fiber, or Chopped Strand for any of these? Which one for which purpose?

Would a thin layer of epoxy mat be better than fillers for bedding the stringers and gluing down the floor?

81nautique wrote: "We don't need no stinkin bad saw" That would be too easy. Only stationary tool I have is my table saw.

Well, you could always get one of the new flexible radius cutting saw blades for the table saw!

Ha. Good one.

"We don't need no stinkin bad saw" That would be too easy. Only stationary tool I have is my table saw.

If you don't have a good jigsaw I can recommend this one, I bought myself this one for xmas and it is an amazing tool.

Tim,

Are your drawings accurate enough to actually cut from or are they for a Bill of materials?

How do you plan to transfer the dimensions to your stock? Do you have access to a plotter so you could make full size patterns or do you have to transfer everything by hand.

TRBenj wrote: Joe, you did all your cutting with a jigsaw? Geez, that sounds like a lot of work. I was thinking either a tablesaw or circular saw for the long straight runs. A jigsaw on the smaller, more intricate pieces definitely makes sense.

Keegan,
Instead of trying to explain Tim's drawings, I feel looking at some pictures would give you a better idea. Start at about page 18 of Gregs weeding the pumpkin patch thread. You'll get a good idea of where the parts fit plus the reason fo the different shapes.

EDIT: Start on page 17 as it has some good pictures before Greg started putting in some of the floorboards. Here's a better link directly to the page

Guy's, have you tried a Diamond cut jigsaw blade. I use one all the time here at work to cut layered fiberglass that is a 1/4" thick or more with no problem. We also use it to cut A/C flooring in the cabin that is aluminum honeycomb core sandwiched between fiberglass. It's about 3/8" thick and the blade goes through that too.

when we cut out our pieces for the stringers we used a table saw to rip the boards, sistered them up 1/2" 3/4" and 1/2" switching back and forth 5' 1" and 8' either or to get 13'1" for the Mains, then we traced them with the original stringers and jig sawed them. Then we used a planner to put the angles to somewhat match up to the hull.


critter a grinder would create alot of dust. with the table saw we attached a vacuum to the shoot out so the dust was to a minimal.

Hey Tim you guys working on the boat this weekend? I might be bored saturday lol as im not going to VT this weekend.

RainDog wrote: Tim, You should really consider planning out your projects instead of hacking into it with out thinking it through...

At prices around 250 for a 4x8 sheet, you don't want to just start cutting that coosa without a plan...





Coosa first claimed they would CNC cut the pieces for me... then backed out.. too bad it would have saved a lot of cutting.

Tim I ended up using a Jigsaw for most of the cutting to keep the dust at a minimum. I started off thinking a Zip saw would be the ticket but it was more trouble that it was worth even after acquiring various guides it was not easy to ever get a straight line, and it generated more dust. I went through a good sized pack of assorted dewalt jig saw blades, the coosa was surprisingly hard on them.

TRBenj wrote: I took some depth measurements this weekend so I was able to lay out a rough cross section for the ribs and bulkheads. Not much holding us back from ordering materials now. When I did the cross section of the stringers, I realized that with the taller primaries required by the new engine cradle (without cutting it up, anyways), I realized that the exhaust hoses wouldnt fit between them and the floor if left full height over their entire length. So, I cut them down behind the engine to closer to stock level. No need to waste material there anyways, I suppose. In order to clear where the exhaust hoses enter the bilge, I think the stringers and cradle will have to be notched at the top. The plan is to run 4" hose. I also have a plan for the battery box drain. Im not crazy about having clamped connections below the floor, so I want to use PVC here as well. A few 22 degree elbows installed between the middle bulkheads should give me some slope so that it self drains. We've come to the conclusion that no matter what, its almost inevitable that water will find its way under the floor- superior construction techniques and all. Therefore, Im leaving provisions to get the water back out. Like many here have done in the past (namely Joe in his '83), the under floor area will drain together via cut outs in the ribs where they join the secondaries. The front bulkheads will have notches where they join the keel board. Right now, the only compartments that self drain (to the bilge) are the ones on either side of the engine (note the half moon drains in the primaries). Since we want to through bolt the cradle instead of lagging it, the floor over the primaries cant be installed until after the cradle is in- so getting them sealed off from the top would be problematic. Everything else is sealed off from these, and there are 3 strategically placed access points to drain the subfloor area, should water ever get in. There will be no floor from the rearmost ribs back (essentially the last 10", under the gas tank), so any water in these 2 rear cavities can be reached with a pump if the nose of the boat is raised. To remove any water that collects at the low point of the hull in front, a 6" port will be installed on the front wall of the battery box. Right now, I think the access hole will be capped with an inspection plate similar to the one used over the driveshaft packing nut.

These diagrams are great, but since I am new to this could you please explain the holes in the bulkheads? Why it goes from three big ones to down to the end where there are 4 on the left and 2 on the right... I know this is probably common knowledge to all yall salty dawgs but it would help me understand the flow and layout.
Thanks
Keegan