Tom Barb & All - XL SPRAY SHIELD

[Steve Sanford]

All~

Tom Barb just asked me about the "XL Spray Shields" I have been making for many years now. So, I thought I would give an overview here. This does not depict the full step-by-step building process.



It is based on the stock spray shield from the South Bay Duckboat (brainchild of Red Magnus and Ray Milliken, circa late 1960s). The XL is both taller and wider than the original.



Yes, the force fields are humming menacingly at the vessel levitates here at Pencil Brook Boatworks.... Much more hide (for a sitting gunner) and more protection from errant seas.



Here it is on a South Bay. It extends rail-to-rail on deck.



Here it is with polypropylene webbing - instead of the traditional laminated wooden rails.



Here it is on a Duck Invader. I have been happily surprised to see how many different gunning boats it fits. Anything near 3 or 4 inches of crown in 4 or 5 feet of beam seems to work.



Note the shield is fairly vertical because of the flatter deck.



Here it is on a Duck Wrangler. Almost no rake - but still effective.



I built the mold about 10 or 12 years ago. The main shield is easy; the flange requires more demanding woodworking. Frame is 1/2-inch AC plywood and the sheathing is tempered Masonite (MDF). The joint between shield and flange is filled and faired - followed by sealing, priming and 2 topcoats of gloss enamel. Making sure the fiberglass does not stick can be done with cellophane packing tape - or mold release wax.



I wax several times then brush or spray on a film.



Layup is: 1708 biaxial with mat - 2mm Coremat - 1708 biaxial with mat. I stagger the flange cuts on the biaxial layers - and cut a separate strip of the Coremat for for the flange - rather than struggle with the bend during the layup and saturation.



Resin is polyester. The less expensive polyester resin is better than epoxy when the laminates are all plastics. (i.e., no wood) But, I do not use it in the shop (health and persistent fumes) - so I only make these shields during the warmer months when I can work outside.



Once saturated, the shield usually hardens within an hour. Nevertheless, I let it bake in the sun and leave it on the mold overnight.



Of course, the shield is a bit oversize and so needs trimming.



I usually pop it off slowly - starting with a putty knife or softwood wedges. Trimming involves a variety of saws and sanders. I wear leather gloves during the early handling because of the very sharp 'glass splinters. (It is not a fun part of the job....)



I use the same mold for laminating wooden thatch rails. I add the spacers to the rails after they are off the mold. (Sorry for the out-of-focus!)



I make these as stand-alone parts - when I am not doing a full restoration on a vessel. If you want to make your own mold, I can take a few dimensions that can help you design one.

All the best,

SJS

 

[RM Anderson]

Steve,
Excellent instruction! I know my way around epoxy pretty well but polyester and vinylester resins I am clueless.
Any resources that you can recommend?
RM

 

[Taylor Smith]

Thanks, I've been wondering how you made that.

 

[Steve Sanford]

Steve,
Excellent instruction! I know my way around epoxy pretty well but polyester and vinylester resins I am clueless.
Any resources that you can recommend?
RM

RM~

re using fiberglass - of all kinds - for boatbuilding, this FishBump is excellent instruction.

https://www.youtube.com/watch?v=GpSyq9iLv0w

Nothing magical about polyester/vinylester except that is a much faster reaction. So, you need to be very aware of ambient temps, sunshine, wind - because it should be done outside. I usually work in the shade and move the piece into the sun if I can.

As with epoxy projects, prep and organization are very import. For example, just before I begin (which means the mold is prepared with cellophane, wax, film).

1) All pieces are cut to size and stacked in order of use.

2) Work surface is covered with plastic. Acetone, rags, extra empty containers, mixing sticks (tongue depressors) chip brushes, etc.. placed within easy reach.

3) I pour out the 3 or 4 pints (I usually fill 16-ounce containers to about 14 ounces) but do not add catalyst until I need to.

4) I mark 1-ounce cups for the amount of catalyst I think I will need in the conditions (more in cold, less. Note that thicker layups generate more heat than thinner ones - so less catalyst. I do not fill these cups until just before I need use them - because the MEKP is volatile.

5) Barrier cream on my hands before I don throwaway gloves (with the box nearby).

6) I spread catalyzed resin with a foam roller (usually 3 or 4 inches wide) and 3-inch chip brushes as needed. The small ridged rollers are essential for working resin into the layup and working bubbles out. I use aluminum - and clean with acetone - but plastic rollers are available too.

7) I usually saturate the layup on the flat - on a piece of plastic (6 mil or so). To keep the catalyzed resin cool, I pour it over the layup and then move it around with the roller and brush. Leaving catalyzed resin in a cup too long will both ruin the product and get very hot. If the resin starts to gel, abandon that batch and move on to the next pint. I set such failures out of harm's way - and where a fire would do no damage.

8) I transfer the saturated layup onto the mold for the final shaping and working excess resin out. One hopes for a graceful and flawless transfer during this toreador-like step.

9) In addition to extra care handling the sharp edges, finishing a poly layup is similar to finishing one made with epoxy. Dust mask is necessary even outside once the power saws and sanders come out. After sanding down to 80 or 100-grit, I wipe with acetone, then begin applying my duckboat paint.

NOTE: Resin (poly or epoxy) will not stick to polyethylene film - the common plastic used as drop cloths or for vapor barriers - but it cannot be used for mold release! The gases from the curing resin will cause the plastic beneath to bubble and wrinkle and so the cured finish will be full of imperfections (Yes, I learned this the hard way.)

NOTE 2: It is quite amazing how adept one can get viz. the clock when using polyester resin. I imagine pros count on this so they can move hulls, decks, parts out of molds regularly and rapidly. Pencil Brook Boatworks can afford a more deliberate pace....

Hope this helps!

SJS

 

[RM Anderson]

RM~

re using fiberglass - of all kinds - for boatbuilding, this FishBump is excellent instruction.

https://www.youtube.com/watch?v=GpSyq9iLv0w

Nothing magical about polyester/vinylester except that is a much faster reaction. So, you need to be very aware of ambient temps, sunshine, wind - because it should be done outside. I usually work in the shade and move the piece into the sun if I can.

As with epoxy projects, prep and organization are very import. For example, just before I begin (which means the mold is prepared with cellophane, wax, film).

1) All pieces are cut to size and stacked in order of use.

2) Work surface is covered with plastic. Acetone, rags, extra empty containers, mixing sticks (tongue depressors) chip brushes, etc.. placed within easy reach.

3) I pour out the 3 or 4 pints (I usually fill 16-ounce containers to about 14 ounces) but do not add catalyst until I need to.

4) I mark 1-ounce cups for the amount of catalyst I think I will need in the conditions (more in cold, less. Note that thicker layups generate more heat than thinner ones - so less catalyst. I do not fill these cups until just before I need use them - because the MEKP is volatile.

5) Barrier cream on my hands before I don throwaway gloves (with the box nearby).

6) I spread catalyzed resin with a foam roller (usually 3 or 4 inches wide) and 3-inch chip brushes as needed. The small ridged rollers are essential for working resin into the layup and working bubbles out. I use aluminum - and clean with acetone - but plastic rollers are available too.

7) I usually saturate the layup on the flat - on a piece of plastic (6 mil or so). To keep the catalyzed resin cool, I pour it over the layup and then move it around with the roller and brush. Leaving catalyzed resin in a cup too long will both ruin the product and get very hot. If the resin starts to gel, abandon that batch and move on to the next pint. I set such failures out of harm's way - and where a fire would do no damage.

8) I transfer the saturated layup onto the mold for the final shaping and working excess resin out. One hopes for a graceful and flawless transfer during this toreador-like step.

9) In addition to extra care handling the sharp edges, finishing a poly layup is similar to finishing one made with epoxy. Dust mask is necessary even outside once the power saws and sanders come out. After sanding down to 80 or 100-grit, I wipe with acetone, then begin applying my duckboat paint.

NOTE: Resin (poly or epoxy) will not stick to polyethylene film - the common plastic used as drop cloths or for vapor barriers - but it cannot be used for mold release! The gases from the curing resin will cause the plastic beneath to bubble and wrinkle and so the cured finish will be full of imperfections (Yes, I learned this the hard way.)

NOTE 2: It is quite amazing how adept one can get viz. the clock when using polyester resin. I imagine pros count on this so they can move hulls, decks, parts out of molds regularly and rapidly. Pencil Brook Boatworks can afford a more deliberate pace....

Hope this helps!

SJS

Steve,
Good tips; I can't thank you enough. I am looking at taking things to a different level. "One of" construction is very inefficient.
RM