New Style Bertram 31 Side Opening Air Boxes
These ready to install Air Boxes, for side
induction air are specifically designed for the
Bertram 31.
(Shown here is Ricky Saunders' "Miss Olive")
Principal features include:
Optimum air volume
Up to 400 hp diesel. Diesel engines need far more air than do gas engines. The rule of thumb for diesel
engines is 1/2 square inch of free air delivery per each rated horse power at full RPM.
Noise reduction
Air delivered from hull
sides, below the shear line. With proper sound insulation in the engine box, all engine noises are reduced to under 30 dB, even on the Cummins 250/300 installed into the Bahia Mar model
Cleaner air
Even in a head sea with smoky diesel engines, the inducted air is always fresh. No ingestion of
engine exhaust, as is possible with cockpit air supplies.
Visual appeal
Another "Signature Design", the simplicity of lines complements the B31 profile and the "Drop-In Design" makes installation very easy even on a newly painted hull. No need to repaint the hull after installation!
Price per pair: $1,600.00 USD plus packing and shipping. (USA east coast shipping & handling averages $75.00 using UPS or FedEx ground.)
Minimum Deposit Required: $800.00
Shipping time: Under 4 - 6 weeks.
Overseas shipments available, but must be paid in full at time of order. Payment by wire transfer only, shipping costs will be calculated based on shipping address.
How they work:
 (Click for larger image)
 (Click for larger image)
Kit will contain the following:
Port and Starboard Air Box Assemblies
Each box has 3 elements:
Main Box
Air Stack
Baffle Grill
Foam installation spacers, wedges, and mounting hardware
Template to cut side holes
Can be used for both sides, simply trace
the hole to be cut.
4 printed pages of Installation Instructions and tips
Technical Support: Via phone, email, or
Bertram31.com General Discussion Board.
( http://bertram31.com/bb/bbs.cgi )
Construction of the Air Box is 100% polyester resin and fiberglass. The baffle assembly is made from
cast acrylic. The standoffs are clear and the baffle panels can be ordered in clear, white or black. Off white
is not a stocked color, but is available as a special order color and adds $50.00 to the price. Other
special order colors include: red, blue, & green.
Installation should be done using epoxy
resin and Cabosil. Addition of fiberglass mat or cloth
as tabbing is not necessary, but never hurts. An alternative
adhesive would be methacrylic, (super strong and requires less
surface prep or thickening, but expensive and more difficult
to obtain in small quantities)
The Air Box has been designed to give
optimum free air delivery for any engine up to 300 hp.
Acceptable air delivery for engines up to 400 hp. Air
delivery is calculated for diesel application, so any
size gas engine is more than covered. Air delivery is 150 sq. inches per box.
Installation Instructions and Options: (For full Graphic installation account on Ricky Saunder's B31 click here.)
Installation will be a 3 part project and can be accomplished even with the engines in place. It is recommended that all bonding be done with either epoxy or methacrylic adhesive.
Parts list:
2 pcs - Main Air Box
1 pcs - Hole template for hull cut out
2 pcs - Air stack
2 pcs - Acrylic grill (includes 6 1/4"-20 SS machine screws and fender washers)
2 pcs - Foam spacers to hold shape dimensions of main box
2 pcs - Foam spacers to hold shape dimensions of air stack
2 pcs - Foam wedge blocks to support stack while adhesive cures
The first step is to determine the exact location of the holes to be cut into the hull. It is critical that the height placement be made so that a minimum of 2 3/4" of space is left above the top of the air stack. 3 1/2" is the maximum space necessary.
From the inside of the hull, measure down 5" below the underside of the gunnel. Make this measurement both at the forward and aft ends of the engine compartment and about 10" away from the bulkheads. Drill an 1/8" hole through the hull at these two points. This will spot the top cut line for the main box on the outside of the hull.
Draw a straight line, from bulkhead to bulkhead, using the two drilled holes as the cardinal points. Measure the distance between the two bulkheads and subtract 50" and divide this number by two. Measure from each bulkhead this length and make a mark on the straight line. Drop down 2 1/8" below these marks and drill a 1/8" hole through the hull. This will mark the centering of the main box between the bulkheads.
Move to the outside of hull and position the hole template so that the 1/8" centering holes are visible at each end and the height holes are just visible at the top line of the template. You may adjust the attitude of the template slightly to make the projected main box hole align with the guard rail. When satisfied, tape the template to the hull and draw the cutout with a pencil. Remove the template.
There are several ways to cut the hole in the hull, but in any case, the tools used should be a non-toothed tool. A composite cut off disk, carbide encrusted blade, or diamond encrusted blade are the various type of blades to be used for long cuts in fiberglass. The two ends of the hole can be cut with a standard toothed 4" hole saw. Measure the diameter and center carefully and pre-drill a 1/8" pilot hole at the center point.
Cut the two circular end holes first, then the top and bottom lines. You will need to adjust the size of the ends up to template line with a 2" drum sander attachment on a hand drill. The top and bottom line cuts are best accomplished with high speed angle grinder fitted with the appropriate cut of disk. I use a RotoZip® power tool fitted with a diamond encrusted disk. The tool is light and the disk is thinner than a composite disk, making the job quicker and cleaner. Clean up and adjust the top and bottom cuts with a angle grinder fitted with a 60 grit sanding disk.
Bring the hole size up to the point that the main box fits with minimal gap, but not tightly. There will be a small amount of gap between the hull and the box lip at each end. This can be adjusted to minimum and equalized using a drywall screw and 3/16" fender washer at each end. Place the box into the hole and mark on the hull where the lip will set. Remove the box an drill a 1/8" hole on this mark, angling the drill back away from the cutout at about a 45 angle.
With the box still removed, pre-tap a short drywall screw into each of the end holes and remove. Re-insert the box, add a fender washer to the two dry wall screws and screw them into place so that the fender washer contacts both the hull and the box lip. Adjust the tension of the two screws so the end gap is minimized and equalized at both ends of the box. Insert the foam spacer into the box. The fit should now be optimized.
Make a pencil mark on the hull completely around the box lip, remove the drywall screws and the box.
Using 1" blue masking tape, carefully tape around the pencil mark, touching the mark, but not inside of it. Also mask out the lip of the box within 1/16" of the edge. Carefully grind away all paint and/or gelcoat on the bond area of the hull to within 1/16" of the masking tape. The bonding surface of the box lip has been filled with course material will not require any further preparation. Wipe down both surfaces with denatured alcohol.
If using epoxy, both bonding surfaces should be primed with straight epoxy, catalyzed according to the manufacturers specs. Using a clean rag, wipe away all excess resin.
Into the remaining mixed epoxy, add enough Cabosil to thicken it to the consistency of peanut butter. Apply this mix to the bonding surface of the box lip with enough excess, that when the box is bedded into place, there will be squeeze out.
Insert the box, replace the drywall screws & fender washers, clean up all excess epoxy completely, and remove the tape. Go back over the joint area with a rag and denatured alcohol to remove all traces of the epoxy from exposed surfaces. Allow the epoxy to fully cure for 24 hours before moving to the next step. (See Options Notes below)
Once the epoxy has cured, remove the drywall screws and do a final cleanup around the joint area. Remove the foam spacer from the box. You are now ready to install the air stack.
Prep the bond area the same as before. Since this joint will not be very visible after final installation, taping out the surrounding area is optional, but taping the lip of the stack is advisable. Prime the bond surfaces, wipe, and bed in the same manner that you did the box. Use the foam spacer & wedges supplied to force the stack into place and hold it there while the epoxy cures.
After initial cleanup of this step is complete, re-mask the box joint leaving 1/16" of the hull showing and 1/16" of the lip showing at the joint. Apply a bead of 3M 5200 or 4200. or 3M 101 caulk completely around the joint. With your finger tip, wipe all the excess compound away, leaving a very small fillet at the joint line. Remove the masking tape while the compound is still wet.
After the epoxy on the stack has cured, do a final clean up of the box interior, remove the foam space from the stack and install the acrylic grill. On all B31 models, except the Bahia Mar, this will be a two man job.
Before installing the grill, apply a small bead of caulk to the vertical centerline of each of the three stand offs, and a dab into the hole. Carefully rest the grill into the box, but not making contact with the caulk. At this point one man will need to be inside the boat to set the machine screws, the other outside to guide the grill into place.
From the inside, add another dab of caulk around the screw holes. Start all three screws by hand for about 4 turns and then tighten them evenly with a screw driver. Don't use a power driver or screw gun. Tighten each screw only to the point of being snug. Do not over tighten or you'll run the risk of breaking the acrylic standoff.
Your installation is now complete in under three days...
Allow sufficient time for all of the caulking to completely cure before washing down the box area.
Options Notes:
Inside reinforcement of main box: It is not necessary to use fiberglass tabbing to the inside of the hull, but at the very minimum a generous fillet of epoxy should be added completely around the joint. On hulls later than 1972, the thickness of the layup is significantly thinner than on earlier models. I would recommend adding a strip of 1/2" or 3/4" plywood both above and below the box. The strips should be about 3" wide and run from bulkhead to bulkhead. The bonding surfaces should be ground down to bare fiberglass and cleaned with denatured alcohol & primed. Bed the strips in with thickened epoxy, and coat the exposed well with straight epoxy. These strips will add back any vertical rigidity lost by cutting the hole for the box.
Grill supports: I recommend that the lower grill strip be supported corresponding to each of the three acrylic stand offs. This can be done easily with small blocks of Starboard and 3M 5200. Cut pieces 1" x 1" to fit between the lower panel and the box. Put a dab of 5200 on each end of the block, gently lift the grill upward and insert the block as far back as possible, but not beyond the back edge of the grill strip. Wipe away any excess 5200.
Please feel free to contact me for clarification of anything that you're not sure of or need consultation on. 1.325.248.0809
For additional information, please contact:
Capt Patrick McCrary
834 Scott Dr.
LLANO, TX
78643
325.248.0809
bertram31@bertram31.com
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site creation and maintenance by:Capt Patrick McCrary
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834 Scott Dr., LLANO, TX 33404
Telephone 325.248.0809
Web site questions or comments to:
bertram31@bertram31.com
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