I used scrap pieces of the Tempered Hardboard to check that I had 'fair' curves on the pieces.
'Zero' in the band saw to a 'reference' vertical position.
Not finished yet, there's the matter of the notches in the back of the dash to accept the deck strongbacks. Some folks cut through notches and then put a veneer on the dash to conceal the notches, I am trying to avoid any extra 'layering'. The tricky part is that the notch bottoms need to be horizontal for the strongbacks to seat properly.
Time to use a Slab-O-Wood that I made earlier, and in fact I sliced two pieces of wood to make 4 tapered slices or 'wedges'. I drilled a hole in the middle of one of these tapered pieces then drilled and countersunk holes so the 'wedge' could be mounted to the bottom of a router set up with a 'plunge' base, and then reattached the original router plate to the bottom of the wedge so I could install a routing guide. I then had to create a template for the router guide to follow, and with a few test cuts to fine tune things away I went.
A) I intend to route cabling though the holes
B) I intend to hang things from the holes
C) It makes the gussets lighter
Now time for a little more irreverence. I will build my entire transom/motor well assembly before I even mount a frame on the jig, and I will build the transom as a monolithic slab. I'm doing this because it seems a lot easier to build and finish this assembly 'on the bench' and I believe it will give me the 'esthetic' I want.
First step is to set up a 'mock up' of the entire transom/motor well area to verify clearances for the motor and steering system and to determine the cable/wiring/fuel line routing that works the best. That sheet of plywood I used for the frame outlines gets a second use here.
The throttle and shift cables for the motor run out the front end of the side of the transom, then will curve down and run UNDER the floor to the controls that will be right of the 'drivers seat' which will be on the left or port side of the boat. This boat will be used primarily at our cottage in Northern Ontario and we always dock with the left or port side of the boat against the dock, both at the cottage and at the marina.
The wires exiting the motor are for a water temperature gauge and a tachometer, and the tubing exiting there is for a water pressure gauge, not taking any chances with this oldie goldie of a motor.
After much research going with a Teleflex Rack NFB system for steering. Replacing the original tilt tube with one large enough in diameter to accommodate the steering system was a project onto itself. I am having a friend fabricate a custom adapter to connect the steering link to the lower cowl of the motor.
The rearward facing vent should give me passive bilge ventilation after I install two intake cowls on either side of the aft end of the boat. I'm including provisions to connect the vent to a bilge vent system as at this point in time I'm leaning towards a fully enclosed rear half of the boat.
Let's start by deciding to use a sliding dovetail joint to connect the sides of the motor well to the transom, this is a VERY strong joint, that, by it's very nature, secures the two parts together physically. This will enable the motor well to actually be structural support to the transom.
First step is to cut in plain flat bottomed dadoes in the transom for the sides, with the length of the dado angled in top to bottom and the bottom of the dado angled to 'tilt' the sides inward as they run forward. This employs the router guide to locate the dado lengthwise, a stop to end the dado at the correct point and the reuse of one of those 12 degree 'wedges' I made earlier to angle the bottom of the dado.
To wind up with this.
Then it's a matter of removing the flat bottomed router bit and installing a dovetail bit to cut the sliding dovetail, once a few test cuts are made to get a snug fit. The result of the second router pass yields this.
Now since I am mounting a vent in the front end of the motor well I need the sides to extend further forward than the bottom of the motor well. This calls for another blind dado joint for 'cleanliness' and strength.
I cannot use a sliding dovetail joint here because come assembly time the sides of the motor well must slide down and towards each other as they are installed, so the sides can only 'trap' the bottom in a flat bottomed dado.
Since the sides of the motor well angle outwards towards the top the dado for the bottom must be angled relative to the side. Here, once again, the 'wedge' pieces I cut out come in handy.
The photo above is the set up to route the blind dadoes in the sides of the motor well to accept the bottom of the motor well. You might notice the extra little 'stick' of wood increasing the angle of the router relative to the motor well side being routed. When you get into a 'box' with angled sides the geometry gets a little complicated and the 'extra' 'stick' gave me the true angle I needed.
The result of the previous task yielded this 'dry fit' of the transom/motor well assembly. The sides of the transom rise above the transom at this time, they will be angled to match the slope of the deck and be flush with the top of the transom later. You might notice the right side of the motor well had moved outward a bit in the photo and you can see the tail end of the blind dado cut in the side to accept the bottom.
The bottom of the transom was created by gluing two boards together since the motor well bottom is close to two feet deep. The edges to be glued were trued on a jointer, biscuited and glued with Titebond III, with the grain matched as best as possible. You can never have too many clamps.
The following are two photos of the next 'dry fit', viewing the transom/motor well assembly.
You can see that the sides of the motor well have been blind dadoed to accept the front of the motor well, and that the tops of the motor well sides have been beveled 3 degree to match the curvature of the deck side to side and angled up 6 degrees off true horizontal to match the slope of the deck going forward.
The front of the motor well has also been made and it's top edge is curved to match the side to side curve of the deck and bevelled 6 degree to match the slope of the deck going forward as well.
The piece of wood at the very front of the motor well is just a 'spare' piece, but you can see the 'slots' in the edge of this piece that are the slots cuts for the installation of 'biscuits' used to edge join pieces to strengthen the joint and keep the two pieces aligned.
The transom itself was fabricated from two pieces cut from the same length of 8:4 white oak stock planed down to 1 5/8" thickness. The ends to be joined were trued up on a jointer and two rows of biscuits were installed at glue up, with a lot of clamps and Titebond III.
I cut the bottom straight edges of the transom with a circular saw following a clamped down straight edge guide.I then placed the full scale template or pattern I had made out of tempered hardboard on the transom 'slab' and traced the outline in pencil, using the pencil mark as a guideline for 'rough' cutting out the curved sides of the transom on a band saw. I then re clamped the hardboard template to the 'rough' cut slab and used a straight cut router bit with a bearing to 'follow' the hardboard template to cut the transom slab to spec.
In case you are building a Zip and wondering if I did the calculations to allow for 'bevelling' the transom, I did. The method I will be using to bevel the transom sides will leave the front and back dimensions and profile of the transom identical, so no compensation was required.
I will note that the height of the transom will be about 1/8" shy of the plans after bevelling the top of the transom, I could have compensated for this as well, but decided it wasn't essential to me. I used a 12 degree tapered bit with a bearing to bevel the top of the transom. The 'jig' in the picture is used to reduce the 12 degree bevel of the tapered router bit to the 6 degree bevel required per the plans.
I then decided to make my own 'fillets', thinking that building up epoxy with filler just wouldn't look right to me. These 'fillets' are for the bottom inside corners of the motor well to:
A) Add some strength to the corner joints.
B) Prevent or minimize 'pooling'of water
C) Provide an additional layer of water protection
D) Look attractive as well be functional
E) All of the above
Step One - Run some pieces of left over Red Oak hardwood flooring through a router table using a 3/8" cove bit, giving me a 3/4" diamer half circle 'fillet'. Using the 'groove' edge of the hardwood flooring allowed me to route the 'fillet' in one pass without having to 'hog out' too much material at one time.
Step Two - Run the routed edge of the piece of hardwood flooring through a quick pass on a table saw.
Step Three - Run the piece of hardwood flooring through two passes on another table saw to cut the 'back sides' of the fillet to match the angle between the sides and bottom of the motor well.
NOTE: In this photo all you see is the 'remainder' of the piece of hardwood, the 'fillet' having been 'cut out'.
A photo of yet another 'dry fit' with the 'fillets' in place. At this time I have also cut out and 'dry fit' the vent that will be going in the front of the motor well. The 'fillets' were eventually 'poxied' in place using 3/4" dowel rod wrapped in parchment paper to get the 'sharp' edges of the 'fillet' tight to the bottom and sides.
Here's a shot of the two motor well sides removed from the 'dry fit' and now drilled for cable routing. Here you can clearly see the two blind dadoes cut into the sides to accommodate the bottom and front.
In the far left of the above photo you can see I had a little bit of fun and made a 'cover plate' or 'escutcheon' out of a scrap piece of white oak to cover the rubber boot flange. This is the exit point for the motor's electrical harness and the fuel line.
On the far right are the two 'waterproof' flanges that will accept a rubber 'sleeves' and a compression nut to guide the motor throttle and steering cables out and through the transom side.
The remaining flange and grommet are for the exit of the steering cable.
THIS WAS MY FIRST MAJOR OOPS
I was enjoying being able to cut all these holes with the parts on a drill press, not in a boat, and knowing that I had figured out all the routing when I 'mocked up' the entire transom/motor well.
But having learned the hard way, too many times, I have become an adherent to the rule:
"Measure twice - Cut once"
In this regard I went up to the motor on a stand in our family room to double and triple check where the center of the tilt tube for the motor was with respect to the top of the transom, PRIOR to cutting that hole.
Upon transferring those same said measurements to the dry fit so as to accurately locate the 2" rubber boot I had for that application I was dumbfounded when the center line for the tilt tube came to exit the side of the motor well less than 1/4" below where the underside of the deck will be!!!!!!
Eventually the shock wore off and I realized that between the transom 'mock up' and actual construction I had done further research and decided to raise the transom height from 15" to 16 1/2", without considering the fact that this also raised the exit point for the steering cable.
Think, think - scramble,scramble - mumble,mumble - scrounge,scrounge.
Noticed the two transom drain plugs I had originally ordered and had decided not to use. They were white nylon drain tubes with no sealing flange on one end and I just wasn't happy with them when I got them so I had ordered copper 'flare' type drain tubes.
Since it was already pre drilled and countersunk for screws, I severed the flange from the nylon tube on the band saw, cut a straight line across clipping part of the outer circle of the flare so it could sit 'tight' to the underside of the future deck. Good so far but would like some type of 'seal' or 'vibration' isolation.
Think, think - scramble,scramble - mumble,mumble - scrounge,scrounge.
Found 2 old rubber grommets from a former life as an automotive mechanic. Drilled a 1 3/8" hole as an exit for the steering cable so there was just a sliver left at the top of the hole. Then drilled out the inside diameter of the 'flange' so the rubber grommet would fit in the flange, and voila, hopefully a decent save for an oops.
Here's a close up of the 'fix'.
The inside hole in the rubber grommet has yet to be 'enlarged' to accommodate the steering cable. I'm counting on being able to get about 1/2" of 'drop' from the steering cable between the end of the tilt tube and the side of the transom, a span of close to 12".
Next I fabricated the transom knees, yes that's plural. Having a slab transom means not wanting to have any unwarranted or avoidable fasteners showing on the pretty side of the transom.
To that end I decided to use my 'transom eyes' to do double duty, and as it turned out, to do 'triple' duty.
For transom eyes I am using some 316 stainless steel u-bolts. These u-bolts are used as the 'mechanical' fasteners for the transom knees, avoids the use of additional fasteners, and provides some extra reinforcement to the 'slab' of a transom (in that each leg of each u-bolt penetrates through a different section of the horizontally divided slab transom).
Since I opted to somewhat shorten my transom knees to keep them below the motor well I felt that adding an extra knee would compensate. I also need the two knees to provide a secure backing for the 2 'transom eyes'/u-bolts.
Here's a close up of the transom knee during a 'dry fit'. The u-bolts I really wanted to use were not available in a length sufficient to go through the transom and the knee. I therefore used a fostner bit chucked into a drill press to 'rabbet' out a recess for the the thick u-bolt plate and nuts.
In as much as the 'grain' between the two sections of the transom slab is noticeable on the inside of the transom, I was able match the grain up pretty darn well on the outside of the transom.
Having 'dry fit' the knees I could then use drill press and fostner bits to drill the holes through the transom and the knees. I then drilled these holes 'oversize' and back filled them with 'poxie' so that when I re drill them to the actual finished size there will be a 'sleeve' of 'poxie' surrounding the 'penetration'. I did this to both the knees as well as the transom, including the holes in the transom for the motor mounting bolts
As for the motor well drain tubes I did not bore the holes for those oversize. A little voice inside me head felt more comfortable with the narrow flare of the copper drain tubes bearing directly against the white oak.
What I did do, however, is provide secondary water infiltration protection for the drain tube via an alternate method. Through experimentation I found that a 1/8" round over bit fit the underside of the tilt tube flare to a tee. I also discovered that by setting the 1/8" round over bit 'proud' of the router base plate I created a recessed shoulder for the flare drop into perfectly. This causes the outermost face of the drain tube flare to be flush with the face of the transom, that way I can 'poxy' and fiberglass over the flared face.
This I felt was another advantage to building the transom/motor well assembly before the boat was 'righted', being ablel to use a drill press for all my boring needs in the transom.
In my continued pursuit of detailing this thing to no end I had to figure out how to cut the drain tube to the correct length to ensure that, once installed and flared, the flares would indeed sit in the recessed shoulders I had created. To this end I 'sacrificed' an extra drain tube I had ordered and flared it with the proper tool without installing it. I then measured the difference in height between an unflared and flared tubes to calculate the decrease in length caused by flaring. This I did by 'stacking' feeler gauges from my former life as an automotive mechanic, and if you're interested, it came to about 0.075".
I should note here that one of my pet peeves in all the boats I've owned is that the bottom of the motor well drain tube is always an infuriating bit above the bottom of the well itself, leaving that annoying bit of water sitting there frustrating one, even if that's only because one lets it frustrate him. This is as it must be if the drain tubes are installed 'after the fact'.
But what if you install the drain tubes before building the motor well? You can get the inside of the drain tube essentially flush with the top of the motor well bottom. Not only that but you get the advantage of those cute little 'fillets' you made actually directing the water to the drain tube and eliminating that tiny little 'dead' corner.
The bevelling of the transom edges is simply done with two tapered router bits. One with a 12 degree bevel for the bottom edge per plan specs and one with a 10 degree bevel for the side edges per plan specs.
The 1/2 sheet of ply I used for the transom mock up got clamped to the actual transom and routed with a bearing straight cut bit to duplicate the profile from the actual transom to the template.
That ply template then got spaced out from the inside of the transom and clamped then it was a straight forward process to rout in the bevel. leaving the outward face of the transom intact.
Then all the surface area of the transom/motor well assembly was fiberglassed and epoxied, then epoxied again, and finally sanded smooth as a babies face.
I then created a guide or template jig with 'patterns' for both keel and batten notchs, loaded the router with a 'collar' to follow the jig and a straight cut router bit. I took several passes, continually increasing the depth of cut on the plunge router set up, but slowly and surely all the notches were cut out. With the template all the notches are extremely consistent in dimensions for 'snug' fitting to the various members later.