2024 2100SE Radar mount

[Double Hall]

My Parker Dealer has done a dozen or more just the way I am planning on doing it. They stopped having their installers weld stuff because on a brand new t-top frame it looks like absolute hack garbage as I saw one of those too. It looked like a burned in piece of raw aluminum.
There will be two layers of King Starboard, the second layer will be under the dome and the canvas adding just a slight rise to the canvas, A 4 degree wedge will be above the canvas and the whole thing sandwiches together nicely. Both layers of the Starboard will be rounded to a 1/4" radius on a router table ( in my woodworking shop) like I've done to teak, mahogony, oak, and a dozen other hardwoods. The installations I just saw a couple of days ago down on the dealers dock where they also run a marina were probably strong enough for me to stand on the dome if the dome actually would take it.
Seems like there is a clear mindset on what is the right way to do this on this forum with little creativity. Have you read the previous post from the mechanical engineer? Seems to me that welding has zero forgiveness and may not be the cats meow everyone thinks it is.
Has anyone giving this advice actually seen a 2023-2024 t-top frame a provided by Parker? There are two flat pieces of aluminum welded in from the factory 22" apart that are there just for this purpose and to add an electronics box to the rig.
Take a double layer of 1/2" Starboard and try flexing or bending it.

Why did I even ask?

I'm out.

Don't go anywhere... I just responded to your Hull Truth post as well. I'm in the same boat and want to take the same approach as you. Are you fabricating the wedge and board yourself? I'm very interested. Take to DM if you don't want other feedback.

 

[pelagic2530]

My Parker Dealer has done a dozen or more just the way I am planning on doing it. They stopped having their installers weld stuff because on a brand new t-top frame it looks like absolute hack garbage as I saw one of those too. It looked like a burned in piece of raw aluminum.
There will be two layers of King Starboard, the second layer will be under the dome and the canvas adding just a slight rise to the canvas, A 4 degree wedge will be above the canvas and the whole thing sandwiches together nicely. Both layers of the Starboard will be rounded to a 1/4" radius on a router table ( in my woodworking shop) like I've done to teak, mahogony, oak, and a dozen other hardwoods. The installations I just saw a couple of days ago down on the dealers dock where they also run a marina were probably strong enough for me to stand on the dome if the dome actually would take it.
Seems like there is a clear mindset on what is the right way to do this on this forum with little creativity. Have you read the previous post from the mechanical engineer? Seems to me that welding has zero forgiveness and may not be the cats meow everyone thinks it is.
Has anyone giving this advice actually seen a 2023-2024 t-top frame a provided by Parker? There are two flat pieces of aluminum welded in from the factory 22" apart that are there just for this purpose and to add an electronics box to the rig.
Take a double layer of 1/2" Starboard and try flexing or bending it.

Why did I even ask?

I'm out.

I’m looking forward to seeing how this turns out.

I’m not sure I’d take the concept of “this is the way the Parker dealer does it” as gospel. I’ve seen dealers do some pretty shoddy work in the interest of getting boats in and out of the shop quickly.

The logic for using the welded in aluminum frame is sound. Generally speaking, it’s the long-standing preferred way to attach things to a t-top, and there’s a reason for that. But with the smaller, lighter domes available now, and the fact that you’re not adding an extra hunk of metal in the form of a pedestal, you’ll probably be ok with using the thicker plastic. Keep in mind that the 4 degree wedge piece on top isn’t going to really give you much in the way of support- most are only about the footprint of the dome itself, which won’t increase the rigidity of the overall span between the supports unless you make it approximately the same overall size as the plate on the bottom, which would make for a very large top
wedge surface that I would think would look… odd. Perhaps I’m just not envisioning your plan correctly.

FYI, welded aluminum supports SHOULDN’T look the way you’re describing if it’s done by a skilled welder at a proper shop- again, leading me to possibly question the work coming out of your dealer’s rigging shop. Regardless, I think your logic is workable and I’m curious to see how it all comes together for you.

 

[Puck-n-Fish]

welded aluminum supports SHOULDN’T look the way you’re describing if it’s done by a skilled welder at a proper shop

 

[Westerly Fluke Guy]

Don't go anywhere... I just responded to your Hull Truth post as well. I'm in the same boat and want to take the same approach as you. Are you fabricating the wedge and board yourself? I'm very interested. Take to DM if you don't want other feedback.

I replied to you over at THT. These guys over here are one trick ponies.

 

[Westerly Fluke Guy]

Hi. I'm mech engineer.Just finished similar project for a friend's electronics upgrade on a cc dv t top. No idea if following helps or not. You can build this any way that works for your combo of equip. and existing layout of cross bars of your roof- just need to think it through structurally. Prev poster is absolutely correct in that the loads get high when you mount heavy stuff at this height, but it's not difficult cult to figure out a clean looking ng solution. Bolting can be stronger or weaker than welding and vice versa all depending upon the design. Welding tends to result in a clean OEM look and take less volume, but bolts and plates worked out great for us, and as I said, strength is a matter of design. Aluminum aircraft bodies are riveted not welded for a reason. Fasteners can have a certain degree of give whereas welds are extremely rigid and can crack. Same thing in a bridge, many joints bolted.

As far as starboard or any plastic structural member goes, it depends on the span and if there are existing members to which it will be fastened vs it spanning a large open area. I'd guess that if you are planning the plastic plate to span an open section of more than maybe 12 inch and it has the full load of a dome scanner and metal adapter stantion then I'd go to 3/4 thick. Remember that the stiffness or the amount of deflection increases alot when you make a plate thicker. Twice the thickness results in 8x less deflection, whereas if you double the width of the plate the deflection halves, all assuming the same load. That said, if the plate is under the canvas then the thicker it is the more likely, over time edges and corners will sever the canvas.

My friend bought a short metal angled adapter that sits between the dome and the t top frame. If I remember correctly the lower flange of that adapter had 4 holes which we carefully positioned and thru bolted existing cross members. The adapter sits on top of the canvas and he put silicone caulk between the canvas and the lower flange of the adapter at the locations where he drilled thru the canvas.

You MUST thi nk through any thru holes i n existing members because these will definitely compromise the strength of those members and lead to stress cracks eventually if not done carefully. Use smallest diameter, as few as possible and choose thru location carefully.

Another way to do it in a stronger way would have been to use the same adapter mounted over the canvas but NOT to drill thru cross members, rather fashion an interior plate that sits on the interior ceiling below the existing cross bars and then you clamp the adapter plate to the interior plate and effectively sandwich the existing members thereby avoiding drilling thru.

A third design is to solidly bolt the stb. Plate to the frame where the area of the plate can be cut to find strong mounting bolt locations to the frame and then the scan er and equip is easily bolted to that plate. For example, you run a long plate fully across the top, flexed and then fastened to the two pipes that run fore aft on either side of the top.
This allows mounting of multiple units like a pa, dome and gps unit which can then be situated at the exact place to give a nice look. This means more plate. In my friend's case he ended up mounting gps to the dome adapter unit, so did not really need such a big area plate. One major benefit of this approach is that if done cleverly, you can avoid any holes in the canvas. I avoid popping holes in a continuous barrier membrane like a t top if at all avoidable. Another downside is that the plate is visible since in that approach it sits over the canvas, but if color matches that of roof material it will look just fine in my opinion.

Definitely buy good sst bolts washers etc from a real supplier and figure out exact min adequate length as prev.poster said. A nice finish on interior is to use cap nuts, but to do that you got to really get the length spot on. A few extra washers can help. Life is way too short to go cutting sst. Bolts. It very tough stuff. Hacked protruding long bolts not spaced evenly are the best way to make it look like an amateur low budget aftermarket install. And dangerous if you're ever getting your head up there for maintenance

Hard to advise exactly without seeing your setup, etc. Every situation has unique elements and owner desires to consider.

If u post a pic or provide more details I'm happy to chime in if it's useful.

The other pia for us was making sure we could route the coax cable and wiring inside existing cross tube and then down one of the four uprights. It impacted the exact location and thru bolt locations.

Photos sent via PM.

 

[mbaltay]

Photos sent via P

Nice, brand spanking new.sweet.

Let me know if you want more specific suggestions. Alot depends on your detailed info. Aesthetics equip. Color scheme etc. I assume the second picture showing the trees is from the cockpit looking forward off the bow.
It's hard to be sure, but from what I can tell, the two aluminum flat stringers are already pitched down. Does your scanner use coax cable, and if so where do you plan to run it down to the console?

It's worth double checkiNG the pitch angle. That set up looks to me to be more like 1-2 degrees forward between the stringers and the roof plane. A delta of 3/4 inch over 36 inches equates to about 1.5 degrees, if my trig. is right. I have to believe it should be setup for a standard angle , but I'm pretty sure parker does not fab the Top themselves, so I would not take it for granted that the angle is correct for your setup. Fortunately it's easy enough to add subtract spacers. Or build it into final layout. Need to know the angle between top and hull plane etc.

What all are you planning to mount up top now or future, and I assume it would be in that open location which looks to be about maybe 40 inches wide and 30 inches long fore-aft?
If you send me the exact dimensions I'll calculate the thickness plastic or aluminum. I'd use. My buddy added scanner, pa, horn gps and running light, and he was particular about the final look that he thought was most cool. With the layout you have, you have a lot of choices, but got to figure that in ahead. Send dimension across from inside edge to inside edge of aluminum flat stringer plate and then the width of the plate (5 inch?) and thickness maybe 3/8?. From what I can see and I think you mentioned, the two stringers are aligned to the curve of the cross pipe.

This looks ideally suited to slap in a cross member as you are planning cleanly attached to the stringers.
The cross member which I think you are planning would then take to the curve and this provides a really nice clean simple install which is already set to the correct pitch, and which you can make the plate area any way you want to fit current and or future equip. The slightly arced shape are f the cross member is a structural advantage like u see on a bridge or a long tractor trailer bed that is already arced.

If it were my boat I'd calculate the pros and cons of using plastic or aluminum or sst cross member material, for price, look and install ease. Do you want it to match the other alternative shiny members or be black to hide it? Thru bolts with the right hardware
Would look clean enough for my taste. If you wanted to make it look factory, then you could simply weld in a plate from the underside , probably avoiding any need to remove the top and do that in the field with a standard portable welder. The final look of weld will be mostly dependent on the skill and quality of the weld. Everything has pros cons. Weld is permanent. In case of doing it on interior below the plates it eliminates need to remove top canvas, but is then somewhat more visible. The other thing is that your t top is nice polished aluminum maybe even treated with anti oxidizer. If you use aluminum bolted or welded, you'd want to polish and finish it to match. Metal cross member has structural size advantages. Big hassle with welder is finding someone willing to come to your site and do a nice job for a small job, also if you do not pre bend aluminum plate you'd have to clamp it to the stringers and it will forever causeceach side to be in rotational stress and tgst is exactly the type situatuon ehete youll start to crack tbe welds, not the new ones, rather the existing stringer to pipe. That said it's no big deal to bend al plate by hand

You can get a 4ft x 3/4 x 4 inch starboard plate from McMaster for a out 40$. (It's essentially HDPE and claims moisture resistant, but I'm dubious it's anything more than hdpe.), But the 4 inch width is a bit narrow for my gut instinct, id have to calculate it. My guess is that the dimension across the top from outside to outside is right around 48 inch. I worry less about motion fore aft, rather side to side give. Plastic plate or anything bolted has advantage of being able to adjust tilt angle if you need later. It has advantage of being available in black so blends in without paint and very durable.

To me at first glance, I don't see the advantage of a top plate, vs the extra cost, work and holes in the canvas. Happy to elaborate. It depends a bit on exactly what u r mounting and how you plan to waterproof holes. If the advantage is somehow for waterproofing or tear mitigation, then you can always add a local plate just the footprint of the scanner. If my rig, I'd not have any top plate, unless after laying it all out there is some unknown benefit that I can't think of now. Structure is not. I'd probably bolt in a pre bowed al plate maybe 5/8 thick x the width of the dome base, use 8 countersink sst flat socket heads maybe 4 at each side and look into McMaster to find some sort of flat t nuts or something that can be torqued but that will in no way grab at the canvas. Id definitely figure out if I wanted the upper surface of the new cross bar to be below or flush with canvas. If it's lower and you pull it down in center at dome then u just made an inverted umbrella and you'll have a puddle up there non stop. Too much upwards and put stress tears on t top. Neither good. Argues strongly to stick in a thin rubber or foam. Like you said, definitely rounded edges. I think the other advantage of the way that is set up is that then the coax cable runs along the top of the cross member and maybe directly down one of the upright tubes. Based on my buddy's install, avoid bends.. then you simply drill tap a few holes into the top of the al plate to attach a few cable clamps, but do not drill through so invisible from below. #10 or 1/4 dia sst. It's a toss up vs. Maybe 8-12 inch wide x 3/4 hdpe. The big diff to me is the added volume vs the black blend, so in the end really aesthetic preference trumps IMHO. Please do not hold me to those dims as anything more than educated guesses.

Sorry if you already knew all this of are ahead of me, or if this is overkill. I can do alot of this in my head so I go through all the details without a lot of time and the **** I tend to do usually comes out sweet at the best price and stuff I don't need other people involved, except selectively. You happen to be lucky that I enrolled in the forum while helping buddy so I just happen to have my mind on this right now. Best

MB

 

[Westerly Fluke Guy]

Nice, brand spanking new.sweet.

Let me know if you want more specific suggestions. Alot depends on your detailed info. Aesthetics equip. Color scheme etc. I assume the second picture showing the trees is from the cockpit looking forward off the bow.
It's hard to be sure, but from what I can tell, the two aluminum flat stringers are already pitched down. Does your scanner use coax cable, and if so where do you plan to run it down to the console?

It's worth double checkiNG the pitch angle. That set up looks to me to be more like 1-2 degrees forward between the stringers and the roof plane. A delta of 3/4 inch over 36 inches equates to about 1.5 degrees, if my trig. is right. I have to believe it should be setup for a standard angle , but I'm pretty sure parker does not fab the Top themselves, so I would not take it for granted that the angle is correct for your setup. Fortunately it's easy enough to add subtract spacers. Or build it into final layout. Need to know the angle between top and hull plane etc.

What all are you planning to mount up top now or future, and I assume it would be in that open location which looks to be about maybe 40 inches wide and 30 inches long fore-aft?
If you send me the exact dimensions I'll calculate the thickness plastic or aluminum. I'd use. My buddy added scanner, pa, horn gps and running light, and he was particular about the final look that he thought was most cool. With the layout you have, you have a lot of choices, but got to figure that in ahead. Send dimension across from inside edge to inside edge of aluminum flat stringer plate and then the width of the plate (5 inch?) and thickness maybe 3/8?. From what I can see and I think you mentioned, the two stringers are aligned to the curve of the cross pipe.

This looks ideally suited to slap in a cross member as you are planning cleanly attached to the stringers.
The cross member which I think you are planning would then take to the curve and this provides a really nice clean simple install which is already set to the correct pitch, and which you can make the plate area any way you want to fit current and or future equip. The slightly arced shape are f the cross member is a structural advantage like u see on a bridge or a long tractor trailer bed that is already arced.

If it were my boat I'd calculate the pros and cons of using plastic or aluminum or sst cross member material, for price, look and install ease. Do you want it to match the other alternative shiny members or be black to hide it? Thru bolts with the right hardware
Would look clean enough for my taste. If you wanted to make it look factory, then you could simply weld in a plate from the underside , probably avoiding any need to remove the top and do that in the field with a standard portable welder. The final look of weld will be mostly dependent on the skill and quality of the weld. Everything has pros cons. Weld is permanent. In case of doing it on interior below the plates it eliminates need to remove top canvas, but is then somewhat more visible. The other thing is that your t top is nice polished aluminum maybe even treated with anti oxidizer. If you use aluminum bolted or welded, you'd want to polish and finish it to match. Metal cross member has structural size advantages. Big hassle with welder is finding someone willing to come to your site and do a nice job for a small job, also if you do not pre bend aluminum plate you'd have to clamp it to the stringers and it will forever causeceach side to be in rotational stress and tgst is exactly the type situatuon ehete youll start to crack tbe welds, not the new ones, rather the existing stringer to pipe. That said it's no big deal to bend al plate by hand

You can get a 4ft x 3/4 x 4 inch starboard plate from McMaster for a out 40$. (It's essentially HDPE and claims moisture resistant, but I'm dubious it's anything more than hdpe.), But the 4 inch width is a bit narrow for my gut instinct, id have to calculate it. My guess is that the dimension across the top from outside to outside is right around 48 inch. I worry less about motion fore aft, rather side to side give. Plastic plate or anything bolted has advantage of being able to adjust tilt angle if you need later. It has advantage of being available in black so blends in without paint and very durable.

To me at first glance, I don't see the advantage of a top plate, vs the extra cost, work and holes in the canvas. Happy to elaborate. It depends a bit on exactly what u r mounting and how you plan to waterproof holes. If the advantage is somehow for waterproofing or tear mitigation, then you can always add a local plate just the footprint of the scanner. If my rig, I'd not have any top plate, unless after laying it all out there is some unknown benefit that I can't think of now. Structure is not. I'd probably bolt in a pre bowed al plate maybe 5/8 thick x the width of the dome base, use 8 countersink sst flat socket heads maybe 4 at each side and look into McMaster to find some sort of flat t nuts or something that can be torqued but that will in no way grab at the canvas. Id definitely figure out if I wanted the upper surface of the new cross bar to be below or flush with canvas. If it's lower and you pull it down in center at dome then u just made an inverted umbrella and you'll have a puddle up there non stop. Too much upwards and put stress tears on t top. Neither good. Argues strongly to stick in a thin rubber or foam. Like you said, definitely rounded edges. I think the other advantage of the way that is set up is that then the coax cable runs along the top of the cross member and maybe directly down one of the upright tubes. Based on my buddy's install, avoid bends.. then you simply drill tap a few holes into the top of the al plate to attach a few cable clamps, but do not drill through so invisible from below. #10 or 1/4 dia sst. It's a toss up vs. Maybe 8-12 inch wide x 3/4 hdpe. The big diff to me is the added volume vs the black blend, so in the end really aesthetic preference trumps IMHO. Please do not hold me to those dims as anything more than educated guesses.

Sorry if you already knew all this of are ahead of me, or if this is overkill. I can do alot of this in my head so I go through all the details without a lot of time and the **** I tend to do usually comes out sweet at the best price and stuff I don't need other people involved, except selectively. You happen to be lucky that I enrolled in the forum while helping buddy so I just happen to have my mind on this right now. Best

MB

Measured to the outside of the two flats welded in from the factory it is 27"
I took a digital angle gauge, zeroed it at the center of the top, and checked the angle of the flats.
They follow the curve contour somewhat with the right one being about 3-1/2 degrees and the left one is around 4-1/2 degrees.
I plan on spanning it with a 1/2" thick by 10" wide piece of aluminum.
The ends at 27" will have around 1/4" clearance.
I also plan on putting a piece of Starboard on top of it in the middle area to get me up near the underside of the canvas. I will see when O get the aluminum bolted in.
After I get my material up under the canvas where it ever so slightly supports it I am installing a 5" Seaview aft leaning modular post and universal top plate.
If I need to pitch the dome down a bit I can use stainless steel spacers from McMaster.

 

[pelagic2530]

Measured to the outside of the two flats welded in from the factory it is 27"
I took a digital angle gauge, zeroed it at the center of the top, and checked the angle of the flats.
They follow the curve contour somewhat with the right one being about 3-1/2 degrees and the left one is around 4-1/2 degrees.
I plan on spanning it with a 1/2" thick by 10" wide piece of aluminum.
The ends at 27" will have around 1/4" clearance.
I also plan on putting a piece of Starboard on top of it in the middle area to get me up near the underside of the canvas. I will see when O get the aluminum bolted in.
After I get my material up under the canvas where it ever so slightly supports it I am installing a 5" Seaview aft leaning modular post and universal top plate.
If I need to pitch the dome down a bit I can use stainless steel spacers from McMaster.

I think this sounds like a great install plan that I bet you’ll be very happy with. Probably a better solution than relying on plastic to span the gap, especially with the addition of the pedestal.

If you’re so inclined, I’d love to see pictures of your final install when it’s complete.

 

[Bodick93]

Don't be an *** to people that have solved a thousand problems you've yet to encounter, W.F.G.
That's my best piece of advice about your radar mount. Peace.

 

[afitzray]

I replied to you over at THT. These guys over here are one trick ponies.

Sounds like you're upset that no one told you how smart you are for your idea so you're going to play somewhere else. Have fun.

 

[mbaltay]

Hi. I'm in germany returning Sunday.

What is the diameter of the radar coax cable, and what is your plan. ?

27 inch , means actual span is like 20 inch inside to inside. So strength not going to be a big deal at all, can go thinner.

Do not torque the flats. If bolted flat to the flat, at 4 degrees it would be two inches higher at the other side. You could run it flat and then you'd need 1/& inch spacers at the far sides. If go thinner on al plate then can bend if to match.

I'll look at this sun next n 4 u. Plan it out.
Also check the forward tilt angle now and figure out where if shims are needed and design it in. By my estimate the ramp of those flats is like 1-2 deg., But cannot know actual because t top itself may be tilted.


Bigger question where run cable so invisible from below?

MB



Depending on cable route and if u want to see it or not, might need to

 

[Westerly Fluke Guy]

Hi. I'm in germany returning Sunday.

What is the diameter of the radar coax cable, and what is your plan. ?

27 inch , means actual span is like 20 inch inside to inside. So strength not going to be a big deal at all, can go thinner.

Do not torque the flats. If bolted flat to the flat, at 4 degrees it would be two inches higher at the other side. You could run it flat and then you'd need 1/& inch spacers at the far sides. If go thinner on al plate then can bend if to match.

I'll look at this sun next n 4 u. Plan it out.
Also check the forward tilt angle now and figure out where if shims are needed and design it in. By my estimate the ramp of those flats is like 1-2 deg., But cannot know actual because t top itself may be tilted.


Bigger question where run cable so invisible from below?

MB



Depending on cable route and if u want to see it or not, might need to

 

[Westerly Fluke Guy]

It's standard Garmin radar data cable (fancy CAT 5E) with an adapter which can be removed as well as a power cable.
I have accessed the T-Top frame on the port side to mimic what the factory has done on the starboard side for nav. light, spreader light, VHF cable, and front spreader light (spare wire left by the factory.
I plan on unlacing the top enough to get on top of the framework and run inside the rectangular tubes part way then jump out to the unit.

The flats measured with a digital angle gauge are slightly under 4 degrees on one side and about 4.5 degrees on the other.
The 1/2 x 10 aluminum will be bolted up there with angled washers to fill the gap or simply just not torqued like an animal.
I went to aluminum as a base because after getting my starboard I immediately saw the flex which would occur and the fact that I have added a Seaview 5" post up top.

I will stay in touch.
Thanks for the input to date.

 

[Westerly Fluke Guy]

Sounds like you're upset that no one told you how smart you are for your idea so you're going to play somewhere else. Have fun.

Actually I got tired of the two words "weld it"

 

[Westerly Fluke Guy]

Don't be an *** to people that have solved a thousand problems you've yet to encounter, W.F.G.
That's my best piece of advice about your radar mount. Peace.

Weld, weld, weld.
Sorry but there are a hell of a lot better ways.

 

[Westerly Fluke Guy]

Do not torque the flats. If bolted flat to the flat, at 4 degrees it would be two inches higher at the other side. You could run it flat and then you'd need 1/& inch spacers at the far sides. If go thinner on al plate then can bend if to match

I have some stainless steel leveling washer sets left over from a previous boat I did some similar work to.
The flat 1/2" plate can be securely bolted to the 1/4" aluminum frame flats without stressing the flat stock.

McMaster Carr P/N 91944A430

 

[Westerly Fluke Guy]

I have decided to forego the Seaview modular raised mount as I dont want to move the all-around light and keep it simple.
Do any of you have your cables coming through a cable clam(s) outside the area of the dome?
I'm concerned about the sun baking at the cables.
Garmin domes are not very forgiving for hiding them under it and the cables are pretty robust as far as diameter and stiffness.

 

[pelagic2530]

I have decided to forego the Seaview modular raised mount as I dont want to move the all-around light and keep it simple.
Do any of you have your cables coming through a cable clam(s) outside the area of the dome?
I'm concerned about the sun baking at the cables.
Garmin domes are not very forgiving for hiding them under it and the cables are pretty robust as far as diameter and stiffness.

Use some split-loom conduit to protect the cables from UV rays. The conduit lasts a few years before it gets crispy and needs to be replaced, but it’s a 5 minute job to do so and it’s better than the cable breaking down. You can also special order UV stable stuff, but it’s pricey and hard to find in short lengths.

I prefer the Scanstrut cable glands over the Blue Sea System ones. Better quality components in my opinion, and they look nicer.

 

[Westerly Fluke Guy]

OK.
Pictures coming soon.
The Seaview raised mount and modular plate have been scrapped because I don't want to move my nav./all-around light.
I am fabricating a piece of 1/2" thick aluminum 10" wide by 27" long to span the factory cross members. The aluminum has also been radiused on the ends and top to provide a smooth surface in the case of canvas contact.
To compensate for the unevenness of the factory aluminum braces I have used leveling washers which adjust to the varying angle of the factory braces.
Leveling washers are McMaster Carr Part No. 91944A430
The canvas is black so all Starboard will be black.
I have made a piece of black Starboard 1/2" thick which is 12" wide by 16" long mounted lengthwise across the aluminum. The starboard has also been radiused 1/4" on top to allow for a smooth surface for canvas contact.
When the radar dome is mounted from the top through the Starboard and aluminum it will provide around 6" of useable space behind it for the attachment of two cable clams for the power and data cables.
Two more pieces of 1/2" thick Starboard 10" x 12" have been 1/4" radiused and attached to each other to provide a 1" high spacer for the radar dome to sit atop. The black Starboard allows for it to go almost un-noticeable against the black canvas.

 

[mbaltay]

OK.
Pictures coming soon.
The Seaview raised mount and modular plate have been scrapped because I don't want to move my nav./all-around light.
I am fabricating a piece of 1/2" thick aluminum 10" wide by 27" long to span the factory cross members. The aluminum has also been radiused on the ends and top to provide a smooth surface in the case of canvas contact.
To compensate for the unevenness of the factory aluminum braces I have used leveling washers which adjust to the varying angle of the factory braces.
Leveling washers are McMaster Carr Part No. 91944A430
The canvas is black so all Starboard will be black.
I have made a piece of black Starboard 1/2" thick which is 12" wide by 16" long mounted lengthwise across the aluminum. The starboard has also been radiused 1/4" on top to allow for a smooth surface for canvas contact.
When the radar dome is mounted from the top through the Starboard and aluminum it will provide around 6" of useable space behind it for the attachment of two cable clams for the power and data cables.
Two more pieces of 1/2" thick Starboard 10" x 12" have been 1/4" radiused and attached to each other to provide a 1" high spacer for the radar dome to sit atop. The black Starboard allows for it to go almost un-noticeable against the black canvas.

Seems like your getting there. Couple thoughts: I looked at Garmin power and data cables and they seem to be about maybe 3/8 dia. Each. If it were my ship, I'd just run the cables down the inside of the radome through your two exterior elevation plates and then 90 bend and through a channel in the interior black plate. That way you have several benefits.
No visible cabling, glands or uv exposure, fewer holes in the membrane, and then you would not see the cables inside either. I guess it depends somewhat where u run the cables down to console, but it seemed like there was a pretty good down tube right at the outside of the area where u r working. Also, from what I understand your interior plastic plate is going to be wider than the 10 inch aluminum. I presume that is to accommodate the extra 6 inch area where you plan to mount the cable thru holes. If u run the cables down inside and then between the canvas and aluminum out to the side, you can make the interior plate 10 inch and flush with aluminum, or even better narrower. Garmin does not show the four mounting hole footprint dimensions so that may be why you need 10 inches wide.

Then you ought to be able to just split that interior plate on a table saw to make it into two pieces, where you leave a gap down the middle say 1 inch wide separation between the two halves. Then you essentially have a cable runway that is like 3/4 high by maybe 1 inch wide. Cables run down interior, make a 3 or 4 inch dia hole in both top plates ( not sure exactly) gentle radius on the cables and pass them thru canvas and into the raceway. Out to the side and down al tube. The primary purpose of the interior plates is spacing between al and canvas. For that matter, why need a plate at all? Why not just four large plastic pieces maybe few inches round with your radiused soft edges, then cable just runs along the top of al plate.

This all seems like a lot of discussion, but that's the nature of doing stuff in the blog mode etc. That huge plastic plate seems like a bit overkill to me, unless im missing something or you have to mount other stuff up there. Apologize if I missed that.