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Author Topic:   Installing T-Top - Deck Fastening w/out backing plates?
anthonylisske posted 12-07-2005 05:20 PM ET (US)   Profile for anthonylisske   Send Email to anthonylisske  
Hi all,

I am installing an atlantic tower made T-Top on my whaler and I wanted to find out how people have fastened these things to the deck. I am having the boat transported to key west for a few months and I have to install the top in the next week.

Related info.
1973 21 foot Outrage
Cloth T-top

Thanks in advance

Jerry Townsend posted 12-07-2005 08:30 PM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
The loads on a T-top are the weight and the aerodynamic loads - which can far overweigh the weight. In other words, the net load can be, and will be, at a relatively low speed (underway - or being trailered) trying to lift the T-top. As such, I strongly recommend that you use back-up plates and bolts. Much better than screws - which would work well - if the load was principally downward. --- Jerry/Idaho
LHG posted 12-08-2005 03:21 PM ET (US)     Profile for LHG    
I hate to say this, but with that older model Whaler, the floor was never designed for the high withdrawl loadings from a tee top. I even know of someone who had his tee top pull out from the floor mounting on same model, while running at 25 MPH.

The problem is that these older whalers only have 1/2" x 4" plywood strips, in very limited areas, in the boat boat floor where such connections can be made. Check out the wood pad locating drawing before installing. If you don't hit those pads with motiple screws, forget about it. There is no way backing plates can be used in the floor of this boat, since you cannot get under the boat skin. "Molly" type fasteners are also not recommended, as they will "pop" the floor skin from the foam, causing soft soft spots and weakening of the boat's structural integrity

swist posted 12-08-2005 10:16 PM ET (US)     Profile for swist  Send Email to swist     
I have to agree with LHG. This is not a good idea.
Any structure which has weight at the top of a vertical member supported only at the bottom, and that weight is subject to lateral forces, will generate a very large moment which put huge stresses on the fasteners and their backing. The most common case of this is pedestal seats. You put some 200 lb guy on top of a 3' post, and he swings side to side in a rolling boat, and you can (and I have seen it) actually rip the backing plate through the deck if the deck material is thin enough and the backing doesn't cover a very large area. Whalers are the absolutely worst possible scenario for installing things like this - the small plywood in places under the inner liner is meant to secure loads which generate their sideways moments much closer to the fasteners.

As another case in point one of my older boats had a 9' radar pedestal which was through bolted with backing plates to the deck, and then an intermediate brace tied it to the side of the cabin about 4' up - there was a huge thick backing plate behind a 1/4" fiberglass wall. The radome didn't weigh much more than 25 lbs and it was effectively at the end of only a 5' post - doesn't sound like a big deal and I thought the installation was as heavy duty as it could have possibly been - but after ONE season of light offshore use, very serious stress cracks appeared in the cabin wall. It needed more side-to-side support higher up, preferably via diagonal members that formed triangles which limit the side to side movement of the load.

I would be very wary of what you are contemplating.

Jerry Townsend posted 12-09-2005 12:55 AM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
Swist - realize that there is a HUGE difference between a 200 lb person sitting on a 3' pedestal or a 25 lb radom on a 9' post - and a T-top - because the T-top is supported via four, separated, vertical supports. Attaching a T-top via four bolts and back-up plates to a 1" (or thicker) floor is satisfactory - and in fact, that is how BW mounts a T-top.

In fact, a 25 lb radom on a 9' post and attached to a 1/4 inch RFG wall 5' from the radom will not work - almost by definition - the wall is only supporting the load in one direction while that radom is moving in virutally every direction.

Now, I don't know about the thin flooring that Larry (LHG) mentions on the older boats. If that is the case, then the floor would have to be built up. And, I don't know about the raising/removing the flooring on the older boats (as Larry mentions) - as on my '96 17 Outrage, the floor can be raised or removed. But then, I recall seeing photographs taken by some CW members renovating their older boats - and have removed the floor.

Larry also mentions another item that bears addressing - where a device/piece-of-equipment was ripped out. The point is this: make sure that all bolts/screws/etc are tight - because should they loosen up and the device can move, pound, jerk etc around - the loads on that attachment are essentially changed to impact loads and are, in essense doubled! ---- Jerry/Idaho

HAPPYJIM posted 12-09-2005 05:21 AM ET (US)     Profile for HAPPYJIM  Send Email to HAPPYJIM     
Most of the T-tops I've seen are bolted to the console also. With 4 floor attachments and 4 on the console, I would think that would hold pretty well. Cloth covering would be almost no weight to speak of. How many attachment points does it have?
swist posted 12-09-2005 07:36 AM ET (US)     Profile for swist  Send Email to swist     
" Attaching a T-top via four bolts and back-up plates to a 1" (or thicker) floor is satisfactory - and in fact, that is how BW mounts a T-top."

Your points are well taken Jerry - but it is still highly dependent on the design of the structure - I will admit my examples are worst case (single vertical member with a load on top), but even with two or four supports, there has to be enough support *somewhere* to keep the structure from racking under a sideways stress produced when the boat rolls, or a fore-aft stress produced by the boat pitching. This can be accomplished by a combination of heavy material and small diagonal braces near the top or bottom (or as someone said, tying the structure to the console somehow).

But to get back to the original point, how are you going to secure something to a 1" deck with backing plates on a Whaler?

anthonylisske posted 12-09-2005 10:06 AM ET (US)     Profile for anthonylisske  Send Email to anthonylisske     

Unfortunately, I agree with all of the points that were made! I think LHG is correct, the floor is thinner with no access to the particular mounting points for backing plates.

I have two direct mounts to the console (which was removed and replaced rock solid, so I am not worried about the console mounting) I am considering ordering two more mounting/stabilizer bars after thinking about the floor thickness and the 1/2 inch backer.

I looked at the wood diagram and I should atleast get 2 out of 4 bolts on each stanchion foot.

I wanted to mount an electronics box for a new standard horizon cp1000 chartplotter fishfinder, but maybe I will keep that else where. (I am open to suggestions)

I also agree that with just the cloth top, I should be able to mount it, but I drive the boat in excess of 50MPH most of the time and I think that I would be much more susceptable to windage and "pounding" problems than the average BW'er.

Thanks for the input and keep it coming. I am going to fiddle and plan a little more tonight when I get home.


P.S. Atlantic Towers (they just say bed in 5200 and lag bolt it)and most of my family think I am worrying too much, but I am thinking more along the lines with you guys. I have even had a couple of hours missed sleep trying to figure it out. I appreciate the input.

rtk posted 12-09-2005 11:01 AM ET (US)     Profile for rtk  Send Email to rtk     
Using 3M5200 is the way to go. My t-top hardtop is screwed and glued to the deck with 3M5200. It is also attached to the console in five different places.

I had to reattach mine last year. Plain Jane silicon was used, and all the screws did not enter the wood areas on the deck. All of the deck attachments worked free.

I mounted larger aluminum plates to the deck and then mounted the feet to that. Everywhere the t-top is attached is bedded with 3M5200.

Two seasons of use and the t-top is solid as a rock, it does not move.

If you are not confident the deck can handle the t-top, a good number of attachment points to the console will help secure the top. Just need to make sure the console can handle the loads.


LHG posted 12-09-2005 05:14 PM ET (US)     Profile for LHG    
Jerry - First of all, this hull is not built like yours, evidently. Backing plates are not an option in the floor. What we have here is the typical older Whaler hull, with nothing but foam between the boat floor and the boat bottom. BW only installed these 1/2" x 4" plywood strips where console bases and seat bases are attached, usually with #14 x 1" wood screws. Trust me, where one is only screwing into the inner skin laminate in the non skid floor, there is precious little withdrawl resistance, and the screws strip easily. BW specifically states that such screws should only be used for LIGHT loads, such as a cooler cleat, etc. Certainly not a tee top. Even transferring some of the tee top loading to the console may not work.

For an old Whaler, I think the Atlantic Tower recommendations are ridiculous, and specifically not meant for an older Whaler type hull. Under loading, the Whaler floor skin can easily be "popped" from the foam, ruining the boat's bond, the source of it's strength.

As the owner of one of these 21' boats, 1971 version, I can say that screwing into the 3/16" thick glass, non plywood backed areas of the floor, gives minimal withdrawl load holding power, if any. The same applies to any 13' or 16' hull of same vintage, blue interior.

I don't think a vintage hull like this should even have a tee-top, based on the hull's inability to carry one. I would install, like I have, the Mills Flying Top Set, for superior weather protection and no loading problems

LHG posted 12-09-2005 05:26 PM ET (US)     Profile for LHG    
Here's the Mills Flying top. Windshield and Forward shelter connect to this, giving complete weather protection. src=ph

rtk posted 12-09-2005 07:46 PM ET (US)     Profile for rtk  Send Email to rtk     
LHG is correct that the screws will not hold in a soft cored deck. In my case, the t-top was not built so the feet of the top that rest on the deck were centered on the wood area provided by the factory for such an installation.

My deck appears to be a balsa core, with wood and Whaler Board reinforced areas for securing screws and small lags. Two of three screws were not in the reinforced area, they were screwed into the cored deck. The movement of the t-top worked the screws and opened up the screw hole so much even a very large screw could not bite. The core material just cannot hold a screw well, it is too soft.

It was quite a project to correct the problem. I wanted the t-top so removal was not an option. Alot of hours later, I think it is ok. Cored decks just are not easy to work with, and very hard to reinforce after the boat is built.

As LHG states, if you cannot find a good reinforced area on the deck to secure the top you are likely to have problems with the installation. A nice weather canvas setup may be a better alternative. The boats really do look sharp with them.


kamie posted 12-10-2005 06:56 PM ET (US)     Profile for kamie  Send Email to kamie     
I have a t-top on an 18 Outrage and while it's solid and attached to the floor and the console it is a huge sail on the boat. I would not install a t-top on a boat where you couldn't reinforce the deck. The installers of the t-top on mine also reinforced the console where it attaches with wood. The other concern is the speed at which you operate the boat, hope you like going slower than 50 MPH cause your speed is going to drop and the handling of the boat will change.
raydent99 posted 12-11-2005 01:49 AM ET (US)     Profile for raydent99  Send Email to raydent99     
Boston Whaler offered a T-top option that you could order with the Super Console. This is from the 1988 Boston Whaler Specifications (2/1/88):

40" Super Console Options include:

Top-mounted electronics box (replaces aluminum frame windshield and console rail with plexiglass windshield and console side grab rails) $392

Four tackle drawers with teak access doors $364

Tee-top with enclosed communication center
Console without forward storage unit $3926

Console with forward storage unit $3926

If the boat wasn't meant to have a t-top, why would it be listed in Whaler's option list from 1988?

The tee-top option wasn't offered with the standard console...which suggests to me that it uses the 40" super console for much of it's support.

I put one on my 25' outrage cuddy earlier this year. Secured it with 4 side stanchions thru-bolted to the console, 4 very large lag screws and 5200 at each of the four bases, and the forward crossbar was thru-bolted to the front portion of the Super Console in at least 4 or 5 places.

In order for this top to come up, it has to rip the entire super console up. And the super console is screwed to the floor every few inches along it's base. Essentially, the whole floor would have to come up. And for that to happen, the cuddy cabin (which sits on top of the floor) would have to rip off.

Plotman posted 12-11-2005 10:04 AM ET (US)     Profile for Plotman  Send Email to Plotman     
Raydent - you haven't read this thread very carefully. Many NEWER whalers have appropriate wood backing in the deck, or removable deck sections that will allow the use of backing plates below the deck.

A 1971 outrage has NONE of this. Surmising that just because whaler offered T-Tops as an option on some boats in it line 17 years after the boat in question was built that it is OK to put a T-Top on thie '71 Outrage is silly.

Smallfrye posted 12-12-2005 03:56 PM ET (US)     Profile for Smallfrye  Send Email to Smallfrye     
When mounting a t- top on a '90 model OR, I had the same concerns about the 1" floor holding the lift of the top. It was a lot of work but I removed the floor and manufactured aluminum plates that I attached to the hull at the top of the foreward well and at the front of the fuel tank compartment. These plates extended under the floor where the Top was attached. After the floor was reinstalled with heavier screws than original, the assembly held the top very well. I travel 350 miles @60-65mph and run in 2-4' seas all day for over three years with no pull out or loosening of the floor screws.
This seemed to work well.
good luck
Buckda posted 12-13-2005 02:39 PM ET (US)     Profile for Buckda  Send Email to Buckda     
Again - we're talking about a '71 Outrage. These boats are very different from the 1980's Outrages and beyond.

This boat HAS MORE IN COMMON WITH A MONTAUK than the current or even 1980's Outrage hulls in terms of how the deck is constructed.

Read carefully - the earlier replies address these differences, which have a significant impact on the feasability of adding a T-Top.

I'm not saying that it can't be done, but to do it properly on this boat could require some significant modifications to the deck...a surgery that would take more than a few nights in the garage after work.

Even on the newer boats, the addition of backing plates under the deck like smallfrye describes is still a lot of work, but is probably the appropriate measure to make it work.

As for Atlantic Towers...I had a great experience with them in terms of craftsmanship and customer service, however, I don't put a lot of credence on their instructions for installation. Keep in mind that they work with a lot of different boats, and the vagaries of the Whaler construction may not allow you to follow their instructions.

Also - as part of that experience, it became clear that they didn't really plan for the "pounding" that a Whaler goes through in the original construction, requiring some warranty work to "beef" it up. I'd recommend that you talk to your designer/engineer at Atlantic and see if you can't get some reinforcement added to that structure before you put it on and wire it up. This will save you time and headache afterwards.

LHG posted 12-13-2005 02:59 PM ET (US)     Profile for LHG    
Dave - Anthony's boat is a 1973, which means it has a built in 40 gallon tank, and floor cover plate. However, in looking at the wood locating diagram for this hull, the tank cover is narrow and the boat still only has those 1/2" x 4" wood strips for mounting the console and seat. Assuming the tee top floor mounts are wider than the console, wood pads may not be available for using wood screws into the floor.

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