How do I remove Fishmaster Deck?

[meerkat]

I need to remove the decking on my 2001 Fishmaster 176 to get at damaged beams and leaking rivets.

Does anyone know how the side decking is attached? (Side decking covers the compartment filled with foam)

The middle deck is just screwed down but the side deck is covered with vinyl so I can't see how it is attached. It looks looks like it is plywood pop-riveted down through a plate and then to the structural member in the front of the picture (running fore and aft). The seat pedestals also seem to be attached to the plate. How is it attached to the side of the boat? There are screws holding the AL sheet sides to the plywood deck in the back of the picture. Is this all there is?

Many thanks for any input.

 

[Rickairmedic]

Re: How do I remove Fishmaster Deck?

Meerkat Most of the TinCans the deck is held in with rivets but yours is alot newer I would try the screws and see what happens but there may be rivets under the vinyl you cant see.


Rick

 

[meerkat]

Re: How do I remove Fishmaster Deck?

Rick - it was rivets under the aluminum holding the side decks down - but I had to take the side moldings off first (don't know the correct nautical term). You can see the side molding in the top of the picture - the decks run underneath the molding.

Glad I did as there was a lot of water in the foam & the back of the deck up against the transom was not draining into the bilge (blocked with foam) so the water was pooling. For foam that is not supposed to hold water there was a lot of it around! No damage yet but it would have been a problem eventually.

I will be really careful when I replace everything to make sure I have proper drainage.

Thanks!

 

[meerkat]

Re: How do I remove Fishmaster Deck?

oops! I meant to say rivets under the vinyl holding the side decks down...

 

[Gnarly]

Re: How do I remove Fishmaster Deck?

hows that repair coming anyways, post some pics up if you can.

 

[meerkat]

Re: How do I remove Fishmaster Deck?

Gnarly - I have all the decks & foam out so I now can see the entire frame.

I have heard of a few other guys with exactly the same problem with this boat so I will take some pictures and post because you cannot see the real problem untill you remove the decks & foam. The cracked welds and loose rivets we discussed before are a symptom and not the cause of the problem.

There are two beams running forward of the bulkhead that we discussed before (that you cannot see till you remove the deck). These beams are pop riveted to a piece of marine ply that in turn is pop-riveted to the bow stringers. Well these beams are actually broken right off. IMHO there is a design weakness in this boat. Difficult to explain without the pictures but essentially the frame in the back 2/3 of the boat is not connected to the bow in any substantial way & in big water this allows excessive flexing of the bow as you plow through each wave. Eventually this sets up the fatigue and cracking.

I am figuring out how to repair and beef up the frame so I get better frame continuity between the back 2/3 of the boat and the bow. I will post pics of what I come up with. It is going to take more than the extra bulkhead we discussed before.

Again thanks for the input.

 

[Kainon]

Re: How do I remove Fishmaster Deck?

Do you think it might be a tensile strength of the rivets? I used alum when replacing a few broken ones on mine, where I thought about SS ones, but I didn't want an issue with dissimilar metals.

 

[Gnarly]

Re: How do I remove Fishmaster Deck?

Hey Meerkat
Im glad you got the deck up but sorry to hear there are more issues than you thought with it. I am interested in seeing the pictures but am currently on a course and will be travelling over the next few days so if I dont pipe up its only because Im on the road.
It'll be interesting to see how they put this thing together, rivets are designed to work primarily in shear not tension and riveting to wood doesnt make any sense at all,
Makes you wonder what goes through some people's heads when they do stuff like that and what kind of engineering and testing actually goes into them or do they just whack something together and market it. These boats are built cheaply there's no denying it but so is just about every other thing that drives, floats or flies today.

 

[meerkat]

Re: How do I remove Fishmaster Deck?

I think I have figured out the problem with this boat...

The way it was designed, you are supposed to have a beam created with the ply deck forming the top of the beam; the hull forming the bottom of the beam; and then a series of ribs & stringers inbetween holding the top and bottom of the beam together. Then you foam inbetween the plywood and the deck to glue the whole beam together. Yes - I know the foam is for floatation, but it also adds strength to the beam. Problem is that the ply is not one solid piece. It is in 5 seperate pieces (see 1 - 5 on picture) and none of the pieces are joined together in any way! In particular pieces 2, 3 an 4 are totally independent of each other; right where the tapered sides of the bow join the parallel sides of the boat. This ply join is open - it is not joined to the rest of the ply and each piece is thus free to move independantly of the rest of the ply decking. This creates a stress riser just where all the problems have surfaced. It is kind of like taking an I-beam and cutting through the top of the "I" which compromises the integrity of the I-beam.

So every time I hit a wave what is supposed to happen is that as the bow wants to move up, the "beam" lifts the whole of the boat with the bow, but instead the stress riser ply join localizes the stress at the join and allows the bow to flex upwards relative to the rest of the boat. If this happens once, no big deal, but after numerous repetitions, the rivets start to loosen and eventually the welds crack.

In addition, there was no foam between the deck and the hull in the forward section of the boat - again compromising the strenght of the beam.

What I am doing is getting the frame (ribs and stringers) re-welded and riveted with some additional bracing. Then I will cut the new decking on a different pattern. I will have solid ply over the high stress areas and move the joints much further back in the boat (lower stress area). In addition I will butt joint the ply so that structurally the ply is essentially one solid piece. In addition I am going to add structural foam in the forward part of the boat (4lb). Hopefully that will fix the problem.

Make sense?

 

[70HorseForce]

Re: How do I remove Fishmaster Deck?

I just recently replaced the decking in my 1995 Fishmaster170. It was not an easy task.I too noticed the foam blocking the water drainage. While I had it apart I decided to move the consoles and windshield forward to allow for more room to fish out the back. Got in way too deep having to cut down both consoles to allow for the live well clearance. But once I started I was committed. Once my project was done and I was able to get it on the water I was plesantly surprised at how good it handled and I was still able to get plenty of lift on the nose when trimming the motor.

 

[Gnarly]

Re: How do I remove Fishmaster Deck?

Hows the repair coming?
Hopefully good!!

 

[meerkat]

Re: How do I remove Fishmaster Deck?

Did not do much over the winter - too damn cold! But I have all the rivets whacked down tight - no leaks now. I also got someone to weld all the cracked joints. My son-in-law has a machine to bend aluminum plate so I am making up a series of brackets and reinforcing by riveting plate sandwiches across all the welds. Also welded in some additional bracing across the area where I had the problems. I can get to both sides so am using structural rivets not pop-rivets.

They totally did not build this boat to handle lake erie. It is really obvious with it all apart that the problem was when you hit a wave the force causes the bow to flex back slightly towards the stern - this in turn translates into a sideways outwards force on the boat gunwales that pushed the sides out and cracked the welds. That is what I am reinforcing to make sure the sides stay connected

Still got a lot of work to do but I want to do it right. Hopefully I will have it done before the summer - but may miss some of the spring fishing. Have to go steelheading in the rivers instead!

Thanks for asking!

 

[meerkat]

Re: How do I remove Fishmaster Deck?

Gnarly - I am going to take some pictures today and post. I would appreciate our comment. in the meantime - do you have any thoughts on what aluminum to use for the brackets and bracing? I am figuring 5052 but also thinking about 6061? I will be bending it into brackets, riveting across welds and strengthening the beams.

 

[meerkat]

Re: How do I remove Fishmaster Deck?

Okay - here are the pictures.

First the diagram. The black down arrow shows the wave force on the boat which is translated into a resultant outward force shown by the horizontal black arrows.

First picture shows the same thing with red arrows indicating the forces. Blue arrows show the cracked welds and the black circles the popped rivets. The third (most forward) cross brace is a new one I added - so you will see there was very little to counter the sideways force and the welds cracked and the rivets popped.

Second picture shows the center "box" repairs so far. Red circles show the new/repaired welds. In the picture there are two north south beams on either side of the keel. The boat came with a join in these beams near the top of the picture. That was welded up as shown with the red circles on the beam. The blue circles show bracing added across an area that had been flexing and had fatigue cracks. The green circle shows the additional bracing added. I intend to add cross bracing as shown in purple to hold the sides of the center box together against the lateral force.

Third picture shows new pieces added (red X). The red circles show the welding across the north south members. The blue lines show the additional bracing I intend to add that will reinforce across the welds and hold the sides of the box (boat) together.

Fourth picture shows the bow bracing added to help stop the translation of wave force into outward force.

Hope this makes sense and I welcome any comment & suggestion. I do not want to put it all back together and land up with the same problem!

Thanks!

 

[Gnarly]

Re: How do I remove Fishmaster Deck?

I'm glad to hear your finally having some success getting it figured out, there is a fair bit of difference between the two alloys

5052 H34 tensile is 38kpsi, yeild strength 31Kpsi and ultimate shear strength is 21 Kpsi the H indicates strain hardened with manganese and silicon alloy

6061 T6 stacks up 45kpsi tensile, 40 kpsi yeild strenghth and 30Kpsi ultimate shear strength T indicates thermally treated (solution heat treating) and its alloyed with silicon and magnesium

If you could buy an existing 6061 T6 extrusion that would work for your most critical areas (angle , channel, tee , I beam) thats the way I would go and use 5052 doublers to reinforce less critical areas, there is no law that says you cant place doublers on the inside of the hull skins and use flush 100 degree countersunk rivets for a still smooth outer hull. If you can, try to use solid rivets in your repair areas put in wet with a sealant if you cant use a good structural pull rivet and try to be as straight on to the work with the puller as possible, sealant is a good idea as well.

 

[Gnarly]

Re: How do I remove Fishmaster Deck?

looks like a well thought out repair scheme, I personally would be tempted to put some L bracket doublers in the blue weld repair areas (big ones) to tie it into the main structure riveting to both pieces for added insurance and the hull possibly adding some diagonal bracing in order to strengthen it further, is there some way you could tie the bow plate repairs into the extrusion in the keel in the form of a stem like a wooden boat? even if it was two parralel extrusions bolted / riveted / welded from the two plates to the center beam back in the reinforced box beam area and gusseted together? I'm just wondering if it may transfer the forces to the structure of the boat and reduce the bow flex that appears to be busting everything up.

 

[meerkat]

Re: How do I remove Fishmaster Deck?

Gnarly - appreciate the input.

The internet is a wonderful thing so I can get pretty well anything and have it shipped - so I will look for the extrusions you suggest. speedymetals.com has pretty well everything I need and I will not have to mortgage my house to pay for it...

One question on the different grades though - which would be better if I need to fabricate (bend) my own angle brackets for a non-standard angle where an extrusion (standard angle) would not work? The 6061 obviously is the stronger of the two but I do not know what happens after you bend it. Like I said, my son-in-law has the equipment for bending - I just need to pick the right alloy.

Thanks again

 

[Gnarly]

Re: How do I remove Fishmaster Deck?

5052 would do fine for bending to suit or 5086, like wood sheet aluminum has grain and its imperitive you bend across the grain as much as possible not with it as it will just crack on you especially if your going to make 90 degree bends , make sure to watch the bend radius and use radius blocks in order not to impose more stress to the material than nescessary.

 

[meerkat]

Re: How do I remove Fishmaster Deck?

Gnarly - do you have any thoughts on using stainless bolts versus solid aluminum rivets?

In some cases I am going to have to draw plates together and it just seems it would be easier to use a stainless bolt with a nylon lock nut. I have access to a compressor, pneumatic hammer etc. so setting the rivets is not a problem - it just seems that in some cases I would get a better joint integrity with the bolt versus the rivet.

I have everything prototyped out in poster board and masking tape - now I need to convert it to Aluminum and install it.

 

[Gnarly]

Re: How do I remove Fishmaster Deck?

Nothing wrong with using stainless fastners to pull something together, or even hi lock rivets which are essentially a pan headed bolt with a tension or shear collar depending on the application, just use a stainless washer against the stainless bolt head/nut and an aluminum washer against the skin/extrusion to make the washers sacrificial in the event of galvanic corrosion if you have the room. Rivets are light,cheap and easy and thats the biggest benefit to using them , nuts and bolts certainly have their place especially when holding structural members together.