Catamaran Wheel House and Hardtop

Discussion in 'Wooden Boat Building and Restoration' started by pacific green, Jun 9, 2020.

  1. pacific green
    Joined: Oct 2017
    Posts: 10
    Likes: 1, Points: 3
    Location: earth

    pacific green Junior Member

    I am going to attempt to follow the plans to construct a wheelhouse on top of my Bobcat Catamaran as was laid out in Wave Runner 5 2007 http://www.999100.co.uk/wave_runner5.htm

    At the outset it all seems very easy but the more I study it the harder I seem to make it. For instance I want to increase the width of the cabin to the full 12 foot width and extend the structure to the back of the cockpit railing to create one very large open hard top.

    If I go with an open concept and avoid the cut out of the original roof then I do not have to factor in installing windows and the wind resistance is actually less.

    So I am trying to design on open frame 12 foot wide by 16 foot long open frame hard top built half on the cabin and half on the existing cockpit railing.

    Some of my biggest questions are which type of wood to use for the stringers and battens and where to source those materials in Vancouver. I think I can get away with 3/8 ply for the roof sections and will need 8 of those sheets.

    Here is the original restoration work and skinning of the cabin top.

    upload_2020-6-8_22-3-19.png
    What size of wood was used to make the roof layout and should I use the same to create the open concept hardtop? I have studied these same pictures and pictures and plans of cabins for the last couple of months. To me it looks like 1x2 and 1x4. I am contemplating using 1x4 and 2x4 construction for the hard top on 2 foot centers but this just seems wrong. I have been looking for cabin plans with not much luck.
    upload_2020-6-8_22-4-20.png
    upload_2020-6-8_22-8-1.png

    upload_2020-6-8_22-8-55.png
    upload_2020-6-8_22-11-47.png
    A framed in Doghouse starting here and extending headroom height all the way back to the cockpit railing would be ideal withe the cutout inside the boat but I simply feel I do not have the skills to replicate that kind of work with windows and doors. But an open concept I could probably do. It has to be about 20 inches above the cabin roof the entire width and back towards that railing.
    upload_2020-6-8_22-14-52.png
     
  2. bajansailor
    Joined: Oct 2007
    Posts: 937
    Likes: 244, Points: 43, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

    I was just reading your previous post last year about your electric catamaran - very impressive!
    Solar Catamaran Completes Third PNW Season. https://www.boatdesign.net/threads/solar-catamaran-completes-third-pnw-season.60924/

    In the last photo above I see winches, jammers and sheet tracks - do you still have sails as well, or just electric propulsion?

    Re the shelter that you want to build over your cockpit - in view of the large area (16' x 12') it might be easier to build the support structure in tubular aluminium, and have a lightweight fibreglass roof on top? In similar fashion to many 'bimini' type awnings on powerboats?
     
  3. fallguy
    Joined: Dec 2016
    Posts: 2,975
    Likes: 330, Points: 83, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    I would use clear vg douglas fir. You need to lay the grains in the correct direction. One way will sag more. Grains up and down in the install is what you'll want.

    I am having a bit of a time trying to understand what you are up to. The picture of you? inside looks like a rather nice, albeit confusing internal layout. But is that a current picture or the target picture? I think it is the target and not you.

    It will be near to impossible to build a clear span of 12 feet with 1x and 2x4 and 3/8" plywood. You will need to either modify the roof thickness or modify the structure. You will have too much variation in traditional lumber and none of those lumbers will self support in 12' span. The roof will sag, in my opinion, if I am understanding you at all. Those timbers they used are all sawn and that means they are certainly not construction lumber. They are either laminations or some very sturdy stuff like clear vg fir. The 1 bys are on one foot centers or so. and the deeper lumber is on 2 foots or so.

    If you laminate the timbers; you will have a much better chance of succeeding.

    You need to also declare whether anything is going atop, like you for maintenance, or solar, or anything because that changes the loading.

    Another thing that will improve the chances of success is laminating the roof to the beams with thickened epoxy. Making the structures uniform by not using flexible glues will help keep it from sagging as well.
     
    bajansailor likes this.
  4. fallguy
    Joined: Dec 2016
    Posts: 2,975
    Likes: 330, Points: 83, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    Here is a picture of a laminating jig. These are for an 8' span and this is redwood which is not ideal. I had it available and it is old growth reclaimed tank stave.

    A laminating jig is used in order to get the bend because these beams won't bend at their final thickness. We laminated 3 pieces of 1/2" thick lumber here to build to 1.5". There are four beams on the jig curing. Thickened epoxy was used for the bond. Typically you build these 10% overbent. I did not and lost some camber.

    53BEAE8F-E2A4-4A40-93BB-790FEEDD76A5.jpeg
     
    bajansailor likes this.
  5. fallguy
    Joined: Dec 2016
    Posts: 2,975
    Likes: 330, Points: 83, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    9CF088BC-68AC-421A-9EAA-6B61D118162F.jpeg My roof above; fyi, is 6mm okume with a 12mm Gurit foam bonded to it. Then I rolled out one layer of 17 oz fiberglass over it. It is strong emough to carry me on 8' spans, but I won't jump up and down on it. The 6mm okume is a bit light for that.

    For a 12' span, I would think making these 3-4" thick in clear vg fir would work well. If you want the intersecting structure; then the 4".

    I liked this method because it was straightforward building. The beams went on the walls and the ply on the beams and the foam on the ply and the glass on the core.

    The ply down below in the pic is just a holding jig. The wood on the beam ends is just a tank stave to keep them from lifting. And the center beam is to keep them flat from below. It worked quite well.

    Should add these beams are on 11.6" centers.

    We sort of tested the roof design and felt it would support a 100 pound point load and designed with a factor of 2. So a 200 pound man can walk the roof on occassion and we can put solar panels up there. We also designed the walls below for buckling loads and added an intersecting wall each side because this boat is subject to snow load.
     
    Last edited: Jun 9, 2020
    bajansailor likes this.
  6. pacific green
    Joined: Oct 2017
    Posts: 10
    Likes: 1, Points: 3
    Location: earth

    pacific green Junior Member

    The roof impediments have been removed somewhat crudely, the sail bags were tossed and it is just electric propulsion. I still have the old mast, boom and new 42' aluminum extrusion at bluewater spars and rigging and even located the original receipt for it last week but suffice to say that dream just never happened. The old mast might make a great shelter while painting the boat might have to see if I can go pick it up.

    Yes I was thinking of tubular aluminum as a design choice right along the lines of mounting a truck canopy on the top and glassing it down. I had welders come out to the boat when it was at berth but nothing ever materialized and I would expect much the same if I were to try again that route this time around. I am waiting on a quote for 4 500 watt panels that match the dimensions of the cockpit and I believe they will provide the basis of the cockpit roof. These things are massive 84 pounds each and will cover the entire cockpit and over the cabin roof. So now I am looking at constructing the support structure to hold them up. Here are the new panels https://www.heliene.com/wp-content/uploads/documents/SpecSheets/Heliene96M_Silver_NA-Rev.03.pdf and I hope I get to order them - should have a quote later today.

    In the beginning of the fifth year on the Fraser on January 15, 2020 there was a nasty winter storm and a metal encrusted beam but a hole in her on the starboard hull and she had enough of that and hauled herself out to the boat yard. She now demands that we fix the hole and clean up her hulls and catch up on the topside paint and bright work. This we can accomplish and surveyed the damage last week, some kitchen appliances the two big holes and two smaller drill holes I paid for.

    We took out her water tanks to access the holes and it is perfectly between the stringers so should be an easy fix. We lost a couple induction cook tops an inverter unfortunately and probably a 12 v trolling motor for the dingy and perhaps a 400 ft submersible light work class ROV remains to be seen. We did spend the night on her and flipped the switch on the solar and ran off the batteries and shore power that night. Have already ordered a replacement inverter. Left a light on and the dehumidifier running.

    As far as impressive it does have some unique qualities/capabilities and is very affordable to live aboard for extended duration of days. Our longest was 28 days out. Depending on how fast or how much of the PNW one wants to see actual gasoline usage for the Honda generators would be substantially less if the captain would just relax. But on average a gallon a day perhaps two. If we drop the new panels on then that will cut the gasoline usage in half again or almost completely eliminate it in some situations.
     

    Attached Files:

  7. pacific green
    Joined: Oct 2017
    Posts: 10
    Likes: 1, Points: 3
    Location: earth

    pacific green Junior Member

    Yes Tom used a fish eye lens to take that picture before he sold me the catamaran. It technically is the current cabin layout and that is not me but still the captain of the boat at the time.

    Likely and from what I can tell they put a double skin over the entire cockpit side and top. Each piece was further epoxy filleted. I will find a picture. We have no problem traversing the cabin top for whatever purpose.
    upload_2020-6-9_9-54-15.png


    If you laminate the timbers; you will have a much better chance of succeeding.

    As part of simplifying the flexible solar panel layout I had intended creating the roof structure with enough room to hold 10 of these panels as an attachment below the 330W.pdf file. I am still waiting on a shipping quote for those but with an ETFE cover sheet. So I was going to just go with a flat roof thus no bending of wood stringers. Not really big on the flexible panels after my last 2160 watts after five years I am at 1440 watts but we beat them up bad - the remaining panels still make 10 to 20 amps.

    I am waiting on the ultimate solar quote from https://www.heliene.com/wp-content/uploads/documents/SpecSheets/Heliene96M_Silver_NA-Rev.03.pdf as the logistics and deliver will be much easier and they then form the basis of the roof structure by themselves. It will then cover the entire cockpit and partially over the cabin. I will create uprights and build up from the cockpit railing with wood to above head height. After that is done i can frame the back in with the traditional and economical blue tarp or choose from a multitude of other methods like ply and epoxy construction with doors and windows that lift upright to attach to the roof when wanting an open cockpit. Otherwise sunbrella fabric might suffice. All depends on her attenuation in the water after 320 lbs of panels are hoisted upon her aft section - she could certainly use some weight there as she is a little front heavy from historical pictures of the vessels water line poise.
     

    Attached Files:

  8. pacific green
    Joined: Oct 2017
    Posts: 10
    Likes: 1, Points: 3
    Location: earth

    pacific green Junior Member

    That is a great looking roof. Typical cabin construction though I have seen them embed the stringers right into the beams with a notch. I believe this is how mine was built and from other examples on youtube and websites how they do it. I was considering a sandwich made from EPS foam and veneer all laminated. I am only making a flat surface so I do not need to bend the roof structure. I read many discussions about using proper marine foam versus EPS and concluded it could be done easily enough with EPS and veneer. Save that for another discussion.

    That is very well constructed. Another fine example. I frequently find myself staring at cabin construction pictures from various builds of catamarans by designers. I will have to incorporate a many of the building techniques to mount my 334 lbs of panels off the cockpit railing and over the first few feet of the cabin with these solar panels that will effectively become the roof. https://www.heliene.com/wp-content/uploads/documents/SpecSheets/Heliene96M_Silver_NA-Rev.03.pdf

    You can see the dimension of the panels when I epoxy all four of them will cover an area 154 inches by 103.2 inches. Likely I will epoxy all four together for a seamless roof and hoist it upon whatever structure I have designed to support them. Wood so far is looking like the solution although I will not discount traditional solar panel mounting hardware. The frames seem quite robust but certainly not self supporting. So I am envisioning a wood frame under them.
     
  9. pacific green
    Joined: Oct 2017
    Posts: 10
    Likes: 1, Points: 3
    Location: earth

    pacific green Junior Member

    Blog Posts https://my-new-cat.weebly.com/boat-build/previous/3
    If I go with an entire structure over the top I will have to follow some of these design concepts. I like how this eliminates many of the complex curves by making the angles more manageable. Also the common 2x4 and 1x4 construction used to do it.
     
  10. fallguy
    Joined: Dec 2016
    Posts: 2,975
    Likes: 330, Points: 83, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    If you build it flat; it will need to be made stronger and have you considered snow loads? There is no reason to not put a bit of slope to it. The solar impacts are nearly zero.

    Also, realize a flat roof ponds water if you get any sag or low spot. Flat is almost never.

    I really recommend you rethink the flat idea due to the 12' span. Unless you are pitched for n aft, that is..even then, camber offers strength

    You also don't want 12' of water sheeting off into the cockpit underway in rain, etc. perhaps this is well thought out already
     
  11. fallguy
    Joined: Dec 2016
    Posts: 2,975
    Likes: 330, Points: 83, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    My roof is stringerless; just beams. This pic just has a jig that is removed after the glasswork and fairing and main inside walls were done. 7FB29766-4D74-4B03-B28F-0E15D442C9FB.jpeg
     

  12. pacific green
    Joined: Oct 2017
    Posts: 10
    Likes: 1, Points: 3
    Location: earth

    pacific green Junior Member

    I would slope it for water collection one way or another. The water inlet is starboard amidships and can be easily reached with a hose from a fitting attached on the forward right side around the lip of the frame the solar panels will sit in.

    Still waiting on finalizing which solar panels to purchase. Options are thin film solar or rigid panels. The rigid panels from https://www.heliene.com/wp-content/uploads/documents/SpecSheets/Heliene96M_Silver_NA-Rev.03.pdf are starting to look more likely. This design allows for the complete covering of the cockpit with 4 panels - it will also cover a portion of the cabin. The dimensions when combined are 154 inches by 103.2 inches. From cockpit railing to cockpit railing is 144 inches so I will end up with a 5 inch overhang on either side. Working forward I do not know exactly where the width of two of these panels 103.2 inches will fall in terms of the cabin roof. I am hoping somewhere around the main cabin door or slightly past. I only need around 20 inches above the cabin roof and around 36 inches around the cockpit railing to get the structure made to support these and provide head room under it so perhaps 56 inch upright frame constructed around the railing.


    upload_2020-6-9_13-23-34.png
    upload_2020-6-9_13-1-24.png
    upload_2020-6-9_13-9-31.png
    So it looks like I will be a couple feet over the cabin if I lined it up with the back of the cockpit railing. But I could very well move it backwards three feet and laminate some 4x4 beams up from the back of the very rear cockpit locker and make my frame from there. It then becomes the start of the davit system for the porte bote as well. I would probably slope the rear starboard side in that case for water collection. The more I study this scenario the more likely it becomes. From the diagrams I have 8'4" from the very rear cockpit locker to the front of the cabin. The panels are 8'6". I hope I get a nice quote from Heliene.
     
Loading...
Similar Threads
  1. MCP
    Replies:
    32
    Views:
    5,505
  2. Beav222
    Replies:
    21
    Views:
    3,878
  3. Martin Ellison
    Replies:
    8
    Views:
    2,552
  4. Chris Ostlind
    Replies:
    0
    Views:
    5,978
  5. AuzzieBrent
    Replies:
    2
    Views:
    4,309
  6. wailingdave
    Replies:
    6
    Views:
    4,217
  7. wailingdave
    Replies:
    6
    Views:
    4,357
  8. bswindell
    Replies:
    5
    Views:
    1,602
  9. fredrosse
    Replies:
    9
    Views:
    4,635
  10. fraggin
    Replies:
    1
    Views:
    1,588
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.