So I started sanding a section of my deck due to a few cracks in the paint (refer to my previous post). Anyhow, after sanding the paint back I put some pressure on the deck between the centerboard case and the rear beam and the top veneer of the ply in that section cracked a little. This area flexes a bit, and I knew I was going to have to re deck eventually, but it looks as if I might have to turn this into a winter project.
I have cut a small section around the crack, and it appears that the deck is made up of two pieces of 3 - 4 mm ply with a peice of foam sandwiched between them. The top ply has come apart from the foam, hence the flexing.
So it is looking like I may have to replace the section of decking between the front and rear beams. If anyone has any suggestions of the best way to do this, I'm all ears. my biggest concern is separating the existing decking without damaging the hulls. I'm sure someone has had to do this before, any pointers would be awesome.
I recently removed the deck plate of my Blade with a heat gun. It was very straight forward, as usual I should have been a little more patient. I've no idea if this method will work for you.
I removed the deck of my timber mossie with a router. I put a hole saw through the deck first then set the router at the exact thickness of the ply I found there.
Using a TCT bit I then ran the router over all of the deck that was attached to something. The TCT bit was essential as it ate through everything in the way including the nails.
This left only a very thin bit of glue over everything including the foam bulkheads. Any imperfections were then sanded ready for redecking when all the faults were fixed.
Roughly cut out the correct shape from a new piece of ply and glue and nail on ( make sure to use Monel or copper nails!) when dry use the router again, different bit this time with the little bearing at the bottom, and run it around the edge of the gunn'l.
A bit of a sand and a paint and your done... Sounds easy, probably takes 3 hours plus paint and the hardest part is putting the first hole in your Mossie!
Andrew, if you have Facebook, search for Simon Hallsworth and check out the photos on his site of restoration of Sail #1762, Reincarnation. Not too sure how to do this if you are not a friend. Facebook is not a strength for me. I was a consultant for the exercise. Contact me if unsuccessful. ppearce@internode.on.net
Using a router sounds like the way to go, and the method which reduces the possibility of doing accidental damage to the hulls. I will be removing the hulls from the beams this weekend and building some kind of a jig to hold them in place. I'll then take to them with a router and see what I find.
Philip, I have seen those photos on the Mosquito website. I have a feeling that the boat pictured has quite a few more foam bulkheads than what mine does (based on what I can see through the inspection ports). From the small hole I have made in the deck, it appears that the deck is made up of two pieces of 3 - 4mm ply with foam sandwiched between them. As noted above, the upper deck has separated from the foam in the area between the centerboard cases and the rear beam. The foam does not smell or look like it is in a very good state in that area and I am hoping that there is a simpler, and hopefully lighter, alternative to supporting the decks. This all depends on the difficulty of attempting to replicate the existing 'foam sandwich' decks I am removing, or ease of implementing an alternative support method.
I noticed that in the restoration photos of Reincarnation, the stringers were replaced with ply I beams of some sort? It looks and feels as if there is only one stringer running the length of the decks, I assume due to the foam core being able to support more weight. Perhaps the addition of additional foam bulkheads and I Beams such as this may be a possible alternative? Do you have any further details, or recommend any books, detailing how these are constructed?
I wasn't planning on doing all this work when I purchased this boat, and whilst I can't wait to get it on the water, I am actually starting to enjoy the experience of fixing it up. Hopefully once I am finished, I should have a decent boat which will last me a number of seasons, and some new woodwork skills I never thought I needed
Thanks again for your help.
Cheers,
Andrew Assassin 1363
Posted By: Anonymous
Re: Redecking mosquito - 04/11/1207:57 AM
Nooooooooooooooooooooooooo,
it wasn't meant to be this hard. I'm sure we discussed fixing things after they broke so you could go sailing before the weather turned.
In answer to your other question the other day. When you come to repainting look into Durepox as in theory it is easier to sand and polish in repairs than the most.
I know, but then the deck cracked, and so I cut around the crack to patch it, then I saw and smelt the foam, and I couldn't just patch it knowing it was like that... My current car doesn't have a tow ball, so I would be using up all my favors very quickly borrowing friends cars to get the boat from Sugarloaf to home as new cracks appeared. I figure, considering I've started repairs, I may as well try and fix all issues I can find so that It doesn't give me issues once I finally start sailing it. There is sailing through winter at Sugarloaf, so I'll be still able to sail it once I'm done.
I will have a look at durapox, I haven't heard of that before. I think the reason why the paint was cracking in so many spots is because the previous owner painted it with automotive 2 PAC.
First, throw the timber composite deck away and replace with 4mm ply. I did mine (now done several the same way) using the same method as Trevor but replaced it with 4mm, albeit the ply had a layer of glass on each side. The glass adds strength as one side is in compression and the other in extension (the opposite).
As for paint, not sure where this "urban myth" of auto paint has come from, but I have done all my mossies in auto with not an issue and I am talking of about 6+ boats now (counting my son's, timber and glass) .. our boats would still be some of the best looking boats on the beach, my present one in metallic and now 3 seasons old... there is always the issue of quality and application. We have and will continue to use 2 pk Polyurethane ... but then that is what marine paint basically is, and a car sits in the weather as much as a catamaran. I would not use auto tho' on a boat that is permanently moored and sitting in a marina.
Marine paint is the same as industrial paints,, auto paints have different stuff in them, but use any one of them, auto is a bit harder as it is thinner than marine or industrial paints and more expensive. whats good to use is international paints as its easy to spray and roll and brush, easy to sand and easy to polish
I really appreciate the feedback. Interesting about the 2 pac, a big advantage of doing this vs patching things up is that I wont have to worry about getting it colour matched. I will be brushing the paint I end up purchasing (I dont think my landlord would appreciate me spraying paint in the garage - she lives next to me...) ;), I have heard good things about the International paints, somebody else has suggested a product call 'Norglass' apparently produced in Sydney.
I will probably replace the composite deck with some fibreglassed 4mm ply as you suggested, will 6 ounce square open weave type cloth be sufficient? I will probably wait until I have taken the decks off before purchasing any ply or glass, and will most probably have more questions!
Thanks again for all your help, it makes cutting holes in my new boat a lot less daunting...
Andrew, Reincarnation had many foam bulkheads. The foam was low grade and the deck stringers were set directly into it with insufficient'engineering' long-term. The tops of these bulkheads were removed and replaced with 4mm ply I-beams. No stringers were necessary as the I-beams supports the 4mm deck, not the foam. dkd suggestion of applying (6oz?) glass to the ply will work, espescially on the underside were it will be under tension when loaded, crew sitting on it. Applying it to a flat sheet then bending it to the required curvature will place all the 3 layers of veneers under tension that may result in some splitting. Applying another layer to the upper surface will bind this top veneer. You will have to consult dkd about any support of the deck, ie. bulkheads/stringers. I can email info on the construction of the I-beams if required, yes can be slow but NO deck failures of the 4mm ply after 17 years of some serious sailing.
Guess your choices are getting endless, all of us are happy to help if required.
As for your paint issue, My other boat is painted with International/Awlgrip for the simple issue that it can be rolled and tipped off. Much much easier if you don't have access to spray booth or not wanting to piss neighbour/landlord off. Each has a purpose, and this boat has been done in International/Awlgrip for just the reasons you state.
The down side of International is the lack of colour choice, Awlgrip is a little better, much wider range and can be rolled and tipped off and stunning when done properly.
So I have 'almost' removed the top ply section of the composite deck on the port hull. I have kept the beams attached for now, as it keeps the hulls nice and stable, so I haven't removed the 50mm section of deck next to the beams. Its taking me aaages, I borrowed a friends battery powered Ryobi laminate router, with only 1 battery that lasts about 15 minutes, so its slow going, but they say slow and steady...
The foam between the two pieces of ply isn't a uniform thickness, it has been shaped to increase the curve of the deck. Whilst the lower sheet is curved slightly, it isn't curved as much as the top section was, so I am a little concerned that if I was to install stringers into the existing foam bulkheads (there are no stringers at the moment), the decks wouldn't be curved enough to measure as per the building rules:
5.13 The deck curvature shall be within 5 mm of the deck template as drawn on the plan but the gunwale may be radiused to a maximum of 3 mm.
That said, without a copy of the plans, my thoughts are if I create a template based on the existing curvature, and then use this when constructing I Beams, I should be OK.
There are currently 3 foam bulkheads between the rear beam bulkhead and the centerboard case. A couple of these have cracks which I will need to repair. There is a single foam bulkhead between the centerboard case and the front beams. I think I will add some more.
Philip, I would really appreciate it if you could send me the construction method for the I-Beams, my email is ASchnull@gmail.com.
Thanks again for all your help, I can't wait to get to the point where all I need to worry about is the color paint I choose
So I have removed the majority of the mid decks, and separated the hulls from the beams. I will be assembling a cradle tomorrow to hold the hulls level so that I can continue on.
It looks as if this boat had a hull replaced at some point. Foam bulkheads are in different spots, one deck was composite with no stringers, the other single ply with stringers. It looks as if the second ply sheet on the composite deck was added after some pretty rough repair work to the lower ply, and the foam used to raise the upper deck from the repairs. I have removed both ply sheets using a router, though unfortunately I will have to spend quite a bit of time sanding this flat.
My next move is to fix up / possibly replace the foam bulkheads, as a number of these are cracked, and most probably add some extras. Can anyone recommend a foam sheet supplier and the type of foam I should be purchasing? The existing foam is white, and roughly 25mm thick. I assume I should be purchasing some kind of closed cell foam, but want to make sure I purchase the correct one.
It also appears that the front ply bulkhead of the starboard hull has separated from the inside edge of the hull. The fiberglass tape on both sides of the bulkhead is sheared along the inside edge. I am not sure whether to try to remove and replace the bulkhead, as there is a roughly 5mm gap between the bulkhead and the edge of the hull in the top 100mm section of the bulkhead, or fill the gap, re-glue and tape it in as is. Unfortunately, I think this means I will either have to cut another hole in the deck forward of the front beam to get to the other side of the bulkhead, or remove the front deck section as well (there is already one hole but out when I needed to get to the chain plate).. I should have enough ply, I have ordered 2 sheets of 4mm gaboon which should be more than I will need for the mid deck replacement.
In regards to the I-Beams, it looks like in the photos that the foam is cut to the same level as the bottom edge of the timber strip which runs along the gunwhales, but I cant tell whether the ply strip is glued to the edge of the gunwhale, or to the underside?
So i have removed the decks, have started to replace a few of the foam bulkheads, and have also added a couple more. Although before I fiberglass the new foam bulkheads in, I just want to confirm that I purchased the right (or wrong) type of foam... I have used 40mm SL grade EPS foam sheet(Expanded Polystyrene), but further research has given me that sinking feeling (no pun intended) that I should have used XPS (Extruded Polystyrene)instead, as this is 'closed cell' and has a resistance to absorbing water. Is this correct? It shouldn't be too hard to re-cut the bulkheads from new foam, but I have no idea where to purchase this... Any suggestions?
I fixed the starboard bulkhead with an epoxy glue fillet (this epoxy stuff is really amazing). Next move once I have taped the foam bulkheads in will be to complete the ply I-Beam supports.
I would have used a closed cell foam for the reason you mention, it does not absorb water.
Several sources, any good boat-builder should have sheets of it. A surfboard manufacturer/repairer or probably the easiest is to go to one of the composite material suppliers, FGI, Huntsman or Applied Composite Technologies and get good quality stuff, maybe like Durakore .... ask them for their recommendation.
Personally I would use the latter one, they have been in the business for long time and always seem happy to help. There is my "two-bobs" worth.
The older of our boats has glass of about maybe 4oz on the inside and 2oz layer on the outside, as Philip said, puts inside into tension and the external layer goes into compression and really does nothing much more than stop the outer ply layer from splitting.
Thought I would upload a couple of photos of where I am with the boat (its been keeping me busy most weekends since end of last season). The relatively simple tasks of 'redecking' the boat, ended up becoming a complete rebuild. It probably didn't need to be, but its kept me entertained. In hindsight I think I could have built a new pair of hulls in the time this has taken me.
I have replaced all foam bulkheads, the ply front chainplate bulkheads, starboard hull front bulkhead at the main beam and all stringers. Foredeck has been glued on in this photo. I have purchased some centreboards thinking I could pack the existing cases with foam to get them to fit, unfortunately the new boards were a couple of mm too wide for the existing cases, so I have removed them and will be installing new cases (as far back as rules allow, 10 degree angle). The old slots have been glasses up.
I am about to drill new beam holes, then send the aluminum beams (incl centre) to an anodizer whilst I glass in the new centreboard cases. Remainder of the decks will be glued on once the centreboard cases are in. Should be fairing and painting the hulls after that.
I went to purchase some SS bolts and the supplier only had 304 stainless steel bolts in stock. Are these OK to use for the beam and dolphin striker mounts, or should I try and find these in 316 stainless?
Posted By: Anonymous
Re: Redecking mosquito - 10/22/1204:55 AM
From a structural point of view the advantage of 316 over 304 is so marginal that it doesn't matter. From a corrosions point of view 316 is significantly better so using 304 will get you on the water but 316 will mean you probably don't need to look at the bolts again while you own the boat.
