 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
| HomeDiscussion GroupsBoatsPaddle BoatsSailingCruisingBuildingElectronics Related Topics CarsMotorcyclesMore Topics ... |
Boat Forum / Building / October 2007Forming rounded corners with Fiberglass and ply.
Thanks to everyone for the replies to my prior questions about epoxy and fiberglass (discounting the use of polyester). You help and experience is appreciated. I'm planning to build a dodger for my sailboat, still researching and discovering.. After photographing hundreds of hard dodgers, and studying them carefully, I know that hard angular corners will not look good on my boat. I need to round the edges/corners to match the rest of the boat. What techniques should I research for changing the hard corners where two ply surfaces connect? How do I shape those round edges smoothly to have a professional looking curve? Plywood seems to be a good core for the large surfaces. I may use two or three 1/4 ply layers glued with epoxy. 1/4 inch ply will allow some curve to the sides and top, and having multiple layers will provide strength. This is a 50 foot boat, so 1/2 to 3/4 inch thickness would not look too flimsy, and the boat can accommodate the weight. My question at this time is how do you make a smooth tidy round corner where the sides and top meet, and where the sides and the front of the dodger meet. It seems that connecting the ply large surfaces together would add structural strength, but that would cause a hard angular appearance. Thanks for your input, (and please forgive my lack of experience). -Koos. Use a quarter round trim strip to form the corner, where you have a radius on the outside, and a square corner inside, which you can trim or fillet. For other than 90 degree corners, trim the strip on a table saw. Use thin plywood and build up the edges to meet the trim strip depth and accept screws holding it together. Arrange to remove the plywood mold plug from the inside by covering the outside with waxed paper. After you have built up sufficient thickness of glass, drill out the screw heads and remove the screws to remove the mold panels. Fill the screw holes. I considered just glassing over the old canvas, for that slouch hatted look. Terry K > Use a quarter round trim strip to form the corner, where you have a > radius on the outside, and a square corner inside, which you can trim [quoted text clipped - 11 lines] > > Terry K Thanks Terry, that is very helpful. I think you are suggesting that I make rounded corners from molds, to be added to the structure afterwards. So I would make the structure using wood in the corners to provide strength, and then add the rounded corners and finish them. that is my interpretation.. I might be able to use the existing cabin-house as a male mold to get the same curve? Using wax paper and protecting the area with plastic, I could perhaps use fiberglass and epoxy to form the corners for adding to the dodger later. Let me know if you think this is a crazy/ unworkable idea. Thanks for the ideas. -Koos. > What techniques should I research for changing the hard corners where > two ply surfaces connect? How do I shape those round edges smoothly to [quoted text clipped - 5 lines] > strength. This is a 50 foot boat, so 1/2 to 3/4 inch thickness would > not look too flimsy, and the boat can accommodate the weight. You are going to end up making a male mold and then doing a classic "one off" construction. I definitely would NOT use plywood as a core material, but rather use 1/2" Divinycell foam. Best guess is probably about $3/sq ft for full 4x8 sheets. Probably get the job done with 2 sheets so estimate maybe $200 for foam. Foam can be cut into strips to go around corners, I've done it several times. You do realize that this will be at least a 2 year project and cost at least $1K before you are done. Lew > You are going to end up making a male mold and then doing a classic > "one off" construction. [quoted text clipped - 14 lines] > > Lew Thanks Lew, Thanks for the foam suggestion. Why not ply? Because it rots? Because it's heavy? Other reasons? I should explain that the sunbrella dodger/bimini/surround I have now is ugly, too vertical and also it has aged. It would cost $2,000 to $5,000 to fix it or to replace it (change the shape). I'd like to make a full hard dodger and combined hard bimini to cover the entire cockpit. Then add sunbrella sides and soft windows aft of the dodger. I'd like to be able to open the center window of the dodger, for ventilation. I may have a window in the ceiling (bimini) to see the sails, but probably not. I will probably have brackets for mounting solar panels, and may include a conduit for power cables. To have a shipyard build this would be very expensive (double the above numbers), and I'm not confident that I would like the result. So I expect my project to be expensive, when it's all done. I plan to make some form of disposable mock-up, to determine the details. It should be the right height, it should allow visibility, it should be aesthetically acceptable, it should allow crew to work the lines and winches etc. Until I'm happy with this aspect, I won't begin construction. Yes it will take a long time, especially considering my other projects.. I was hoping to get it done within a year though (probably not).. Thanks for your advice. -Koos. > Thanks for the foam suggestion. Why not ply? Because it rots? Because > it's heavy? Other reasons? Before I get into the details, one question. Is this by chance a center cockpit boat? Lew > Before I get into the details, one question. > > Is this by chance a center cockpit boat? > > Lew Yes it is. A Gulfstar 50 center cockpit Ketch. They usually have an ugly phone-booth style dodger and surround/windows. Something like this one; http://tinyurl.com/34bc4k May I add a question? With the foam, should I plan to build a wood frame to provide the structural strength? So the foam is attached to the frame, rather than just fiberglassing the foam pieces to each other? Also, your website, any updates? I'm interested in your project. Your help is appreciated - thanks! -Koos. > Yes it is. A Gulfstar 50 center cockpit Ketch. They usually have an > ugly phone-booth style dodger and surround/windows. Something like > this one; > http://tinyurl.com/34bc4k AH HA, new game plan. Look at the "roof" of the bimini/dodger of that G/S50.. Think, "How would I make that out of cored fiberglass and use roll up side and front curtains?". You simplify comstruction as well as end up with a place to "plant your solar garden." It is/was my game plan. If that interests you, get back to me. BTW, don't think of it as a telephone booth, think of it as a covered patio.<G> http://LewsSailBoat.googlepages.com/home Lew > AH HA, new game plan. > Look at the "roof" of the bimini/dodger of that G/S50.. [quoted text clipped - 8 lines] > http://LewsSailBoat.googlepages.com/home > Lew Lew, A patio is right. It was made for sitting in, not sailing in. Forward visibility is compromised (smudgy, warped) especially in our fog and rain. Hard windows would be better. Crew have to fight it to use the winches (can't even make make a half, never mind a full turn). It leaks and drips in too many places, even into the companionway. The boom scrapes and chafes on the stainless tubing, tearing the sunbrella. It's very ugly, does not fit the lines of the boat, see here http://tinyurl.com/36ofeo I have to totally redesign it, or use the boat as a dockside patio, or sell the boat.. So I want what you say, but with a hard dodger up front, and redesign the patio cover to make it functional and visually acceptable. I've been googling the foam, thanks for the lead on that. I've seen your advert before, in the live-aboard list I think. I'm sorry to hear you are selling, but I'm sure you have thought about it and are making a difficult but good decision. Best wishes, -Koos. <koosvander@gmail.com> wrote> > A patio is right. It was made for sitting in, not sailing in. > I have to totally redesign it, or use the boat as a dockside patio, or > sell the boat.. > > So I want what you say, but with a hard dodger up front, and redesign > the patio cover to make it functional and visually acceptable. OK. You build the hard bimini on the ground, then put it in place with a crane since it will be about 12 ft x 12 ft, maybe more, and weigh 250-300 lbs. It will be totally self supporting requiring only some 2" pipe posts in the corner to support it. It will be totally clear underneath, part of the beauty of foam core construction. You will probably have to raise the boom about 12" and recut the main, especially when you include the solar panels. Get a copy of Fred Bingham's book, Practical Yacht Joinery. It has a lot of info that will be useful for this project. You will need a roll of 17OZ double bias glass (Knytex DB170), probably about 6 sheets of 3/4" Divinycell, a 500 lb drum (55 gal) of laminating epoxy and a couple of 5 gal pails of hardener. You will also need a couple of 30 lb bags of Dic-A-Perl, HP500, to make fairing putty. As far as the front "windows" are concerned, have to think about that a while. This is a simple, straight forward process, but a hell of a lot of hard work Are you sure you want to open up this can of worms? Lew > OK. > [quoted text clipped - 30 lines] > > Lew If you want to scare me off, tell me about the itch of fiberglass, I dread it.. I think I'll adjust the dodger downward rather then adjust the boom upward. It's a tall dodger now, so there is room for adjustment. I was imagining that it would be built in place, is that a bad idea? My boom and six dock apes should hold 350 pounds, but will use a crane if we have to. I'm surprised at the amount of epoxy needed. Thanks for the warning. -Koos. <koosvander@gmail.com> > If you want to scare me off, tell me about the itch of fiberglass, I > dread it.. I understand. > I think I'll adjust the dodger downward rather then adjust the boom > upward. It's a tall dodger now, so there is room for adjustment. It's your call, but you need at about 6'-8" standing room as a basic design goal. Might trim an inch or even two, but that is cutting it close. > I was imagining that it would be built in place, is that a bad idea? YES, bad idea. Trying to work while up in the air as oppossed to standing on the ground. Sanding dust and excess resin dripping on the boat raather than on the ground. Want me to go on? > My boom and six dock apes should hold 350 pounds, but will use a crane > if we have to. In this application, the boom just gets in the way. A crane doesn't get an itch. A crane doesn't loose it's grip. A crane doesn't get distracted by a pretty girl. Want me to go on? > I'm surprised at the amount of epoxy needed. Thanks for the warning. Do the calculation yourself. Use 17 OZ/sq yard per layer of glass. Lets say 3 layers of glass per skin or 6 layers for both skins or 102 OZ/sq yard of bimini. 102/9 = 11.33 OZ/sq ft or 102/9/16 = 0.708 or 0.71 lbs/sq ft. Assume the epoxy weight = glass weight + 20% for drips, waste, etc 120%*0.71=0.85lbs/sq ft of bimini If you add a 4th layer of glass, add 34%. If you have 150 sq ft of bimini, you could get by with 150 lbs of epoxy which would be about 4, 5 gal pails. By the time you buy 4 pails, you are probably 75%-80% of a drum price. That's why I suggested a drum, you can always find some good use for a half a drum of resin<G>. Lew Thanks for the details Lew. I ordered that book you mentioned (already have his "simplified" book). -Koos. > Thanks for the details Lew. > I ordered that book you mentioned (already have his "simplified" > book). Take a look at how cambers are laid out, that will be your starting place. Lew I must be missing something here. A dodger is just a roof. Why all the epoxy and glass? I wouldn't use any glass and just use wood and epoxy for sealing. You should be able to build it in place and wood is alot easier to work with than glass. Either paint it or leave it natural. Bob On Aug 23, 11:03 am, koosvan...@gmail.com wrote: > Thanks to everyone for the replies to my prior questions about epoxy > and fiberglass (discounting the use of polyester). You help and [quoted text clipped - 26 lines] > > -Koos. > I must be missing something here. A dodger is just a roof. Why all the > epoxy and glass? I wouldn't use any glass and just use wood and epoxy > for sealing. You should be able to build it in place and wood is alot > easier to work with than glass. Either paint it or leave it natural. This is going to be a large, say 12x12 rigid dinghy that will support a solar panel farm. Wood is heavy, wood will rot, and wood is weak when compared to a foam core complete with knitted glass and epoxy skins. The above structure would add a lot of weight high above the water line if made of wood. Just for reference, a 4x8x1/2 sheet of plywood weighs about 42#, while a 4x8x3/4 sheet of Divinycell weighs about 16#-17#. Lew On Mon, 27 Aug 2007 20:21:58 -0700, "Lew Hodgett" <lewhodgett@earthlink.net> wrote stuff and I replied: >This is going to be a large, say 12x12 rigid dinghy that will support >a solar panel farm. > >Wood is heavy, wood will rot, and wood is weak when compared to a foam >core complete with knitted glass and epoxy skins. Canoes and Kayakers will disagree. I had this discussion with one of the SNGlue/Strip kayakers, and they were very strong about wood vs foam....either snglue or strip. However, I have to admit that if the result is stiffness, noit inpact strength, then fioam wins at a given weight. >The above structure would add a lot of weight high above the water >line if made of wood. But not if made of wood (strip or sng ply) with the same skins or less (agaon local impact strength) >Just for reference, a 4x8x1/2 sheet of plywood weighs about 42#, while >a 4x8x3/4 sheet of Divinycell weighs about 16#-17#. For this purpose you need quite thin ply...1/4 or 3/8, and then less glass or WHY because it's better for puncture. Moot point. Just presenting the other POV. In my time I have tried both, and find it hard to really fight one way or the other. >Lew Human bevaviour: Bestiality with a brain >>I must be missing something here. A dodger is just a roof. Why all > [quoted text clipped - 23 lines] > > Lew That's for the foam panels only. Add the glass and epoxy and it will be nearer 43 pounds :) > That's for the foam panels only. > > Add the glass and epoxy and it will be nearer 43 pounds :) The total weight is a function of the number of layers of glass in the skins, so the total weight probably exceeds 43#, but did you bother to calculate the stiffness of the foam/glass sandwich which is what truly drives the design? Lew coming back to this subject.... Hard Dodger story at SailNet http://www.sailnet.com/forums/showthread.php?t=37194 |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2009 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.