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Resurrecting the MiniCup
MiniCup #`1 is still sitting on sawhorses while I decide whether or
not to rebuild her. #2 which I have been using developed cracks from rot in the 3/16" poor quality ply I used on her even though she had been glassed with 4 oz glass and epoxy. While fixing this I found more rot so ended up covering her entire rear with another layer of glass. Am almost done. However, she seems to have absorbed some water that I cannot get rid of as she seems heavy even with ports cut in all her spaces. Am looking over the old MiniCup plans and considering how to design a modern version that will be much lighter. Considering using 3mm Okuome Ply covered with 8 oz glass all over with stiffening ribs of foam and glass. All interior joints would be glass taped and interior epoxied as well to seal the wood. Transom would be reinforced with thicker ply and G10 glass composite for the rudder stresses. Cockpit and mast step would be self bailing and all hardware of either bronze or SS. Instead of being a "hardware store boat", I'd specify buying actual boatbuilding screws and pulleys made for boats. I'd reccomend buying 1/8" Al tubing for the mast and 1/16" for the two other spars. The sail should be sewn from white polytarp, none of this duct tape stuff and visqueen. I have devised a much improved gooseneck where the two spars attach to the mast. Any other ideas? |
Resurrecting the MiniCup
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Resurrecting the MiniCup
On Sat, 25 Sep 2010 12:58:15 -0700 (PDT), Frogwatch
wrote: MiniCup #`1 is still sitting on sawhorses while I decide whether or not to rebuild her. #2 which I have been using developed cracks from rot in the 3/16" poor quality ply I used on her even though she had been glassed with 4 oz glass and epoxy. While fixing this I found more rot so ended up covering her entire rear with another layer of glass. Am almost done. However, she seems to have absorbed some water that I cannot get rid of as she seems heavy even with ports cut in all her spaces. Am looking over the old MiniCup plans and considering how to design a modern version that will be much lighter. Considering using 3mm Okuome Ply covered with 8 oz glass all over with stiffening ribs of foam and glass. All interior joints would be glass taped and interior epoxied as well to seal the wood. Transom would be reinforced with thicker ply and G10 glass composite for the rudder stresses. Cockpit and mast step would be self bailing and all hardware of either bronze or SS. Instead of being a "hardware store boat", I'd specify buying actual boatbuilding screws and pulleys made for boats. I'd reccomend buying 1/8" Al tubing for the mast and 1/16" for the two other spars. The sail should be sewn from white polytarp, none of this duct tape stuff and visqueen. I have devised a much improved gooseneck where the two spars attach to the mast. Any other ideas? If this sail boat isn't going to be dragged up on the beach and then jumped in but is always going to be afloat when supporting a load I don't see a thing wrong with your plans. I currently build dinghys about the size of a Mini Cup out of 3 mm ply sides and bottom. The transom would be 8 mm ply with a doubled where the engine mount is and a honeycomb seat top bracing it on the inside. Designed for a 3 HP motor. I do add a 3 mm doubler in the area where the oar locks are mounted as I am afraid of the sides flexing if someone puts long oars in it. I cover the entire outside with the lightest cloth I can locate - probably about 4 oz. cloth in your numbers. The inside bottom is also covered, more for a wearing surface. All joints are faired and taped, as the boats are stitch and glue. My boats have a small bow seat, more as a structural member then a seat and a stern seat. Both are topped with honeycomb that I make my self with 3mm ply skins and core. the center thwart is the same thing, i.e.. skins and core. I used to build essentially the same design with 1/4 inch ply but it was really too heavy for one man to handle without davets, thus the change to 3 mm. Cheers, Bruce (bruceinbangkokatgmaildotcom) |
Resurrecting the MiniCup
In article ,
says... On Sat, 25 Sep 2010 18:21:02 -0400, I am Tosk wrote: In article 084c9f63-3d17-496f-8a21-74c4d53f4a02 , says... MiniCup #`1 is still sitting on sawhorses while I decide whether or not to rebuild her. #2 which I have been using developed cracks from rot in the 3/16" poor quality ply I used on her even though she had been glassed with 4 oz glass and epoxy. While fixing this I found more rot so ended up covering her entire rear with another layer of glass. Am almost done. However, she seems to have absorbed some water that I cannot get rid of as she seems heavy even with ports cut in all her spaces. Am looking over the old MiniCup plans and considering how to design a modern version that will be much lighter. Considering using 3mm Okuome Ply covered with 8 oz glass all over with stiffening ribs of foam and glass. All interior joints would be glass taped and interior epoxied as well to seal the wood. Transom would be reinforced with thicker ply and G10 glass composite for the rudder stresses. Cockpit and mast step would be self bailing and all hardware of either bronze or SS. Instead of being a "hardware store boat", I'd specify buying actual boatbuilding screws and pulleys made for boats. I'd reccomend buying 1/8" Al tubing for the mast and 1/16" for the two other spars. The sail should be sewn from white polytarp, none of this duct tape stuff and visqueen. I have devised a much improved gooseneck where the two spars attach to the mast. Any other ideas? Sounds to me like you are going to use 1/8 inch ply and glass for structure.. Glass doesn't add structure really it should be used for protection if not laminated into a hull... Use 6mm plywood and protect it with 4 oz tight weave if you need abrasion protection and such... Err.. why is it that glass over plywood doesn't add structure while glass cloth over foam does? Cheers, Bruce (bruceinbangkokatgmaildotcom) Laminated glass might. One layer over a 3mm plywood, not so much... In most applications for small boats such as this, the glass is more as a sealer and protection than a structural component. Especially one layer of 4 oz tight weave... -- OH, I could do the 105 footer, but I would hate to waste the last few seconds of my life with my eyes closed, screaming like a little girl...;) |
Resurrecting the MiniCup
On Sep 27, 6:58*am, I am Tosk wrote:
In article , says... On Sat, 25 Sep 2010 18:21:02 -0400, I am Tosk wrote: In article 084c9f63-3d17-496f-8a21-74c4d53f4a02 , says... MiniCup #`1 is still sitting on sawhorses while I decide whether or not to rebuild her. *#2 which I have been using developed cracks from rot in the 3/16" poor quality ply I used on her even though she had been glassed with 4 oz glass and epoxy. *While fixing this I found more rot so ended up covering her entire rear with another layer of glass. *Am almost done. *However, she seems to have absorbed some water that I cannot get rid of as she seems heavy even with ports cut in all her spaces. Am looking over the old MiniCup plans and considering how to design a modern version that will be much lighter. *Considering using 3mm Okuome Ply covered with 8 oz glass all over with stiffening ribs of foam and glass. All interior joints would be glass taped and interior epoxied as well to seal the wood. Transom would be reinforced with thicker ply and G10 glass composite for the rudder stresses. *Cockpit and mast step would be self bailing and all hardware of either bronze or SS. *Instead of being a "hardware store boat", I'd specify buying actual boatbuilding screws and pulleys made for boats. *I'd reccomend buying 1/8" Al tubing for the mast and 1/16" for the two other spars.. The sail should be sewn from white polytarp, none of this duct tape stuff and visqueen. *I have devised a much improved gooseneck where the two spars attach to the mast. *Any other ideas? Sounds to me like you are going to use 1/8 inch ply and glass for structure.. Glass doesn't add structure really it should be used for protection if not laminated into a hull... Use 6mm plywood and protect it with 4 oz tight weave if you need abrasion protection and such... Err.. why is it that glass over plywood doesn't add structure while glass cloth over foam does? Cheers, Bruce (bruceinbangkokatgmaildotcom) Laminated glass might. One layer over a 3mm plywood, not so much... In most applications for small boats such as this, the glass is more as a sealer and protection than a structural component. Especially one layer of 4 oz tight weave... -- OH, I could do the 105 footer, but I would hate to waste the last few seconds of my life with my eyes closed, screaming like a little girl...;) More thoughts. Bottom would have 8 oz glass for better wear. The cockpit would be glassed inside with 4 oz. All seams taped with 6 oz with epoxy filets inside and out. The center widthwise support made from 2X2" would not be used. It only serves to stiffen the joint of two sheets and this can be done with glass. Most of the curve of the bottom would be produced by the fore and aft cockpit bulkheads. These would all have 3/4 X 3/4" reinforcing at the edges just as the MiniCup does for ease of screwing together and to yield a large glue surface. These will all be epoxy filleted and glassed. My MiniCups made from 3/16" ply have needed reinforcing across the wide foredeck and aft deck areas so I will provide this. The transom of the original MiniCup is very poor and I had to make it stronger. I will use 1/4" ply glassed on both sides AND the G10 composite to attach the rudder pintles (or are they gudgeons?) to the transom. The transom will be attached with 20 oz biax to the sides and bottom. I do not see how to make this boat as stitch and glue so will simply update the use of "stringers" as attachments for the sides to the bottom and deck to sides. |
Resurrecting the MiniCup
|
Resurrecting the MiniCup
On Mon, 27 Sep 2010 10:57:13 -0700 (PDT), Frogwatch
wrote: On Sep 27, 6:58*am, I am Tosk wrote: In article , says... On Sat, 25 Sep 2010 18:21:02 -0400, I am Tosk wrote: In article 084c9f63-3d17-496f-8a21-74c4d53f4a02 , says... MiniCup #`1 is still sitting on sawhorses while I decide whether or not to rebuild her. *#2 which I have been using developed cracks from rot in the 3/16" poor quality ply I used on her even though she had been glassed with 4 oz glass and epoxy. *While fixing this I found more rot so ended up covering her entire rear with another layer of glass. *Am almost done. *However, she seems to have absorbed some water that I cannot get rid of as she seems heavy even with ports cut in all her spaces. Am looking over the old MiniCup plans and considering how to design a modern version that will be much lighter. *Considering using 3mm Okuome Ply covered with 8 oz glass all over with stiffening ribs of foam and glass. All interior joints would be glass taped and interior epoxied as well to seal the wood. Transom would be reinforced with thicker ply and G10 glass composite for the rudder stresses. *Cockpit and mast step would be self bailing and all hardware of either bronze or SS. *Instead of being a "hardware store boat", I'd specify buying actual boatbuilding screws and pulleys made for boats. *I'd reccomend buying 1/8" Al tubing for the mast and 1/16" for the two other spars. The sail should be sewn from white polytarp, none of this duct tape stuff and visqueen. *I have devised a much improved gooseneck where the two spars attach to the mast. *Any other ideas? Sounds to me like you are going to use 1/8 inch ply and glass for structure.. Glass doesn't add structure really it should be used for protection if not laminated into a hull... Use 6mm plywood and protect it with 4 oz tight weave if you need abrasion protection and such... Err.. why is it that glass over plywood doesn't add structure while glass cloth over foam does? Cheers, Bruce (bruceinbangkokatgmaildotcom) Laminated glass might. One layer over a 3mm plywood, not so much... In most applications for small boats such as this, the glass is more as a sealer and protection than a structural component. Especially one layer of 4 oz tight weave... -- OH, I could do the 105 footer, but I would hate to waste the last few seconds of my life with my eyes closed, screaming like a little girl...;) More thoughts. Bottom would have 8 oz glass for better wear. The cockpit would be glassed inside with 4 oz. All seams taped with 6 oz with epoxy filets inside and out. I'm not sure that is the best solution, although it certainly can be argued. My own experience is that if one plans on dragging a fiberglass boat up on beaches it is better to use some form of sacrificial "wear strips" - perhaps wood laths glued on the bottom to protect the bottom, although this certainly can be argued. By the way, I'm sure that you know that 8 oz. cloth actually weighs approximately twice that figure when installed due to the resin used. The fillets are there to ensure that the cloth adheres to the complete joint as glass cloth cannot be bent 90 degrees. So anywhere the cloth is planned to be applied the surfaces must be a smooth radius. It is "epoxy filler", by the way :-) The center widthwise support made from 2X2" would not be used. It only serves to stiffen the joint of two sheets and this can be done with glass. Most of the curve of the bottom would be produced by the fore and aft cockpit bulkheads. These would all have 3/4 X 3/4" reinforcing at the edges just as the MiniCup does for ease of screwing together and to yield a large glue surface. These will all be epoxy filleted and glassed. My MiniCups made from 3/16" ply have needed reinforcing across the wide foredeck and aft deck areas so I will provide this. The transom of the original MiniCup is very poor and I had to make it stronger. I will use 1/4" ply glassed on both sides AND the G10 composite to attach the rudder pintles (or are they gudgeons?) to the transom. The transom will be attached with 20 oz biax to the sides and bottom. I do not see how to make this boat as stitch and glue so will simply update the use of "stringers" as attachments for the sides to the bottom and deck to sides. I have essentially stopped using fasteners in building small wooden boats as a properly designed epoxy joint is already stringer then the parent wood. A thought about the stringers - they might be 3/4 X 3/4 three sided stringers which would give the gluing surfaces and reduce the requirement of fairing considerably. Epoxy is heavy and the less one can use the lighter the structure. Cheers, Bruce (bruceinbangkokatgmaildotcom) |
Resurrecting the MiniCup
On Mon, 27 Sep 2010 06:58:45 -0400, I am Tosk
wrote: In article , says... On Sat, 25 Sep 2010 18:21:02 -0400, I am Tosk wrote: In article 084c9f63-3d17-496f-8a21-74c4d53f4a02 , says... MiniCup #`1 is still sitting on sawhorses while I decide whether or not to rebuild her. #2 which I have been using developed cracks from rot in the 3/16" poor quality ply I used on her even though she had been glassed with 4 oz glass and epoxy. While fixing this I found more rot so ended up covering her entire rear with another layer of glass. Am almost done. However, she seems to have absorbed some water that I cannot get rid of as she seems heavy even with ports cut in all her spaces. Am looking over the old MiniCup plans and considering how to design a modern version that will be much lighter. Considering using 3mm Okuome Ply covered with 8 oz glass all over with stiffening ribs of foam and glass. All interior joints would be glass taped and interior epoxied as well to seal the wood. Transom would be reinforced with thicker ply and G10 glass composite for the rudder stresses. Cockpit and mast step would be self bailing and all hardware of either bronze or SS. Instead of being a "hardware store boat", I'd specify buying actual boatbuilding screws and pulleys made for boats. I'd reccomend buying 1/8" Al tubing for the mast and 1/16" for the two other spars. The sail should be sewn from white polytarp, none of this duct tape stuff and visqueen. I have devised a much improved gooseneck where the two spars attach to the mast. Any other ideas? Sounds to me like you are going to use 1/8 inch ply and glass for structure.. Glass doesn't add structure really it should be used for protection if not laminated into a hull... Use 6mm plywood and protect it with 4 oz tight weave if you need abrasion protection and such... Err.. why is it that glass over plywood doesn't add structure while glass cloth over foam does? Cheers, Bruce (bruceinbangkokatgmaildotcom) Laminated glass might. One layer over a 3mm plywood, not so much... In most applications for small boats such as this, the glass is more as a sealer and protection than a structural component. Especially one layer of 4 oz tight weave... Agreed that a layer of glass on one side is inferior to glass on both sides but I would argue that it is far more then simply a sealer. In fact if it is simply a sealer there would be no sense in applying the cloth as glass cloth is far from being water proof, quite the contrary in fact. If sealing were the sole purpose then all the boat designers wouldn't be recommending "glass over...." . The layer of glass actually makes the 3 mm ply substantially more resistant to bending then bare ply would be. A parallel might be fabric covered aircraft where the airframe is covered with a cloth which is perhaps less strong then a bed sheet, which is then reinforced with coats of cellulose dope. Cheers, Bruce (bruceinbangkokatgmaildotcom) |
Resurrecting the MiniCup
In article ,
says... On Mon, 27 Sep 2010 06:58:45 -0400, I am Tosk wrote: In article , says... On Sat, 25 Sep 2010 18:21:02 -0400, I am Tosk wrote: In article 084c9f63-3d17-496f-8a21-74c4d53f4a02 , says... MiniCup #`1 is still sitting on sawhorses while I decide whether or not to rebuild her. #2 which I have been using developed cracks from rot in the 3/16" poor quality ply I used on her even though she had been glassed with 4 oz glass and epoxy. While fixing this I found more rot so ended up covering her entire rear with another layer of glass. Am almost done. However, she seems to have absorbed some water that I cannot get rid of as she seems heavy even with ports cut in all her spaces. Am looking over the old MiniCup plans and considering how to design a modern version that will be much lighter. Considering using 3mm Okuome Ply covered with 8 oz glass all over with stiffening ribs of foam and glass. All interior joints would be glass taped and interior epoxied as well to seal the wood. Transom would be reinforced with thicker ply and G10 glass composite for the rudder stresses. Cockpit and mast step would be self bailing and all hardware of either bronze or SS. Instead of being a "hardware store boat", I'd specify buying actual boatbuilding screws and pulleys made for boats. I'd reccomend buying 1/8" Al tubing for the mast and 1/16" for the two other spars. The sail should be sewn from white polytarp, none of this duct tape stuff and visqueen. I have devised a much improved gooseneck where the two spars attach to the mast. Any other ideas? Sounds to me like you are going to use 1/8 inch ply and glass for structure.. Glass doesn't add structure really it should be used for protection if not laminated into a hull... Use 6mm plywood and protect it with 4 oz tight weave if you need abrasion protection and such... Err.. why is it that glass over plywood doesn't add structure while glass cloth over foam does? Cheers, Bruce (bruceinbangkokatgmaildotcom) Laminated glass might. One layer over a 3mm plywood, not so much... In most applications for small boats such as this, the glass is more as a sealer and protection than a structural component. Especially one layer of 4 oz tight weave... Agreed that a layer of glass on one side is inferior to glass on both sides but I would argue that it is far more then simply a sealer. Not what I said at all, for smaller boats, glass on both sides only invites more rotting and moisture retention... In fact if it is simply a sealer there would be no sense in applying the cloth as glass cloth is far from being water proof, quite the contrary in fact. Of course there would be "sense" in applying the glass. To understand you must first understand that glass it to hold resin, resin is to fill glass.. They work together, it's just the way it is... If sealing were the sole purpose then all the boat designers wouldn't be recommending "glass over...." . Sure they would, cause glass it to hold resin... The layer of glass actually makes the 3 mm ply substantially more resistant to bending then bare ply would be. A parallel might be fabric covered aircraft where the airframe is covered with a cloth which is perhaps less strong then a bed sheet, which is then reinforced with coats of cellulose dope. Don't know much about airplanes but I bet the framework is substantial under that skin. Either way, a 4 oz layer of glass over 6mm Occoume does not all all that much stiffness. Glass is good for adding structure when laminated into fillets, but trying to use it to stiffen a plywood hull is a waste of time and poor design. The guy who taught me to use glass and resin had over 40 years in the shop, fabricating with glass, resin, and other combinations of materials. He knew more than either of the two distributors I bought from as to be expected as his experience was all hands on in the shop. Most boat builders I know don't really understand as much about glass and resin as they think they do, but I know how my ideas are taken here and not to be an ass, I know how you are about being challenged on such issues so I will leave this as my last post to this thread.. Take it for what it's worth... I will note that I have built over 50 plywood, glass, and resin, stitch and tape, tack and tape, and glue and screw type boats in my day... Cheers to you too;) Scotty from SmallBoats.com Cheers, Bruce (bruceinbangkokatgmaildotcom) -- OH, I could do the 105 footer, but I would hate to waste the last few seconds of my life with my eyes closed, screaming like a little girl...;) |
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