Ply Construction - Wharram Builders and Friends2024-03-29T16:00:21Zhttps://wharrambuilders.ning.com/forum/topics/ply-construction?commentId=2195841%3AComment%3A291794&x=1&feed=yes&xn_auth=noHi Roger, thanks for your rep…tag:wharrambuilders.ning.com,2022-01-22:2195841:Comment:2917942022-01-22T18:38:24.071ZLovakohttps://wharrambuilders.ning.com/profile/Lovako
<p>Hi Roger, thanks for your reply, imensly appreciated.</p>
<p>I understand all you say and am thankful for constructive information.</p>
<p>I just need to remind all that here where I am i only have ply and fibreglass to work with - no foam sandwich is available. It is the "sticks" Not even epoxy glue is available. We make use of thickened resin with baby powder.</p>
<p>We are 300 years behind time. I am realy so appreciative of all input.</p>
<p>Thanks and take care</p>
<p>Dries -…</p>
<p>Hi Roger, thanks for your reply, imensly appreciated.</p>
<p>I understand all you say and am thankful for constructive information.</p>
<p>I just need to remind all that here where I am i only have ply and fibreglass to work with - no foam sandwich is available. It is the "sticks" Not even epoxy glue is available. We make use of thickened resin with baby powder.</p>
<p>We are 300 years behind time. I am realy so appreciative of all input.</p>
<p>Thanks and take care</p>
<p>Dries - Madagascar</p> I know from my own projects t…tag:wharrambuilders.ning.com,2022-01-11:2195841:Comment:2917472022-01-11T01:25:04.453ZRogerhttps://wharrambuilders.ning.com/profile/RogerSullivan
<p>I know from my own projects that 6mm (1/4") plywood glassed on <span style="text-decoration: underline;">both</span> sides with 6oz cloth is extremely stiff and strong. I don't have any data, but would expect it to be at least as strong as 9mm ply, but is also better protected from the elements and wear and tear. WEST have data on relative stiffness and strength of glass and ply combinations if you look around on the interwebs.</p>
<p>I know from my own projects that 6mm (1/4") plywood glassed on <span style="text-decoration: underline;">both</span> sides with 6oz cloth is extremely stiff and strong. I don't have any data, but would expect it to be at least as strong as 9mm ply, but is also better protected from the elements and wear and tear. WEST have data on relative stiffness and strength of glass and ply combinations if you look around on the interwebs.</p> Chopped Strand Mat adds weigh…tag:wharrambuilders.ning.com,2022-01-09:2195841:Comment:2914572022-01-09T16:45:52.940ZDean Wilkersonhttps://wharrambuilders.ning.com/profile/DeanWilkerson
<p>Chopped Strand Mat adds weight, but very little strength. Fiberglass epoxy adds an immense amount of strength, so much so that foam sandwich can be a direct replacement for plywood in many instances. There is some disagreement as to what can be used for direct replacement. Infusion makes a big difference in weight, avoiding excess resin while insuring a properly saturated efficient structure, epoxy resin beyond what is actually needed is just useless weight. It will also ensure a good…</p>
<p>Chopped Strand Mat adds weight, but very little strength. Fiberglass epoxy adds an immense amount of strength, so much so that foam sandwich can be a direct replacement for plywood in many instances. There is some disagreement as to what can be used for direct replacement. Infusion makes a big difference in weight, avoiding excess resin while insuring a properly saturated efficient structure, epoxy resin beyond what is actually needed is just useless weight. It will also ensure a good bond to the core. You can find information on boatdesign.net, and other places. My inclination would be to use a fairly thick core.... core thickness greatly increases stiffness. I won't give equivalency figures, because I feel some are radically conservative, and others are on the "optimistic" side. Of course a foam sandwich structure is also basically immune to rot. Marine PVC foams are often drilled and or sliced to provide adhesion and allow flex when being laid up. I wouldn't build something like this with foam without doing my "due diligence", which would include lots of reading, and some test pieces. </p>
<p> Plywood is not an "efficient" structural material in terms of strength to weight ratio, usually requiring lots of additional structure because it lacks sufficient stiffness to span large areas without support... unless you resort to excessively thick plywood. Ideally the highest tensile strength should be on at the surface, declining toward the center. The I beam is the model of structural efficiency, and foam core somewhat mimics this model. I used to have some truck bed material that was an extruded aluminum material that essentially amounted to many small Ibeams joined together forming a solid deck. Incredibly stiff and rugged. To me that is a near perfect model of what you are trying to achieve with foam core. In a perfect world we would have a foam that varies in density from high density surface to low density at the center like an egg just beyond the "soft boil" stage....... and it would be shot through with fiber... something we will of course never see........... how could you manufacture it? I like foam sandwich for the fact that you can build a boat without stringers (to catch moisture and dirt and grow mold, and foam adds insulation... reducing or eliminating condensation, and properly done foam sandwich runs about 66% of the weight of plywood on stringers for the same strength, and of course zero rot. With your project, the only benefits are reduced weight and elimination of rot...... both of which are significant. If interested in this topic, I recommend using Google extensively and using your own judgment. Rob Denny designer of the Harry Proa is one of the gurus of foam sandwich and you can find a lot of his writings on the web. IMHO he leans more toward the "optimistic", than the "conservative" side, but he practices what he preaches, and has a lot of experience with infused foam sandwich.</p> Ian R, instead of pulling peo…tag:wharrambuilders.ning.com,2022-01-09:2195841:Comment:2915512022-01-09T08:44:46.544ZIain & Cherry Mae Cairnshttps://wharrambuilders.ning.com/profile/IainCairns
<p>Ian R, instead of pulling people down with any idea's they may have about their boat, sail your perfect boat out into the middle of the bay,, throw the anchor over the bow ,, however don't let go.</p>
<p>Lovato is asking for collective thought, and you berate him.</p>
<p>Dude !!!!</p>
<p>Ian R, instead of pulling people down with any idea's they may have about their boat, sail your perfect boat out into the middle of the bay,, throw the anchor over the bow ,, however don't let go.</p>
<p>Lovato is asking for collective thought, and you berate him.</p>
<p>Dude !!!!</p> Hello again Lovato:
Yes you…tag:wharrambuilders.ning.com,2021-12-24:2195841:Comment:2917192021-12-24T22:58:13.876ZIan Rhttps://wharrambuilders.ning.com/profile/IanR
<p>Hello again Lovato:</p>
<p></p>
<p>Yes you may have built a 42ft boat, but let's face it, one boat is not the same as another.</p>
<p></p>
<p>My boat is almost 30 yrs old and looks new: how about your boat?</p>
<p></p>
<p>I have got to laugh, you even try to ban me for commenting on your ideas (sic)!</p>
<p> </p>
<p>Well I wish you a happy Christmas wherever you are and good sailing.</p>
<p></p>
<p></p>
<p>Hello again Lovato:</p>
<p></p>
<p>Yes you may have built a 42ft boat, but let's face it, one boat is not the same as another.</p>
<p></p>
<p>My boat is almost 30 yrs old and looks new: how about your boat?</p>
<p></p>
<p>I have got to laugh, you even try to ban me for commenting on your ideas (sic)!</p>
<p> </p>
<p>Well I wish you a happy Christmas wherever you are and good sailing.</p>
<p></p>
<p></p> I agree that CSM is a poor ch…tag:wharrambuilders.ning.com,2021-12-21:2195841:Comment:2916532021-12-21T17:13:31.519ZDean Wilkersonhttps://wharrambuilders.ning.com/profile/DeanWilkerson
<p>I agree that CSM is a poor choice, but woven fiber makes sense. However there is another option if stiffness is the goal, and that is foam sandwich. You could also use thin ply on one face in lieu of glass if you want that wood look, provided you use the proper procedure to get a good bond. A piece of 1" divinicell for example with two glass faces would yield a very strong stiff floor that would still be quite light weight.</p>
<p>Here are a few files that may be useful... I don't…</p>
<p>I agree that CSM is a poor choice, but woven fiber makes sense. However there is another option if stiffness is the goal, and that is foam sandwich. You could also use thin ply on one face in lieu of glass if you want that wood look, provided you use the proper procedure to get a good bond. A piece of 1" divinicell for example with two glass faces would yield a very strong stiff floor that would still be quite light weight.</p>
<p>Here are a few files that may be useful... I don't know how to interpret the top line (thickness) in this first chart, but flexural strength and weight are pretty obvious......... where do the 7 and 37 figures come from and what do they mean?</p>
<p><a href="https://external-content.duckduckgo.com/iu/?u=http%3A%2F%2Fwww.flight-mechanic.com%2Fwp-content%2Fuploads%2F2017%2F11%2F7-18.jpg&f=1&nofb=1" target="_blank" rel="noopener"><img src="https://external-content.duckduckgo.com/iu/?u=http%3A%2F%2Fwww.flight-mechanic.com%2Fwp-content%2Fuploads%2F2017%2F11%2F7-18.jpg&f=1&nofb=1&profile=RESIZE_710x" class="align-full"/></a><a href="https://storage.ning.com/topology/rest/1.0/file/get/9933250880?profile=original" target="_blank" rel="noopener"><img src="https://storage.ning.com/topology/rest/1.0/file/get/9933250880?profile=RESIZE_710x" class="align-full"/></a><a href="https://storage.ning.com/topology/rest/1.0/file/get/9933256275?profile=original" target="_blank" rel="noopener"><img src="https://storage.ning.com/topology/rest/1.0/file/get/9933256275?profile=RESIZE_710x" class="align-full"/></a></p>
<p></p>
<p></p> Hi Robert, Im all ears when p…tag:wharrambuilders.ning.com,2021-10-29:2195841:Comment:2910952021-10-29T07:38:49.917ZLovakohttps://wharrambuilders.ning.com/profile/Lovako
<p>Hi Robert, Im all ears when people answer me in a decent way.</p>
<p>I built a large box hanging between beam 2 and 3 on a lip with x3 25mm stainless safety pins on each beam. My box lasted 10 years but must be rebuilt as the frame was built from soft wood. I now intend to use Sui, a hard wood that can stand the elements very well “weatherproof” found here in Madagascar. I will build in the same way except my floor frame will be 70mm and not the 100mm I used previously.</p>
<p>My thinking…</p>
<p>Hi Robert, Im all ears when people answer me in a decent way.</p>
<p>I built a large box hanging between beam 2 and 3 on a lip with x3 25mm stainless safety pins on each beam. My box lasted 10 years but must be rebuilt as the frame was built from soft wood. I now intend to use Sui, a hard wood that can stand the elements very well “weatherproof” found here in Madagascar. I will build in the same way except my floor frame will be 70mm and not the 100mm I used previously.</p>
<p>My thinking is, instead of using 9mm ply I wondered if I can go for a thinner ply glass cloth covered to save weight? Not sure it will work as cloth/resin is a heavy in it’s self.</p>
<p>Maybe I need to do an experiment, weigh and see. :-( only once I get back to MADland, im stuck in SA till borders open.</p>
<p>Your input is much appreciated.<a href="https://storage.ning.com/topology/rest/1.0/file/get/9747188493?profile=original" target="_blank" rel="noopener"><img src="https://storage.ning.com/topology/rest/1.0/file/get/9747188493?profile=RESIZE_710x" class="align-full"/></a></p>
<p></p> I am also rebuilding the boxe…tag:wharrambuilders.ning.com,2021-10-28:2195841:Comment:2909982021-10-28T15:56:46.915ZRoberthttps://wharrambuilders.ning.com/profile/Robert232
I am also rebuilding the boxes on my Pahi 42.<br />
<br />
Would suggest avoiding chopped strand because of poor strength to weight ratio. Skins of woven cloth on both sides is a good idea—especially for water and abrasion resistance.<br />
<br />
In fiberglass sandwich construction, increasing core thickness gives better stiffness at lower weight compared to increasing skin thickness.<br />
<br />
Ribs/tophat reinforcements can increase strength with little extra weight. I have to put some thought into the best strategy.<br />
<br />
Please…
I am also rebuilding the boxes on my Pahi 42.<br />
<br />
Would suggest avoiding chopped strand because of poor strength to weight ratio. Skins of woven cloth on both sides is a good idea—especially for water and abrasion resistance.<br />
<br />
In fiberglass sandwich construction, increasing core thickness gives better stiffness at lower weight compared to increasing skin thickness.<br />
<br />
Ribs/tophat reinforcements can increase strength with little extra weight. I have to put some thought into the best strategy.<br />
<br />
Please share any insights you come up with. Smart arse, i happen to have…tag:wharrambuilders.ning.com,2021-10-23:2195841:Comment:2905942021-10-23T08:23:32.450ZLovakohttps://wharrambuilders.ning.com/profile/Lovako
<p>Smart arse, i happen to have built my 42ft not a 31 dingy.</p>
<p>I used cloth.</p>
<p>Please get off my discussion</p>
<p></p>
<p>Smart arse, i happen to have built my 42ft not a 31 dingy.</p>
<p>I used cloth.</p>
<p>Please get off my discussion</p>
<p></p> If you were meaning fibreglas…tag:wharrambuilders.ning.com,2021-10-22:2195841:Comment:2908932021-10-22T21:10:06.747ZIan Rhttps://wharrambuilders.ning.com/profile/IanR
<p>If you were meaning fibreglass cloth in epoxy, that's a different thing. Since you mentioned chopped strand that would indicate you don't know the difference between epoxy/fibreglass laminating and fibreglass laminating.</p>
<p></p>
<p>In which case get someone else to fix your boat. No apologies for being brusque....you might kill someone.</p>
<p>If you were meaning fibreglass cloth in epoxy, that's a different thing. Since you mentioned chopped strand that would indicate you don't know the difference between epoxy/fibreglass laminating and fibreglass laminating.</p>
<p></p>
<p>In which case get someone else to fix your boat. No apologies for being brusque....you might kill someone.</p>