resin bonding issue Apoxy vs Vinyl vs Ploy

Cebu, please consider the good advise you have been given here. After nearly a half century in the repair side of this business, I can asuure you that core failures are quite common. Sometimes with no obvious external evidence, and occuring in the best core materials available.
I understand the financial considerations but with all the effort and money involved in any boatbuilding project, to try and save money on core selection just doesn't make sense.
Do some more research and try to find one successful cardboard cored boat still in operation. One. The only cardboard construction I can find are one day wonders, built for a single race, and most don't finish the race.
Cardboard and water just don't mix.

 

To even consider using cardboard for a core is idiotic !
Yes i have seen it being used and i have seen that it lasted less time than it took to make the panel it was used on . Dont waste your time and dont waste your materials !!

 

Cebu is a place in the Philippines and Tricel has been around for a while that is made from Kraft paper.

 

Yes it is. Always warm and sunny. Plenty of nice beaches.

 

That is a "B flute" single layer design. It also has the "p flute" where the undulation is much wider. Both comes in single layer or triple layer. Both are not limited to cardboard variety as there are plastic ones.

From an engineering standpoint, it is similar to corrugated roofs in houses, or the smaller but much wider corrugations seen in long span roofing, except there is a skin on both sides.

Technically, you are using it as a core material. You are limited by the thickness available. The core acts in compression, the skin acts in tension or compression depending on where the force is applied.

The thickness determines flexibility. The skin is the stressed member of the structure. With a little force, it will flex a little, giving a high impact strength. With more force, it will flex more, so you need to increase the thickness (maybe a double layer ype). As you increase thickness, the skin (as it moves away from the neutral axis) receives more stress, so a little more skin thickness is required (or higher strength material).

Conversely, you can decrease the panel size. The panel edges bounded by the frames and stiffeners. Deflection of the panel is determined by the scantlings bounding the panel. Stiff equals small panel size or thick panels and large panel size.

Let us go back to the core. The core is stiffened by closely spaced longitudinals. In reality, the core is generally in compression with shear greatest in the mid section or neutral axis. To optimize the material property of the paper, it must be vertical, like the "honeycomb" core. "Nomex" honeycomb (paper) or Nidacore (plastic), or a deviation, balsa cut in endgrain (vertical fibers).

You are comparing a structure between an aircraft and a boat. The requirements is very different.

So will it work? Yes and No. For aircraft, yes but it is not the optimum material. Honeycomb, foam core. and even balsa is the better choice.

For boat, No. It gets wet all the time and forces are much greater.

You need to consult a structural engineer should you ever want to pursue the project.

 

In Holland there is a company selling drywall - cardboard - drywall sandwich panels. Makes walls in minutes. (install a wooden triangular piece on the floor, and a square one on the ceiling. Slide the panels right in. Even with light buttons and the like.

For boats? Perhaps some interior, but nothing structural.

 

I would like to take a moment to thank all who have taken time to help me discuss my cardboard project. All inventors out there have to take chances and have been told that they are stupid or crazy and wasting their time. I may be one of them but I still see many advantages in this method. But my method may need to be altered. I do not yet see any of your concerns as valid but core separations due to resin not fully wicking deep into the inner corrugation. But this discussion also has made me see another area of failure none of us spotted. That being the constant crashing of the hull on waves causing the inner resin soaked corrugations shattering because they are brittle. I checked out the Tricel, War Whoop mentioned. It is for Marine use and is a variation of the cardboard method I suggested. I have also thought of using smaller strips of cardboard 12 to 18 inches wide. They would be glassed in and separated by 3 to 4” of just glass-to-glass to act as solid fiberglass ribs then another set of strips of cardboard re-laid. I also thought of having ¼ holes in the cardboard for columns of resin connecting one layer of fiberglass to another separated by cardboard.

Here is a question for all of you helping me. I saw a photo somewhere and I cannot find it. The fiberglasser had used what looked like a sheet of flexible foam with holes in it. It would allow the resin to fill the holes just like the ¼ holes I suggested in my process. This might be a good substitute for my cardboard idea. Anyone know what it is? Where I can get it and know of anyone who has used it. The boat must be as strong as light. I cannot stress how important that the weight be kept as low as possible. If I am on the river and stuck in the backwater pools of the Mississippi on a sandbar I must be able to get myself unstuck by myself. I could be lost in there for weeks and not see someone.

I have also thought of a test for the core separation issue. I plan on building a test panel 1.5’ x 1.5’ in the configuration I had proposed. I would then let it cure for a few weeks then place it on the yard grass and hit it with a rubber mallet a few hundred times. I would then cut it in half with a bandsaw and check the separation. I also plan on building a 0.5’ x 0.5’ test panel and coat it with a sealer like I would use on my boat. I would then submerse it in a tub of water and leave it sit over the winter and the cut it in half and check for damage. Any other test ideas are welcome. I used to due destructive testing for the handheld computers that the Pepsi drivers use and the grocery clerks use. So testing is something I have experience with but still I cannot think of everything.

Again thank you all for staying with this discussion. You are the only ones I have to sound out my ideas on. Oh and do a reality check on my ideas.



ThanX

Cebu

 

Just to keep record straight, people make boats out of cardboard every year. My university has a contest every year to see which boat sinks first, last, etc... Prizes are given for ingenuity, design, and theme. I won one year and was promptly disqualified for using polyester on cardboard, it did last longer than rest. Others sunk my boat out of envy.

That said, cardboard is not very strong and would not add anything to boat. I have since experimented with epoxy encapsulate polyester, foam covered with poly/epoxy and Aluminum framed epoxy. In search for the cheapest lightest boat, I have found is an aluminum frame covered by a tarp with polyester and epoxy.

 

http://www.ibiblio.org/eldritch/nhb/paperc/intro.html

http://kcupery.home.isp-direct.com/PBArtic/shell.html

 

What are your actual desires? If you want to go boating, by far the best thing would to be to buy a used boat, motor and trailer. You could be on the water next week. It's enticing to design and build your own and have a big accomplishment to your credit, but it will probably cost a lot more and you might not get on the water until 2012.

What do you plan to use the boat for?

Do you happen to know any last name Davis people there in Cedar Rapids?

 

I need at least 18 to 20 foot Jon boat for the Mississippi river because of the large wakes and whirlpools on the river. Jon boats that large are very hard to find and new ones are very expensive. Also aluminum punctures to easy and there are a lot of underwater obstructions in the river due to frequent floods. Aluminum is also very noisy and scares fish. I would still have to spend $1000 or more to out fit it with a wood and carpet floor, live wells, steering console.

Also I have found the following material that I might substitute for the cardboard. It does not have the holes in it like the one I saw.

http://www.soundproofingamerica.com/AMF.pdf
http://www.rochfordsupply.com/shop/Foam/Closed_Cell/Blue_Closed_Cell_Foam/index.html

I would enclose it in the same manner as the cardboard - strips 12" to 18" with all fiberglass ribs in-between and layered glass-glass-glass-foam-glass-foam-glass-foam-glass-glass


So does any one think think this is too many layers?
How many layers of glass are in a fishing boat?

Could I get away with only?
glass-glass-foam-glass-foam-glass

Also I don't know any Davis.

And War Whoop is right Cebu is in the Philippines, and the place my wife is from. The most amazing place on earth after Hong Kong.

 

Two guys had a fiberglass shop and came up with an idea of using foam logs and fiberglass to build boats. They had a falling out and one of them patented the idea and did well with his company called Carolina Skiffs. The other guy patented an idea very similar to your alternating cardboard strips (using foam) trying to cash in also, but was the proverbial day late and a dollar short, the market and momentum was already captured by his ex friend.

If you use the 'search' abilities here, you can find where I've posted particulars about the Carolina Skiff patents, how they have expired and are public domain now which means anybody can use the process for free. You'll see where I've posted about using tile board for a jon boat mold, using cheap readily available roofing foam with polyester resin, experiments with cheap Home Depot foam and holes to form columns of resin between layers of glass, and holes threaded with fiberglass roven to form fiberglass reinforced columns of resin between layers of glass that tie them together in compression and tension.

What you want to do with the cardboard is creative and has merit as War Whoop showed with his site cite Tricel, (you do see the difference between your cardboard and their cardboard?) but you are not actually inventing anything new. It is very hard to think of anything new that hasn't been thought of before and usually tried also. The Carolina Skiff patent was an almost direct copy of insulated bulkheads used in fishing boats, illustrated and described years before in National Fisherman.

So, if you want to put your money into your idea because you want to see if it will work, go ahead and do it. You'll surely learn something and gain some experience, you might end up with something worthwhile and usable.

****I see you've posted in the meantime about some other foams. They won't work, they are too flexible.

 

I was leaning on the polyethylene foam - LDPE for the core, it's the kind of foam the backpackers use to put under their sleeping bag. it appears that it is compatible with polyester resin. Also it is cheap has great strength and tear resistance, light weight but is quite flexible. I have found the design.net article on foam cores at

http://www.boatdesign.net/articles/foam-core/index.htm

It does not discuss LDPE and was no help. You stated that it should be rigid. My understanding is that the thickness is most important from this article not being rigid. I will need to spend more time on the math in the article to see how this variable effects the structure. Unless you have a better source. ThankX for the info.


CEBU

 

Cebu,

I see you are hell bent on making it work. and longevity is not an issue. No need to reinvent the wheel, just make it turn.

You can substitute manila hemp for fiberglass for the skin. It is just as good. Much research has been done on "organic fibers". It is just not popular at present.

If you can find "V" flute cardboard, it is much stronger. This is an "isogrid" structure and NASA is using this principle. Some universities have also done research on 3d isogrid lattice work.

Since the core is a series of longitudinals stiffeners and good only for longitudinal strength, try laminating the core on a -45 degree x + 45 degree orientation. Better yet, try 0,-45,+45, 90 degree for isotrophic qualities.

Try to find a paper core that is sugar free. Termites like sugar. To make it fireproof, dip it in borax solution. To make it water resistant and fire resistant, dip it in phenolic resin. That is "nomex" technology.

Good luck!

 

RX nice post,Cebu do not forget in a core panel where the point of maximum shear is at and consider that in your design also increasing the cross section will help .The Polyethylene foams there will be bonding issues using common resins.