Balsa core lamination

[rjdubiel]

Ok, I remember now! I have a venturi pump and the pucks to hook the pump up to the part your bagging. You can use if you wanted, it runs of an air compressor, Just it needs a big compressor or one that can keep up and a nice electric bill that month (thats what i did). Vacuum bag supplies are not that expensive at all, just need peal ply, the bagging material and some of the sealing tape. I did little 3 foot sections at a time to make sure I did it correct, next time, if there is another, I will do big sections all at once. But something does not sound right from your posts. Most here like some sort of corebond, or thickened resin to bed the balsa into like laying tile.

Make sure you have the boat supported correct and straight, if on the trailer still make sure that the bunks are not pushing the hull up by the weight of the boat pushing down on the trailer (no core and the boat is like a flimsy potato chip). I had to get my boat off the trailer and on the floor to get it straight and in the original correct form. The bow weight would deform the bottom of the boat until i supported the boat with a jig and a strap from the bow to the ceiling to remove weight of the bow pushing down. I left the cap on and completely removed the core, stringers and transom.

[tunnels]

I have 13mm core (1/2"). I will ask the guy at the supply store about triaxial mat. If I don't put full stringers in can I get away without putting a plywood floor in? I want to put a knee in braving the transom to the floor.

Why use a plywood floor ?? in less than a year it will have absorbed enough moisture and water to double its original light weight !!
sorry not that I don't like wood just I don't like wood under and including floors !! ! the knee thing and wooden transoms are another thing as well by building a proper shaped glass transom and using shape to achieve strength you can have a solid glass transom with step back and simply cut the old one off and dump it and glass the new one on inside and out , save weight and never have to worry about ever replacing the transom for the rest of the life of the boat and no knees needed the internal strengthening is done with a aft deck and splash well all glass !its not hard to do just takes a little planning of how and what to use . shape in panels is a great way to make panels strong but not heavy use the right glass and its amazingly stiff !! take a look at your car !! theres not one panel any where that's just flat ! every panel had creases and curves and shape but the skins are really thin and the steel it made from is stronger also . so using things like double bias glass and that triaxle plus unidirectional glass . There I no place for those exotics like carbon and Kevlar , so you can use the same principle of shape equals strength . Boats in general are prehistoric and way behind in there design and the way they are built. Some things haven't changed in 100 years !
oh and if you cant find that triaxle just use 1 x double bias and 1x layer of unidirectional over the top !! and there's you triaxle .the orientation of fibers is where its all at these days and the aircraft industry Is learning and also the automotive industry but the marine industry I still trying to get to the starting gates as usual !

[GregAdams]

I try to keep my answers in this forum relevant to the original question. I don't tell you how I do it. I just tell you what I think is a good way for you to do it with your skills and equipment.
Yes you can vacuum the core in. You do not NEED to vac the core in. If you have the know-how and equipment great. If you don't, many hand laid boats have been built with the core bonded with a a core adhesive by hand.
Yes you can replace the core and leave the stringers out of your hull as suggested. Be mindful of the fact that it will have longitudinal flex. That can have some shock abatement effects in rough water at 50 mph. If you plan on going 95 mph though, the whole boat will be supported by the running plank, and you might want to reconsider whether flex in the running plank is a good idea.

[XstreamVking]

A box stringer running down the keel will do all you need. |_| <This is an upside down illustration. My King has this from the factory and core pcs going up to the floor to hull joint and is a real strong/light hull.. Also makes a good way to secure/support the floor for even more strength. Very simple. Check out my build thread for some pics...

[dwilfong]

Mix the resin with Cabosill. Then use a tile trowel to lay it on the hull. Do a test run first to see how the mix stands up and set time.
Don't over saturate the core before you set it. That will just make the setting mix runnier and not stay in place.
Do not pre wet the hull either. Use the mix and flat trowel it first to just cover it. Then add more mix and use the notched part.
A big roller will set the core just fine. start in the middle and roll it out to the sides.
Ester resins some time will not bond with old ester resins. Epoxy is your best bet. It is a mechanical bond not a chemical bond.
Old glass work is hard to bond to with a chemical bond.
DB1700 over top of the core is your best bet also.
Ester resins will wick moisture also over time. Epoxy will not.................
Core bond is expensive and the supply house will try and promote it. Epoxy and cabosill is your best bang for the buck.

[tunnels]

Just be careful the amount of carbosil you use because all it does is thicken resin that's all it has no guts what so ever !! and over loaded makes resin brittle and shatters like window pain glass .

[powerabout]

Tunnels
What was suggested replacement for a ply floor?
Cheers

[tunnels]

me I would naturally make a composite floor ! 18 mm thick Nida core would be my first choice depending in its area size ! movement is not a worry as I like soft underfoot !, braced at the back and just 2 layers of glass But id make it on a nice flat shiny bench and molding openings and make the floor as a one piece , a total lift out so its possible to get in there it some at a later date ! !
Tell you what I saw recently was a aluminum checker plate floor because the guy wanted a permanent hard wearing easy to clean floor ! just had some bracing welded on the underside where it was needed ! But was able to be taken out and had a slight camber so semi flat on top but dropped off ever so slightly around the outside drained into the bilge with a big pump up and out !!

I never think to much about cost of making because to me its a oncer and never have to do it again
Same with the transom I've made at times they were only oncers as well plus made them on my work bench over a rough thin ply mold and then fitted to the back of the boat glassed inside and out ! each one has been great for the boats I've fitted them to , I try to use bits of the old splash well just to get the shapes needed when reducing and changing the shapes ! why waste it !

[dwilfong]

Cabosill / resin mixed 50/50 by volume is a good mix. Cabosill is very light and fluffy so a 50/50 by volume is not a overly saturated mix. When mixed with Epoxy it is not as brittle as mixed with Ester resins. The Epoxy still maintains its sheer factor and compression. Esters do not bond the same to the Cabosill in a mix as Epoxy in a mix. Esters depend on a chemical bond as Epoxy's do not. The cabosill is just suspended in a ester with no real bond and sheer off in the resin. Epoxy bonds to the Cabosill and makes a solid matrix. .
That is why epoxy is so much better for repair work. It has a mechanical high sheer/tinsel strength bond.
Controlling the heat and cure time with epoxy is what makes it the best choice. Esters over or under activated with MEKP will lose all the strength properties and bonding effectiveness. It is a crap shoot at best if you do not have experience in how to mix it properly.
Epoxy is a no brainer,2 to 1 by volume.......KISS...........................
Go to Wallmart and get solo red cups. then get the small shooter cups. 2 small cups of part 1 and 1 small cup of part 2 pour in a red cup and perfect every time. for large mix use the large cups and then mix in a disposable paint bucket.
Stupid simple...................never a bad mix......................lot of kick time to work with it.
Fast , medium and slow activators to choose from. Medium is the best all around and best for strength when curing.
Epoxy has gone way down in price and availability is much better today than in the past. Forget about West System it is a over priced rip off aimed at the consumer boater.
Move up to the present day..............times have changed for the better.

[Gmcviper]

I have poly resin already so that is what i have to work with. I layed a test piece it the boat today. This is my method, I opened the kerfs of the balsa and used a brush to coat them. Then i flipped it over and coated the mesh side of the balsa with resin. I wet a piece of cloth on the hull rolled it out removing all air. Then i put another layer of resin on the balsa since it had absorbed all of the previous coat. i placed the balsa on the mat mesh side down, put a coat of resin over the top of the balsa and wighted it with sand bags to ensure contact to the hull.

As far as plans for stringers and floor. At this moment i will be putting stringers in i was thinking i would build them taller than factory and make a counsel out of it. I don't think i will put a "floor" in it ,I believe it is a moisture trap with little to no air flow and it will lead to rot down the road. I plan to put a seat box in similar to factory, since i'm planing no floor i plan to put a bulkhead just in front of the splash well and one or two under the bow to replace the boxed in are up there.

thank you for all of the responses!

[tunnels]

Balsa is relatively easy to work with !! Yes it absorbs lots of resin if you keep wetting it out all the time But if you roll a generous coat over the surface so its really wet and then let it gel then place it down onto the wet surface then the soaking and possibilities of getting voids and dry patch's never happens and as for loading it with sand bags ok for small jobs but a light vacuum suck is all that's needed an make a much better job . The scrim side is best facing up not down as it holds the sheets much flatter and smoother !
When making big boats with a experienced crew and a chopper gun we laid down wet glass and laid the pre wet balsa then pressed by hand into the wet glass and bought the resin up to the surface then wet the top surface and rolled firmly then gunned a 450 gram od csm over the top and rolled it out all done in a ongoing action from end to end same with laying the sheets of precut foam always the scrim side up and wet out the underside and pressed the sheets by hand and draw the surplus resin and any air to the surface then wet the surface and roll pressing firmly and skinning the top surface with a 450 gram csm spray . no weights ,no vac bagging just simple pressing and rolling and covering immediately with csm and the bottom then the side of a 36 foot hull could be done in less than 2 hours with just 4 people ! The boxes of balsa were kit setted and came to us all numbered and in the right sequence to start from the stern end and work to the bow ! and as one side was finished and hardened then the hull was rolled over to the do the same on the other side !
The biggest secret is in the planning and how the job is to be done and once started its doesn't stop for anything till the last piece of balsa or foam is laid and covered and rolled out !! By doing the job completely there is no way the core material can lift off the wet surface and begin to float as its completely encapsulated totally .
Same can be done with small home built panels as well saves time saves resin and if you use peel ply over the top makes a smooth really nice finish and all goes hard and cures all at the same time !!

[Gmcviper]

That sounds like a good method. I am working alone and don't think I can work fast enough to do it. My plan is to lay a piece on one side then while that is setting up I will work on the other side. I just checked my piece, I'm confident that it has a good bond.

[tunnels]

Always pre-cut all the total side you want to start and lay then the same for the other side .
You should be able to comfortably do the whole of one side of a small hull like you have ,just start at the back and do a 2 foot long patch and when its down then mix another brew of resin and carry on the same again , then when that's done that then another brew and carry on the same till you get to the end !! always checking everything is straight and pushed up with no gaps anywhere then when the final piece on the side you started is hard then do the other side, always starting from the transom working forward towards the bow and just do a couple of feet long at a time till you are comfortable with the system and the wetting out process you can adjust you catalyst ratio to suit the speed you are able to work at and not get flustered ! always checking everything as you progress !! each 2 foot long patch when its laid you can stop and carry on again if you have a loo call or need a beer or what ever . never stop in the middle of a patch as the resin will gel for sure !! plan and think a little I never use any brushes !!, just medium nap paint rollers not to wide 200 mm !!. each time either wash out the roller of scrap it with a knife to get as much resin as possible out so its will be easier to wash and flick out the acetone and roll till its dry !!
Its amazing the guysthat get caught with a solid roller totally filled with hard hot resin . Even guys that do this job all the time .

[GregAdams]

You can add fumed silica to make a DIY core adhesive and it is cheap. However, the commercial blends are lighter, more flexible, and tougher. If you are building a runabout it might be a shortcut. If you are building something light and fast you might want to avoid shortcuts.
Vinylester is often used to make fuel tanks. It can handle petrol sitting in a tank 24/7 for years and it can handle get wet occasionally.
Scrim up is easiest in your hull shape.

[tunnels]

fumed silica is carbosil under a different name !! all it does is thicken the resin has no guts what so ever . I wouldn't use just that ,no way !