Plywood core joint

JSP · 24 July 2009, 13:23

Hoping to start a bit of a project soon which involves a plywood core made into a box and then covered in glass.
Needs to be very strong though. So to those who have made their own consoles, jockey seats etc out of plywood and glass could you recommend the best joint for the corners and top of the plywood. Or will the fibreglass hold it all in places?

doggypaddle · 24 July 2009, 13:35

I may be wrong, but i think you will find if you use a couple of panel pins and some wood glue the fibre glass will then hold it all together. I am just thinking how strong hexalite panels are and theyre just .75mm aluminum sheet spaced apart by a honeycomb of material thats as thick as kitchen foil

theyre strong enough for aircraft floors! i guess the strength is in the outer skins. have you thought of using something like foam/cellular material as a core to make it lighter?

JSP · 24 July 2009, 13:46

Quote:

Originally Posted by doggypaddle

I may be wrong, but i think you will find if you use a couple of panel pins and some wood glue the fibre glass will then hold it all together. I am just thinking how strong hexalite panels are and theyre just .75mm aluminum sheet spaced apart by a honeycomb of material thats as thick as kitchen foil

theyre strong enough for aircraft floors! i guess the strength is in the outer skins. have you thought of using something like foam/cellular material as a core to make it lighter?

Cheers mate, yes I have thought about using foam. But I've had it confirmed off two very good sources now that foam wont be strong enough. I'm going to be using 18mm ply. I want to build a 10cm high box to raise the console up plus house the bottom of my fuel tank. So the strength is important.

My plan is to glass the sides on the box inside and out onto the deck. Then fit the top. So the joint between the top and side needs to be something that can slide together.
So do you think Stainless pins and wood glue could do it? Would make life easier!

doggypaddle · 24 July 2009, 13:50

i would say it would ! the glue joint if made with a good gap filling polyeurathane wood glue will be as strong as the wood!
you could always put some triangular webs of hardwood i the corners made from 2x2 cut down. it would be less radius to get the glass into the corner too.
jwalker should have experience of this?

JSP · 24 July 2009, 13:57

Quote:

Originally Posted by doggypaddle

i would say it would ! the glue joint if made with a good gap filling polyeurathane wood glue will be as strong as the wood!
you could always put some triangular webs of hardwood i the corners made from 2x2 cut down. it would be less radius to get the glass into the corner too.
jwalker should have experience of this?

That is a bloody good idea!
With 18mm being so thick I also plan to round of the corners to make glassing easier.
The console will be glassed over the box and on to the deck.

Hope I like it

jyasaki · 24 July 2009, 15:28

Biscuits should allow you to assemble a strong wood joint in situ.

http://www.taunton.com/finewoodworki...t.aspx?id=2991

jky

JSP · 24 July 2009, 15:45

Quote:

Originally Posted by jyasaki

Biscuits should allow you to assemble a strong wood joint in situ.

http://www.taunton.com/finewoodworki...t.aspx?id=2991

jky

Would love a biscuit jointer but funds wont allow. Thought about using my router to do it but I know I'll feck it up.

slimtim · 24 July 2009, 16:03

John,

Take a look at my thread of my build (http://rib.net/forum/showthread.php?...=super+student) ...somewhere in there you will find details of how I made my console by glassing over ply. I was using 9mm and 5.5mm ply and joined most of the corners by filleting with epoxy. With some of the right angle joins I used 1x1inch baton, stainless screws and that expanding wood glue stuff...its not coming apart in a hurry

For what you want to do, the 18mm ply will be pretty strong and if you make the join between the top and the sides by having the top on top of the sides (join underneath the bottom surface of the top...does that make sense?!!) then there will be minimal load on your joint. A carefully wood glued edge should suffice with the glass over the top as well.

When you glass over the ply, you will need to use the stuff I specify in my thread (I think its called G4) to help the polyester resin stick to the wood (unless you're going to spend lots of money and use epoxy resin to wet out your fibre glass). An angle grinder is very useful too for rounding edges and taking off cured bits of glass.

Hope that helps a bit, I can go into more detail if needed.

Tim

slimtim · 24 July 2009, 16:08

Actually, your main loads will probably be from people hanging off your console is sharp turns and heavy seas so you could screw 1x1inch baton round the inside of your joins to make them super strong. Won't make it much heavier and you won't need to glass the inside.

JSP · 24 July 2009, 16:34

Your the main man Tim!!
I want to glass the sides to the deck first, both inside and out. So this means the top can only be fitted afterwards. The baton idea is sitting rather well at the moment then

I could make the box (the deck forms the bottom of the box) with the top on and then fix to the deck but this means only glassing the outisde to the deck. Which wouldn't be as strong?

AllenF · 25 July 2009, 07:42

If you used Pouring foam then glassed it it would be PLENTY strong enough. they make dashboards etc in cars from pouring foam and thats only Vinyl covered
take a look at
http://www.uscomposites.com/foam.html
It works out cheaper than 18mm ply
Basically you mix the two part together pour it into a box mould and its like the s@?t in the can ......five minutes and woooooof its everywhere expands like hell
Then shape it to what YOU want (if your clever and cocky you can run your cables inside the foam to make connecting electrics easier.. failing that run a bit of conduit {plastic} in there)

slimtim · 25 July 2009, 11:45

Quote:

Originally Posted by JSP

Your the main man Tim!!
I want to glass the sides to the deck first, both inside and out. So this means the top can only be fitted afterwards. The baton idea is sitting rather well at the moment then

I could make the box (the deck forms the bottom of the box) with the top on and then fix to the deck but this means only glassing the outisde to the deck. Which wouldn't be as strong?

Can you draw a simple sketch of what you plan to do? Maybe some pics of where its going.

I think you may have a little bit of trouble glassing it to the deck and getting a good join and/or making it look nice. I am however assuming you will be fitting this to the moulded deck of an SR4? The way around this is to build in a small external flange and use the traditional method of fixing it down with self tapping screws and sikaflex. My console is only glassed on the outside, I have coated the inside with epoxy to protect it.

JSP · 25 July 2009, 12:11

Tim, this is a very very quick sketch using Paint on vista
And it's on a 5.4 SR

JSP · 25 July 2009, 12:13

Quote:

Originally Posted by JSP

Tim, this is a very very quick sketch using Paint on vista
And it's on a 5.4 SR

Just to add the cross section drawing that I've so expertly done

is the box section that forms one side of the hole box. Make sense?

JSP · 25 July 2009, 12:14

Quote:

Originally Posted by AllenF

If you used Pouring foam then glassed it it would be PLENTY strong enough. they make dashboards etc in cars from pouring foam and thats only Vinyl covered
take a look at
http://www.uscomposites.com/foam.html
It works out cheaper than 18mm ply
Basically you mix the two part together pour it into a box mould and its like the s@?t in the can ......five minutes and woooooof its everywhere expands like hell
Then shape it to what YOU want (if your clever and cocky you can run your cables inside the foam to make connecting electrics easier.. failing that run a bit of conduit {plastic} in there)

Thanks Alan, I've had it off two boat builders that foam would not be strong enough.
Cheers

slimtim · 25 July 2009, 12:42

ah right ok, a bit different from what I had visualised. Is the back staying open so you can get the fuel tank in and out? The console won't end up being too high will it?

JSP · 25 July 2009, 12:56

Quote:

Originally Posted by slimtim

ah right ok, a bit different from what I had visualised. Is the back staying open so you can get the fuel tank in and out? The console won't end up being too high will it?

Yeah the back on the box and the console is going to be open but going to make a fibreglasss cover that covers all of it (he says

) and the tank will be strapped into place.

The main reason for making it is to get it at the right hight as the console alone is to low for me.
Then hight of the box is yet to be measured as I've not been up to mocking it all up.

chewy · 25 July 2009, 17:02

Drawing updated: Rev 2

Endeavour · 25 July 2009, 17:42

Hi John.

Can you post a picture of the console that needs raising..

Steve

chewy · 25 July 2009, 17:58

Quote:

Originally Posted by Endeavour

Hi John.

Can you post a picture of the console that needs raising..

Steve

http://rib.net/forum/showthread.php?...hlight=console