My new baby! 6.8 Meter fiber over wood fishing boat !

Well i bought the book anyways, hope its a good one !!

Basically most small yards buy the wood trunks and dry them themselves (as pictures posted).
This means I will have to visit a sawmill in Egypt to have a look at how they handle drying wood.

I do have a question about the lobster since i can not use paint, how do i protect against UV rays? Varnish ?

 

just for general epoxy work the gougeon brothers book is very good.

http://www.amazon.com/Gougeon-Brothers-Boat-Construction-Materials/dp/0878121668

they pimp their own products a bit but still a very good book. I bought the old version as a teenager and teh new blue covered version few years back.

 

Yes UV protecting varnish. Not UV resistant! That means the varnish itself gets not destroyed, but it does not protect the Ep.

The sawmills will have a better system to dra their timber, they have to sell it afterwards.

The Gougeon "brothers on boat construction" is the classic book on wood epoxy building and a must have, no doubt.

Regards
Richard

 

Apex any brands you recommend for the varnish?


Gougeon "brothers on boat construction" added to my cart ! any other books i should pick up as well as to get them shipped at one go ?

 

We use von Höveling 2k PU, but there are many other brands with similar quality on the market.
Use what you have already there, if it is a reputable brand and provides UV protection.

No other books on that topic* and even this one is almost completely handled in the net.

Richard

*come in my mind

 

Ill do some digging then
While im on the subject of books, any recommendation for good books on fiberglass construction ?

 

Righto i was asked today a rather embracing question ... how much epoxy do i need for my lobster boat .... which i replied .. i have no clue ...

So can any one help me calculate a rough estimate on how much do i need ?
http://www.selway-fisher.com/Mcup16.htm
The boat is a lobster 15
OA 14'11" 4.57m
Beam 5'11" 1.8m
Hull Mid Depth 2'3" 0.68m
Draft 8" 0.2m
Approx Dry Weight 250 lbs 113 kg (WRC)

Strip plank
Major strip wood requirements for hull
2460' of 3/8" x 3/4" (750m of 10x19mm)
(Wood might be changed to Mahagony if i can import it, or mulberry.

 

I guess you will find some basic info coming with the plans.

The rule of thumb on mahogany (mulberry should be about the same) is,
160 gsm for the first Ep coat, 120 gsm for the two following. Assumed a 340 gsm glass layer, which makes 2x 340 gram m² + 15% added resin weight on your first project, then 2 coats of neat resin to fill the gaps, each about 120 gsm again.
Then filler, maybe more filler and so on........

 

Ahh ok u lost me there ....

160 first + 120 secound = 280 gsm.
the 340 is the fiberglass ? and by x 2 you mean 2 layers ??

Sorry im confused >.<

 

Neat resin on wood:

first coat = 160 gram m²
second and third coat 120 g each
= 400 gram m²

sheathing:

one layer glass 340 gram m²
resin to wet out, same weight as glass but with 10 to 20% amateur surcharge
= 680 + 10% 750 gram m²

cosmetics:

two coats to fill the valleys = 240 gsm

total?

 

Thx apex !!

So .... (ok i suck at math)
340 + 750 + 240 = 1330 grams / m2 (The 750 is basically 2 layers of resin to wet out the glass with the noob surcharge.)

OK i hope thats right (i think i killed a couple of brain cells in the process)

Now .... how much m2 on my boat ??

4.57m x 0.68m x 2 x safety factor (curves etc..) = ?

 

Let me kill some more:

The 750 gram are 340 gram glass, 340 gram + 20% gram resin! ONE layer.
This can be reduced to 340 + 10% resin when the skills are better, or even plain 340 gram, no surcharge when the people are experts.

 

Yep my I.Q dropped a couple of points .... this is my first time so apologies for the slow comprehension of this complicated process.

Am i mistaken to believe weight calculation (and therefore thickness) is different from how much epoxy is being applied?
(since the weight of glass will not equate to epoxy being used?)

What i would do is first apply the first layer of epoxy on the hull 160 gram m2 (this includes the area on the surface and the top and bottom gluing to stick the planks together).

The second and third layer are applied with 120 x 2 = 240 gram m2 which will be applied consecutively.
----------------------------

epoxy wetting for glass 340 x 20% = 408 gram m2

So i would need to apply 400 + 408 gram m2 = 808 gram per m2

----------------------------

blargh

 

Lets start again. That way I can hidden correct the mistake I made......


First you hammer the junk together, the glue used here was not part of my estimation.

Now you have to apply the glass sheathing. I assumed that the glass is 340 gram m²

In general the weight of the resin you need to wet it out, is about equal to glass weight. But in homebuilding rarely a 50/50 layup is achieved.

We therefore add 10 - 20% resin weight. Resin only!

thats 340 + 374 in the better case or 340 + 408 in the worst. Pick your poison.

But before we apply the glass, we have to saturate the wood! Otherwise the dry wood "sucks" out your glass layup.

And here I made the mistake. I looked for my calculations on varnished surface where you would need 3 coats of neat Ep to close the cavities.

We do not need three coats, two are fine, because we cover the surface with glass.

Now:

1 coat neat ep at 160gsm
1 coat at 120gsm (of course the second coat is not sucked in as the first will be)
= 280 gsm

then 340 gsm glass wetted out by say 400 gram resin = 740 gsm

followed by
2 coats resin at about 120 gsm each.
=240 gsm
total = 1260 gram m²

Thats it

 

very nicely done apex

Well im gona put everything on an excel sheet, i know i wount stick unless i do so.

So i still need to account for the glue used to "hammer" the planks together. I also need to included the inner hull as well which we did not account for.
It will not take the same amount of layers therefore less resin than the outside. which means i will have an m2 for outside and m2 for inside ( i think).

I also need to figure out how much m2 is needed for my lobster boat ...

I never new why my math teacher got so pissed off in class with me .... took me 15 years to figure out i have the mathematical brain capacity of a frozen chicken ..

I am gona go lay down now my head hurts ....