How much epoxy resin?

[John Abbott]

I am looking at the Tiki 30 and ordered the study plans, but I am unsure from the materials list just how much epoxy is required.  Does anyone know approximately how many gallons would be needed for the Tiki 30?  While I am asking if you could comment on the fiberglass too that would be helpful (in terms of how much, what type and are multiple layers required etc.)  This will help with estimating costs of the project.  Thanks.

[Galway Bay]

When I did a large re-build I estimated per sheet of ply for the inside 300 g resin per coat sealing [ no glass ] and for the outside sheathing 1 kg of 300 g cloth + 1.5 kg resin per coat. Ply sheet  = 3 sq m. I found this pretty accurate. This seemed to include enough for gluing as well.

High finishes use more resin - all that filling and sanding !

Gougeon Bros. book is well worth having for answers to all these questions even if like me you use another resin.

[Peter Brook]

Not sure if this will help or not........

Study plans for Tiki 38 and 46 both give figures for resin, glass and fillers as below:-

38		46
Epoxy
Resin Kg	450	450
Hardener Kg	100	90
Glass
150mm wide tape  m	200	100
200g.m2 80cm Glass Cloth	400	400
Filler
403A Kg	5.25
403C Kg		20
406B  Kg		1.5
407B Kg or	10.5	10.5
409B Kg  and	9
406B Kg	1.5
410B Kg	3	4.5
423  Kg		0.2

I have images of full plans for Tiki 30, I will look ASAP and see if they include estimates.

[Robert]

Galway Bay mentions the book available here: http://www.westsystem.com/ss/assets/HowTo-Publications/GougeonBook%... 

It covers estimating all materials for a wooden boat, and seems like a good guide on many things besides.

R

[Galway Bay]

Thanks Robert for the link - a very valuable resource.

I also would like to know - how many layers / coats do builders use ? How many coats does JWD recommend ? Inside and out ? This is the second part of John's question and it interests me also.  

[Peter Brook]

Gougeon recommend as minimum at least 2 coats if not rubbed down after, or 3 coats if rubbed down prior to further coating (paint/varnish).  This would seem to be appropriate to interior/non-glassed areas.

When using glass, first coat to wet out, then subsequent coat(s) sufficient to fill weave is Gougeon recommendation (especially for clear coating).  As an alternative, one coat to wet out, then straight to filled epoxy for fairing.  Once this is rubbed down to smooth surface, 2 further coats unfilled epoxy to seal and provide a good surface for final coating!  

I guess though since Gougeon also sell epoxy, their advice might be seen as slight overkill to achieve better sales...  That said, their book is excellent and most recommendations are backed up by research and testing. 

Wharram plans include their recommendation on glassing.  They suggest one coat to wet out weave, then add coat(s) of filled epoxy directly onto weave for fairing, then straight to appropriate primers/topcoat.

I am planning to build in the Philippines and sourcing marine ply is difficult and it appears that some thicknesses may not be available.  As I may have to go for closest size available to the Wharram Design recommendations, I might adjust epoxy/glass protocol to compensate accordingly.  Hopefully, I can do this with the recommendation/approval of the designer.  Again, the Gougeon book does give figures for strength/flexibility of various ply thicknesses with different epoxy/glass combinations.  It really is an excellent resource, not just for epoxy usage, but for comprehensive boat building techniques.

[John Barlycorn]

You might also find this link useful;

http://www.thirtythreefiftyfive.com/bb/index.php and click on 'calculators'

I wrote these epoxy coverage and unit conversion calculators for my own use, and decided to put them up on the web in case anyone else could use them. They're based on the Gougeon formulae and other published industry data.

[Galway Bay]

We often see comments on this site about the accuracy of JWD estimates for epoxy etc. Many builders go over the estimates but do they add extra coats ? Are extra coats needed ?

I have built a number of small dinghies / kayaks and find 2 coats + paint is successful if all the joints are well sealed / covered with glass tape. A third coat outside gives peace of mind while the bottom panels will benefit from a layer of glass cloth if rough usage is envisaged. Sealing ply edges ie. at gunnel etc. is the most difficult part and my only problems have started here. I have been told that the D. Fir ply always needs glass as it checks.

On my Wharram I used 2 coats to seal inside. Then just a quick light sand to key for paint. Outside I used 2 layers of 300g cloth and more below the waterline and even more on each side of the keel. I had in mind that this boat will suffer rough usage in fishing ports, drying out on unknown bottoms,  against old stone quays etc. If I could provide a more sheltered life for it I would be happy with one coat of 200g - and maybe two below the water.

For the historians among you the original sheathing was polyester resin+ 450g mat + 600g cloth worked wet-on-dry with a total layup weight of 3kg. / sq M. This was common on Wharram cats at the time. I always suspected that an owner with problems had not used this full spec. For comparison my epoxy sheath weighs 1.2 kg/M while a single glass coat should weigh approx. 0.7 kg/M. On a 30 ft boat the weight saved could be as much as 200 kg. Still the old sheath was really really tough - practically a second boat !!

[John Abbott]

I want to thank you all for your comments and resources as this information has been very helpful. 

[Omar M. Rashash]

What Galway said and-

When you're applying fiberglass cloth to wood, you only need enough epoxy to hold the glass to the wood.  Any epoxy over that amount is parasitic weight and does nothing to increase the strength of the composite.  Once the glass has adhered to the wood, any additional coats should be epoxy, thickened with your choice of fairing compound.  You will use less epoxy, and have an easier time sanding, if you don't use un-thickened epoxy to fill the weave in the glass.  Additional coats of un-thickened epoxy should only be used to fill the weave when doing clear coat on kayaks or brightwork.  For greater abrasion resistance, the use of one of the synthetic cloths, Xynole or Dynel, is better than multiple layers of fiberglass.

I've been trained in the proper application of epoxy and fiberglass. and supposedly know how to do it.  I understand that any epoxy applied to the boat, either remains as added weight, or must be removed by sanding.  When I build, I'm constantly reminding myself to use the minimum amount of epoxy to accomplish the required task.  I know at what point I can sand no further without cutting into the glass.  However, I too find myself using more epoxy, and coming in at a heavier build weight, than specified.

The only conclusions I'm left with is that the materials (and time) estimates are based upon a very basic boat with just enough epoxy to hold it together and a very (ahem) workboat-like finish.  I'd treat the epoxy estimate as a starting point for my first epoxy order with the understanding there will be a second order to finish the boat.  How much you will actually need will be a function of how fast you climb the learning curve, how much time you're willing to put into the finish, and the quality of the finish you desire.  IIRC, the finishing aspect of a boat is at least 1/2 of the labor expended.

[Peter Brook]

I located the scanned page of the Tiki 30 plans which I believe were circa 2001.

Epoxy, Fillers and Glass Cloth.  Codes are from West Product Catalogue:-

Product Code                 Pack SIze            Description                                      Quantity

Either C Pack                                                        25Kg Resin and 5Kg Hardener                          8-9 

Or 105C                                 25kg                     Resin                                                                 8-9

and 205/6                               5kg                      Hardener                                                          8-9

301C                                                                    Pump Set 5:1                                                    1

403A                                  0.75 kg                     Microfibres                                                        5

Either 410B and                     1.5kg                      Microlite       

406B                                     1.5kg                      Colloidal Silica

Or 407B and                         3.5kg                      Low Density Filler                                               2 (Fillets)

410B                                     1.5kg                      Microlite                                                            2 (Fairing)

733B                                      50m                       150mm Glass Tape                                             2

741                                      100m                       80cm width 200 g/m2m Glass Cloth                    1

741-50                                    50m                      80cm width 200 g/m2m Glass Cloth                    1

7410                                       10m                      80cm width 200 g/m2m Glass Cloth                    1

This is exactly as written, so missing quantities and strange combination of 100m 50m and 10mm of Glass Cloth must make sense to Wharram Designs at least...

I am no expert, but I suspect different ambient/material temperatures would make a difference as to how thick or thin each layer is, thus how many coats may be needed for a given level of protection/weave filling.  In addition, the waste that each builder generates must vary too.  Rollers for example seem to take an extraordinary amount of resin before being ready to roll and most of these seems to remain as waste at the end!  Different plywoods and woods themselves will soak up differing amounts of resin before building a satisfactory coating.  Again, temperature and even moisture % in the wood/ply might alter take-up.  

For myself, despite not maximising any advantage of bulk purchase, I will get around 75% of the total epoxy recommendation, then purchase any remainder as needed.  With plywood though, I will over-order as I would not want to have to mix different specifications if one supplier cannot continue with identical specification (a common problem apparently in the Philippines).  I am lucky that I have lots of storage space!

Good luck with your plans

[paul anderson]

You will always need more epoxy than you think,trust me.

[Rogerio Martin]

The JW plans call 270 kg, and 200g/m² fiberglass, In TikiRio I use 320 kgs and  330g/m² biaxial (150m)