Why nails with epoxy?

[Éric Bouvéron]

On the plans, lot of nails are used to hold pieces with epoxy. Epoxy and clamps or under pression with some weight is not good enough?

[Éric Bouvéron]

Ok, excellent, Budget Boater.
So, except everything else, (time, number of clamps involved, etc...) the answer is that glue is enough to hold the pieces together. Nails are only convenient, but not necessary and screws may be removed.
Your exemple makes a lot of sense, obviously here nails may be (are) necessary to speed up the process, but not for the integrity of the structure.
Thank you again everybody

[Omar M. Rashash]

Screws (and fender washers) are the poor man's clamp, for all the reason Budget Boater mentions. Even for places where clamps may work, sometimes the screws make for a better joint. If you utilize nails or staples to apply clamping pressure, you then have to decide to either leave them in place or plan on removal. If they are going to be left in place, they need to be of a marine friendly metal. There are places where leaving the screws as a permanent part of the solution is beneficial, such as block of wood that may be subject to high levels of sheer. Sufficient force to sheer the epoxy only joint can be prevented by leaving the screws in place.

[Patrick John McGrath]

Omar M. Rashash said:

Screws (and fender washers) are the poor man's clamp, for all the reason Budget Boater mentions. Even for places where clamps may work, sometimes the screws make for a better joint. If you utilize nails or staples to apply clamping pressure, you then have to decide to either leave them in place or plan on removal. If they are going to be left in place, they need to be of a marine friendly metal. There are places where leaving the screws as a permanent part of the solution is beneficial, such as block of wood that may be subject to high levels of sheer. Sufficient force to sheer the epoxy only joint can be prevented by leaving the screws in place.

I completely agree with Omar.  Most modern wooden boat structures, from Piver to the Gougeon Bros and beyond, are ply on solid wood frame.  Screws or ring nails are the clamps. A structure stressed to failure will rarely fail at the glue line, but in the Fibres of the wood adjacent to the glue line. An un-suported glue joint may be strong enough in most cases, but supported by a PERMANENT clamp is much more secure in the long run.      Belt and braces again.

A situation where this is Not true is when high tensile fabrics are used in conjunction with glues to bond parts, like rigging shrouds, to gunnels, spreading the shearing loads out over the surface of the hull, rather than using metal bolts.  Due to the relentless stress reversals on the bolts, they eventually loosen up the bolt hole and allow moisture in to start wood rot.

Using ring nails, screws or bolts to hold two pieces of wood together is a completely different matter.  

 

[Patrick John McGrath]

agur said:

Im building my Tiki 21 and so far I can not see 19mm nails as a structural members. 19mm A2/A4 stainless steel wood screws - yes, probably.

From the Tiki 21 plans and building instructions I could not find a line where those 19mm nails are referred as a structural members...

If the whatever part of your boat starts to delaminate, you are in trouble anyway - I could not imagine how those copper nails would hold the thing together.

Maybe Im wrong. But I have seen in some traditionally built wooden yachts (still sailing) nails wriggling silently out from the decaying wood... inanimate matter could evince manifest itself surprisingly vital

And what concerns hitting the container or underwater rock... well, its better not to do so... but Im not sure if those small nails prefigure itself a life vest under the seat in such circumstances...

What I discovered during building process is, that nailing the things down is pretty messy and could produce similar waves in the glue like indicated in one post above. For me worked much better clamping and/or using temporary screws.

I shall use those 19mm nails only in parts where other options are not reasonable - in gluing the deck for example.

But Im not an expert... just thoughts based on empirical cognition.

Agur, We're not talking about 19mm copper nails. They are pretty useless for our needs. We are talking about phosphor bronze ring nails, a completely different animal.

Readily available, cheap as chips and only need a careful hammer to set in place. 

For permanent attachment of heavier wooden components SS screws are best, and phosphor bronze are next best.

For goodness sake NEVER use zinc coated steel screws, or brass screws. Sea water will destroy them in short order. The screw or ring nail should be three times the length of the thickness of ply you are using. EG:- 19 mil for 1/4" ply. 

The diameter of the fastener is important too. The shank should be comenturus  to the length.

Not too thin, (weak), nor too fat,(unnecessary weight, cost, large bore hole,etc:).    

 

[wakataitea]

do not use nails. banging around on your hull will move other parts.

no profesional crapenter or boatbuilder is using nails anymore. Nails are for building a shet or a treehouse for your kids...

use SS screws and do not take them out. it is a pain in the ass to fill this holes with epoxy. you will get air bubbles under the glass and this you don't want.

pre drill the hole and make sure the screw pulls the parts together and not seperating them.

sink the srew 1-2mm into the wood to be able to make a propper filling on top of it.

clamps are nice but you work will be slow. i used them to keep parts under pressure till i had the screws in...

if you want to go sailing with you boat before you get 100 years old, use screws...

SS 304 screws are perfect and not much more expensive then others. screws will support you joins on the long run...

[Budget Boater]

Long ago, I assisted in building a high tech commercial power cat. Once it was completed, the owner/designer was confused by the lack of speed (which was extremely important for this vessel) of nearly two knots at cruising RPM.

We spent a few days going over everything, including the plans, discussions with the company that did the final assembly, and so on. Then suddenly, during a brainstorming session on the lack of speed, the owner burst out, "it's the screws!"

It seems he had neglected to include the nearly 2000lbs of screws used to assemble the boat in the total weight calculations. It cost him nearly $25,000 to rectify the error with new props to account for the extra weight.

[wakataitea]

the epoxy is to thick to use i a small syringe with a nedle etc...

if the ply carries so much moisture that the nails and screws are rusting or rooting, then the ply is to wet at all. before covering the ply with epoxy or glas or paint etc, it should not have a moisture content from more then 7-12%.

old boat root because the moisture goes into the wood are was traped inside. you get dry root and all this stuff.

a propper sealed plywood hull last 100years.

weak joins, trapped moisture and not a good surface sealing are the main problem may boat root away...

[wakataitea]

Budget Boater said:

Long ago, I assisted in building a high tech commercial power cat. Once it was completed, the owner/designer was confused by the lack of speed (which was extremely important for this vessel) of nearly two knots at cruising RPM.

We spent a few days going over everything, including the plans, discussions with the company that did the final assembly, and so on. Then suddenly, during a brainstorming session on the lack of speed, the owner burst out, "it's the screws!"

It seems he had neglected to include the nearly 2000lbs of screws used to assemble the boat in the total weight calculations. It cost him nearly $25,000 to rectify the error with new props to account for the extra weight.

i do not believe this. 2000LBs this are 900kg... was the boat the sice of the titanic???

i use on my tiki46 maybe 15 kg of 306 SScrews and i screwed every thing togeather. we are talking abiut building a wharram and not a racing cat. i used Gaboon ply insteed of mahogani. this saves you 500kg on weight for a tiki46. if you look at, what the people put on stuff on board once they go cruising, then we knw that this screws can not be an issue.

[Robert]

I used bronze nails, and pre-drilled the ply sheets with 2mm holes so the nails can be inserted into the ply with a light tap.

When fitting the ply, the glue is applied to the stringers and the marked areas on the sheets and 2 clamps are used to fix the alignment.  After this all the nails are inserted, about 80+ per sheet.  Then the nails are driven in using an air hammer and a 5Kg free weight on the back side.  This allows a sheet to be fixed quickly and it really pulls the ply onto the stringer as the nails are the ringed type and the air hammer's action seems to work well with this.

In total I think I may have used 1 Kg of nails for 1 entire hull of my Tiki 46 build.  To be fair I cannot say it is better than using screws, just that for some reason at the time I bought the nails I was paranoid about stainless steel screws in the hull.

Lastly, I do not see the nails or screws as structural and the plans specifically refer to the hull panel fixing screws as temporary fasteners.

R

[Éric Bouvéron]

 Thanks you all for your feedback. I appreciate it.

Agur, when you glue two pieces of ply, or anything else in wood,  if you have problem with the slipping of the pieces you may use one or two dowels to hold these pieces together. You make a blank fitting, drill the holes in the wood, put the glue and re-assemble with the dowels as guides. However, I made up my mnd with the screws, and will try to avoid them, whenever possible.

Good luck with your project in Estonia. I hope to start mine this week... if my plywood arrives, that is.

Éric

[Éric Bouvéron]

Put the pieces together and hold them with clamps. Drill holes at some places. Unclamp, put your glue, and insert wooden dowels in the holes. When you assemble them again with the glue, your pieces will be at the exact place as when you clamped them at first, and will not slip when you fasten them either with screws or nails. Yo may of course leave the dowels inside, as long as they are coated or covered.

[Budget Boater]

It was an 82' commercial charter power catamaran that carried 100 people at 33 knots using two 600hp John Deere diesels with two 20kW generators to keep all of the systems running. It is more than possible to use 2000lb of screws in such construction. Most people have little concept of weights and how they can affect a vessel. On another power cat that we installed the electrical and environmental systems, we saved 3000lbs in wire weight by going with 240VAC and 24VDC systems. I am not talking about Wharrams here. However, the rules still apply: 40 extra pounds here, 100 there, 30 here, 10 there, and it all starts to add up.

wakataitea said:

Budget Boater said:

Long ago, I assisted in building a high tech commercial power cat. Once it was completed, the owner/designer was confused by the lack of speed (which was extremely important for this vessel) of nearly two knots at cruising RPM.

We spent a few days going over everything, including the plans, discussions with the company that did the final assembly, and so on. Then suddenly, during a brainstorming session on the lack of speed, the owner burst out, "it's the screws!"

It seems he had neglected to include the nearly 2000lbs of screws used to assemble the boat in the total weight calculations. It cost him nearly $25,000 to rectify the error with new props to account for the extra weight.

i do not believe this. 2000LBs this are 900kg... was the boat the sice of the titanic???

i use on my tiki46 maybe 15 kg of 306 SScrews and i screwed every thing togeather. we are talking abiut building a wharram and not a racing cat. i used Gaboon ply insteed of mahogani. this saves you 500kg on weight for a tiki46. if you look at, what the people put on stuff on board once they go cruising, then we knw that this screws can not be an issue.