Young head on old shoulders.....

34' fin keeler, Edge resorinol glued strip (40x20mm). 1969

I am currently renovating the above owing to over generous backstay tension, leading to glue lines letting go just forward
of the mast step.
I think probably all the glue lines are somewhat tired from 35yrs of immersion anyway. And, it was our first race in 30knts plus with a lot
of windward work. Less aggresion on the backstay and a new flatter main would be kinder.

Below is a photo link to the boat.

http://www.imagestation.com/album/index.html?id=2130491226

login- roly05 password- roly24

I would really appreciate any input/thoughts on methodology laid out below.

Our fix is to undertake the following:

Dry hull to < than 20% MC.

Skillsaw out bad glue lines and edge nails having secured stripplanks to ribs.

Replace any planks that are suspect or probably replank to the waterline as
BWL planks are not drying to suitable levels.

Reglue old reamed out open glue lines (topsides) with epoxy/microfibres.

Glass hull (inverted) with one 20oz triaxial at 90deg to planks. (Warp) with epoxy, to gunwales.

Glass deck with two layers 6oz woven e-glass, over gunwales. (overlap)

Replace the mast step to to redistribute the mast load more evenly over a greater area.

Fair, paint etc.

I understand sheathing integrity must be maintained 100% for this to be feasible and the consequences are rot if not maintained.

The other option is to reglue lines and just paint.
Decisions!

It is only after the journey thus far I am beginning to appreciate the evolution
of the wooden boat.
At the very least, they are made of a material improved over millions of year s to withstand zillions of stress cycles.

Its how they are put together that counts.

Any input appreciated!

 

Sorry Roly, mistake now corrected

Roly,

Nice boat, please read this thread on glassing a wooden boat and make decide from there.

http://www.boatdesign.net/forums/showthread.php?t=4614

 

Gidday Peter,
Did you post an url?
It must not have come up.
It is odd, because I suspect a lot of wooden boats have multiple coats of paint which
are comparable with a thin layer of epoxy/glass. No?
It seems sheathing with glass has a much better chance of success if done from new which infers that the combination works but the variables must be controlled precisely.


“The opinion of the majority is not necessarily correct” – Yi Qing Cui

Quite, or we would have no progress,but following majority opinion generally improves the non-thinkers chances of being correct.

 

Roly, forgot to post the URL, is now corrected.

No, paint still breaths and moves, epoxy/glass does not!

One very important variable is the construction design of the boat.

 

I assume an edge glued and nailed strip planker is not a traditional method of build ,rather, a transition between traditional carvel and strip wood sandwich or wood/glass composite. I see it, correct me if I am wrong, as a monocoq. structure with minimal frames, where movement of the planks relative to each other should be negligible.
So, is this not a design that lends itself to sheathing?
Thanks for your input!

 

Yes, this is a design that lends it well to sheathing, for exactly the reasons you stated in your last post, a stable structure. Cost is a consideration as is the additional labor in application, fairing and fairing and fairing. Then there's the maintenance issue regarding the intactness of the skin. This is a typical planking method (edge nails and resorcinol as the adhesive, though epoxy is more common currently) and insures a long lived, watertight structure. I love resorcinol myself (except the color) and it works great.

The wood cored (sandwich) construction methods are newer applications for strip planking and rely on different engineering principles then the method employed on your hull. Traditional strip (your boat) can tolerate a sheathing, but should be used for abrasion resistance qualities only (in which case other fabrics should be strongly considered) the structure clearly has survived a number of decades without a sheathing, so strength isn't the need. If you're looking for better impact resistance, the heavy sheathing should be inside the hull, which brings me to wonder why the 20 ounce skinning.

Why do you feel the need to add the weight, labor and materials of a 'glass sheath? You'll be making any structural repairs, replacing 35 year old bottom planking and giving her a good once over, are there other issues you're looking to address with this treatment? You will need a substantial inner and out layering of fabrics to turn this into a sandwich, with a healthy weight burden for your efforts.

Epoxy in the seams will work, though the "Skillsaw" (reciprocating saw?) will remove quite a bit of material from the seams and play the devil with frames and the back side of planking. It's a ***** anyway you do it, but I prefer methods that permit me to screw up without hacking half way through a frame or something. These techniques may require taking a hacksaw blade to each fastener by hand, to limit damage to a single stroke, rather then the wind down cycle of a power tool, after the trigger is released. It's in this regard that restoration or repair can be very frustrating and insist on clever solutions to difficult issues, such as limiting damage during fastener removal. I recently re-fastened a lap hull, 42 frames on 7" centers with 3 clenches between each frame, 14 planks per side. Each clench had it's head drilled out and the clench was driven through, the screws into the frames had their heads drilled and a bolt extractor was needed to remove the screw without damage. About 20% of the screws did come out with a screw driver, the rest were drilled, all the clenches were drilled. About 4,000 clenches and 2,500 screws later . . . I only buggered three holes (I got lucky) It's a lot easier to build then to repair certain construction types. Strip plank is one of those types that make us drink.

Personally, I'd continue to dry the hull. The bottom will eventually dry out, you can work on the topsides and other areas in the mean time. I'd be afraid to use a reciprocating saw on the seams, though a hacking can be filled with wood butcher's friend (epoxy). This is one of those judgment calls that I'd want to see up close and personal. I'd likely remove several planks at a time and install replacements as I went. This assumes the framing is repaired on in good shape. I'd give her a light sheathing on the deck and hull using polyester, rather then 'glass (it conforms better to compound shapes and has three times the abrasion resistance). After your done, remember she's now longer a front of the fleet boat, so go easy on the backstay.

Deck stepped sticks are hard on hulls, especially if the compression post isn't a real good fit and the athwartship members (partners and deck beams) hefty enough to take the loads out to the hull. You'd be well served by going over this area very closely and insuring the loads get transmitted to the planking.

 

PAR- Many thanks for your input. Too many variables have me reeling!

To your queries:
Why do you feel the need to add the weight, labor and materials of a 'glass sheath
To stiffen the hull tranversely (when the timber X grain and glue lines are in tension from the rig loads) and, I suspect diminished holding power of the slight internal ribs/frames. Glass would be in tension as the mast loads the hull. The one dimension rigidity of strip planking concerns me.Also the+- 45 strands should supply some torsional rigidity.
Less water absorbtion of the hull.
Added confidence for a bluewater adventure to Tonga. If it was 3 Skin veneer
I would be much more comfortable.
are there other issues you're looking to address with this treatment?
SWIMBO said, "Fix it and fix it good, or I won't set foot in it."
I would still be sailing otherwise.

.other fabrics should be strongly considered
I considered Xynol (Sp) but does it come in a triax or Uni ?
Can't see the point in glassing with the dirrection of planking.

a substantial inner and out layering of fabrics to turn this into a sandwich Can you sheath externally and use the frames for internal stiffening with
liberal sathering of frames, ribs, crevices with unthinned epoxy. I don't think it would be practical to glass the interior.

It's a ***** anyway you do it,
I can imagine. I plan to only skilsaw 3/4 way thru. Better that than cutting frames. Also , less mess inside.

Personally, I'd continue to dry the hull.
It has been drying for six months. BWL is now back to 30% (was down to 22% in summer and is sweating as the dew point is dropping and humidity rising, I am paying rent and want to go sailing! Topsides are still below 15%.
I am loath to force dry and epoxy is not recommended for salt impregnated timber so the only solution seems to be to replace it. Keelson could be a problem! Where do you stop?

Deck stepped sticks are hard on hulls
Mast is keel steped. ( too short spread of load-hence point loading and leak)

Could a lighter material be substituted BWL, say wrc. This would save me 100lbs? Kinda weird having denser topsides tho'.
Hope this aint too tedious-- Thanks again for your time.
Thanks also to Peter ~

 

On one of the other threads, someone suggested vaccume bagging to dry out a hull. Might have been for a foam core.

It seems this boat has all the torsional strength needed already. 30 years of proof. The wood should be stronger with the sheathing as it should remain at a lower moisture level. So maybe uniglass would be appropriate. And the inside of the hull? Planning to glass it also? I talked with Mr. MacNaughton several months ago. If I remember correctly, he claimed the only way to glass sheath strip planking was equal weights of sheathing insided and out. (accept for a bit more for abrasion resistance on the bottom)

Epoxy is sensitive to moisture content of the wood. Becareful

You could kiln dry the hull. as is. Would require several cases of ruhm, lemons, triple sec, 3 or 4 weber grills, meat delivery during the next month. Would make you feel like you are on the sea ... or at least the time will go bye pleasantly. smile

 

Maybe set a dehumidifier in the hull. serious this time

regards

 

This looks to be an early IOR yacht, which means it's construction was relatively light, rig powerful, raced pretty hard in the first several years of it's life, maybe longer and now 30 plus years later it is showing signs. It survived because it was a strip planked hull, most of it's breed are in land fills.

You'll need a lot of glass to help share the rig loads and provide torsional reinforcement, which means more weight (read even more stress and loading) Unless you are trying to fix worn out planking, frames, floors, bulkheads with a workboat style of sheathing (1/4" or thicker) your skinning schedule will provide little more then abrasion resistance and some moisture penetration.

If you want to "fix" this boat, increase the skimpy frame thickness, maybe laminating on top of them or sisters or decreasing the spacing with additional frames. The planking is probably shot, I know you didn't want to hear that, but there it is. If the bottom can't be dried out, it'll not take your sheathing, nor any new fasteners or other repairs well either. You may have to "cook" her in order to get it dry.

The only way sandwich construction works is when the outer 'glass skin (well bonded to the wood core and to the inner skin) has to stretch to conform to a bending load. Similarly the inner skin has to compress to the same load. Since 'glass doesn't like either very well (stiff stuff) the resulting panel is quite ridged. Any variation from this uses different engineering concepts, which would have to be worked out. Coating with un-reinforced epoxy (no fillers or fabric) will impart very little strength to the structure. Unless you are using epoxy as a coating (thinned or unthined) it must have a reinforcement (filler and/or fabric) to provide strength.

Strip planking is a very strong way to build, especially if you need a relatively clean interior, free off large frames and other structural members. It's probable the whole of the structure has issues. Fasteners loose, glue lines and joints releasing their grip, soaked lumber, the movement of the structural members making things worse as time goes on. The real fix is to replace the worn out planking, repair, refasten and restore joints in the structural members and generally go over the structure to insure things are tight again. You can redesign the mast step if you like, though it looks to be bridging 5 floors. You could add some additional structure, be that a heavy sheathing, addition frames, floors, bulkheads, deck beams or whatever, knowing you'll pick up a weight penalty through this effort.

Personally, I don't think you'll need the additional structure added. I think new planking (CPES it if you like) with new fasteners and epoxy joints will firm her up a lot. If this is coupled with replacement of all the structural member fasteners, you'll get a lot of life out of this old gal. I think everything is "working" from a hard life and age. Once the boat is refastened she'll be solid again. I'd recommend a high quality paint for her too.

Is there a reason you feel she needs additional torsional support? If so, I'd think about some exotic fabric banding, rather then a heavy sheathing.

 

Limiting the folly factor.....

All makes sense-Thankyou. Having not given the boat an adequate sea trial
I am proceeding gingerly to minimise additional folly. (My surveyor, in retrospect, was "**** on a bull".) The responsiblity though is all mine. (red face!)

I don't have a problem with replanking, except getting the keelson to low enough moisture content to accept the new garboard.Also,the moisture content of the frames and floors is a concern.I have some 200x200mm heart Kauri stock, so I may put temp. fasteners in while replanking and replace the
floors when the replanking is complete.
As pointed out, removing and replacing planking, section at a time, would be the safest method.
I think, next week we will invert the boat, closed bag it and start force drying
it with fan heaters and dehumidifiers monitoring as we go and hope it doesn't explode! (distortion is definitely in the back of my mind)
I could live with the moisture if I wasn't regluing. Replacing the keelson, I want to avoid!
The glass sheath is secondary right now.

 

If it is of any value to anyone of similar inexperience,or predicament, I can post pictorial update of progress, decisions made and reasons (right or wrong!)

I have an option of WRC below the waterline as opposed to kauri to save weight.
Kauri density is approx 560kg/m3 , wrc 380kg/m3. Is this a feasible? I will most probably sheath the hull.
Considering that the kauri would be on the topsides (in a semi-vertical plane) and the cedar around the bilge to the keelson. Good kauri stock is difficult to obtain and expensive. $2600 to $4000 a cube. On the negative you want to save wt above the c of m. not below.

My expectations of strength enhancement are high and weight gain low; perhaps unrealistic but there you are. You achieve in proportion to what you attempt.

 

Your planking material provides a very large majority of the longitudinal strength in this type of hull. Changing to a less dense species (conciderably less) means you'll need thicker stock to provide similar structural benefit. Saving weight is a wonderful thing, but best done in the design process not after a shape is employed and a target displacement met. Use light weight hardware aloft, remove the engine and sail it the old fashion way, but try to avoid changing the yachts scantlings without a complete understanding of the principles, concepts and engineering involved. You seem to have a good knowledge base, but may lack some of the engineering abilities to pull off what you're attempting.

You could use lighter weight planking, coupled with exotic fabrics set in epoxy to compensate for the strength differences, possibly coming in with a lighter boat. If you do manage to lighten the boat a substantial amount you'll likely need to add ballast (cool, it can be down low, right) but this may require re-rigging the sail plan for the increased loading.

These compounded difficulties are quite typical of how fundamental design changes can impact several areas of the yacht. I'd strongly consider a different course then substantially weaker bottom planks, a sheath (there goes any weight savings) where one isn't needed and other wise major deviations from the original scantlings, without running the numbers on the structure and the resulting dynamic qualities on the yacht.

 

Opps! 35oz/kg

Thankyou PAR for your rationale on retro changing design variables. I suspect that many old boats undergo quick fixes and this is inadvertently done anyway, as is the case with the coach roof on Pukka.
When you consider one crew member possibly adds 80kg of above c.of m. surely the sheathing is of less significance and these numbers do not have
a marked effect on righting moment, rig tension/mast compression and % increase in displacement.

Regarding the western red cedar;I prefer kauri anyway. I just don't like the price!
Correct me if I am wrong but I calculated the wt burden of a sheath as follows:
1 x 20oz sheath of epoxy over 40m2 of hull area =
40 x 20 (epoxy) =800 /35 = 23 kg @ 40/60 saturation = 58kg
Filler coats + fairing allow 20kg
Gross weight gain = 78kg
Minus moisture removal from extg hull approx 0.5m3 from 30% to 15% = 0.15 x 560 x 0.5 = 42kg

.*. Nett displ. gain = 36kg....... not that bad.

Also to consider is the external buoyancy of the sheath at 40m2 x .001m=0.04m3 = 40kg. ( assuming 1layer 20oz triax. = 1mm lam. thickness)
The coach roof has been added to over the years and now consists of 4 x 9mm H/wood ply! 36mm! All that weigh up high, now if I could just lower that mass somehow?
Of course there there is a displ. gain for deck sheath to be added.

Diag. scribe thru first pic = WL. Note dark bwl planks after 6mths drying!

 

My 2 cents.
Replace planking below wl with kauri,gluing with epoxy.
Cut open all suspect glue lines 1/2 way through in topsides that look suspect.Fill these with epoxy /silica.
Fair and paint..I wouldn't glass the outside.The boat has done just fine the way it was and there is no reason it won't give good service this way again.
Inside..replace any frames/floors etc that need it.Add a few new ones(extras) to take rig stresses.

My boat(smaller) is triple diagonal kauri,great timber.
Yours looks to be a Stewart 34?

Cheers
tactic