Stringer replacement wood.

[Woodonglass]

Re: Stringer replacement wood.

Ok, once again, both the article posted an the book link are speaking of Yachts and large boats. We have very few of those type restorations going on here on the forum. Our typical boats are under 20 ft. As I stated before I was in a SPIRITED Debate with the PRO's of this forum, some of whom are still active and some are not, and the consensus was that on the smaller boats the hard spots are not as critical of an issue as they are on the larger boats. In all my time on here, I don't believe I've ever dealt with a boat that had this issue. Believe me some of them should have because the MFG's from the past use to use 2x8's for stringers and lay em directly on the hull and tab em in. The length of the hull and the span between bulk heads would make it more likely for this to occur. On a 14 to 16 ft'r mmmm.... not so much. Not saying we shouldn't use bedding material cuz I personally think we should and I'm a proponent of PB, but regardless of what's used the likelihood of having a problem with HardSpot cracking and crazing in the hull for a small boat is fairly minimal. Again Just an Old Dumb Okies opinion based on what he's gleaned here on the forum. Worth every thing you paid for it.

 

[tpenfield]

Re: Stringer replacement wood.

Ok, once again, both the article posted an the book link are speaking of Yachts and large boats. We have very few of those type restorations going on here on the forum. Our typical boats are under 20 ft. As I stated before I was in a SPIRITED Debate with the PRO's of this forum, some of whom are still active and some are not, and the consensus was that on the smaller boats the hard spots are not as critical of an issue as they are on the larger boats. In all my time on here, I don't believe I've ever dealt with a boat that had this issue. Believe me some of them should have because the MFG's from the past use to use 2x8's for stringers and lay em directly on the hull and tab em in. The length of the hull and the span between bulk heads would make it more likely for this to occur. On a 14 to 16 ft'r mmmm.... not so much. Not saying we shouldn't use bedding material cuz I personally think we should and I'm a proponent of PB, but regardless of what's used the likelihood of having a problem with HardSpot cracking and crazing in the hull for a small boat is fairly minimal. Again Just an Old Dumb Okies opinion based on what he's gleaned here on the forum. Worth every thing you paid for it.

Very valid opinion. I too do not believe the stringer offset is critical on smaller boats. Boats that would tend to be used on large bodies of water (big, big lakes and ocean going) are larger and the impact absorption aspects of the hull are much more critical. I think for someone bedding stringers on a small runabout, bowrider or bass boat, getting the tabbing secured well is probably the better focus.

 

[DeepBlue2010]

Re: Stringer replacement wood.

Well, gentlemen, I don’t think we are discussing if, when and in what kind of boat hard spots will develop. We – and the factory for that matter – got passed this point when we raised the stringers a 1/8-1/4 of an inch above hull. This by itself will greatly reduce the possibility of developing hard spots.

I believe we are discussing the subject of what to fill this 1/8-1/4 of an inch gap with. Some factories like Bayliner filled it with absolutely nothing. But that is how air pockets, delamination and water intrusion of the stringers happens.

As of what to fill this gap with, I know the PB is very popular around here and I am not against it at all. I expressed my concerns in the linked thread and I hope you would at least agree that there is some merit to them. I think this represents an opportunity for further testing and research which I am sure I will be doing soon.


As of the development of the hard spots themselves, I am not convinced at all with a blanket statement such as “They are important in big boats and not that important in small ones”. I think this is over simplification. The laminate thinness, the dimensions of the unsupported panels, sea conditions, the center of gravity of the vessel, and a plethora of other factors will play a significant role in the formation of hard spots in any type of Fiber Reinforced Plastic hull. Simple measures to avoid them are much better than the alternative of having to deal with them down the road and we all know what does this entails.

 

[Woodonglass]

Re: Stringer replacement wood.

As I have stated, in All of my searching, and study on this forum and the various other forums I frequent in the past several years, I can't recall ever having seen a discussion concerning the repairs of hull cracks caused by Stringer hard spots in boats of 20 ft or less. It doesn't seem to be that much of an issue to be of serious concern. I truly believe we put to much behind it. Use what you thinks best and move on. Just make sure you get good adhesion to the hull with the tabbing and subsequent layers of glass because that's where the rubber meets the road as the PO has stated.

 

[DeepBlue2010]

Re: Stringer replacement wood.

I rest my case.

 

[ondarvr]

Re: Stringer replacement wood.

The majority of small boat builders today don't bed the stringers, typically the stringer grid is pre-made if possible and dropped in place then glassed over, they don't even pre-coat the wood with resin, although most do use pressure treated plywood.

More builders are using pre-made all glass stringer grids now though, they use polyester putty or Plexus (or similar product) to bond it in place.

 

[fishcrazy50]

Re: Stringer replacement wood.

Coremat, Divinycell or leave a 1/8" air gap.

 

[Woodonglass]

Re: Stringer replacement wood.

The majority of small boat builders today don't bed the stringers, typically the stringer grid is pre-made if possible and dropped in place then glassed over, they don't even pre-coat the wood with resin, although most do use pressure treated plywood.

More builders are using pre-made all glass stringer grids now though, they use polyester putty or Plexus (or similar product) to bond it in place.

Yep, If you google this you can see these grids and the Flat top pyramid designs they are incorporating. Some of the Old Larson's used similar stringer designs back in the 50's and 60's. Guess there's really nothing new under the Sun!!!!

 

[DUNK51]

Re: Stringer replacement wood.

wow! I have been a mechanic for many years and have learned to think before putting a project in gear and all of you have given me a lot to think about. I like the idea of something that will absorb shock under the stringers but I too worry about adhesion. From reading everybody's post if I do a wide radius at the bottom of the stringers and two or three layers of tabbing that will spread out the stress and reduce cracking.? My boat is a small bass boat but some of the wakes I hit really jar the boat(my fault) but they sneak up on me and I would not like anything pulling loose.

 

[jbcurt00]

Re: Stringer replacement wood.

IMO:
If a boat's stringer system is built w/ relatively good care & attention (you hope an original factory stringer fab, setup, install & glassing would be)
and
If the hull & deck are similarly well built (same hope for the factory work)
and
If a boat is relatively well maintained and stored properly (I suspect this is the failure point for most of the boats we see in the dry dock)

I would expect most boats will never experience the torn tabbing, stringer (&/or glass) delamination and other problems associated w/ keeping the original stringers well adhered to the hull & deck and doing what they were intended to do.

The hull~stringers(bulkheads too)~deck of a boat is a system. W/out the other 2 portions of the system working properly, doing what they were designed to do, expecting the 3rd to remain unaffected is fool hearty, IMO. Being a system, when 1 portion is compromised (particularly decks) there is likely to be damage & compromise in another portion of the system (primarily the stringers).

All that ^^^ said, as backyard boat builders, I'd prefer to err on the side of caution.

Is PB/PL totally necessary in a rebuild if the factory originally used no bedding for the stringers? Since some of the boats we see in the dry dock are from makers that are no longer in business, it'd be difficult to find anyone associated w/ the boat's original construction to ask whether it'd be better to PB/PL bed the stringers or use no bedding, just leaving a 1/4"+/- gap below the stringer & using the tabbing only.

Boat building has changed over time, no surprise. If the production schedule & costs to make a boat were unchanged no matter which way the original maker built the boat, PB/PL/no bedding under the stringers, which way would most builders have built the boat? I don't know that either.

What I do know is most of the backyard boat builders here @ iboats are rebuilding the 1 boat we'll ever rebuild. Most of us are also complete rookies doing boat fab work and fiberglass work.

Rather then using 4 or 5 types of fiberglass cloth & mat, or heavy woven roving (which can be difficult to form over edges & contours, hard to fully wet out & takes a lot of resin) the condensed method is using 1708 & CSM only. To ensure the 'best' possible combination of strength & ease of fabrication, holding the stringer up off the hull 1/4", and bedding the stringer allows us to put a radius fillet along the 90degree corner between hull & stringer. This will ensure that the fiberglass transitions smoothly from hull to stringer & is firmly attached to both and has no weak, unsupported areas prone to cracking &/or failure.

You might be able to look back thru my posts from a long time ago. I was firmly & vocally a PL bedding advocate for all the reasons stated previously in this thread. And for filleting as well. That is no longer the case. Whether from the nature of PL & polyester resin, inadequate cure times or improper prep & installation, there have been more then a few builds that had unsatisfactory results when using PL for bedding or fillets.

If there's even just a small possibility for a problem, I'd rather avoid it & the cost of a setback. Using PL for bedding &/or filleting may or may not create a problem. If it does, you may not know it until it's become a much bigger problem. Will that be before or after you put the deck back on &/or start using the rebuilt boat?

For me, the purpose of the bedding/filleting is equal parts holding up the stringer in general, adhering the stringer to the hull, spreading any load transferred thru the hull to the stringer & deck, and giving the fiberglass a good transition from the hull to the stringer. To me, PB checks all those boxes much better then PL does, allows much quicker progress & does it all at a lower overall cost to me. Even as novice boat builders, the multiple steps: PB bedding, filleting, tabbing & glass wrapping of stringers, allows the margin for error to be spread across many layers of the build & the likelihood of a major problem from improper fabrication, is much smaller, particularly in the stringer/hull interface.

The transom is also an integral part of the overall boat 'system'. It is also likely to be affected when there is a problem w/ the deck &/or stringers.

Lastly, IMO, proper use, maintenance and storage will prevent most if not all the long term water damage we see in most rebuilds.

The maker of your bass boat knew the hull wasn't a particularly good wave/wake cutter & that it was likely to be run hard & fast. Rebuild it similarly to the way it was originally, to the best of your ability and you will likely get many decades of use out of it, frequent, jarring wake crossings or not.

Carp, I need a cup of coffee & a donut after that ^^^

 

[DUNK51]

Re: Stringer replacement wood.

THANKS! jbcurt00 reading that reply made me feel better about my decision. when I look at what the workmanship looked like that I took out and the boat lasted from 1977 till now I now feel I will have no problems. I hope:nevreness:

 

[jbcurt00]

Re: Stringer replacement wood.

BTW: I wouldn't over do the size of the fillets, it'll just use more resin & fillers to make them bigger. Roughly the same size as the radius of the previous tabbing & etc that was originally installed.

 

[Woodonglass]

Re: Stringer replacement wood.

Uhhmmm, I'm pretty sure if you do your stringers as described here..., "Fabricating Decks, Stringers, and Transoms"
Your boat, with proper care and maintenance,will last for several decades!!!!

 

[jbcurt00]

Re: Stringer replacement wood.

Uhhmmm, I'm pretty sure if you do your stringers as described here..., "Fabricating Decks, Stringers, and Transoms"
Your boat, with proper care and maintenance,will last for several decades!!!!

If anyone thought I was suggesting other wise, nope. Exactly that ^^^

 

[Woodonglass]

Re: Stringer replacement wood.

Nope, I've been down this road Soooooo many times and it seems to always come back to the basics!!!! K.I.S.S principle seems to always work pretty well.:laugh: