First project - 1972 Crestliner Stinger project

[solamax]

Hi all

Just bought this boat last week. This is going to be my first boat project. Will try to keep it updated. Started ripping out the floor.

 

[GT1000000]

Re: First project - 1972 Crestliner Stinger project

Hi and welcome to the dry dock, solamax...

Very nice looking project you have got yourself...

Any information you need to get this boat ship shape again, the super knowledgeable guys here will be glad to offer...

Best regards and have fun!
GT1M

 

[jbcurt00]

Re: First project - 1972 Crestliner Stinger project

I brought this over from your other thread @ this boat:

I have a 1972 Crestliner stinger. I am in the process of redoing my stringers and floor b/c it is rotted. I took everything out and notice that huge part of the fiberglass on the bottom seems like it has separated and flexes when I step on it. I cut a section out and notice underneath the fiberglass is very wet, looks like rotted wood. Does the bottom of the inside of a boat ever dry out completely? Do I have to cut out the whole section and redo it? How many layers of fiberglass do I need and what type? Is this normal for this age boat? I am going to use West System products. Anyone ever had this issue before? Thanks in advance.

And the pix you posted:

This is the hull you're pulling the fiberglass away in this pix, below the stringers. Not the deck on top of the stringers? And below this upper layer of glass (the glass just above your putty knife) there is a wet wooden surface? Sounds like a wood cored hull. I don't know if 1972 Crestliner's were built that way, but it certainly sounds like this 1 was...

 

[solamax]

Re: First project - 1972 Crestliner Stinger project

jbcurt00

Thanks. After doing some research, I found that the hull has a Balsa Wood core. I ripped it all out b/c it was rotted. Whomever redid the floor really did a crappy job. They never used Marine grade wood nor seal and glass the regular plywood. They pour foam only on one side of the hull and half the hull had 2 layers of plywood and the other only has one. I am deciding if I want to use Balsa again or Divinycell. Anyone know where (online) I can get a good epoxy resin comparable to West System but at a lower cost? My local marine shop charges almost $160 for the resin and hardener (West system) after tax.

 

[solamax]

Re: First project - 1972 Crestliner Stinger project

Here is more pic

 

[Georgesalmon]

Re: First project - 1972 Crestliner Stinger project

Why do you need epoxy? The boat was made with polyester and lasted 40 years. The wood rotted not the composite. Just sayin, Lot of extra money for very little if any gain. You will also need special fiberglass for epoxy. The binders in the average fiberglass material are soluble in styrene and won't work right with epoxy.

 

[solamax]

Re: First project - 1972 Crestliner Stinger project

Question here

I removed all the Balsa wood and am cleaning and grinding the residue off for a good surface to work with. I notice that the hull is scary thin. I believe some areas are 1/8" thick. Is this too thin? I want to put a few more layer of glass to thicken it before the new Balsa or Divinycell. What type and weight of cloth (csm, cloth, roven woven?) should I use and how many layers should I put under and over the new Balsa or Divinycell? Btw, it is a 14 footer. Thanks all.

 

[Scott Danforth]

Re: First project - 1972 Crestliner Stinger project

the hull is fiberglass on both sides of the Balsa core. that is what gives it the strength. yes, it will only be 1/8" thick on either side.

re-coreing will require you to vacuum bag too get a good bond.

 

[Georgesalmon]

Re: First project - 1972 Crestliner Stinger project

Scott is right, the balsa is only there to seperate the skins. The thicker the core the further apart the skins and the stiffer the bottom. You can add material to the bottom before the core but if you do, you should also add material to the top of the core. The cored material performs best when the skins are the same thickness on both sides. Course your not building a battleship so those things really don't apply. I would put one layer on the bottom before I started just to make a nice new layer to bond my new core in. You just need some 1.5oz CSM to do that. If you put a few layers of anything on the bottom you might be able to elimate the core and put in stringers instead. If you can recreate the stiffness the core provided you don't need the core. My 20' has a 1/4" bottom with four stringers a keel and three bulkheads.

 

[jbcurt00]

Re: First project - 1972 Crestliner Stinger project

You might want to do an advanced search on Balsa Core from the resto forum home page & read thru some of the other threads that have had balsa core posts. Here are the first 16:

• [h=3]1988 Cruisers Rogue 2800 - Balsa core or not?[/h]
  
  Forum:
  Boat Topics and Questions (not engine topics)
  
  
  
• [h=3]Replacing wood core on swim platform: advice needed[/h]
  
  Forum:
  Boat Restoration, Building, and Hull Repair
  
  
  
• [h=3]making a new swim platform using 1708 biaxle cloth[/h]
  
  Forum:
  Boat Restoration, Building, and Hull Repair
  
  
  
• [h=3]Nida Bond Core Bedding Compound[/h]
  
  Forum:
  Boat Restoration, Building, and Hull Repair
  
  
  
• [h=3]Should i pick this baby up if it looks good tomorrow?[/h]
  
  Forum:
  Boat Topics and Questions (not engine topics)
  
  
  
  
• [h=3]New to forum, buying my first boat this week, have a few basic questions.[/h]
  
  Forum:
  Boat Topics and Questions (not engine topics)
  
  
  
• [h=3]Balsa wood core rotting in a carver [/h]
  
  Forum:
  Boat Restoration, Building, and Hull Repair
  
  
  
• [h=3]Help! 1970 GW Invader 10' Restoration[/h]
  
  Forum:
  Boat Restoration, Building, and Hull Repair
  
  
  
• [h=3]Balsa Wood?[/h]
  
  Forum:
  Boat Restoration, Building, and Hull Repair
  
  
  
• [h=3]Core Hull[/h]
  
  Forum:
  Boat Topics and Questions (not engine topics)
  
  
  
• [h=3]my floor does the wave ! help[/h]
  
  Forum:
  Boat Restoration, Building, and Hull Repair
  
  
  
• [h=3]Silverline Tiburon balsa core rotted...want to replace with solid glass[/h]
  
  Forum:
  Boat Restoration, Building, and Hull Repair
  
  
  
• [h=3]1978 15' HydroStream Viper questions[/h]
  
  Forum:
  Boat Topics and Questions (not engine topics)
  
  
  
• [h=3]What type of foam board works with Poly?[/h]
  
  Forum:
  Boat Restoration, Building, and Hull Repair
  
  
  
• [h=3]Expert help, advice and recommendation needed on Hull[/h]
  
  Forum:
  Boat Restoration, Building, and Hull Repair
  
  
  
• [h=3]core repair[/h]
  
  Forum:
  Boat Restoration, Building, and
  
  
  

Google found these results:

1. [h=3]Replacing a Rotted Balsa Core Section in the Cockpit Floor [/h]

   
   

2. [h=3]Easier way for balsa core deck replacement? - Boat Design Forums [/h]

   
   

3. [h=3]Fiberglass deck repair-Part 1, Replacing damaged balsa core [/h]

   
   

4. [h=3]Replacing damaged balsa core [/h]

   
   
   

5. [h=3]Chapter 1: Hull and Deck Structure [/h]
   	Now, you are ready to replace the core. At this point, you should clean the work area of debris and dust. Replacing the balsa core. If you wish to replace the bad ...

   
   

6. [h=3]Balsa Core Hull - replacement guide ... [/h]

   
   

7. [h=3]Balsa core hull repairs ? [/h]

And not to discourage you, but from here re-coring a balsa hull sounds like a long, rough road to travel, if glassing isn't tough enough. I think it has been suggested in the past for small runabouts, it may be more cost effective & successful to apply alternating layers of CSM & 1708 using poly resin, and build the hull's glass thickness rather then re-coring. And then doing a more typical stringer install.

BUT please don't take just my word on that. As you work to clean up the hull & prep for either method, spend lots of time researching how you'll re-do the balsa core & whether you want to try & use epoxy or poly.

BTW: Polyester resin will not bond very well to epoxy. Although for building hull thickness, it may offer slightly added strength, when used with the correct cloth, over the poly resin's strength. CSM is definitely NOT epoxy friendly. But you'd want to make sure & keep it away from surfaces that will require poly resin work after you finish the hull repair.

 

[Scott Danforth]

Re: First project - 1972 Crestliner Stinger project

here is rough overview of replacing balsa core based on my limited experience:

remove outer layer of fiberglass
remove damaged area of balsa
clean area with grinder
fit new balsa core
remove new balsa core and apply core bond
tape plastic over repair and apply vacuum
let cure
remove plastic
add fairing compound to fill minor voids
apply outer layers of fiberglass (1708, etc.)
should bag here too
let cure
lightly sand
apply gel
let cure
sand and buff

I omitted the steps of dropping the core bond on the ground, making a resin sculpture, and opening up multiple bottles of liquid helper and burning out the shop vac because we didnt have a vacuum pump.

 

[solamax]

Re: First project - 1972 Crestliner Stinger project

Thanks for everyones input.

I really like the idea of just building up the thickness and not using Balsa. I am also now considering using poly vs epoxy. I will stiffen the hull with extra stringers. Question - If the hull is currently 1/8" thick, how many more layers of 1.5oz csm will I need to buildup another 1/8" or is it better to mix the cloth and csm together? Is there such a thing as overkill when installing stringers. I am also planning to pour foam the cavities as well. Also is the Bondo resin they sell at HD good for this type of work or where can I get good poly resin? Thanks.

 

[Scott Danforth]

Re: First project - 1972 Crestliner Stinger project

DO NOT use the bondo resin. it is waxed, and ok if you have a small project. go to uscomposites.com

converting from balsa core to stringers is outside of my experience or knowledge. I am sure it can be done, however I would start to question the costs.

 

[solamax]

Re: First project - 1972 Crestliner Stinger project

This is what I was planning to do. Please advise if its not a good idea. All the balsa is out and its preped and grinded. Since the hull is only 1/8", I plan to layer 1708 with epoxy until I achieved a minimal thickness of 1/4" or 3/8" which is probably an additional 2-3 layers. Then add stringers, bulkheads to stiffen it up. This way I can eliminate the Balsa and not have to worry about rotting. Being only a 14 ft, the cost is not as high as I thought. I plan to get my supplies from Raka. Any thoughts will be appreciated. Thanks.

 

[Georgesalmon]

Re: First project - 1972 Crestliner Stinger project

Don't need epoxy. Use polyester and one layer 0f 1.5oz CSM will give you about .045". If you put down multiple layers of CSM the thickness will build faster because there will be more resin unless you really try hard to prevent that with squegies. The amount of resin used has a lot to do with thickness. Most home layups are resin rich. Three layers of CSM and one of 1708 will most likely give you the 1/4 to 3/8" your looking for. You can calculate the amount of resin you need by knowing the weight of fiberglass you need. CSM at 1.5oz/sqft and 1708 at 17oz/sq Yard + .75oz/sqft for the mat attached. Notice the difference one is sqft and one is sqyd. Once you figure the weight multiply by 2 and that would be resin needed in pounds. Figure 9lbs/gallon for polyester resin is close enough. Thats a 66/33 resin glass ratio.IMHO

 

[solamax]

Re: First project - 1972 Crestliner Stinger project

Georgesalmon

How about vinylester instead. I been hearing how weak the poly is compared to vinyl or epoxy. Also it's no completely waterproof.

 

[jbcurt00]

Re: First project - 1972 Crestliner Stinger project

How about vinylester instead. I been hearing how weak the poly is compared to vinyl or epoxy. Also it's no completely waterproof.

Time & $.

The rest of the hull is probably not vinylester or epoxy

I don't know the kick (cure) time of vinylester, but epoxy can significantly longer to kick then poly. You can thin it or increase the catalyst ratio, but then you are compromising the primary benefit of the epoxy, strength, so that shouldn't be done.

Both are more expensive, and for you purposes, you'd still need to add cloth, which further increases the cost of either over comparable coverage w/ poly resin.

From MAS Epoxy's website:
[h=1]About Epoxies, Vinylesters, & Polyesters
[/h]

​

THE RESIN FAMILIES: Epoxies Vinylesters Polyesters


Epoxies, polyesters and vinylesters represent two resin families. Epoxies belong to a family of resins which are epoxy functional, which means they can be cured with amine curing agents at room temperatures to form excellent adhesives and composite resins. Polyesters and vinylesters belong to another family of resins containing an unsaturated polyester or hybridized vinylester backbone which is catalyzed with a peroxide (normally Conap and MEKP) to condense into a cross-linked solid resin.
RESINS AND ADHESIVES
Resins (liquid plastics, i.e. epoxies, polyesters and vinylesters) are commonly used in many applications when wetting out fiber reinforcing in order to saturate the fibers and form an FRP (fiber reinforced plastic) part. Whether the part utilizes fiberglass fibers, carbon fiber, Kevlar aramid, or wood fibers adhesions to and wetting of the fibers is a critical step in the production of a quality part.
EPOXIES
Epoxies represent some of the most versatile resins available to the composite manufacturer. Generally, in all categories of work, the builder/repairer will realize the greatest degree of bond strength, waterproofing and toughness with well formulated epoxies. New generation MAS Epoxies have curing systems which are phenol free (representing a safe step forward for all resin users). Atmospheric moisture is of little concern, as blush-free MAS systems allow builders and repairers to laminate and bond with little or no surface preparation between applications as long as mix ratios are followed and mixing is adequate. Shrinkage of MAS epoxies is below .03% eliminating prerelease. In the case where a part, originally manufactured utilizing polyester or vinylester, has yielded to strain and cracked, a well-reinforced epoxy repair will tenaciously hold to the substrate with 2000 psi strrength (vinylester: 500 psi). Many high strain repair areas and lightweight parts must flex and strain without micro fracturing. MAS resins have the ability to flex with the fibers while maintaining permanence and adhesion. Whether a part or repair is made of wood, carbon, Kevlar, fiberglass, core material or hybrids of the above, MAS Epoxies will wet and permanently stick to the composite. Just a quick note: one composite manufacturer recently eliminated a peroxide cured and extremely pricey custom-formulated aerospace adhesive (fancy packaging and all) with a standard MAS product. The benefits included reduced price, increased strength, and elimination of shrink problems from the bond line. When MAS Epoxies are used for a chemical resistant barrier (barrier coating) the finished coating system has excellent resistance to water uptake (below .5%) and the user can be confident that subsequent finishes will stick to the new epoxy and the epoxy will stick to the surface. New generation MAS epoxies feature many of the advantages of low viscosity and accurately tailored gel and cure times. Permanent repairs and the highest quality custom aerospace construction have been enjoying the advantages of epoxies since the sixties. MAS brings these advantages to the builder and repairer at room temperatures, and we're gearing up for more surprises in the 21st century.

VINYLESTER
Vinylesters represent a resin development step in the right direction. While still utilizing a polyester resin type of cross-linking (i.e. peroxide cured). These hybrid resins are toughened with epoxy molecules within the backbone. Shrinkage is less of a concern with vinylesters and prerelease of the part from the mold is reduced. The toughening effect of the resin modifications makes for a better resistance to micro fracturing and some of the secondary functionality of the backbone assists in adhesion to substrates. Vinylesters are capable of forming secondary bonds around 500 PSI (MAS Epoxies 2000 PSI). Resistance of vinylester resin to moisture is good and some commercial barrier coatings have been marketed utilizing this resin family. The down side of the vinylesters include sensitivity to mixing, handling, high VOC's (in the form of styrene), atmospheric moisture and temperature sensitivity (sometimes it just will not cure). Good tough vinylester is also quite pricey when compared to polyesters, in fact the dollars per pound approach that of epoxies. Vinylesters definitely represent an improvement over polyesters when considering standard peroxide curing, however adhesion to dissimilar and already cured substrates is still far below perfect and many vinylester hulls suffer similar massive delamination of the hull skins from core and bulkhead substrates. Additionally since almost all barrier-coating applications are after market it is essential that the coating system have maximal bonding strength to the original substrate. Vinylester resins only show good fiber adhesion to standard glass fiber, standard low adhesions to more exotic fibers (Kevlar/carbon fiber) and wood.

Open surface curing of both vinylesters and polyesters requires a surfacing agent. Subsequent applications require careful surface preparation if reasonable adhesion is to be achieved.
POLYESTER
Polyesters are one of the least expensive resins available to the FRP boat builder utilizing female tooling in the form of a mold. Polyester has the advantage of being extremely inexpensive when compared with other thermoset resins i.e. vinylesters and epoxies. If the upside is cheap pricing, the down side includes poor adhesions, high water absorption, high shrinkage, and high VOC's. Polyester resins are only compatible with fiberglass fibers. Polyester is best suited for applications insensitive to weight and do not require high adhesion or fracture toughness. For instance if a simple inexpensive solid fiberglass part must be fabricated in open tooling in one operation and requires no secondary bonding. If shape accuracy is not critical, resistance to water is of no concern, and ventilation of the workspace is excellent, then polyester's a great candidate. Polyesters historically exhibit poor performance in the areas of adhesion and elongation, rendering the finished part prone to micro cracking and secondary bond failures. These parameters become more important when we consider adhering dissimilar materials within the same part or welding any materials that are not the usual fiberglass strand substrate. Finished polyester hulls are still suffering from osmotic blistering when untreated by an epoxy barrier coating against water. Boat yards are filled with hull and superstructures suffering from massive areas of core disbonding or delamination resulting from an adhesive mismatch with the industry at large (i.e. depending on polyester as an adhesive).

 

[solamax]

Re: First project - 1972 Crestliner Stinger project

So far everything to do the floor will be under $500 which seem reasonable. It includes the epoxy, fiberglass, foam, tools, stringers, deck, etc. Poly or Vinyl is about $100 cheaper.

 

[solamax]

Re: First project - 1972 Crestliner Stinger project

Update

Just ordered everything needed to glass the floor, waiting for it to arrive. Also ordered some tyvek suit b/c working with fiberglass sucks, LOL. Question. What is the best way to get off the gummy glue residue left from the vinyl covering on the sidewalls? I don't want to grind it if I don't have to. Also is there any site that will show me some diagrams of stringer layouts for a 14 footer? I can't seem to find any. The previous stringer (not too sure if it's the original setup) was just one 2x4 that ran from the bottom of the Bow to about a foot away from Transom at the middle (total length was about 8ft only). Seem a little weak to me, maybe its because they had a Balsa core and that was stiff enough? Will post more pics in the up coming days. Thanks for everyones reply so far. You guys have no idea how much I've learn in the last few weeks just going through this forum and from youtube as well as other sites. Just want to say thanks and keep up the good works.

 

[Templar7]

Brand new to this forum. I just picked up the exact same model for a summer project
I will be uploading pics in the next few days. I'm sure I'll have allot to pick your brain about.