F27 Beam failure

guerdon

Anarchist
You could repair the damage if you have someone with working knowledge of composites guide you.  One trick for alignment, is to use bolts with fender washers  @12"  centers along the seams act as clamps between the separated sections.  Layup the end section till. cured, then grind the next section  work along the seam slowly until the length is fully reinforced, then remove the bolted sections, grind and repair those.  I have done some 10' sections this way without molds that required minimal faring.  Good luck.

 

Bruno

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Until the development of epoxy foams the selection of syntactic expansion foams suitable for closing in a mold product was not great.

 

Zonker

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Yeah not quite sure why the expanding foam - by the time you make the beam skins strong enough for the load they shouldn't oil can over that narrow span. But Ian was a clever guy so he must have a had a reason. Maybe holding dimensional tolerances so the sides didn't move in and out when glued together.

As to if it can be repaired - composites are very good at repairability. You just have to be good with a grinder and sander. In this case the only dimensionally critical part is the part of the beam that slots into the main hull notch. So as long as that fits the beam can be slightly ugly/lumpy elsewhere.

If I was repairing these, I'd cut off the gluing flanges in way of the damage, clamp the torn top skin in place, grind and re-glass the sides. THEN I would scarf the main break in top and bottom skins with very long scarf ratios on top and bottom faces because there is carbon fiber in at least the top and bottom skins right. Carbon needs long scarf ratios (like 50:1) to develop the interlam bonds between the old intact skins and new skins. 

For missing bits: I might pre-form some new boat building foam, lay an inside skin on it and then join it to where the old broken bit is. Then use that to create new top and bottom skins.

THEN more foam panels for the missing sides. Lay up new sides, lapping onto the new top and bottom faces. 

I will add that among beginners making composite repairs there is a hesistancy to remove enough of the damaged areas. Much simpler to just make a square cut  and have a nice square edge for your new repairs to start working from.

 
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Carbon repair scarf is 100:1 by the way. Start going 100:1 down the broken areas onto good material and virtually all of the beam will be "repaired". If you know the layup ( Peter seems to think he has these ), sometimes its just simpler, less overall hours, more cost effective and physcologically better ( who has never worried about a repair being as good as before ) to make a mold of an existing beam and get on with making a new one. It will save you a heap of time as well. 

I have the layup and beam design of the F85SR if you wanted to strengthen the beams for any reason or you wanted to build without a mold.

 

trisail

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Yeah not quite sure why the expanding foam - by the time you make the beam skins strong enough for the load they shouldn't oil can over that narrow span. But Ian was a clever guy so he must have a had a reason. Maybe holding dimensional tolerances so the sides didn't move in and out when glued together.

As to if it can be repaired - composites are very good at repairability. You just have to be good with a grinder and sander. In this case the only dimensionally critical part is the part of the beam that slots into the main hull notch. So as long as that fits the beam can be slightly ugly/lumpy elsewhere.

If I was repairing these, I'd cut off the gluing flanges in way of the damage, clamp the torn top skin in place, grind and re-glass the sides. THEN I would scarf the main break in top and bottom skins with very long scarf ratios on top and bottom faces because there is carbon fiber in at least the top and bottom skins right. Carbon needs long scarf ratios (like 50:1) to develop the interlam bonds between the old intact skins and new skins. 

For missing bits: I might pre-form some new boat building foam, lay an inside skin on it and then join it to where the old broken bit is. Then use that to create new top and bottom skins.

THEN more foam panels for the missing sides. Lay up new sides, lapping onto the new top and bottom faces. 

I will add that among beginners making composite repairs there is a hesistancy to remove enough of the damaged areas. Much simpler to just make a square cut  and have a nice square edge for your new repairs to start working from.
I fully agree.

The easiest would be to hunt for a written off F27 and salvage two beams.

Having built an F9, including the beams, these boats are repairable. Step one is to get a set of beam plans for the F82. Buy a disc sander and mask.

One possibility is to take dimensions off the starboard beams and then follow the procedures as per Ian's instructions, adapting the measurements to suit.

The other possibility is to take a mould off the top and bottom of a starboard beam and use the laminating schedule off the F82 plans.

Ian said on more than one occasion that the homebuilt beams were far superior because they were one-piece and did nor have the flanges. 

But good luck.

 

Zonker

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100:1 for pre-preg under lab conditions. 50:1 for vacuum bagged hand layup where the material UTS of the underlying material won't be nearly as strong.

 

Russell Brown

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I would think that a less-than-labratory fix with lots of cover lamination would work. So interesting that the failure didn't happen near hardware or connectives. It looks like the classic "knuckle under" failure, where the beams fail at the outboard ends with the ama folding under the beams.

 

boardhead

Anarchist
I would align and locally scarf/laminate the remnants together and essentially create a male mold. Fair and thin down the old laminate to a wafer thin shell then laminate a properly fiber oriented new beam over it expecting nothing from the mold, structurally, just a form.

The glued flange deal sucks and could easily be abandoned in favor of continuous filaments connecting the top and bottom elements at plus/minus 45 to better address the shear loading. Maybe the net attachment loading contributed to  the fail - did any serious porkers party on that net!!

I have to believe that expanded foam filler was for flotation and agree with Zonker that expecting it to offer and meaningful column support to the laminate would be optimistic.

 
I would align and locally scarf/laminate the remnants together and essentially create a male mold. Fair and thin down the old laminate to a wafer thin shell then laminate a properly fiber oriented new beam over it expecting nothing from the mold, structurally, just a form.
Why bother to take all the time to scarf together all the remnants and create a form when you already have the perfect form on the other AMA. You just have to think female form and not male form. At the end of the day which process is going to be quicker time wise ?

When you come to sell the boat and two beams are looking like someones had a go at repairing them badly as compared to having two complete new beams made, I wonder how much that will effect the resale value ?

 

boardhead

Anarchist
Why bother to take all the time to scarf together all the remnants and create a form when you already have the perfect form on the other AMA. You just have to think female form and not male form. At the end of the day which process is going to be quicker time wise ?

When you come to sell the boat and two beams are looking like someones had a go at repairing them badly as compared to having two complete new beams made, I wonder how much that will effect the resale value ?
Because you would be replicating the same questionable method of two halves, stuck together, which put too much emphasis on appearance and cost, less on structural integrity. Better to lose the flanges on the other two beams (like this model did on the ama deck joint) so they match the repaired beams and save yourself the time and materials on a mold nobody needs.

Hey - grind the gel coat off the “good” beams and wrap them in some filaments that add strength and rigidity in place of deadweight. 

 

Wess

Super Anarchist
The akas broke at the outside end. 

Thanks for the pointer to "Drag files here..." I don't think that was there when I composed the first post.

See photos. 

View attachment 449884

View attachment 449885

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Holy shit; sorry to read and see this.  They are great boats but you really need to stay on top of beam maintenance.

Steve Marsh who runs Finish Line, http://finishlineotc.com, in Florida may have “spare parts”.  He has picked up some damaged F27’s in the past or Don Wigston, also in Florida, runs Windcraft. https://windcraftmultihulls.com

the New England team you reached out to probably have reached out to them, they all are Corsair dealers.  
 

It is hard to tell from the pictures, but one looks like the Aka seam may have separated.....Ian has/had a bulletin probably moved to here: https://fct.groups.io/g/F-Boats/files which seems to have the old yahoo group archives.

Could you tell if one Aka caved first? Followed by cascading failures?

I would look up the bulletin and check the starboard side per the guide.
What TRi said. Steve would be my first call.  He had beams.  Not sure if he still does.

I think this picture shows exactly the type of failure described in the PDF file. Starts at the beam seam, hits the bolt hole (stress raiser) then  cracks the side and slowly peels the beam. IMO, the top of this picture is where the failure ended. It started at the bottom.

"Should the glue line fail here, and be undetected, the failure will grow along the join flange until it reaches a bolt, which then acts as a stress raiser.
A vertical crack running up the side of the beam may then develop from that bolt.
Now it gets serious and must be repaired without delay
"

You may have had this sort of partial failure for a long time and just didn't see it. So this beam probably failed first and then 

View attachment 449920
Yes, this exactly.

Not sure I would do this repair though. Doubt the resale if ever close to what it should be.  Just too many questions. If insured I assume its totaled... take the money and run and buy a different one.

 

boardhead

Anarchist
Go with Zonker - learn and enjoy, you can make it stronger than new and be confident in what is under the candy coat.

Finance, insurance, lack of any practical skills are sucking the life blood out and spark of the younger generation.

Write the boat off for that failure - are you kidding!

 
They appear to be a different design than a Corsair 27, interesting.
I'm not sure what is meant by this. The boat is of the design before the amas were changed to reduce production cost and difficulty. So, yes it is different than the later design, but it is a Corsair F27 nonetheless.

 

Zonker

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If insured, yes you could total it. But a well done repair can be invisible (except for missing flanges will be different from stock)

You can always document it well, or not disclose it to the seller, your choice.

 
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