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Reardon
04-15-2010, 01:41 PM
Does anyone have any idea what the difference in strength would be between a fillet reinforced with chopped strand and/or milled fiber versus a fillet that has a layer of cloth in it?

The application would be for a small 12-16' s&g sailboat at the chines and transom.

RodB
04-15-2010, 02:00 PM
The majority of the strength of filleted joints comes from the fiberglass fabric (usually biaxial 4" tape) not the fillet. The fillet is mainly used to offer a radiused surface that allows the fabric to curve nicely around the joint... ie., fiberglass does not handle sharp corners well.

There are some experts on this forum that should be able to tell you the strength difference you asked about... but in general terms, the fabric backed joint with standard filleting mixture (50:50 cabosil and wood flour) would be much better.

RodB

jgmarine
04-15-2010, 02:01 PM
Hi,
You should use a 10 oz cloth, vs chopped matt , or better yet, for extra strength, 3X as strong.....
a 14 oz. biaxial cloth, combines 4 oz. mat and woven roving, run diagonally criss cross.
I used this to repair a hull keel joint crack on a C & C 32.

Jack

mmd
04-15-2010, 02:09 PM
"Does anyone have any idea what the difference in strength would be between a fillet reinforced with chopped strand and/or milled fiber versus a fillet that has a layer of cloth in it?"

Yup.

I don't have my texts on composite materials engineering with me here at the shipyard, so this is from memory, but I think that I recall that the average laminate of CSM in resin has about 25% the tensile strength of a woven fabric reinforcement in resin.

andrewe
04-15-2010, 02:11 PM
CSM is normally used with polyester resin, not epoxy, because the binder is not soluble in epoxy.This means that it will not conform to double curves. Someone told me that there are CSMs that are compatable with epoxy. But I havn't been interested enough to look as they are not very good in hi tec layups.
A

Figment
04-15-2010, 02:12 PM
Wow. Remind me again why anyone ever uses CSM?

Brian Palmer
04-15-2010, 02:19 PM
Wow. Remind me again why anyone ever uses CSM?

'Cause you can practically squirt a whole boat out of a resin gun and a big spool of roving.

Actually it is good with heavier uni-directional materials fabrics as a backing, and between layers, and to prevent fabric print through next to the gel coat, but is not very good by itself.

Brian

mmd
04-15-2010, 02:22 PM
Fast, cheap, low-tech, doesn't require skilled labour...

Need I go on?

Reardon
04-15-2010, 03:14 PM
Thanks All!

P.I. Stazzer-Newt
04-15-2010, 03:38 PM
Wow. Remind me again why anyone ever uses CSM?

Did you ever wrap a low volume slalom kayak round a rock?

A strong hull matched to a strong deck will still fold, and it your legs happen to be in the crease zone - a very bad thing happens.
The inclusion of a short run of CSM in the right place gives you a (slightly) better chance that the crease will be somewhere that does not trap the boater....

JimConlin
04-15-2010, 03:58 PM
It's miserable stuff.
Low in strength, both because the fibers are short, in random directions and resin-rich.
The common varieties don't like to bend around corners with epoxy.
Not pleasant to handle, either dry or wet.
Very difficult to get smooth without slobbering lots of expensive and heavy goo on it.

As has been said. it's useful in preventing print-through , but keep it thin. Other than that, it makes sense only in high-volume manufacture of low-quality glass boats.

For finishing fillets, selvedge-edge glass tape is good and convenient, but half of the fibers are going in a useless direction. It's a bit more work, but I sometimes use glass cloth on the bias (XXXXX) or even double bias topped with cloth for heavy structure.

Candyfloss
04-15-2010, 04:23 PM
Best practice is two layers of 300g double bias tapes 100mm wide, lapped 25mm, which is to say, the edge of one is layed on 25mm from the edge of the other, the whole layup centered on the joint. This gives a 600g layup over the joint, tapering out to 300g at the edges to avoid hardspots.

Cuyahoga Chuck
04-15-2010, 04:24 PM
Does anyone have any idea what the difference in strength would be between a fillet reinforced with chopped strand and/or milled fiber versus a fillet that has a layer of cloth in it?

The application would be for a small 12-16' s&g sailboat at the chines and transom.

An interior joint is made of an epoxy fillet overlaid with some kind of cloth.
The filleting mix will be strongest if it's thickened with milled cotton fiber, milled fiberglass or woodflour. The thickening agent has to be very small particles if you want to be able to strike off your fillets quickly without a lot of hassle.
A fiberglassglass tape is always laid on top. No tape no strength. One layer inside ,one layer outside is sufficient. NO mat and no roving required for aboat that small. It as has been 90-90 weave glass for a long time but 45-45 biax is now the standard because the thread orientation makes for a stronger joint. The glass tape can be between 6 and 12 oz. depending on how hard you intend to thrash your boat. Heavier weights come out thicker and the edges are harder to sand down.
Here is the bateau.com "how-to " page. Somewhere among those tutorials is one or more that show diagrams of the filleting-taping procedure.
http://www.bateau2.com/howto-index.php

ssor
04-15-2010, 04:32 PM
My lay-ups are usually csm roving csm roving csm roving csm makes beter nthan a1/4 inch with 98 per cent contact between plies. if itwere all roving contact would occur only when strands touched.
But to answer to original question, form the fillet and lay the woven tape into the wet fillet.

wizbang 13
04-15-2010, 05:41 PM
I just use 403 micro fibers. No fg tape. for the amount of resin used in glassing, just make the filet bigger. I wrap and frap my dingys upside down to the deck of the big boat. when the weather gets bad, I tighten the frapping so hard it bends the skiffs, never had a failure. Also, my little 50 mph boat (wizbang) uses no tape, and that little bugger takes more abuse than any 12' sailboat.

Cuyahoga Chuck
04-15-2010, 08:02 PM
I just use 403 micro fibers. No fg tape. for the amount of resin used in glassing, just make the filet bigger. I wrap and frap my dingys upside down to the deck of the big boat. when the weather gets bad, I tighten the frapping so hard it bends the skiffs, never had a failure. Also, my little 50 mph boat (wizbang) uses no tape, and that little bugger takes more abuse than any 12' sailboat.

I use 403 too. It's cheap and works well. But you are pressing your luck if you think a lump of epoxy with microfibers has the tensile strength of hundreds of strands of heavy fiberglass yarn. The only reason fillets came into the picture is because fiberglass tape will not conform to a sharp internal angles. Your fillets would have to be enormouse to have the glued surface of even 4" tape.
I have a 14 ft S&G pirogue that flew off my roofrack at over 60 mph, landed in the road and not one taped seam let go. It survived because I built it the way the designer specified. Occasionally I do things not by the book. When I do that I don't propagate the idea because I'm the one who is speculating and I'm the one that should pay the price if it goes wrong.
I wish you luck with your experimental craft.

gibetheridge
04-15-2010, 09:32 PM
Here's another vote for 403 (cotton fiber) thickened fillets covered with 4" x 6oz. cloth. The cloth will be doing most of the work.

Breakaway
04-15-2010, 10:44 PM
As part of a laminate stack it has uses. By itself, since the fibers are all chopped up, it doesnt bear loads for any distance like the "full-length" fibers in cloth. Even if half the strands in a cloth are "free-loading"--not doing much--they other half is working across the entire run.

ssor
04-16-2010, 10:42 AM
Don't be too quick to sell milled fibers short. Cotton fiber thread has held a lot of shirts together. Think of milled fiber and resin as millions of scarf joints. a fiber that is .001 inches in diameter and .500 inches long makes a very long joint.

Cuyahoga Chuck
04-16-2010, 01:15 PM
Don't be too quick to sell milled fibers short. Cotton fiber thread has held a lot of shirts together. Think of milled fiber and resin as millions of scarf joints. a fiber that is .001 inches in diameter and .500 inches long makes a very long joint.

West 403 is milled cotton fibers but it is nowhere near .001" dia nor " long. If there is a thixatropic ingredient of your dimensions I haven't run across it.
And, I would guess, glass fibers are much stronger in tension than an equal amount of cotton.

ssor
04-16-2010, 01:36 PM
West 403 is milled cotton fibers but it is nowhere near .001" dia nor " long. If there is a thixatropic ingredient of your dimensions I haven't run across it.
And, I would guess, glass fibers are much stronger in tension than an equal amount of cotton.

Cotton fiber is .001" or less in diameter and any length over 12 diameters would meet the requirements for a scarf joint. Of course glass fiber is stronger than cotton fiber. I point is/was that the fillet does contribute significant strength to the joint.
Edit to add: clothes dryer lint from the filter will come close to my dimentions. ;)

Bill Huson
04-16-2010, 02:07 PM
CSM (mat) will print through gel coat. The random fiber pattern makes the print through less noticeable, but it's there. "Veil" is used between the fiberglass layup and gel coat to prevent print through. But veil is expensive, so not many boat manufacturors bother with it.

Technical mumbo-jumbo aside, I would not use mat on a wood boat. Nasty to work with. Ugly. Cheaper to buy per square foot, but in a home workshop hand layup situation one would eat the svaings up in resin since without aggressive rolling with a fluted roller, vacuum bagging, or infusion, mat sucks up the resin.

Candyfloss
04-16-2010, 04:00 PM
Quote SSOR:-

But to answer to original question, form the fillet and lay the woven tape into the wet fillet.

Yes.

Cuyahoga Chuck
04-16-2010, 06:03 PM
Cotton fiber is .001" or less in diameter and any length over 12 diameters would meet the requirements for a scarf joint. Of course glass fiber is stronger than cotton fiber. I point is/was that the fillet does contribute significant strength to the joint.
Edit to add: clothes dryer lint from the filter will come close to my dimentions. ;)

I'm a practitioner of the "wet on wet" technique. One of the elements necessary to get thru' it before the googe hardens in the cup is to have a filleting mix that can be struck off quickly. Once I tried sawdust in place of woodflour and the difference in texture made getting pretty fillets a definite chore.
My fillets are bare minimums because I always try for minimum weight and epoxy is heavier than water. I use just enough filleting mix to get the tape to conform to the angle. The little boat in my avatar came out at 65 lb. Next time I'll do better.

ssor
04-16-2010, 08:10 PM
Fillers for resins are rather like fillers for portland cement. It depends on the requirements of the job. For filling the joints in tile we use fine sand, for laying brick and block the sand can be a bit courser, for pouring a foundation we can use a mix of fine and course sand and gravel. The same holds for fillers for resins. We can use commercial fillers that are so fine that they act like smoke when stirred or we can use the dust from the shop vac filter or even dust from the band saw. One will be right for the job, none will always be wrong. Cost and ease of use are factors. We can be creative and are not bound by any rules but our own.