At some point in it's life, my canoe got skids.
Not the prettiest job.
These things seem quite thick, but I'm not really sure how thick skids generally are supposed to be?
The surface finish is coarse, and there's resin smeared all over the hull.
I'd like to knock these things down (I'm assuming they are too thick), smooth them out, and clean up the ugly areas. I have respirators, a variety of sanders and materials.
I believe they are kevlar, which is a material I am unfamiliar with working with -- the fabric can fuzz up real bad if I sand into it?
I've read around, but still I'd prefer some fresh advice on my particular scenario before diving in. Anybody care to give me some direction?
here's an album of pics:
http://s58.photobucket.com/user/MattWebb502/library/Wenonah%20Odyssey
I’ve done it.
You’re right - sanding doesn’t work well.
My royalex Prospector came with those thick and rough kevlar felt skids, because it was originally set up to be a rental boat (but never actually got used). I found that a farrier’s file works really well on those skids. Smoothed mine out real nice and thinned them slightly without any fuzz. Don’t get in a hurry - it works quick enough going easy. You do have to be careful about not filing the unprotected skin of the boat.
perhaps you can remove them
Yes, they are Kevlar felt. And you are right about them being thick, ugly, and rough. In addition, they are really quite weak when it comes to impact strength. The felt consists of very short fibers that are compressed. The fibers themselves may be strong, but since they are all so short, the material itself has little structural integrity. I have seen literally scores of whitewater Royalex canoes which had these monstrosities applied in which the felt material broke away in big segments. Here is an example:
http://loapc.files.wordpress.com/2008/07/img_0577.jpg
I have removed Kevlar felt plates from a couple of boats but they were both Royalex. Yours appears to be a gel coated composite. The bond between the hull and the plate is not always that strong and you might find that you can get a chisel or a paint scraper blade between the plate and the hull. If the plate starts to lift off, the material is so weak that you can usually just break it off in pieces with finger pressure.
You will almost certainly has some damage to the underlying gel coat. You may be able to clean up the excess ugly resin by wet sanding it off. If you can get the plate off you may have enough underlying damage that you would choose to apply a much better looking and stronger abrasion plate using S fiberglass or Dynel fabric. If so, I can point you to some threads that give detailed info on how to do that.
If you don't feel you can remove them you might be able to smooth them out some and bevel the edges. I have used a Dremel tool to bevel the edges on a few thick Kevlar skid plates and I have found you can sand them some. You can also apply some coats of epoxy afterwards to fill in the depressions and smooth the surface. You should be able to wet sand off some of the excess sloppy resin.
paint your
hull with krylon
https://goo.gl/sRc2ty
if you desire compulsion errr beauty from the object not the experience or find the object drives the experience…which is Ok with us just saying…
then paint the ugly abomination.
fersure itsnot the felt.
Yes ! my Rendezvous has the Official Wenonah Felt Kit.
The OWFK is Beeeeeutiful !
The slob installed your felt forgot the masking tape.
Felt absorbs impact. How could it not ? What do you think the felt is doing when it falls off ? Going to Maine ?
Yeah, well
Forty two layers of Duck tape would absorb impact as well, would be cheaper, and would undoubtedly look better. Slopping anything on the boat stem from truck bed liner to roofing tar will provide some degree of protection. The point is that there are vastly better options for abrasion plates than Kevlar felt.
Better as in stronger, lighter, smoother, thinner, longer lasting, better looking, and cheaper.
how would dynel
absorb impact more than thick felt hardend with your grail, Gflex ?
Impact absorption is thicknesses of material, distance from impact.
NOT.
No
Thickness of hull material imparts stiffness but not necessarily impact resistance. Balsa wood is often used as a core material to thicken, and thereby stiffen, the bottoms of flat water hulls, but if you made a skid plate out of balsa wood it would not offer much protection against impact, no matter how thick it was.
Woven Dynel cloth or fiberglass cloth would never break away in big chunks like Kevlar felt skid plates do. That is because the fibers run through the entire length of the material. You might cut through the fibers of a 'glass or Dynel abrasion plate, but you never have big chunks just break away. Furthermore, if you do have some laceration or abrasion through a 'glass or Dynel abrasion plate, repair is simple. Repairing a Kevlar felt skid plate that has shattered and has pieces missing would be difficult and a waste of time and money.
Woven Kevlar material would impart considerable impact resistance in comparison to Kevlar felt. But it is not a great choice for abrasion plates because the aramid fibers are not nearly as strong in compression as tension, and when the stem of a canoe is impacted, the outer layer of material is subjected to compression. Also, Kevlar can't be sanded and feathered well, and fuzzes up with abrasion.
If you made an abrasion plate using layers of S 'glass and built it up as thick as the typical Kevar felt job, it would be immensely stronger.
Here is one builder's take on the use of different abrasion resistant fabrics for use on wooden kayaks:
http://www.oneoceankayaks.com/Abrasion.htm
He mentions woven Kevlar fabric and discusses the advantages and disadvantages I alluded to. He is not crazy about Dynel because it does not cure clear (an issue for wooden boats but not for synthetic ones) and it soaks up a lot of resin (a valid complaint). Of course, a lot of resin uptake makes for a thicker, but not necessarily stronger plate. He therefore favors the use of S fiberglass. He does not even mention Kevlar felt, because it is crap.
So why do boat buyers like Kevlar felt skid plates? Well, they are Kevlar and everyone "knows" that is strong. Furthermore the material holds its shape when handled and does not fray at the edges so it makes it fairly idiot proof to use.
Why do boat builders like to sell Kevlar felt skid plates to boat buyers? Well, they can be slapped on very, very quickly. And they are Kevlar, which all the boat buyers "know" is very strong. And Kevlar felt is pretty cheap so the profit is enormous given the fact that the installation is typically billed at $200 or more and the installation is quick and easy.
Crap ?
http://www.sciencedirect.com/science/article/pii/S0266353899001852
https://www.google.com/#q=impact+absorption+of+composite+fabrics
Using balsa as an example supporting laminates vs Kevlar felt is illogical and dishonest.
Again, breaking away is energy absorption. The action is visible.
Lamination destruction may be invisible, more expensive in installation and replacement.
Beyond felt and your holy epoxy….Padnetter critical of Gflex ! HERESEY ! ….
The tech would move toward a chemically structured UV resistant and adhering foam…kevlar foam with graphene springs…prob a Velcro Olsonite UOP level venture to the Air Force/Infantry Body Armor….
Felt’s cheap.
If you pursue the GooScholar info, IMHO finding clear chart results of the first reference.
For myself the deal here is kinda ‘XXXX floats wtare runs down hill’ science.
NOT. Not what ?
Crap? He doesn’t…crap ? How do you support this slur on an elegant material ? He told you that or what ?
Whaddya think of aluminum foil cap inserts for the MEK stopper ?
wow
You seemed to be alluding that:
A. An abrasion plate had to be thick to provide impact resistance,
or B: An abrasion plate of material X that was thicker than an abrasion plate of material Y automatically conferred more impact resistance regardless of the materials X and Y,
or C: both.
The fact is that none of the above are true.
As far your reference to an article comparing the impact resistance of woven Kevlar fabric to multidirectional warp knit Kevlar fabric, this has no bearing whatsoever to Kevlar felt which is neither a weave or a knit.
As for your use of the term "laminate", Kevlar felt when applied to the stem of a boat is a laminate.
Regarding the example of balsa wood, the point, which you appear to have missed entirely, is that thickness alone does not confer impact resistance. The logical extension is that one can not judge impact resistance based on the thickness of the material. Granted, for any given material, doubling the thickness will increase the impact resistance, but an abrasion plate can be simultaneously weak and thick, which was what the balsa wood example was intended to convey.
As for why Vaclav Stejskal of One Ocean kayaks did not choose to include kevlar felt among his list of abrasion resistant fabrics for use in kayak construction, no, I have not spoken to him. But he included some rather esoteric fabrics in his list including polypropylene olefin (Spectra/Innegra), Xynole, and Syntex so it is a pretty safe bet that he knows all about Kevlar felt. You can draw your own conclusions as to why he did not feel it worthy of mention in his list of fabrics to provide abrasion protection.
Regarding my statement that Kevlar felt was cheap, it is perhaps not cheap compared to simple E 'glass but it is comparable in cost to S 'glass, Dynel, or plain weave aramid. A piece of Kevlar felt of 5.7 oz/sq yd weight measuring 36 x 40" sells for $27 or less. The wholesale cost to boat builders is doubtless less. Since this is enough to cut out about 4 pairs of skid plates, and since the skid plate kits without resin typically sell for $30 or more, and kits with resin typically go for $80-120, I think the sellers find it a pretty good deal.
As for a skid plate consisting of a "laminate" such as Dynel or S 'glass sustaining some type of invisible damage, or allowing the underlying material to sustain damage without demonstrating any visible deformity, this makes no sense whatsoever.
style !
Your kayak builder in his gross exclusion of ‘felt’ is on a style trip as is the OP ( who seems to own a truly ugly canoe with a beeeeutiful skid plate)
Granted, felt is not as stylish as dynel. Everyone knows this.
Balsa is not Kevlar felt. I have not seen a balsa skid plate. Do you have a photo ?
The idea of an inexpensive single layer dynel or s glass absorbing as much energy as a ¼” of non directional multiaxial kevlar nonwoven felt, applied by the owner…
Is staggering
.
Area 51.
http://www.google.com/patents/US7700503
Style trip?
I’m not on any style trip.
Wtf?
…and thanks for the jab at my “truly ugly” canoe.
All I’m interested in is improving and salvaging what appears to be a slop job install.
So, you don’t think the install and finish could be better?
Your fixation of a skid plate’s
ability to absorb energy puzzles me.
Isn’t the purpose of a skid to… well… skid? Would that not imply its primary duty is abrasion resistance?
And do you put forth the premise that a Kevlar skid plate will resist abrasion as well as a Dynel or S-cloth skid plate?
good point
The stems of most well made canoes are plenty strong and stiff and really don’t require additional impact protection. So for most people who choose to apply a “skid” plate, the purpose is to protect against abrasion. But to do so, the plate must be sufficiently impact resistant to avoid self-destruction which Kevlar felt unfortunately often is not. It does not have to break off in chunks to show it is doing its job.
Dynel is a good material for abrasion plates, keel strips, and rub rails because the fibers really do seem to be unusually abrasion resistant. It is not great for use on wooden boats which are to be clear finished because it retains a milky appearance when fully saturated with resin. The fibers also swell in the resin which can make for a thicker than desired laminate and a textured surface. This latter tendency can be reduced with vacuum bagging, pressure molding, or the use of mold release fabric (peel ply).
S 'glass is very strong and cures clear when fully saturated. It is easily cut and sanded and bonds very strongly to resins. A single layer of 6 oz/sq yd S 'glass can make a thin but strong plate with edges that can be very finely feathered and a surface that stands only a few mils proud of the adjacent hull presenting very little hydrodynamic drag. While the fibers may not be quite as abrasion resistant as Dynel, they are stronger. For a thicker plate, 2 layers of 4 or 6 oz/sq yd S 'glass can be used.
Aramids like Kevlar for all their good properties have some that are not so good. The relative lack of compression strength is a big one for abrasion plates and the outer layers of hulls. The aramid fibers also don’t bond to resins nearly as well as fiberglass and they are much quicker to separate from the resin matrix under stress, leaving intact fibers that have delaminated from the rest of the structure. The fibers are also very hydrophilic which can contribute to delamination problems. The fibers do not respond well to sanding so achieving a smooth plate with finely feathered edges is much more difficult.
Felts consist of many very short fibers oriented in all directions and compressed together. The fibers may be individually strong, but the whole material lacks structural integrity because it has no longer fibers running the length and breadth of the material. It has been used for skid plates simply because it is easy.
Unlike plain weave fabrics which tend to change shape, trading width for length and vice verse, felt maintains it cut shape pretty well. It does not fray along the edges like weaves do making it easier for folks who have no experience with fiber glassing to use. It lays down over curved shapes pretty well and one does not have to worry about cutting it out on the bias as there is no bias. This feature allows the shapes to be oriented in any direction desired making it more economical to use a single rectangle of material for multiple pairs of plates.
But all of those tiny, compressed fibers in the felt form innumerable interstices that wick up excess resin. Couple this with the fact that the skid plate kits that are commercially available usually come with an excess of resin. The resin is typically mixed up in one big batch and has a limited pot life. A boat owner without much prior experience with resin use slops it all on, not wanting to waste any. The result is a very resin rich lamination which makes the skid plate heavy, thick, and brittle.
For those who are interested in alternatives to Kevlar felt skid plates, Mike McCrea started this thread on another forum which offers some detailed DIY advice on how to work with woven cloth to construct an abrasion plate:
http://www.canoetripping.net/forums/forum/general-paddling-discussions/diy/17299-%E2%80%8Bskid-plates-an-evolution
In the case of the OP’s boat, I suggested the possibility of removing the plates as that might be much easier than thinning them, smoothing them, and feathering the edges. The urethane adhesive that comes with most of these skid plate kits often doesn’t bond all that strongly to intact gel coat, especially if the surface prep was hasty or lacking, and the photos definitely suggest this application was a home job. Sometimes the bond can be broken more easily than one would guess allowing the whole plate to be peeled off with relative ease.
stems
IF the hull is visually unacceptable, paint. Paint the felt before attacking it.
Felt on my Rendezvous is painted white on a maroon hull. I can see damage. Painting a vehicle or parts with white functions for seeing first rust.
Kevlar doesn’t sand well. Why would a Kevlar felt sand better than a Kevlar fabric ?
I wanted Blanc’s discussion of bow/stern strips. I’ll avoid distorting what he said but suggest we may be discussing two different materials properties and approaches to stem protection.
Felt absorbs impacts stress within felt. Adding more hull skin with a laminate strengthens a hull. The dividing line is discussed as does the extra skin absorb impact or strengthen the hull that is the hull with a fabric laminate continues absorb all impact where the felted hull receives less impact.
The two concepts are not splitting hairs but widely significant design approaches in all vehicles…including helmets and body armor.
Read:
https://www.google.com/#q=wiki+materials+definitions+strength+
Good info…
and I’ve enjoyed your posts and Mike’s over at the tripping site.
I do my skid patches similarly to how Mike illustrated, I’ve always used S-cloth and epoxy resin. They’ve performed well but I plan to use Dynel on my Magic next spring when I add skid patches to it. I believe I can realize similar performance with less material build. And using peel ply will be a new technique for me, too.
I appreciate the time you’ve taken to post your tutorials. They are most useful for many of us.
Felt absorbs impact?
Maybe if you don’t soak it with resin first…
For something to absorb impact it either has to be elastic (malleable) or it has to be crushed. Resin-soaked and hardened kev felt is neither.
I have had one hard direct impact on the kev felt skid on my Prospector, high up on the stem. It did not crush and it did not deform like rubber or foam. It did leave a mark much like a rock leaves when impacting my car’s windshield. I can tell you that the only place any impact was “absorbed” was on my body when I lunged forward in the boat as it stopped instantly. No - I’m sure the boat also flexed throughout it’s length, absorbing some of the impact. But the skid plate only chipped and slightly cracked - it absorbed nothing.
With that one exception on this one canoe, all other wear and tear on my stems has been abrasion. I see no advantage to these felt skids…none, other than ease of installation - and that’s debatable.
I’m with Steve
my anectdote is when we hit the rock full speed ahead the Kevlar skid plate got a hole punched right through it. Absorbed anything… not.
My thigh absorbed energy and so did the thwart that I broke when my leg hit it and broke it off.
OTOH
OTOH - my Penobscot had been in what must have been a real doozy of an impact when it had no skid plate. Right on the blunt end of the vertical part of the nose, the stem was actually crushed in and permanently deformed in an area about two or three inches in diameter. Above the waterline, so of no consequence to me - but that blow was surely absorbed to some degree by the royalex hull at the point of impact.
yeah blame it
on the felt.