Easily marked / dented boats! Would u buy again?

Just talking to a few locals about my plans to go to a Kevlar boat from glass and they have all cautioned that either they or someone they knew were quite surprised at how easily the boats marked/dented from being on a stone amongst sand/ grass or accidentally knocked while carrying to from the car/storage.

The question I neglected to ask was that if you had the option would you have got a glass composite boat instead or is the fun factor of the lay-up worth the cringe every time u knock it?

And I guess the other question I have is whether these little dings can cause issues with the integrity of the hull or are they just cosmetic blemishes?

The answers could mean the difference between me going from straight glass to the still more $$$ composite/foam core or around $1000 more again for the nomex core kevlar.

$1000 for around 1.5 - 2.5kg, is it worth the dough???

Firstly, when you refer to kevlar I think you mean carbon fibre, as kevlar is very tough and impact resistant and is often used on river canoes here in SA to improve the strength and impact resistance when hitting rocks on a river. It is incredibly tough and impact resistant.

Carbon fibre is very strong, stiff and light, but this stiffness means it does not have good impact resistance and hitting a sharp object will damage it. The bottom line is that with a carbon ski you have to treat it more carefully than a glass ski, especially against impacts.

Is it worth it? I have a carbon Fenn Elite which is about 5kg lighter than the glass equivalent (11kg vs 16kg). If you're a competitive paddler (even if only in your age category) then yes, I think its worth it.

As for repairs, minor dents etc are very easy to repair using a good quality epoxy resin : as long as the cloth isn't punctured, you don't need to do anything fancy, just roughen the area, apply the epoxy and sand and paint (or gelcoat) afterwards.

Thanks for the advice.

I knew that carbon was that way inclined but without mentioning the maker, a couple of the boats the locals own have a big red nose, indicating kevlar. Perhaps it's the way the kevlar is layered?

I guess I'll be happy to be shouted down if a ton of kevlar owners post that they don't have such issues.

Some further homework backs the owners claims of susceptibility to dents...

From one of the manufacturers sites on thier kevlar boat

The Ultra construction is very light and popular with fitness and racing paddlers. It is light, stiff, and extremely strong in the water. Our Ultra disclaimer states that while stronger in the water than the Value and Performance lay-ups, the Ultra is more susceptible to impact damage and requires more care when handling.

OK, I also went onto the website (the "Ultra" was a giveaway as to the manufacturer) and had a look at the construction.

The way I see it, the lack of impact resistance is a result of the ultra light construction, and not the use of Kevlar, which is also used in bulletproof vests, which are a pretty high impact application!

Yep you are spot on Nige, I should have mentioned that the reason I was thinking of shelling out for the Kevlar was as you say, it's used for the downriver boats, in fact the Carbonology Atom ski is being made in a Adventure Racing platform with kevlar hull so they obviously have confidence in it's ability to take a knock, but perhaps they are using a lot more material.

Does the impact susceptibility perhaps have something to do with use of a foam core?

The lack of impact resistance is partially due to the foam core construction but the resin used also plays a big part. In SA we do a lot of white water river racing in "sit in" type kayaks which are made of glass fibre cloth and resin, with Kevlar being an extra cost option. The type of resin used is very flexible and can take an incredible amount of punishment without breaking or puncturing. I once wrapped my double canoe nose to tail around a rock and it sprung back into shape afterwards, and I still finished the race!

I'll have something for you to look at soon Brett...........

Oh no That doesn't sound good

I hope that's not a reference to your shoulder being no good

Kevlar is tough but not as stiff as fibrelass , it is often used in Single skin downriver boats with flexible resins and it can flex around rocks etc . They use it dry in bulletproof vests (aramid 29 alternating with layers of plasic) and now put a layer (aramid 49)in F1 cars to stop broken bits of carbon flying everywhere , whilst kevlar may get you to the end of a race the craft may not be ever used again without lots of duct tape . Epic use it with a thick honeycomb core and the stiffness is from that core with the Kevlar(aramid)trying to stop pointloading punctures. It used to be cheap in OZ but has got up closer towards Carbon prices now. Lats

latman wrote:

Epic use it with a thick honeycomb core and the stiffness is from that core with the Kevlar(aramid)trying to stop pointloading punctures. It used to be cheap in OZ but has got up closer towards Carbon prices now. Lats

Thanks for weighing in Lats, great to hear from someone with some boat building know how....what is "pointloading punctures"?

Also are you saying that the raw Kevlar Material used to be cheap in Oz and is now as pricey as Carbon.

I was also looking at Epics Composite lay-up boats, that have Fibreglass, Kevlar and Carbon layers!! does this make them more difficult to repair should they get a catastrophic failure in surf etc.

Boats quite often get noticable dings and the like when two materials of different flexability are used. By this I mean, if you hit a rock with a kevlar boat covered with gel coat. The kevlar will flex but the gel coat will not. As a result the gel coat will crack and remove itself from the kevlar, kind of like gluing a piece of glass to a piece of plastic and then bending it. A kevlar boat will flex the most, but will be the most impact resistant.

It still amazes me that some manufactures use gel coat over kevlar on the hull of DR boats. It is not necessary. However gel coats on the top deck is very good for UV protection and looks.

Been pondering this as well Shed- what are the implications for hybrid constuctions with multiple layers/variable materials , seems material suceptible to the specific kind of hit (pointy , large compression etc.) would be the weak link . Personally a big fan of fiberglass for durability , ease of repair and cost and when used with techy cores (soric etc.) and vacum infusion seems to make a pretty clean and relatively lightweight composite. Interesting to me would be the differing charecteristic of the resins. ie polyester vs. vinlyester vs. other epoxy etc. Anyone ??? As to the gelcoat , great for boats that get a lot of drag/scratches (sea kayaks , DR , beach breaks) for open water ? epoxy paint (imron etc.) is a ligther albiet less durable choice.

AR_convert wrote:

latman wrote:

Epic use it with a thick honeycomb core and the stiffness is from that core with the Kevlar(aramid)trying to stop pointloading punctures. It used to be cheap in OZ but has got up closer towards Carbon prices now. Lats

Thanks for weighing in Lats, great to hear from someone with some boat building know how....what is "pointloading punctures"?

Also are you saying that the raw Kevlar Material used to be cheap in Oz and is now as pricey as Carbon.

I was also looking at Epics Composite lay-up boats, that have Fibreglass, Kevlar and Carbon layers!! does this make them more difficult to repair should they get a catastrophic failure in surf etc.

I view the damage that can happen to craft 2 ways ,one is a "global " strength like flex with the weight of the paddler opposing the bouyancy of the ends or the weight of water simply flexing/breaking a ski .The other is a damage caused by a localized impact in one small area , like a ding from a collision or racks etc (ie load in one point).One thing kevlar can do is keep all the pieces of a broken structure together and maybe even keep water out but it is still broken.(see me on the carbon/kevlar ski photo)
IMO Kevlar is a pain to repair because it "fluffs up" when sanded (harder to cut when fabricating too)and Nomex core is a pain to fabricate AND repair because of the minimal surface area it offers for bonding to the skins ,carbon has its own issues due to its opaque nature but it at least offers maximal stiffness and is sandable like glassfibre.
Looking at the Epic constructions they used a very light fibrelass next to the Vinyl ester gelcoat and the laminates are done in epoxy resin so a chemistry changeover must happen somewhere.(resins are just as important as reinforcing fibres)

Some great information being shared here.

I have gone away and done some extensive reading on the various materials used in ski/kayak construction and to put it mildly "my head hurts"

Seems this is an area very difficult to give simple one sentence answers too when talking about best applications, advantages, disadvantages, etc. I guess the proof is in all the various combinations manufacturers are using.

Seems to me that despite knowing that Kevlar or Carbon has been used in a lay-up, you can't know how it will perform due to the myriad of ways to layer them, infuse them, etc, which all have an influence on the characteristics of that lay-up.

The proof of a boat simply comes down to how does it perform for a given measure over a given time which again comes back to peoples experiences with a particular boat in particular conditions.

Would anyone disagree if I made the statement that Kevlar may be used as a shock absorber in composite constructions!?

Of all the various websites I have read this site seemed to have a good basic question and answer section that most of us could get our heads around.

Maybe not a shock absorber, but a shock disperser.
I imagine it as transferring the energy to as much of the boat as possible.

I may very well be totally wrong though.

To me it comes down to how you are willing to treat the ski, where you paddle, and how willing and able you are to pay $1000 more for the lighter kevlar core ski.

I was with solid carbon Fenn skis for many years, then with a kevlar core Think for a year, and now with a kevlar core V12 for a year. I prefer the solidity of the solid carbon ski or a solid carbon/glass ski because they don't dent and I can drop the ski or knock it and not have to worry about light hits and light to medium point loads. Having said that, however, I have had two carbon regular layup skis that developed cracks and developed soft spots after only a couple of years of use with some knocks, and I have thus far not had any structural issues with the kevlar-core skis. I also have "backyard repaired" gouges or cracks to both layups and those are easy to do on each, i.e. regular glass on the carbon ski over the crack, and injecting epoxy underneath the kevlar (into the core) which solidified the spot and took out the dent. I'm more gentle with the kevlar-core skis off the water, though.

Unless the dent isn't that big, it shouldn't pose much of a structural issue. Think of a tin can. If you put a tiny dent in it it's still strong but if you put a large dent in it, it'll collapse on you.

On water, I don't know what's best. While the carbon or carbon/glass ski might take more light and medium abuse, it will crack and "hole (v.)" and fill with water whereas a kevlar ski will dent more easily but should stay watertight and increase your chances of making it back to shore. That pic above from latman is very revealing.

Given a choice for my next ski, I think I might still prefer less dent-ability at the risk of cracking and "holing", but not at the expense of more than about 5 lbs weight. And, I'd be very happy with a solid layup (kevlar, carbon, glass, or combo) that came in at about 25 or 26 lbs (11.5-12 kg) . Lighter than that and I worry, heavier than that and I whine! Erik

Erik, thanks for taking the time to reply to my initial questions.

As for your questions, I have a tight area in which I stow my ski involving going around a couple of corners. As careful as I try to be I probably end up banging the ski against something every 2nd or 3rd time I move it in or out of my yard, with my glass ski's this hasn't been a problem.

I also put my ski on the roof and drive to a training session 30km down the road once a week. (I live 200m from the beach I usually train at so I use a kayak trolley othertimes)

Price wise, I am trying to figure out the cost/benefit side of things, like you, around 12kg sounds great but at what expense and at what risk of marking/denting the boat.

If it's a ski I'm wrapt in, it may not matter too much to me as I'll keep it long term and wear the depreciation, so far though I have managed to sell the V10sport and V10L for very close to purchase price as I looked after them. If I get a boat that I decide I want to change in 12 months time I dont want to lose too much because it shows wear and tear too easily.

I guess while writing this I have realised the wise thing to do would be to buy the composite lay-up in whichever ski and if I decide that the ski is ideal for my intended use then I can sell it and get the lighter lay-up down the road.

Still keen to hear others thoughts, I have another week until I can demo a couple of boats.

So I went for a paddle today.

Pulled up, undone the ropes and the ski started to take off.
Decided to get it off the car straight away an get it on the ground.
Lifted it out of the cradles and battled the wind to get it out of the parking lot and onto the grass.

Before I could get all the way to the grass a strong gust almost blew it out of my control so I put the nose of it down on the grass to steady it while I got the rest of the boat closer to the safety of the grass.

Another big gust and the nose of the boat swung around and 'bang', the side of the nose hit a rock sticking up in the ground.
It was a solid sort of noise and I suspected the worse.
I gingerly went to investigate, hoping for the best, but expecting the worse.
Not a mark!, was I happy or what!

I swore to myself at that moment, that I will never own a more vulnerable layup until I just fail to win some sort of world championship.

Long live a solid layup.
(performance V10)

Great Answer Rightarmband. Until you win the world championship - good paddling.

Brett - what did you end up buying - where are the places in Perth that one can demo these boats (epic, fenn, stellar etc). cheers Tom