Nova Craft's Kev/Spectra

Who has used it extensively? Who has evaluated it?

Lots of tensile strength I would guess, but I have to wonder about compression strength, wear, and… repair.

The next step up is Blue Steel, but from what I understand the carbon content in that layup is a bi-weave of kevlar and carbon, with spectra and and some kevlar. And it’s a huge price increase.

Sound off.

All second hand info - but I’ll start with some thoughts.

Spectra is linear polyethylene. It is very strong, though the resin bond is not as good as some other materials. This may well be a moot point as I’m sure it is tough enough.

Novacraft knows what they are doing, and makes decent designs with very good workmanship.

Any foam core composite boat is not going to be particularly durable when dealing with big, hard hits. Put another way - the limiting factor on toughness in a big hit will not be the cloth or resin, but the stiffening. I doubt you would tear kevlar/spectra before doing damage to the core.

I had a plain fiberglass foam-core NC Prospector and the glass was never an issue, though the core did dimple when I ran over rocks.

Bill Layman really likes the Blue Steel, from what I have read.

As to abrasion and general wear/tear, I don’t know. I prefer an outer layer of glass like in a Souris River because it is so easy to sand and refinish.

Yeah, I have no doubts about their designs or workmanship at all.

Mostly I am asking for input on the engineering of their layup(s). I appreciate your input!

Spectra and Rec boats

– Last Updated: Aug-22-10 10:01 PM EST –

Lamination 102 Material selection.

Spectra has limited use in recreational boats because it needs be coated, the coating needs be redone rather often if not used, and the price generally forbids common usage, so it doesn't get recoated as needed.

Notes from 01 Dec 2008 chat w/ Warwick Mills, names and contact info removed. Warwick weaves mill runs of Spectra.

"Spectra is same as Dynema, from DSM. DSM owns patent, licensed Allied which sold Spectra to Honeywell. Spectra is very strong and light. With Sp. Gravity ~0.95 it floats, but does not like to bond. It is always treated before lamination. Treatment lasts 30-90 days, so small runs for most builders, except there are no small runs: 10,000 yds or more is the usual."

Spectra is used by Crozier: carbon outer, Spectra /Dynema inner bagged, then foam / carbon foam covers bagged. Used by Nova: Carbon, kev 29 bi weave/ partials, spectra / carbon kev 29 Bi weave.

The first issue with Spectra is manufacturing process. Prepreg and autoclave, infusion of wet bagging are required. The stuff floats on top of the resin in hand lamination.

The second issue with Spectra is turnover. The chance any builder but WeNoNah would be able to use a roll before it went out of condition is zero. Even WeNoNah would need to co-buy with a body or vehicular armouring manufacturer to keep fresh product through the door.

So the Spectra/Dyneema in a recreational boat is almost without doubt out of condition and should not have been used.

Lastly, a maximum survivable accident with Spectra almost always results in a serious delamination along one side of the Spectra. This is acceptable in a race boat, but most folks want to be able to repair their recreational craft, and a wrecked Spectra hull is a right-off.

That is not to say that it shouldn't be used in race boats, where extreme weight reduction to enhance performance combined with the need to survive a maximum credible accident justify the cost of the manufacturing issues. Dagger used it in the comp boats they built for the Olympics, Mad River used it in several slalom hulls, Crozier and others use in in marathon boats.

The issue with Blue steel is that colored Kevlar is always Kevlar 29, not 49. 29 is the stuff used in bullet proof vests and fire fighting clothing; it does not laminate well. JB Martin recommends using no more than 25% Kevlar 29 in a lamination fabric, Hence Bell's "Tweed" with every other woof a black Kev 29 strand. Blue Steel is a 50/50 bi-weave, so suspect in lamination at double manufacturers suggested usage.

The other issue with Carbon/Kev bi-weaves is that they tend to zipper. The Kev flexes and the tensile strength holds, the carbon doesn't, and breaks as it's tensile strength fails. [The neat quad weave, Carbon and Kev alternating in both directions, as in the fabric used by Kirton solves this issue.]

A third issue is material characteristics. In Armour design we generally want a stiff outer reinforced with a fail proof- high tensile strength inner. With bi-weaves some compression materials are in the inside; some tensile material is on the outside.

Blue steel has three strikes against it as a manufacturing material, it doesn't laminate as well as we'd like, it has a uni-directional zipper problem and we can't control placement of compression/ tensile materials. Then again, boatbuilding is not baseball and Nova's BS hulls are doubtless plenty tough, but they achieve that with volume not science, the engineering isn't solid.

This information is not belief based, which requires faith, not proof, but factual data from filament makers, weavers, industry manufacturers and professionals. Draw your own conclusions about the science and nay sayers.

I don’t have the blue steel but I do have an older Kevlar fiberglass Supernova. I have beat the heck out of the boat and keeps on coming back for more. I can;t believe Novacraft would claim anything they can’t back up.

I believe Charlie
I believe Charlie, and am sure his facts are correct.

My conclusion, though, is not that spectra needs to be avoided because it will de-laminate immediately the first time it is bumped. Rather, that it is not necessary, and not necessarily better than the alternatives.

Those who claim that their hull is tough usually only mean tough relative to their expectations. My old fiberglass NC took some big hits too and didn’t fail catastrophically. I never used it the same way I do Poly boats, though, intentionally ramping over rocks in the river. Most treat new canoes gingerly for a while at least.

If the boat is tough enough for your use, and most importantly in a design that works for you, the materials shouldn’t be the deciding factor. I expect almost all good composites are tough enough for lake tripping, and very few for regular use in shallow rock garden rivers.

Thank you, very much
It’s a dang shame, in some respects. NC makes some classic designs that people love, but as I suspected the layup engineering leaves a lot to be desired. Especially given the fact that they charge a premium over even other manufacturer’s kev/carbon boats for Blue Steel (because they are spending money to buy pricey bi-weaves).

It’s cool they infuse. It just sounds like they need to re-approach their layup. Ditch the spectra and weird bi-weaves, and they could be building a more price attractive and tougher boat.

I can vouch for Sloop’s boat
Sloopsailer is correct in saying that his Supernova is tough. It’s certainly not as tough as poly, but it’s much tougher than the average composite boat. He’s a big guy, and he used to be a lot bigger, and he’s crunched that boat across rocks in ways that would surely create “mushy spots” in the hull of the average fiberglass boat.

Composites can be tough
I wasn’t doubting that Sloops boat was tough - I’m sure it is. I am simply saying that design is more important than materials when comparing high-end boats because most composites fabrics can be pretty durable. Put another way - why spend an extra 1000 on some fancy new material when good boats can be made of fiberglass and kevlar alone in lay-ups that have proven themselves for decades? Obviously I’m not talking about ultralight foam cores for racing, but true tripping lay-ups.

I bought a Hellman a few years back and fortunately/unfortunately have had very few big hits with it. I think it is tough, but have no first-hand knowledge. So far, all the impacts have been of the nature that my old 'glass NC could have handled. I really like the shape of the hull, though, so it is a fine canoe for me.

A challenge
Blue Steel is one of the toughest composites hands down. I have a P16 that has been beaten up and down way worse than any expedition Royalex boat. If need be, I will take video of me with a 5# sledge hitting any part of the boat to prove it’s strength. The gelcoat will spider, the weave will show some stress, but the boat will be no worse.

See, this is why…
…I went with a Royalex boat for now. There seems to be some disagreement on the durability of some composites, and others just seem less suitable to some uses (I’m thinking of poling and foam cross-ribs not being too compatible).

I know one thing - a Tuff-weave Spirit II I just looked at had taken a pretty good hit in the chine right in the middle of the boat. It fractured the gel-coat and you could see signs of de-lamination on the inside. Sure, it wouldn’t sink or fall apart - but the thought of another hard hit in that area would worry me. OTOH - if the material accepts added layers well, it would be very repairable.

Has anyone confirmed that blue steel
is a Kevlar/carbon co-weave? I have not examined a Novacraft bluesteel boat “live” but close up photos I’ve seen suggest that they are just using a Kevlar weave where half the Kevlar strands are dyed.

Novacraft is the only company I know of that has continued to use Spectra in spite of the nuisance factor. Even the whitewater slalom companies don’t bother with it, because it is more inclined to delaminate than Kevlar.

My personal opinion is that the layup found best in “Boatbuilder Manual” tests done 30 years ago is still as good as anything going. SS/KK, or two outer layers of the best S-glass you can obtain (it varies) over two to three inner layers of Kevlar. One could replace one of the inner S-glass layers with carbon. I haven’t seen much indication that people have access to the “Boatbuilders Manual” results, though others like CE Wilson have arrived at similar conclusions.

There’s seldom a reason to put Kevlar fibers on the outside of a boat.

(May not reply for some days—going paddling.)