Spray

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Hi Willem, the plans show a generic cockpit that suits most paddlers, but more importantly can be a starting-point for your own version, fashioned to your wishes and specs. My surfskis are intended for efficient paddling, not fishing – so following the plans does not leave much room for a large centre hatch (at least not a wide one).

The loa is easily altered by changing the c/c distance between molds, but widening the hull is a bit tricky. Normally it requires a redrawing of the station drawing. The easy way is to use a photo-copier where the scale can be adjusted individually on width and height. The precision is often not very good for that kind of adjustment, but since a fair hull is achieved by sanding it is a minor inconvenience.

More beam will cost you a little top speed, and depending on your weight, may lift the hull slightly and expose more freeboard to the wind, while impairing the directional stability (but a good rudder can hide such potential problems quite efficiently).

Major changes like that of course relieves me of responsibility for the performance of the surfski – but kayak design is not rocket science ;-)

Robby, my experience, using 5x20 mm strips, is that 360-370 meter strip will be sufficient for the hull and deck (including a small margin for errors). Allowing for bead and cove, make it approx 380 meter.

If you plan to strip the cockpit as well you'll need something like 400 meter – but most builders laminate the cockpit in glass and carbon fibre.

The volume is 334 litre, if you want to do a more specified calculation.

No, I am not aware of any prefabricated surfski-cockpit. You can buy prefabricated carbon rims, seats and hatch trays etc for kayaks but DIY surfskis are too new yet.

But cockpits doesn't necessarily have to be complicated nor involve risks of screwing up. This is what I note on the plans (among a lot of other surfski-related info):

"Cockpit

The cockpit shown is a standard cockpit that fits most paddlers – long enough for tall paddlers, plus a sliding pedal set-up, similar to the ones used on commercial surfskis.

When changing the cockpit configuration to fit, remember that the position of the bucket seat is crucial to the performance of the craft – you adjust the forward bulkhead and footwell to your own length while keeping the aft parts unchanged.

The cockpit can be built in many ways: it can be stripped like the hull and deck, keeping the overall shape and volume approximately as on the plan.

It kan be built from foam insulating boards between two solid wood bulkheads, again keeping the overall shape and volume (glue 4” foam boards together vertically to fill the cockpit and cut and sand to shape). This is an adaptive process, where you can work the shape in incremental steps by cutting, sanding and filling, until the cockpit is comfortable and efficient.

An even better way (light and beautiful if executed with care) is to use the foam cockpit as a mold for a glassfiber/carbon cockpit structure. Cover the mold in packing tape and release wax, laminate the entire structure – 4-5 layers fiberglass, 1 layer carbon and on top 1 layer fiberglass (to protect the carbon when sanding). Remove the structure from the mold and glue it in the deck cutout."

Arndt, both rudder options are indicated on the plans for both surfskis.

The easiest way to drain the cockpit is with a standard dinghy bailer (fx Super Shute or Anderson Mini Bailer). There is an improved surfski bailer version designed by Swedish designer Magnus deBrito, but as far as I know this is not commercially available yet.

I prefer to join the seat pod and deck first since that will be the most critical bond. The hull-deck joint is of course also important, but with a solid epoxy filling between the two parts, double overlapping glass tapes on the outside and as much as can be reached on the inside, it will be more than strong enough.

Tom, Spray has a stability curve similar to a performance sea kayak, Spindrift slightly less. But since stability is a perceived quality that is a mental issue as much as a kayak quality it is very hard to make recommendations for someone else.

Stability depends mostly on beam, seat height and center of gravity (meaning that the paddler's length and weight is negative for the stability), but hull lengths is also a contributing factor in favor of stability. Thus, these long surfskis are not as tippy as they might appear from the width figure alone.

To get the proper hull shape you should cut the molds back to the inner contour size (easiest done by drawing a saw line with a marking gauge set to 5 mm). But you might use the molds as they are, thereby gaining a little stability. You might also compensate by shortening the hull slightly (by decreasing all horizontal measurements proportionally, fx 2-3% or something like that) – unless you are heavier than say, 90 kg.

Using the outer hull lines as molds, will, of course, affect the overall shape, so you may need to keep an eye on the lines as you add strips to the hull, and perhaps spend an extra hour on fairing before laminating.

You may also, if you prefer and have the time (mail between Australia and Sweden is not exactly quick), return the plans to me in exchange for a set of plans for Spray. If so, I will charge just the cost of printing and shipping (approx 22 AUD).

Jag har inte paddlat Squall+ så det blir lite gissande. Jag tror att skillnaden i initialstabilitet är försumbar, och att några millimeter högre eller lägre sits betyder mer än de små skillnaderna i mått och spantform. Squall+ bör genom sin längd vara en liten aning snabbare, men fart i praktiken sitter ju mer i paddlaren än i skroven.

Spray har en aning mindre tydlig swedform, vilket kan vara en fördel (lugnare rörelser i vågor) eller en nackdel (aningen lägre toppfart). Rocker är ganska lika, men Spray har på konstruktionsvattenlinjen aningen djupare akter men grundare stäv, vilket även det kan vara en fördel (aningen mer kursstabilitet) eller en nackdel (aningen mindre manlöverbarhet) – och framför allt kan det ändras helt med lite packning.

Några exakta jämförelsesiffror har jag inte eftersom mitt ursprungliga ritningsunderlag inte har med de uppdateringar som gjorts på skrovformen.

No, Spray is a dedicated surfski, without any other options than a couple of ideas for the cockpit construction. But a few builders have converted Spray to surfski-kayaks, among them Dan Caouette.

But Panthera is just that: a surfski hull, similar to the Spray hull but with a kayak deck. The differences are that Panthera doesn't need that high stem, necessitated by the open cockpit, and is therefore slightly less affected by winds, and the 2 cm more beam makes Panthera slightly more initially stable.

Spray has a minute edge on speed in general, while maneuverability is the same (providing they are fitted with the same rudder system). Since the "engine" is much more responsible for the speed made good than the hull, this is not an important difference.

No problem. I like kayak related discussions ;-)

Panthera and Njord are similar in general speed potential but have different speed profiles. Panthera is the clear winner in theory, on flat water and in waves – 8/12,4 km/h vs Njord 7,8/ 12,3 km/h. (the first figure is efficient but relaxed touring pace, the second is top speed).

But Njord is an odd dark horse! It is highly efficient in a non-obvious and quite surprising way. When you after a day of relaxed paddling look at the distance and time, you realize that the speed has been considerably higher than anticipated. Too many miles in too few hours and you are not even tired and don't know how it happened!

There is a kind of understated efficiency that I can't really account for and wasn't quite prepared for – though I know Njord moves smoothly and predictably in steep waves in a non-tiring way which lets you keep going in your preferred rhythm through whatever conditions and without any interrupting braces, and I know that these qualities mean that your strength will last longer than in a more "willful" kayak.

So if you were to compete in open sea conditions I might recommend Njord, but for lake/river racing I think Panthera's higher theoretical speed will give you an advantage.

Another consideration is that Njord is designed for an adjustable skeg and will not behave as designed with a rudder - for this reason alone it is not on any racing paddler's shortlist.

Both less beam and more length will increase top speed. More length will have the disadvantage of needing more muscle power to make use of the speed potential, while less beam will reduce the load capacity (and of course the initial stability, but than I wouldn't lose any sleep over).

As a guide (not quite technically correct), the speed gain from less beam is approx linear and that from more length corresponds to the square root of the length – which means that narrowing the hull is more efficient from a speed point of view.

Perhaps a little of both? Adjusting length is very easy (just increase the station mold distance), while slimming the hull is trickier (you can slim the hull in a good quality copier and adjust the minor errors while sanding).

Or, if you accept a little extra fee, I can provide an adjusted plans set with your chosen LOA and BOA (same price as an individually adjusted Black Pearl: €150, instead of the normal Spray price of €102)

Yes, 572 cm LOA (44 cm mold distance) and 50 cm width (BWL 47) will be approx 120 kg load capacity and a faster hull than the standard.

There is no traditional cutout for paddling, but with the pronounced dip in the sheer, the effect will be approx the same.

I did get the meaning of a Njord on the wishlist and thought – YES! My sneaky marketing works ;-)

3/16" cedar strip will be strong enough, but you will need to be careful with the strip line-up since the mold distance is somewhat large for the thin strips and with less margin for sanding. 1/4" combined with harder sanding may be a better bet. Cedar is slightly more brittle than the Norwegian fir we often use in Scandinavia (and which I would have used in 3/16"), but also slightly lighter.

Pete, I have a set of Panthera plans ready, but you have to come and get them – I have a full workload for the coming days with non-negotiable deadlines.

If you can find the time, there is a train (Öresundstågen) from Copenhagen (fx the airport) to Lund, leaving every 10-15 minutes and takes 30 minutes. I can meet you at the train station to hand over the plans or we can have a cup of coffee and a short chat at my place if you have the time. You can contact me on +46721979390

There are of course courier services, but they are almost as expensive as the plans ;-)

Yes, it was a pity – it is always nice to meet builders in person.

The price on the site is the total, including shipping.

Hi John, I have not detailed the rudder installation since a look into a commercial ski will show a good and reliable solution – no reason to reinvent the wheel. But the position and suggested installation are indicated on the plans, as are the general shape of the cockpit pod.

There is no need for bulkheads in a surfski since the cockpit pod is tightly fitted into the hull, creating a watertight volume and stabilizing the midship section. This is also shown on the plans.

The choice between an under-the-hull rudder and an aft-hung touring rudder depends on your intended usage: under-the-hull is the more efficient of the two, and if you focus on speed, racing and avoid shallow waters this would be your best choice. The touring rudder (fx Smarttrack) is easier to use when launching or landing from beaches, or paddling shallow waters, where a fixed rudder would risk being damaged.

(Conversation moved from kid's kayaks page!)

Hallo Björn,

mein nächstes Winterprojekt soll eine Marathon Kajak sein. Bin 180 cm groß und wiege 92 kg. Auf deiner Seite gefällt mir der Spray sehr gut. Ist das Kajak für meine Zwecke geeignet? Über eine Rückantwort bin ich dir sehr dankbar.

liebe grüße

Andreas Ahrens-Sander

Hello Björn,

My next winter project will be a marathon kayak. I am 180 cm tall and weigh 92 kg. On your site I like the spray very well. Is the kayak suitable for my purposes? I am very grateful to you for a reply.

best regards

Andreas Ahrens-Sander

Hallo Andreas

Spray oder Spindrift eignen sich hervorragend als Marathon-Kajak für dich. Spindrift ist schneller aber auch mit weniger Anfangsstabilität.

Tackar!

1. Epoxyn kräver någorlunda temperatur för att härda till full styrka. Men ner till 14-15 grader är helt OK (men epoxyn hinner inte härda färdigt över natten så det kan bli lite förskjutningar i byggprocessen). Egentligen härdar epoxy så fort det är plusgrader, men dels blir hållfastheten dålig och dels tar det veckor att härda vilket gör det svårt att få någon kontinuitet i bygget.

Bygger du med min metod ribba torrt och limma i efterhand kan du klara det mesta av bygget i lägre temperaturer och bra brassa på med lite värme just vid epoxymomenten.

2. Det finns med en grundritning på formen och tips på olika sätt att bygga den, men inte en steg-för-steg byggmanual.

3. De flesta hamnar någonstans mellan 120 och 180 timmar – med extremer både upp och ner.

4. Till en surfski hör en bra vingpaddel, men det finns inga ritningar för sådana. Men du kan såklart paddla surfski med både grönlandspaddel och europaddel (och det finns ritningar till båda på min downloadsida.)

Surfski är generellt långa för att mycket av utvecklingen har skett på tävlingar i öppet hav och de dominerades tidigt av några stora starka hulkar som som kunde dra nytta av längder upp mot 6,5 meter. Men en kort surfski fungerar lika bra som en kort havskajak (även om man inte vinner Molokai Challenge i en sådan).

Lastkapaciiteten varierar linjärt med längden (5% kortare skrov ger 5% lägre lastkapacitet) så du kan enkelt räkna ut att den räcker till för dina behov.

Det är möjligen aningen lättare att bygga en skädda än ett roder, men köper du färdiga delar är skillnaden marginell.

Spray och Frej liknar varandra genom att de har krökt köllinje och är mycket (för att inte säga extremt) manövrerbara. De skiljer sig genom att Frej är konfigurerad med viss kursstabilitet vilket Spray i stort sett saknar. En bil-analogi skulle kunna vara att Frej har nysningssäker familjebilsstyrning medan Spray har en direkt formel-1-styrning. Frej är alltså lite mer laidback i karaktären och Spray lite mer "på", vilket i kombination med ett högeffektivt roder ger spetsegenskaper vid surf i grov sjö och därmed möjlighet att med hjälp av surfen nå högre fart.

En annan analogi är generation-5-jaktplan som får fantastiska flygegenskaper genom att man tagit bort planets naturliga stabilitet i luften och istället tvångsstyr planet genom ständig datorstyrd roderpåverkan.

Med en skädda nerfälld skulle Spray bli tämligen lik Frej i känsla och manöverering – men drar du upp skäddan helt kommr du att märka att den saknar kursstabilitet.

Hi Janne

I have very little experience of and in flat water racers, since I spent almost all my paddling years touring at sea – thus the focus in my catalog on speed, maneuverability and sea-keeping ability in wind, waves and difficult conditions.

But I think that the difference is smaller nowadays. Flat-water racers have over the years got more rocker, since it was discovered that rocker was the least detrimental way to accomodate heavier paddlers – and surfskis have recently done exceptionally well on flat water (outrunning Olympic racers on long-distance races on lakes and rivers).

So I think you might do well with either a Spray, or even better a Spindrift. One prominent advantage of rocker is that the paddler sits lower in the hull and thus get a lower CG, that together with more length increases stability significantly. Therefore you can accept less beam in a surfski than in a racer and have a better stability, both initial and secondary.

I think you can use Spray or Spindrift as they are – Spray is intended to also be used as a touring ski, which means a little extra load capacity, and Spindrift have more internal volume than Spray. Also, since an open surfski is intended for use in big waves the given figure for load capacity is generally lower than for a comparable decked sea kayak - meaning that on flat water the load capacity is larger than the quoted figure.

If you want to change one dimension the LOA is the "cheapest" way to increase stability – increased beam slows the craft down more.

Hej Per

Jag har i datorn en Spindrifttvåa som borde varit färdig för länge sedan – men angelägna uppgifter, både privat och på jobbet, har stökat till planeringen en del (det är hårt jobb att vara pensionär ;-)

Finns intresse kanske det kommer en Spraytvåa också – men det kommer att dröja. Jag har fler todo-projekt på agendan och i datorn innan jag hinner dit.

Nej, du tänker helt rätt. Men surfskis är lite speciella eftersom de har öppen sittbrunn. Vatten på däck är inget stort problem med en täckt sittbrunn, men lite vanskligare med en öppen. Hade Spray haft däck och kapell hade jag satt lastkapaciteten till 130-135 kg. Skillnaden innebär ca 2 cm större djupgående.

För en rimligt stark paddlare som håller fart på kajaken suger länsen ganska snabbt ut det vatten som kan skvätta in i sittbrunnen, men för en som paddlar långsamt kan det ta lite tid. Eftersom jag inte vet vem som kommer att paddlar surfskin har jag varit försiktigt med utfästelserna.

När jag får inte lite fler rapporter om och erfarenheter av Spray i olika situationer, kan jag förmodligen öka lastkapaciteten i tabellen.