Kelsall - KSS Build Method

[Talbot]

Thank you.

I imagine that the type and quality of the core is fundamental to this.

What is the recomendation?

[Nordic cat]

All the commonly used foams are "closed cell" types and don't absorb water.

The strength of say a 20mm foam laminate (80 kg/m3) with 600 g/m2 biax on each side, bagged or infused will offer the same strength as a 9 bly 600 g/m2 biax solid layup.

See the comparison below from ATL composites.

Regards

Alan

[BigCat]

Derek, my understanding is that you have never used balsa coring, and do not speak from experience.

My personal experience of balsa has been positive-- J-boats, Hatteras Yachts, Sweden Yachts, Viking Yachts, and Lagoon Catamarans are made with vinylester / balsa. Their use of vinylester indicates that economy isn't their first concern, but rather strength and longevity.

Properly laminated, balsa cores have a webbing of resin separating each square from its neighbors, and so no rot can spread unless there is delamination. Most fiberglass boat decks have balsa cores, and most boats have no problems with them.

Problems with the core are a sign of poor construction practices. Bolts and other skin penetrations through balsa core (and foam core, also,) should have an annulus of resin puttty larger than the bolt replacing the core where the bolt is installed, or, if highly loaded, the core should be replaced with a high density core or solid fiberglass.

Balsa is stronger than foam, and a structure made with balsa can be lighter than a structure made with foam for that reason.

[44'cruisingcat]

Originally Posted by geekclothing

Hi,
We are considering building a 42' Kelsall designed GRP catamaran. I would like to hear from anyone who has experience with this method, (preferably other than just a workshop). Someone who is building or has built their toy with this method. It seems there is a lot of "testimonials" on the kelsall website from people who have been to workshops but not many who are actually building one of his designs.
Thank you in advance,
Nathan

Would you ben interested in comments from builders using other methods? I haven't built a Kelsall design, I'm building a Bob Oram design in Duflex. I have some pics in the photo gallery, here's one :
http://www.cruisersforum.com/gallery...00&userid=3477

that's a 44 foot hull, and half the bridgedeck floor, in 8 days FROM SCRATCH, (ie. hammering in the first star picket for the strongback) in a dirt floored shed, by ONE MAN working alone.

I think the KSS workshops are a fantastic idea - it gives potential builders hands on experience, and no doubt boosts their confidence immensely. If I build another cat, it will be another Oram, and I have already discussed with Bob the idea of doing a workshop on it. The idea of having people pay me to help build my boat has great appeal! We seriously believe that with enough space, and say a dozen people, we could have TWO 44 foot hulls, complete with the bridgedeck floor, standing side by side after a long weekend's work.

[44'cruisingcat]

Originally Posted by catty

With any boat building system there's good and bad. But to suggest that an amateur builder will get a finished hull and deck in a weekend using KSS is plainly misleading. The recent Australian workshops with many able bodies present couldn't achieve this. At the end of the day with KSS you get a hull shape with flat sides and a roundish bottom that in the words of Mr Kelsal still require fairing and painting . Geeze for the amount of money and time the amateur is investing in the project you may as well build in a method that gives you an optimal and pretty hull shape with very little extra effort such as Mr Farriers verticle strip foam system. Remember a thing of beauty is a joy forever.

I love the "very little extra effort" bit. A mate of mine is building a 40 foot cat using vertical foam strips - he started a full year before me, and he now has a pair of hulls, which he is STILL FAIRING.

That's it, no bridgedeck, no superstructure, just two hulls.

I'm sure it will be a very nice boat when it is finished.

If it were me, I doubt if it ever would be.

A thing of beauty might be a joy forever, but an unfinished boat in your backyard after ten years could be an absolute PITA.

[DerekKelsall]

Originally Posted by Talbot

Thank you.

I imagine that the type and quality of the core is fundamental to this.

What is the recomendation?

In 1965 I chose 75 kg. density cross linked foam, unidirectional glass and polyester resin. Some clients now use vinylester but otherwise no change in our recommendations. Core choice is crucial as is ensuring the bond between skin and foam - lay the glass on the foam or use vacuum bagging or infuse. 40 year old Kelsalls of all types are still sailing and passing survey, with none failing.

Balsa - yes, I have used it. Alongside our own designs, we made a production power race boat called the Tigershark for a year or so which was to a balsa spec. I was never tempted. Balsa in decks was common - Iroquise cats for example. I know current and past owners - great boats with one problem - the decks. I visit yards - recent - 55 footer whole hull sides being replaced. - I could quote dozens more. OK some were not well done but the important point is that had they been PVC foam, the problem would have been minor rather than disaster. A recent visitor reported assisting on repairs to a 6 yo balsa cat, with soft balsa around all windows and transom steps - and I wonder where else. Repairs - how and for how long?

Lots of things are sold on the basis of A is stronger than B. However, where is the gain if B has been proven 100% over 40+ years? Lighter, would mean very thin skins indeed, with more potential for water ingress. We are not going to see lightweight race machines of balsa. My argument. To keep the water out 100%, would need the equivalent of a water tank as the outside skin, I have no axe to grind or materials to sell. As foam suppliers also sell balsa, I do not gain favors with the foam suppliers on this one. I would use Balsa if it made sense to me. THERE IS NO GAIN - the whole industry should grasp the nettle on this one. If you need a stronger core, up the foam density.

Is style lots of curves? Style should follow function is the only way to efficiency. The pictures are there for all to see.

If someone else is making full hull shapes with a gel finish to all of the topside area in a long week end, which includes teaching sessions and a group who have not done it before - this is good news for the DIY builder. Multis started in the hands of the home builder and just about everything I have seen since as what might be called the industry standard has been a step backwards in custom boat building efficiency from the Pivers and the Wharrams of the early sixties. Inefficient methods deter so many potential owner builders. Let's hear more from the designers who are really moving the barriers and progressing the art. Let's see them with their trials and experiments in their workshops - which is the only way to make real improvements. There is still progress to be made for those who are looking.

Derek.
guess my roots are still with the home builder - where I started.

[catty]

Originally Posted by 44'cruisingcat

I love the "very little extra effort" bit. A mate of mine is building a 40 foot cat using vertical foam strips - he started a full year before me, and he now has a pair of hulls, which he is STILL FAIRING.

That's it, no bridgedeck, no superstructure, just two hulls.

I'm sure it will be a very nice boat when it is finished.

If it were me, I doubt if it ever would be.

A thing of beauty might be a joy forever, but an unfinished boat in your backyard after ten years could be an absolute PITA.

Welcome back 44c, I hadn't seen you post for a while.
I'm not sure one example is enough to show a trend as far as building time goes. For instance a flat panel 44c ,Scumble, has been building since 2003, and another by Alan Macari since about 2006. To my knowledge neither is in the water. So the ability to build a rudimentary hull in a few days certainly doesn't seem to get one an instant boat.

[Pat Ross]

Originally Posted by catty

So the ability to build a rudimentary hull in a few days certainly doesn't seem to get one an instant boat.

It would seem to me that a person who builds does so for several good reasons, at least for myself this is true. One very clear reason is finances. Because a person takes longer or the same amount of time to launch with one method or another may be directly due to their desire to own the boat rather than be paying on or for the boat over some period of time, instead pay as you go. It does not mean it is a poor method of building or that is it not a significant improvement over other methods. You would have to have two builders with the same pile of money and time available to make a matched judgement as you are suggesting.

[northerncat]

for me time was the essence(although i did enjoy the build process), i talked to a lot of designers and then to a few builders and flat panel boats came out on top by a figure of between 1000-2000 hours, that and the fact that they are quite cheap to build swayed me to a ply cat, i also liked the fusion and the orams though
sean

[geekclothing]

I think Pat touched on a very important difference which separates Kelsall's KSS from the rest of the kit boats on the market.
When using KSS you make the panels from gelcoat, fibreglass, resin and foam which saves dollars over an ATL kit. (And you can buy materials as you go)

[44'cruisingcat]

Originally Posted by catty

Welcome back 44c, I hadn't seen you post for a while.
I'm not sure one example is enough to show a trend as far as building time goes. For instance a flat panel 44c ,Scumble, has been building since 2003, and another by Alan Macari since about 2006. To my knowledge neither is in the water. So the ability to build a rudimentary hull in a few days certainly doesn't seem to get one an instant boat.

I've met Tom, the builder of Scrumble. He has a very demanding full-time job, which doesn't leave him much time for boatbuilding. Also, being in Darwin means the humidity has an impact on how much of his free time is actually usable for jobs such as fibreglassing. In reality he has probably spent not much more than 1000 hours on his boat so far.

So there isn't much point comparing the build time of Scrumble to that of the vertical strip foam boat I mentioned previously. It is being worked on full time, and after more than 3 years (theoretically he could have worked about 6000 hours so far, although it is likely to be a fair bit less in reality) he currently has a pair of hulls which he is still in the process of fairing.

The ability to have a pair of faired hulls joined by the bridgedeck in under 6 months, compared to it taking 3 years is a significant head-start IMHO. (Working full time)

I happen to know Alan Macari very well. That boat was started in March 2006. It is structurally complete, and the internal fitout is nearly finished. It is expected to launch this year. It will probably have taken between 4000 and 5000 hours to build. (Also bear in mind this is a much bigger boat than the foam one mentioned previously)

The advantage of vertical strip foam construction is that compound curves can be done. The trouble is, they need to be faired. In fact every visible inch of the boat needs to be faired using this method. A duflex or ply boat really only needs the taped joins to be faired, and the weave of the glass to be filled - a far simpler and faster job than trying to get large areas of compound curves fair.

[Robertcateran]

My 2c worth. Too much effort, money and weight is spent on trying to get boats to look 'pretty' rather thasm working properly.
I spent many years on fishing boats, and plan to add no more bog than is necessary to improve the underwater shape.
The edge taping I am happy to leave and the under bridge deck area and topsides need non slip. The underwater needs antifoul. I am aiming at a boat with minimum compound curves. I want a boat with only a slightly domed deck to shed water, and the taping on the gunnels will improve the nonskid. I reckon on saving at least 10-15% on weight and similar in cost and time.
Kelsall methods make sense as do pregalssed panels. I am looking at using a combination of half glassed panels to make the lower area and do some bending for the bilges and cutting a la a chine for the bows - very little cutting as no compound curvature for 2/3 the hulls, and then using panels galssed on both sides for the rest. I was quoted a good price for pre glassed panels from Polycore that was pretty competitive with buying the materials. I may be able to get some one sided glassed panels as well. Approximately $6k for enough sheeting for a 15m/9.5m Harryproa.
Robert

[catty]

An extract from Farriers web pages........

Be careful of claims about low building times, where many required aspects are usually ignored. No sailboat of this size range can be built in just a few weekends, or in "half the time" as is sometimes claimed. This would only be possible by lowering quality, or compromising other factors such as performance, load capacity, or safety, and one should be prepared to spend the necessary time on a project, depending on size and help available.
Beware also of claims about pre-made panel boats. These can offer some labor savings for hulls, but the hulls can also be of an inferior shape, with a low resale value, plus the building time for hulls is actually only a small part of the boat. F-41 hulls alone for instance can be built relatively quickly, but when removed from the form frames much of the basic interior is already in place, and does not have to be added later, as with pre-formed panel boats, where it is much more difficult to do. The great majority of the time actually goes into assembly and interior fitout etc., and this is virtually the same for all boats when done to the same standard.


I dare say you build what you are happy to live with.

[northerncat]

to be fair in the above post ian should say no boat designed by him can be built in half the time, however mine was( iestimate 2400hrs for mine) and i am aware of a few other ply cats not designed by my designer who have finished in the 2-3000 hr mark, its all in the lack of fairing in a flat panel boat as alan says
sean

[DerekKelsall]

It is good to see the debate. I hope it will get more people looking at ways to improve and hopefully more people will find the satisfaction of building their own.
Let me restate – do not expect other designers (or often others in the industry) to endorse KSS, with the exception of those we are already working with in some way. That just a few do see the value of KSS, tells it’s own message. Biased opinion and ‘sales talk’ abound. The only way to judge is whether it makes sense to you.
I did a rough count of the number of boats I have built myself or been closely involved with building (excluding the KSS workshops) and got to around 150 – all kinds and 98 % foam. I know which tasks are labor intensive. Suggesting that a flat panel starting point means compromise is a generalization, which does not apply to KSS. Usually it is applied to hull shapes, where we accept no compromise on KSS full, round bilge hulls. Function and style are KSS priority elsewhere.
Strip is the industry standard. Those using it will defend it. That does not make it efficient. Someone
commented that using transverse strip meant wider foam strips could be used. That is precisely where I started in 1965, using full foam sheets for most of the hulls. We had a great system then and would have stayed with it if my only interest was selling plans. The ONLY problems were that it took huge amounts of time and skill in long-boarding and in reaching to lay and laminate the fiberglass. I tried all kinds of ways to improve but never got far – except for one man who was a genius. A real artist at work, when filling so accurately that only light sanding with a hand sanding block needed. Including painting, on 80 ft. tri GB111 he took a couple of months working solo. (parts were made on our table).
We made the table to get the finish, but immediately found the laminating took a fraction of the time and multiple layers could be done at the same time, vacuum bagging etc. etc., and it was a lot more pleasant. The table opens up so many other avenues for the innovator.
Resin infusion – I make no apologies for coming back to this topic. It just changes the whole project. Gel coat finished parts and very little handling of the sticky stuff and no long-boarding. You need to know the difference between a good laminate and a poor laminate. After that, a test panel and a few small panels and you will not look back.
The big time consuming tasks are. Finish – at the top of the list. Handling small parts. Multiple layers separately. Integrating saloon with hulls. Working off the shop floor, particularly laminating. Fitting furniture units to complex spaces. Interior fit out to complex spaces. I do not suggest that KSS boat building is quick and easy. There is a lot to do and a lot to think about. We talk about completing structure in less than half the time of strip – we have figures a plenty, as others have also noted, and you only have to compare, step by step to see how. Miles of edge glued strip or making full length panels, with specific shape, edge treatment etc., etc. in a day. Why pay more for another flat panel kit which does a lot less? The table is used for lots of other things after making the panels.

Making dagger boards and kick up rudders are items which also take a lot of time – unless someone out there knows a quick way.

KSS Modular Assembly, addresses all the inefficiency items. KSS goes on refining, with bonded assembly as current item being applied, removing more laminating off the boat and neater inside finishing. More KSS designs are going this route.

US KSS WORKSHOP.
We have made a date for the next US KSS workshop. Near Pensacola in Florida, 11th – 14th Sept.
HARD CHINE KSS.
Having talked of efficient hull shapes above and working with other designers, the main project for the workshop is a hard chine project, replacing ply with KSS foam sandwich. (We will go through all aspects of KSS.)
This hard chine style is an option, and a compromise, we have decided to offer for some of our cruising designs. It also neatly ties in with current bonded assembly work. For us, this goes back to our first all panel cat in 1974. We used a 4 inch thick bottom panel into which we shaped a generous chine radius. The 39ft. cat was damaged beyond repair in a recent Florida hurricane.
A final point. A few commented on making a hull in a long week end. The workshop is a hands on, learning event, to introduce materials and method. Production is not a priority other than to get to demonstrate as much as possible of the process. Two or three good boat builders would make more progress.
DIY boat building should be about satisfaction in achievement above all else. I have talked build time efficiency. Whatever the final objective, good progress is a big boost to enthusiasm. Without the enthusiasm, progress is slow and there is little satisfaction. How to build is a BIG decision.

Derek.