Crowther Spindrift

Just posting for the interest as vintage Crowther boats seem to have some following
http://www.gumtree.com.au/s-ad/minn...rowther-spindrift-37-grp-composite/1059503911

Jeff.

 

While bridgedeck clearance is discussed in another thread, I thought someone might be able to describe the point at which it is measured.

I have enclosed a photo of the underside of my Crowther Spindrift.
As the photo shows, the bridgedeck clearance goes from about 1.3m forward then curves like an airfoil to be 0.8m at its lowest point in still water.

Incidentaly, while I have measured the waterline length with a tape measure simply run along the top of the painted waterline and got exactly 40', I still dont know the LOA of this boat.

 

Hi Reefer,

Then you bridgdeck clearance is 0.8 metre, usually the lowest point is aft, you could also measure forward where the curve at the front tangents from strait for clearance forward, the length and shape have some great bearing on the issue, the cutaway that the Crowther designed vessels feature is close to ideal and many modern production vessels have de-evolved from this ideal for spaciousness...

Then the boat will or could be be slightly shorter or longer than the girth you have taken at the boot top line, you could with the help of a level and a batten, also some masking tape to temporarily mark the deck,.... level and measure forward and aft then run a tape with reference to deduction/addition on the deck marks to arrive at something close. Maybe shorter is better for economy in marina berth and longer better for sale........
Jeff.

 

Hi Reefer

Crowther Spindrift Cat

I came across your interesting post and was wondering if you had a pdf copy of the boat plans that you would be willing to email to me. My email is acerowe1876@gmail.com obtaining some plans would greatly help with my project.

kind regards from the UK
Andrew

 

Andrew. Look at "Multihull Structure Thoughts" thread. On page 1 there is an index, look at the length 37 foot and a page number will be next. Look at those pages and on several pages you will find Spindrift 37 plan PDF's.

 

Hello OldMulti

Thank you very much for your advice.

Best wishes from the UK
Andrew

 

Hello OldMulti

I wish to tap into your expert knowledge I hope you can help, what materials would you use to build a 37ft Spindrift Cat lighter & stronger for performance ocean cruising ?
Using the male bulkheads and instead of 12mm ply hulls with 2 layers of 600 gsm E glass each side would you use 9mm ply hulls with 4 layers of biax E glass laid diagonally at opposite 45 degrees angles with vinyl resin for external hull and 3 layers glass internal . Would you build the cabin in 5mm ply & 2 layers of 600 glass each side ?

Alternatively would you use foam sandwich construction & which foam for a budget build . All workmanship done carefully. Which method is quicker . How would you lose weight from 7000lb & build stronger. And could / would you increase the beam from 6.1m to 7.1 m like Chris White does for a wider cabin.

thanks again for your time considering

best wishes from the UK
Andrew

 

Andrew. A Spindrift 37 is a reasonable cat that can cross oceans etc, but it is an old design. Modern plans from a reputable designer may cost money but I can assure you you will get a lighter, faster cat which will be cheaper and faster to build. The hulls on a Spindrift 37 are the old style of foam glass build. You build a male timber frame, put your foam on, put you outer layer of glass on . By now you have faired (sanded) the mold, the foam, the glass to get a smooth surface 3 times. Then you finish it with Gel coat or paint. Then you take the shell of the mold and put glass on the inside.

Modern builds are find a big flat surface put down your outer skin glass dry, lay on top your foam, connect up a vacuum pump and resin infuse, you get a smooth outer surface in literally 25% of the time and minimal surface fairing. Bulkheads are often not plywood but flat panel foam glass builds with unidirectional edging etc. Less plywood often less weight etc. In Australian foam and glass direct from china is cheaper than good marine plywood.

Translation: If you want to change an old design to modernise it, reconsider the idea. I can assure you the plans of a 35 footer is the cheap part. The second hand value of a "modified" old design is not good. A known modern design well built can hold its second hand value a lot better.

PS You can lengthen a design by about 10% without much pain but a 15% greater beam requires a serious recalculation of the materials in the beam structure, not just a approximation of the materials. Sorry, but designer plans are often a cheap investment.

 

Hello OldMulti

Thanks for your detailed reply I have seen the vac bagging technique can you recommend some modern hight tech light & strong designs for smaller cats that I should look at.

thank you
Andrew

 

Andrew. I will make an assumption you want an about 35 foot cat with a bridgedeck cabin, I would look at some of the following designer pages. Richard Woods, Tony Grainer, Kurt Hughes, Schoinning, Mike Waller and Spirit designs. Each have a mid 30 foot something cat of modern light design, that may fill your needs. The build techniques vary but the more flat foam glass panels used in the construction the better and easier it will be. Some offer kits which can speed up the build at a price. Try and use a stock design as they will be cheaper plans. There are many other designers out their that can be good, but if there are several boats already launched the plans will be "corrected and upgraded" by others who have built before. Also often a guy who has built one before will help with any questions if the designer is unavailable. Finally look through the Multihull Structure Thoughts thread for the style of boat you may want. there are many options.

 

Great thanks I’ll take a good look at those designers. You mentioned you get foam & glass from China are they already infused boards what is the brand I’ll have a look at them. I saw the Schionning 1200 that looks an interesting design but too small a payload. Ideally I would like to achieve 10knots + loaded up. What is a modern hull design you mentioned is there a particular Cat you know of with fast but roomy hulls.
Kind regards

Andrew

 

Andrew. Ask local British home builders (mono or multi) who their trusted sources are for these materials. I don't know your import rules and these Chinese companies like quantity orders, so if several people can get together you will find it cheaper. Find out from those who have successfully imported products into Britain, not those who can suggest the cheapest. Scams and quality questions still exist in the foam, fabric and resin game from China. 10 knots is easy from any of the above designers but the load amount is the real test. If you plan to sail around with 10,000 plus lbs payload we are talking about a French accommodation cat of which there are many second hand versions available on the market. These cats may not be as fast as a 10 knot average boat but you get a complete boat nearly ready to sail for less money than it will cost you to build a new design. Only downside is you may have to spend real money fixing up the rig, sails, galley, engines etc. Be careful but some real bargains can be found.

For hull shapes read Richard Woods and Tony Graingers websites, both have good web pages on what to look for in hull shapes and some of the advantages/disadvantages.

 

One you forgot Oldmulti ; Mr denney @ Harryproa

 

Thanks Peter.

I and other Harryproa builders have imported several tonnes of composites from Utek in China. Prices are half or less than what I would pay locally in Aus, which seem to be lower than European prices. eg, fibreglass is ~$US2-3/kg, plus shipping which is maybe 10% depending on quantities. The quality and service is as good as locally sourced, much of which comes from China anyway. You will need to buy full rolls and boxes. I don't get epoxy from China as it is cheaper ($US9 per kg) from Hiltour in Aus, but it may be easier/cheaper for you to have one shipment instead of 2, although there are dangerous goods shipping rates to consider as well.

Shipping agents are hard work for small volume customers but if you consider it the other way round, you can see why. Doing it yourself is more trouble (in Aus) than it is worth.

There are a lot of other low priced boat goods in China, it may be worth paying extra to get your shipment consolidated, but be aware of storage costs. Unless you can get a container's worth, consolidation does not make cheaper shipping, nor reduced import costs. But it does mean everything arrives at once, with only one lot of hassles.

If 1,500 kgs is not enough payload, then you will struggle to find a 40' cat with 10 knot cruise capability.

All true, but this does not include the frame/strongback required, nor all the shaping, fitting and tabbing to join the panels and the fairing this requires. Or building the round bilge hull 'shoe' and floor on many designs. There are easier ways to do it, but not with the catamaran hull shapes currently in vogue.

 

Hi Rob

Thanks for your interesting email however OldMulti did mention in one of his posts that there is a current preference in Aus where some smart builders are now constructing 60ft racing boats with a 4mm plywood core with a specific strong lamination on both sides. There is one massive advantage of this that I can see is using readily available materials in your home town constructed in a smarter way this saves on all the import costs & waiting time & it’s cheaper etc.

I’m currently researching core types & comparing everything against either a 9mm ply or 12mm ply core with the smarter lamination method. I have seen that some builders in the US have taken this one step further for a crusing boat with a tough bitumen final layer below the waterline but that was for an expedition boat. 3/4 Carbon core plastic honeycomb is similar cost to marine ply so I’m looking at as well and laminated Nomex honeycomb is also interesting but there is much labour involved in making your own panels but the process can be quicker using a vacuum. If there is not much weight saving over expensive Corecell , Airex or the pre laminated cores could a 9mm or 12mm ply core with a modern lamination be a sound option for a home builder on a budget who is able to source materials locally ? Dudley Dix told me S glass with good epoxy can careful construction is similar strength to expensive carbon. Is Carbon lattice core or expander metal core & S glass epoxy the future ?

Andrew