1740

Rigging:

Side stays fitted with Ronstan fine adjustment

3 front stays.....
a/ split stay setup for cat rigged
b/ sloop stay and bridle
c/ cat rig with spinnaker single stay and bridle to suit

1 pair of Dyneema adjustable length trap wires
2 pairs of 2mm wire and loops

Ronstan 'Orbit Block' 7:1 mainsheet system

clip-on jib blocks and sheets

Ronstan 40mm ratchet blocks with 6mm sheet.

Boyer blades with EDPM covers

Stainless steel rudder stocks

Glass coated cedar centreboards.

Sails:

Ashby Main with fibrefoam batterns (circa 2006)

Goodall Main (circa 2002)

Horizon Jib

Irwin Spinnaker (circa 2007)

Spars:

Anodised mast with spanner rotation setup
8:1 external haul down system
spinnaker hound loop and

on water

adjustable diamond tensioners with a fixed spreader.

Alloy square section boom with 4wheel car out-haul
spare 2 arrow mast type boom

Carbon-fibre spinnaker pole with internal halyard, tack and control blocks
Blade 16 fibreglass/graphite spinnaker mouth with trampoline material as the spinnaker chute.

Other stuff:

lightweight & well balanced galvinised registered trailer

fibreglass sailbox

barrel beach rollers

Mosquito tuning manual

Mosquito assoc plans with additional building instructions <img src="<>/wink.gif" alt="wink" title="wink" height="15" width="15" />

<img src="<>/smile.gif" alt="smile" title="smile" height="15" width="15" />

So whats this all about then you may ask.......

well the next pic will tell a thousand stories, and this is where my part of Jurassic Karp's history starts.

The Idea is to show what can be done and allow future owners / sailors an insight to this particular cat.

The down right ugly:

starboard hull crack <img src="<>/eek.gif" alt="eek" title="eek" height="15" width="15" />

For those that bothered to read the first post, you'll recall that the original build did not have hull doublers fitted and that a 2nd re-build saw Kevlar added to strengthen up the area around the front beam..... and that a jib was added and subsequently a spinnaker as well, all placing additional load onto the area

So why did did it crack ????? obvious you may think.....
Have another look at the photo <img src="<>/wink.gif" alt="wink" title="wink" height="15" width="15" />

the crack is opening at the beam connection area and although the pic isn't that clear the hull is actually being compressed
to the point where it has bulged out slightly at the bottom of the crack....

so how can the load of sailing cause the crack when all the load on the hull is inwards and upwards when sailing, yet this crack says its trying to go out and down.....

the real cause of the stress fracture is

resonant frequency

A poor trailer design has allowed the hulls to whip up and down during transportation, up to 4

of twist can be seen when towing the boat..... hit a pothole in the road when the hull is flexing downwards and the stress becomes too much....

want to prove it to yourself ?

tear a sheet of paper in half, the inital tear point is the deck line, the bottom part of the sheet of paper will bulge out slightly as you begin the tear, the middle of the sheet where you are tearing it is going up and the ends are going down..... the dead opposite load to

under sail conditions" where the loads are all in the opposite direction

This is proven by the opposite side hull, well actually the front beam near where it joins the port hull, the beam itself has a tension crack across the top edge.... so if sailing was the cause then the crack would be on the bottom of the beam or it would be a compression crack on the top of the beam instead of a tension crack
This crack in the beam is exactly halfway between the hull and the support that holds the front beam when its being trailered around
(pic to come)

When I removed the front and rear beams the rivets that hold the dolphin striker to the bottom edge of the main beam were highly polished, suggesting movement all be it a small amount, further more the vibrations of being transported has flogged out the dolphin striker tensioner.....

all this from a bad trailer carrying setup, and for those wondering what it is.....
the boat is only held by the front and rear beams, 2 mounting locators cradle the front beam, 1 locator in the middle of the rear beam is all that holds the back half of the boat

the front beam instantly becomes the leverage point while the rear mount becomes the hinge, hey presto, one stress fracture

So the repair.....

I've spoken to several known and indeed unknown boat builders on how to tackle the issue, a plan was thought out and with a modification or two we have the best solution and repair method we collectively could design.....

now before everyone starts on how to fix it, your too late <img src="<>/cry.gif" alt="cry" title="cry" height="15" width="15" />

The first stage of glassing was completed tonight.....

relax.... there's more pics to come as the process goes on

now where did I put that RUM
<img src="<>/crazy.gif" alt="crazy" title="crazy" height="15" width="15" />

Pic taken prior to teardown.....

you can see how one side of the boat is cradled on the front beam in this pic....
its duplicated on the port hull....

front beam crack, port hull ..... as promised <img src="<>/cool.gif" alt="cool" title="cool" height="15" width="15" />

this crack is a tension crack not a compression crack

notice where the crack is in relation to the hull and trailer support.... almost exactly in the middle
<img src="<>/wink.gif" alt="wink" title="wink" height="15" width="15" />

closeup of the cracked beam

time for some open heart surgery <img src="<>/cry.gif" alt="cry" title="cry" height="15" width="15" />

and if one hull needs to be repaired then I'll have to

fix

the other one aswell
<img src="<>/smirk.gif" alt="smirk" title="smirk" height="15" width="15" />

you can see dayligt coming through the crack aswell

NB:
5 stringers under the main deck...... <img src="<>/confused.gif" alt="confused" title="confused" height="15" width="15" />

close up shot.....

note where the kevlar finishes...... and the original 260gsm glass tape finishes on the two plates....
and can you see the area thats not been glassed at all, yup right along the crack

better pic to come of that issue
<img src="<>/wink.gif" alt="wink" title="wink" height="15" width="15" />

This is the port hull

this pic shows how the timber ply was left un-glassed and without the additional kevlar layer. the starboard hull is identicle except its cracked, so it would only have been a question of time before this hull failed aswell
<img src="<>/cry.gif" alt="cry" title="cry" height="15" width="15" />

repair time......

now as much as I'm not a fan of those TV advertised

special tools, but wait there's more

adds, I have to sadly admit defeat to the

renovator

, I simply couldnt have done these cuts without it.
Gladly I borrowed this unit so its cost me SFA and thats a good thing
<img src="<>/grin.gif" alt="grin" title="grin" height="15" width="15" />

My 3ply hull doubler sitting roughly in position <img src="<>/wink.gif" alt="wink" title="wink" height="15" width="15" />
the 2 plates have had ~8mm removed from them, this will allow me enough room to fit the additional stiffners that I'm fitting (actually allready done but I wont rush you <img src="<>/wink.gif" alt="wink" title="wink" height="15" width="15" /> )

112 views and not a single comment..... mental note to self, must be doing it right ....

Port hull:
this hull isnt cracked but in this pic you can see the potential for the damage we have on the other hull.
The depressed area at the beam mount is clearly showing signs of the disaster that was going to happen had I left this un-attended....

Great post, keep it going.
Another area of failure with this generation of hulls was the centre decks. They failed over time because the (5) stringers were inserted directly into the top of the foam sub-frames. They could not carry point loading of a knee, or high impact, coming in of the wire with gusto. A picture suggests the centre deck has been removed, and failure is evident. Suggestion: upgrade the deck support method whilst its off. See a previous post by Simon Hallsworth who successfully made this upgrade on a sister boat last winter.
Also he has info on face book. Contact him for info. I can supply some also. Send a PM.
http://www.catsailor.com/forums/ubbthreads.php?ubb=showflat&Number=246814&page=1
http://www.catsailor.com/forums/ubbthreads.php?ubb=showflat&Number=246814&page=2

I intend to <img src="<>/wink.gif" alt="wink" title="wink" height="15" width="15" />
was beginning to wonder if anybody was actually reading it <img src="<>/blush.gif" alt="blush" title="blush" height="15" width="15" />

Glad someone's onto it <img src="<>/grin.gif" alt="grin" title="grin" height="15" width="15" />
The starboard hull main dech has a soft spot..... right about where my boney butt resides <img src="<>/grin.gif" alt="grin" title="grin" height="15" width="15" />

I also posted earlier about the 5 stringers in the starboard hull...... the port hull only has 3 stringers under the main deck <img src="<>/crazy.gif" alt="crazy" title="crazy" height="15" width="15" />
Starboard hull stringers (5 off) are 12mm x 8mm whilst the port hull's stringers (3 off) are 16mm x 12mm, the last owner (Matt) did replace one deck but he's forgotted as to which one, I'm guessing its the port hull as the internal work is much

fresher

in comparision.

Plan at this stage is one of three choices .....

1/ replace the stringers in both hulls with 16mm x 12mm and splash some extra glass over them to aid the foam sub-frames....

2/ make from 3mm ply a 'plate' that runs verticly from hull side to hull side and glass that onto the foam, then cut the top to the deck curve and rebate it aswell for the stringers..... this plate would only be 75mm deep

3/ full

I

beam the main deck..... cut the damaged foam so that its straight from gunwale to gunwale, slide in a 3ply crossmember (~40mm in width), cut a verticle 3ply and shape one side to profile the deck and glass in.... cut stringer slots and fit stringers, then lay a 3rd strip of ply over the verticles.

Option 1.... simple, straight foward quick and easy. Prone to failure eventually is the main drawback.... dont want to do this again <img src="<>/mad.gif" alt="mad" title="mad" height="15" width="15" />
Option 2.... little bit longer in the repair side of things but should outlast the rest of the boat <img src="<>/cool.gif" alt="cool" title="cool" height="15" width="15" />
option 3.... super strong, it really doesnt need the stringers fitted at all, bloody slow process to make all the

i

beams and fit them tho, and the biggest plus is that both sides of the hull are tied together through the

I

beam, thus strengthening the area along the tramp line
<img src="<>/wink.gif" alt="wink" title="wink" height="15" width="15" />

I have 8 lengths of 16mm x 12mm stringers all ready cut, if I go with option 2 I belive I can drop it to 4 stringers per deck, remembering that the deck with 5 has failed and the deck with 3 is fine....

The internal part of the crack repair at this stage is completed with pics to follow shortly, the undamaged hull has also had the same re-inforcing plates added and is also completed..... work on the main deck starts tommorow

Thanks for the links too......

Kingy

I used option 3 on Aldebaran V, 1995. No stringers, never had a problem.
Your option 3; 'new' top of foam must have a capping so the 'I' beam edge does not cut down into the foam. I used 3mm ply but glass resined onto the foam may also work. If you have the WRC stringers already, may be OK but is it necessary to have the 'I' beam full height? Why not have them (the stringer width of) 16mm lower and sit them ontop of the 'I' beam. Glue them onto the 'I' beam (during the application of the glass fabric), glue the stringers onto the 'I' beam, glue the deck onto the stringers, stringers will not move once the deck glue has grip of them also.
Hint, to shape the top of the 'I' beam:
1. cut to length (int. width of hull)
2. place a piece of 16mm timber ontop of the 'new' foam top
3. place the 'I' beam in position ontop of it
4. scribe the deck curvature onto it using a concaved deck curve template spanning across the gunwales
5. remove 'I' beam and cut to scribed line
6. remove 16mm spacer piece, glass, fit and glue shaped 'I' beam. (Devise a method to hold them vertical.)
7. glue stringers onto it.
This method will not need the tops of the 'I' beams to be shaped after fitting. The glued stringers will need only minimal truing.
Step 6 can be left until all items prepared and the gluing done in one application. Label parts for correct location when experiencing

gluing stress

.
NB: ensure the new deck has 2 layers of epoxy applied to the under surface, 1st allowed to gel, 2nd applied during fitting.
Ensure the tops of the stringers are precoated also or they will 'suck' the glue mixture dry and weaken the glue bond.
Trust I am not teaching to 'suck eggs'.
Good luck with it all.

Its not quite decision day yet but its fast approaching as to what I system I choose.

I like the

I

beam the most but the time taken to manafacture the components alone is well out there, even with my $40 band saw (god I love facebook buy/sell sites <img src="<>/grin.gif" alt="grin" title="grin" height="15" width="15" />) it will be a slow process.

the 2nd option I listed is quicker and far lass complicated, single 3inch wide strip cut to the width of the hull and with one side cut to the deck curve and 4 slots to take the stringers, by gluing them onto the side of the foam subframes they would have enough surface area inwhich to spread the load out evenly through the foam....
A 2nd strip could if warranted be placed on the top of the foam to for a

T

.... not as strong as te I beam but certainly a lot quicker.

I hadn't thought of your idea of lowering the

I

beams down the 16mm and then setting the stringers onto them ...
certainly a very strong system
<img src="<>/cool.gif" alt="cool" title="cool" height="15" width="15" />

mmmmmmm more food for thought
<img src="<>/cry.gif" alt="cry" title="cry" height="15" width="15" />

port hull

pic shows the doubler plate installed (about a week ago) and a 2nd stiffner plate having just been fitted, the masking tape is covering small wood wedges that are holding the plate tightly against the doubler plate.
The masking tape is easier to remove if a bit of resin gets hold of it compared to an uncovered wedge being glued to the subframes or plate...

The stiffner plate is there to add additional strength to the compromised hull.
Put simply.... if I cut and scarf in a new section where the actual hull crack is I'm weakening a failed area even more, so the crack is best left well alone other than a slight scarfing and glassing, the stiffner plate is really now the outer hull but just located a bit further internally <img src="<>/wink.gif" alt="wink" title="wink" height="15" width="15" />

starboard hull

doubler plate and stiffner glued in place, 'scratched up' ready to be glassed in
<img src="<>/cool.gif" alt="cool" title="cool" height="15" width="15" />

starboard hull

260gsm cloth laid in place and ready for gluing
The cloth is ~25mm larger than the doubler plate, this should well and truely tie it all together
<img src="<>/wink.gif" alt="wink" title="wink" height="15" width="15" />

3 other strips will be fitted as the resin is applied....

1 will run between the 2 timber sub frames and will run the full depth of the hull

the other 2 will cover the subframe plates and outwards over the stiffner plate, this will tie the subframe plates back to the way it was.

and hey presto.....

the completed product <img src="<>/grin.gif" alt="grin" title="grin" height="15" width="15" />

port hull

starboard hull

chopped glass mat was added to the subframe/stiffner conection where there was a gap.
it shows as an off white haze in the pic.

this was taken shortly after the resing had been applied and it was still tacky when I snapped this shot
<img src="<>/wink.gif" alt="wink" title="wink" height="15" width="15" />

I'm impressed!
Looks like how it should have from day 1.
Are the beam attachment nuts captive under the beam box?
If not, glue foam between the two frame, X mm below the beam box so if the nuts are dropped during assembly, they do not fall all the way down to the keel and then cannot be recovered.

Good work. Keep on posting, interesting read. I am keen to know what you are going to do with trailer modifications .

another quick snapshot.....

as you can see

room

to get my hands into the foredeck side of the hulls was damn tight let alone seeing what I was doing , now imagine having to move the glass mat around and then apply resin and smoooooth it all out....

mutter mutter mutter.....

lack of room was a major pain in the butt <img src="<>/cry.gif" alt="cry" title="cry" height="15" width="15" />

and yes (as you can obviously see) ... surgical tools became a great choice, clamp please nurse.... syringe full of resin please nurse....

repair.... nah this was surgery
<img src="<>/laugh.gif" alt="laugh" title="laugh" height="15" width="15" />

no their not at all, but the design allows me to get access to them fairly easily.
Te rear beam attatchment is a tad more difficult, but if I move the hatches back about 30mm I should have no dramas at all, my arms were just a bit long to do it comfortably..... need a folding wrist at times
<img src="<>/wink.gif" alt="wink" title="wink" height="15" width="15" />

Ahhhhh yeah about that.......

Your in for a bit of a wait <img src="<>/grin.gif" alt="grin" title="grin" height="15" width="15" />

but.....

I'll be widening the main drawbar, which will in turn widen the foward

cradling

points for the front beam <img src="<>/wink.gif" alt="wink" title="wink" height="15" width="15" />
(works out to be about 130mm wider at the beam cradling point)
I'll also be adding as couple of stiffining plates to reduce the drawbar flex.

removing one leaf from the spring pak (softening the ride and we all like a soft ride every now n then <img src="<>/grin.gif" alt="grin" title="grin" height="15" width="15" />)

altering the rear carrying points completely (which caused this issue in the first place <img src="<>/mad.gif" alt="mad" title="mad" height="15" width="15" />)

fitting a larger sailbox (cause the current one is a tad small)

and I'm thinking of increasing the actual wheel size.... mini wheels are ok ..... for minis <img src="<>/crazy.gif" alt="crazy" title="crazy" height="15" width="15" />
oddly enough toyota corolla rims fit perfectly...
<img src="<>/whistle.gif" alt="whistle" title="whistle" height="15" width="15" />

the trailer side isnt an issue for me..... its what I sort of do for a living.....

here's a duel mozzie setup I did a few months ago... <img src="<>/cool.gif" alt="cool" title="cool" height="15" width="15" />

Hi all, interesting setup on trailer, i usally have the top boat upside down, is it much wind-age in that configuration, and is it top heavy?

Matt
The joker 1826
Mossie pres

When I spoke to the owner last about it he was more than happy with it and the way it all works..... they'd towed it a couple of hundred K's and didnt notice any differance from a solo cat to the duel cat towing, so far all's good
<img src="<>/smile.gif" alt="smile" title="smile" height="15" width="15" />

I built it for a father / son combination where there are the odd times when they both wish to go to the same regatta, otherwise the two boats are usually carted around on their own trailers for club events.

The setup in the pic is

slip on

so the extra boat carrying pieces can be stored easily for solo boat use, and easily fitted when the two of them wish to head off together.... it takes about 10mins to slip on the duel carrier setup AND the 2nd mozzie by 2 people.
When the duel setup is removed you'd struggle to spot the differance from a std trailer to this one.....
<img src="<>/smile.gif" alt="smile" title="smile" height="15" width="15" />

Both top and bottom mozzies are carried by the front and rear beams and both masts can easily be placed on the top of the loaded boats from the side and do not interefer (rub) with each other.

the only disadvantage I can see is you HAVE TO remove the top boat in order to get the bottom boat off... no big deal seeing that both boats are going racing

<img src="<>/cool.gif" alt="cool" title="cool" height="15" width="15" />

the soft deck..... <img src="<>/mad.gif" alt="mad" title="mad" height="15" width="15" />

the worst area has ~8mm of defelection with most of the deck easily moving 3~4mm with slight pressure.

with the deck peeled off and the foam sub-frames cut out I then cut up some new ones.....
pic shows the old frames and you can clearly see the collapsed area.
The failing foam wasn't the only issue, two of the timber stringers had also failed, one had snapped and the other had seperated from the glue...... that explains the

rattle

I had when a gentle thump was applied to the deck
<img src="<>/crazy.gif" alt="crazy" title="crazy" height="15" width="15" />

sub-frame #5 had compressed the most, as you can see its actully curved in the opposite direction to the deck shape

The new frames have been cut, given a light coat of resin for added strength, and had a final trim to fit perfectly.
I've also decided on a stringer support design that I'm happy with.
the

I

beam design is great, but the time restraint means many w/ends of toiling away in the shed, secondly, only one deck needs this repair so its pointless in distroying a good deck just for duplication reasons....
So I've come up with a very simple plate that will add support to the stringers, and tie the 2 hull sides together..... it can aslo easilly be slipped into place without major issues in the hull with the good deck.

Although the foam sub-frames are cut and ready to fit, half of them are being fitted with the support plates prior to the final fitting to the hull.

<img src="<>/cool.gif" alt="cool" title="cool" height="15" width="15" />

new subframes being made and test fitted....

the ply on the subframes (laying on the fordeck) will give you a hint as to which way I'm going.....

ready to be glued in <img src="<>/grin.gif" alt="grin" title="grin" height="15" width="15" />

Once they are good n solidly stuck, I'll cut some little rebates for the stringers and then glue in the stringers.
The ply will spread the load accross a large area compared to the stringer just sitting in the foam..... It has the added advantage of tieing the two hull sides together..... and its lighter than the I-beam.... and I can install these on the other side without spending hours n hours cutting/forming/ makeing little bits/glueing..... yawn !!!

I contemplated fitting a

deck plate

(for want of a better word) to each foam subframes, but doing every 2nd frame seemed better and had the right look... in doing every 2nd foamy it comes out to 270mm between each deck plate which is hell of a lot more support than its ever had <img src="<>/wink.gif" alt="wink" title="wink" height="15" width="15" />

the best bit is that each deck plate works nicely into the areas that see a lot of butt action...
<img src="<>/laugh.gif" alt="laugh" title="laugh" height="15" width="15" />

nice break..... gotta love holidays <img src="<>/grin.gif" alt="grin" title="grin" height="15" width="15" />

The new subframes cut to the deck shape and fitted in place