New Deck

I have finally seen the light and have procured a mozzie.
Currently sanded back to bare timber the hulls weigh 22kg.
I feel however to reach overall min weight of 55kg,
More weight needs be lost and the centre deck is 6-8mm ply. The rest of the decking is 3mm. I want to replace the centre deck with 3mm ply with one layer of fibreglass with the hope of losing a kg from each hull. I am no expert on this so I am wondering what other methods or suggestions people have in regards to this topic and what weight lose I might expect to realistically gain...?

Hi Bandit

I think 3mm for the main deck is too thin, make it 4mm with glass, but also check the class rules there might be minimum thickness, good chance you'll lose some weight but I'm not sure how much. Original plans for the Mosquito had two layers of 4mm ply, and back then Gaboon ply wasn't around, so I'm sure theres some savings there if you replace with Gaboon (Okoume)Ply.

Regards

Ok I was thinking the deck is very well fastened down so I might try cutting back the top 4mm sheet and then sanding through the adhesive until I hit the second 4mm sheet. Glass over the top of that with 2 layers of light cloth.
If I can shave a kilo then I might be able to reach min weight. Also I noticed a rule Proposal 6.5 to make the center beam optional. After reading the rules I am confused.
It states

(Accepted at Annual General Meeting, 3rd January 2007:)

Does this mean a proposal has been accepted to be further voted apon? or is the rule officially changed now?

Hi Bandit

Without actually looking I not sure that proposal didn't go through, I stand to be corrected, but I think the centre beam stays.

With regards to your deck, I would start again from scratch, I would get a router if you have access to one, get a straight cutter bit, if the deck is say 6mm, set the router to 5mm and go nuts, start off near a hatch hole so you can make sure your not going all the way through.

Regards

I will try grab some 3mm or less gibbon ply.
I'll beef it up with supports like grey matter and fiberglass the deck.
More deatils on the rule change can be found on page 17 by using this link.

http://home.vicnet.net.au/~nmcca/doc/Mosquito_BRR.pdf

If I cant drop the center beam then I don't think I will make min weight. So clariforcation on this rule is important as I intend to order a tramp designed around this factor.


If it isn't a change then old rule has 2 loop holes..
It isn't clear as the center beam as compulsory only that you have to have a rear and main beam.

Also according to the rules they do specify aluminium for the main and rear beam but they do not specify what material the center beam should be made of only dimensions are listed...
has anybody used carbon tube??
Unless someone else had already done this I would be hesitant as I belive its a loop hole that was unintentional..
Anyone care to argue the pros and cons further??
How far could you go. Could a pool noodle constitute as a beam???

Still I need to establish the rule change first before trying to exploit a loop hole...

Bandit,

as seen from an outside viewpoint, class minimum weight is mostly an psychological issue. The difference between minimum weight and minimum weight+5kg is so minute that not even the olympians would notice. It is nice to have a regatta boat at min. weight, but finishing the race is much more important if you want to win. Marginal structures are known to break from time to time <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

Well after reading that, I guess it is optional, it does say at the top, accepted at the AGM.

I still say 4mm for the deck, but if you've your heart set on it, not much I can say, accept, that adding extra material to beef it up and having two layers of glass, would probably weigh more than having the 4mm with one layer of 100g/m cloth.

Good Luck though, its all good fun.

Regards

The old deck weighs 4kg.
I am hoping 3mm sandwhiched between fiberglass will weigh 3kg saving 1kg per hull.
I also plan on a new one piece tramp with a rear bolt rope and wire sleaves for cable attachment via the beam bolts at the corners.. The new tramp overlaping half of the hull makes this possible in accordance with the new rules.
Thanks for the help so far Matt..

Normally I could weigh the sheets and let you know difference, perhaps someone can, but all my sheets are in my caravan, which is full to the door with other stuff as we've just moved house.

You would have prebend the decks to the approximate curve if your going to glass both sides I would imagine.

I've just put the decks on, glass over and down the sides a bit, 3mm ply on the foredeck, 4mm ply on the main and rear decks.

My mossie which was an original kit boat from the 1970's, the platform alone weighed 75kg or there abouts. It was built up to the deck stage and twenty years later, and about 12 years ago now, I followed the original plans and put the 2 x 4mm decks on, not knowing what I do now. I'm planning a restoration next year and the decks will be No1 job when it happens.

Regards

the decks on my boat are 3mm and glassed on the inside. be carfull as the older boats wouldnot have the same amount of foam frames and timber frames as my boat. if you are replacing your decks put as many foam frames in as possible and some timber frames to support the decks.

Rodert,
What do you mean by glassed on the inside?
How do you do this?

Hey Cam,
Here are some photos of your hulls. <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" />
Thaught You might want to see the damage I've done on your behalf <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" /> <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" /> <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

Can anyone tell By the photos who may have built the hulls?

what i mean is to glass the inside of the deck before fitting them.
1)cut the ply out to the deck shape
2) mark a line around the deck 20mm this is so you don't get resin on this line at this stage so when fitting the decks you get a fresh glue line, no old resin.
3) cut glass cloth to size
4) mix rein and paint onto ply keeping the out side 20mm clean.
5) lay glass cloth on deck and roll through the resin.
6) lay deck on bench with a beam under one side (long side)
7) when the resin starts to go off place a large rubbish bag on top of resin and place a small amount of weight on it to put a slight bend in the timber when cured, to help with deck curve, the plastic bag should not stick to the resin.

The boat was built by someone in Newcastle. I could find out for you if Im bothered going to kurnell tomorrow.

Sorry I haven't replied to your questions about the centre beam rule earlier but I've been away a couple of weeks.

That proposal you have picked up in the 2007 rules was purely a typo. That heading "Rule6.5" and the three paragraphs that follow simply shouldn't be there. It's a mystery to me how they got there, but I must have done it when I updated the rules so I'm sorry to have caused this confusion.

Mick Floyd has already corrected the online rules on the NMCC website.

The text originated 3-4 years ago when a proposal was made to make the centre beam optional, but the idea received no support at the time and never went any further.

In answer to your questions about rule 6.5:

1) The centre beam is definitely not optional - it's in the Mosquito plans and the BRRs don't say it can be left off.

2) The material is not specified and it could be argued that other materials (like carbon) would be permissible, however the size and wall thickness is very specific and this would limit the kinds of materials that would be possible. It's not much of a loop hole since a carbon beam 50mm x 1.5mm may not actually save much weight - should be stronger though!

3) A beam is a "beam". A piece of string or bungee is not a beam, and neither is a pool noodle.

If you are getting a new tramp and your boat had the aluminium tracks down the sides you can save some weight by replacing the tracks and bolt rope with a piece of spectra between the front and rear beams. You just need an eyelet halfway between the beams to tie the tramp down to the hull.

Matt Kirby has his boat set up like this, and some South African Mozzies too, so they might be able to supply some photos if you're interested.

It would be nice for my boat to be within the rules but I like things to be simple and I think the centre beam is an eye sore.
In the interest of assisting change I have gone for a one piece wire mounted tramp via the beams for simplicity and to save stressing my light weight deck.
I will have only 200mm length of centre beam for my traveller cleat to mount from but that’s it.
The tramp will sit under it with a bolt rope mounted to the underside of the rear beam. If people like it they may opt to copy me and the rules may yet be changed.
A beam after all is classified as a support and while mine doesn't span across the tramp to the front beam it still supports my traveller cleat and the rules don't specify the length of the centre beam. Hopefully this is a loop hole.

I think for NSW we need the mossie to be simple and cost effective otherwise the enthusiast who wants to build his own may build another design.

Beam sections are sold in 6.5 mtr lengths and expensive purchase for one beam and until NSW numbers grow we can’t divvy up the left over’s..

I also would like to approach the wooden boat building classes for novices. It’s based here in Sydney and if we offer the mossie plans I hopes they might build up NSW members. The cost will help that factor as a mossie is a good class per dollar value...
Increasing that attribute can only be a good thing or otherwise they may prefer for a little extra, to build a taipan or a new blade...

I also was wondering how the vote system works is it counted by votes received yay or nay then the percentage or is votes not received from members considered a nay vote to affect the percentage?

I hope encourage the KISS Factor of the class and will go ahead with my adopted design (race legal or not) to help promote the changes..

I recently purchased a 6.5 metre length of the correct material for a centre beam and it cost $22. It was cut into 2 pieces for nothing at the aluminium distributor to make it easy to transport home and after making the beam I had enough left over to make an axle for my beach rollers. I dont beleive the cost was excessive and the waste is minimal.

I also dont agree with the majority of the rest of your post, best of luck with your boat that was a Mosquito.

Darryn
1782

I guess it depends on the circumstances but you should know a Mosquito was protested out of a regatta a couple of years ago for not having a centre beam.
If you start beating other classes on handicap they may start asking questions about why your boat looks different from the others!

You're not the first to think whether a stub of tube or a bit of string would do instead of a beam, but the rule says its 50mm dia (or square) for the whole length and just plain common sense says a short piece of tube that goes nowhere is not a "central beam". The plans (which are still referenced by the rules) also show the beam. It's not really a loophole.

On a different tack altogether, I wouldn't consider removing the beam from my boat as I think it would just make it very difficult to sail the boat competitively. When sailing downwind with or without spinnaker we spend a lot of time in the centre of the tramp to get the hull to fly. Without the beam this would be a lot harder.

Other reasons to have a centre beam are to provide a mounting for a centre mainsheet cleat, and to stop your front beam breaking if you rig a spinnaker. There are doubts over whether the beams are strong enough to take the side loads without the centre beam on a sloop rigged boat.

As I mentioned this came up a few years ago as a serious proposal to do away with the centre beam, and it received no support at all.

As far as buying the material I know Bob Keeley in Melbourne has it (03 9555 4622). 50mm tube is pretty basic stuff that I would imagine a lot of chandleries could get. That guy in the little shop near the CYC in Rushcutters Bay springs to mind.

To summarize the voting on rule changes, everyone competing at the nationals gets to vote then at the AGM, and each state association also gets a vote for every 5 members. How the state association decides to cast it's vote on behalf of it's members is entirely up to that state association to organise for themselves.

I encourage a difference of opinion as I am relitivly new to the class..
Here is my reasons for the change.
I have found old mossies popping up here and there but they can be too heavy to be competetive especially for myself at 100kgs.
The old rule min of 65kg was changed to 55kg making these older boats slightly disadvataged. I have lost 4 kg from dropping my center beam and 4 kg from my heavy decking giving me half a chance at reaching min weight with an old boat. Cant see why the optional main beam would cause any issue as most boats these days are all under weight with a main beam an unless I am mistaken it has no bearing on a boats performance. Your spinniker sloop rig boat may put more of a thorn in the idea but I intend to race Cat rig.
If I don't like my changes it wont be hard to install the beam...

You've certainly helped with the weight, but you will put more load on the beams. Cat rigged you will probably be ok as long as your beams are in good condition. Just don't go beating too many Taipans or Hobies!

The other area you can usually save a lot of weight on older boats is by removing most of the fittings! It's surprising how little you really need compared to the way they were rigged 15 or more years ago.

She has a new deck,2 pac paint job, tramp, mast, rigging, boom, beams and a relitivly new sail. I have yet to buy rope but I am more than happy with the results so far. Will keep the clutter on the boat to the min and keep the essentails simple but hopefully effective.
I should hopefully get her wet in this weekend if all goes well. This is why I think NSW numbers could increase if we could revamp the old boats out there..

Who stripped the paint back? <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" /> and you got any pics yet?

Photos will be comming soon X Ben...
Nice work on the paint stripping Will. <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

Progress so far
The thin layer of glass on the decks had to be knocked right back as it was glassed with light weight chopped strand with minimal resin making the deck fairly rough but alot of sanding and a small amount of filler has leveled it out.
The decks are both done and we finished fairing the new inserts in bottom of the centercase to accomodate the smaller center boards.

Wed should be paint day.
The A class rudders arrive tommorow
and I pick up the new beam section tommorow.
The tramp is done just need to put things together.

Any sugestions out there on what to use for rivits??
I am a heavy bloke and I was planning on alu rivits but if there are any better sugestions I am all ears???

Bandit, Aluminium is not strong enough. All the boats we put together we use 3/16 stainless steel rivets. As for the glass on the deck you should use 2 oz matt and the minimum of West System resin. The resin has no UV protection so use paint or clear to cover and protect it. The final surface should be smooth and you should not be able to see the weave of the cloth.
Good Luck
Peter

Yeah its old front deck section that was glassed the previous owner with chopped strand the new main deck is 120gm cloth and west sys resin.
2 pac blue paint to finish.

I glad you set me straight on the rivits First Try. My old mossie had alu rivits and it held together but this boat without the center beam and wire instead if side mounted bolt ropes will load the tramp up a fair bit.


Also I recall using monnell rivits on my Nacra.
They apper to be just as strong as ss butI belive they are less prone to corosion anyone care to comment further on the comparason of SS to Monell.

I think Monel rivets are almost as strong as SS but I too have heard that they go better with aluminium.

The yellow stuff for putting between SS and aluminium to slow the corrision is Duralac. I've heard it's highly toxic, but it does the job.

For low-load items aluminium rivets are ok and will not create the corrosion problem, so I tend to use a mix of aluminium and Monel.

Thanks Tim your definatly on the right track I'll give Whittys a call to see if they have it in stock and my arms will be well and truly buggerd after riviting in so many tough rivits..! I might have to source a monster riviter as my little one will be a struggle..

Yeah that's all I have. It does hurt after a few 4mm monel rivets - esp if you get your hand caught when it goes bang.

Hi Peter

Good to see you on the forum.

Do you have any news about the new boats being built?

For instance, how many, anything different about them, who's building them, what colour, how's the seam being finished etc.

You know - everything. We all want to know

Tim,
Yes stainless steel rivets do require Durlac (Yellow staff). Monel rivets are a good alternative. One small thing 3/16 is all but 5mm I personally would be a little concerned if you are using 4mm. I have seen rivets share off holding things like diamond wire tangs, we drill a extra hole in each tangs for a third rivet because two will give up in the right conditions.
We are building three new boats at the moment, two have been sold and the third is the Association Hulls waiting for a crew. Sorry all hard to get Boyer white. The only change we have made is the mast rotation. We are using the same system as First Try so the rotation can be adjusted from the wire. The Hull Builder is Jim Boyer himself, we have one set of hulls ready for beaming this weekend and the second set will be ready in a couple of weeks. The seam will be fared out so not visible. Rudders and centre board on one boat are from Joe in Bendigo using Jim's moulds and the other will have Tony's latest centre boards and imported rudders. It will be interesting to see the difference. One Boat will be sloop but raced in cat configuration most of the time by a new skipper to Mossie’s with many years of experience in cats and other will be cat rigg with kit. We are also beaming up a new set of Chris hulls with a little luck in time for NSW. Sailing in Central Vic is the same as last year with wheels. Although Waranga Basin may be sailable. The first time anyone will see us on the water will be NSW for there states if we get there, other wise see you a McCrae in November.

Peter

Hey all,
It's just over 2 weeks until the NSW states <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" />
So far it looks like we will have 5 cat rigged and 2 sloop <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />
We are all crossing our fingers that there will be a few new boats (as last post) ready.
It would be great to hear from any others who may be coming.
jive (smik) had some good results at kernell last w/e.
http://www.kcc.asn.au/2007-2008/Results/2007_2008_Olympic_Series_R4.htm
Looks like we will have some good racing.
Cheers

It shows that you dont need a new boat to be competative, So bring out your old boat and have some fun, or maybe I might be able to take some one else's boat out <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />.

Sorry for the thread Hijack.
William
JiVe 1691

Hey ben you forgot the pics <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" />
I recieved the A class rudders and the stocks are in bad shape so another project is in order.
I was wondering if anyone has tried bending alu without a proper bender.
I have a blow torch if heat would help and a large piece of Pvc Pipie 300mm dia to bend around.

I usually try to get 3/16 rivets. I didn't realise 4mm ones were smaller!

So is Tony building centreboards and importing rudders? Where do the rudders come from? Different shape from his previous rudders?

Where did you get Chris hulls? Are these new ones? Is the mould back in action? Who built them?

You answer one question and get a whole load more!

Sorry Cam

Hey Cam Ive got a bloke bending new stocks for jive this w/e if your interested.

Thanks for the pics Ben..

Tim ,
Tony is not importing rudders he still makes them the imported rudders are Dotan.
The Chris hull are new, they were built a two or three years ago and not beamed up. We are starting beaming them afternoon.

Peter

Some blurry photos of Cams hulls

and another

Ben,

Love the colour <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" />

Is it Botany Blue ?

Regards,

Peter

I'll check the lable tonight when coat 2 goes on.
I will look like a smurf after sanding back this coat..
We lost 2kg per hull from changing the deck.
The huls are now 20kg each.

For those needing a good riviter Whitworths have two handed industrial riviters on sale at 34$...

Centre beam weighs 1.45kg plus brackets to fit at either end, 100grams each giving a total of 1.65kg for the center beam assembly, not 4kg.

I note a bracket and short piece of aluminium tube has been refitted, it would weigh 250gms minimum without fasteners so the real weight saving for not having a centre beam is 1.4kgs, definitely not 4kgs.

Darryn
1782

I have also recently weighed a new alu center beam at 1.5 kg.
The old one however was square box tube and was 4kg...
A large difference.

I will attempt to modify the tramp to allow the center beam to run under the tramp and exit through a hole near the rear seaction to allow the bolt rope to mount under the rear beam to deflect water.
Still I belive the debate on making the center beam optional will help older boats in cost and weight factors ways assuming it isn't a crucial part of the mozzie design.
It is about 100$ cheaper to have a 1 peice tramp made over a 2 peice design and there is less rope needed.

Bandit,

2 piece tramp???.....must admit that I ave not seen one of them for many many years and all of us now use 1 piece tramp...looks good and the centre beam can hardly be seen.

the rest I must admit is an interesting read..

David

So is the few pounds you are saving really worth it? I could understand if it was large numbers but we are talking about under 10 pounds here. The difference that will cause would be about the same as one messed up tack, wouldn't you benefit more by just practicing all this time you are trying to save a few pounds?

I don't want this to be offensive, it just is how I see it.

It's a shame you didn't mention the 2-piece tramp earlier. We would have understood better where you were coming from. That explains why you were concerned about the look of the beam - it was a bit puzzling as like David said, the beam is hardly noticeable.

Most of us have forgotten 2-piece tramps even existed. The point is the beam does not affect the size and shape of the tramp at all except there needs to be a small cutout (like a U-shape) at each end.

It's more rare but you can also have the track at the front and lace at the back like this:

Attached is a measurement diagram which I gave to Lindsay to get my tramp made. It has the beam cutout dimensions.

The rear cutout is longer to allow a traveller cleat to be mounted on the beam (and a mainsheet cleat swivel if necessary but I don't use one).

I have made my tramp this way but with a rear bolt rope instead.
I intend to cut a hole instead of the u shape to absorb the sideways load.