Hints & Tips on How to M

Photo: Nick Lindsley

HOME BUILDING A MARBLEHEAD IN BALSA
By Scott Wharton Qld

After making several IOM designs in balsa I was looking for another challenge and decided on the "MONARCH" design by Graham Bantock as a suitable modern design being produced in 2003.
The Monarch is a close sister to Graham's current production design the PRIME NUMBER. The Marine Modeling featured plan comes with a good deal of construction detail, details of carbon/balsa fin/rudder construction and a Rig plan.
(Plans for the Monarch design are produced by SAILSetc and available from Radio Yacht Supplies Australia) See Suppliers of M parts

The design all up weight is 4.8 kg and I worked hard to keep the weight down to this without having to take weight off the lead bulb.

Starting with a base board (100×12×1450mm) cut the shadows to shape and mount at 90º to the base. That's the first day over.

Strip your balsa (or cedar) into 10mm wide strips and fit 2 to 3 per side per day. The ends and edges are glued (balsa or aliphatic) and are pinned with magic tape over the shadows. On completion of planking remove the hull from the base board.

If your hull comes off the board ok then you have the choices of:
1. Glassing the outside and coating the inside with a few coats of resin or
2. Glassing the inside with a few coats of resin to the outside.

I chose option 2, adding carbon reinforcing inside, then fitted a 1.2 mm ply deck and completed the hull. I fitted an RMG winch from my spare IOM and with the help of friends put together A and B rigs. The total all up cost of the boat with two new rigs and a second hand winch came in at $1200.

This boat has no vices and is very well balanced. I am now trying a modified fin, to maximum depth without increasing the overall weight.

I now have the choice of using this hull as a plug or alternatively I can build a multi-chine version in light 1.2mm ply. It is great to have a hobby!!!.

* Editor's Note
Scott in his first competitive outing at the 2005 South Queensland Marblehead Championship finished fifth behind a two Vibes, a Rok and a Strad and had several 2nd placings behind winner and current Australian Champion Greg Torpy. Not bad for an outlay of $1200.

With Thanks to

Graeme Turk
ARYA Publicity Officer

 

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Speeding up that older M

Part 1 by BG

Whilst racing Radio yachts can be both fun & rewarding, I'm sure that many of you have often wondered how you could get that little bit of extra speed from your boat.

Over the next few installments, I would like to see if we cant get that little bit extra from your current Marblehead design sailed.
Below is a starter for things to get you thinking on things that may best help your boat, with weight being one of the main items.

I have dissected this edition to cover the four basic components of your boat
1. Hull
2. Fin, Bulb & Rudder
3. Rigging
4. Sails

1. Hull

- Firstly obtain a set of plans or figures for your design from either the designer/builder if possible. Check that the placement of the fin/mast position & all relevant rigging attachments are in the correct positions. If they are not, don't despair as there may be a perfect explanation offered by the designer/builder or indeed the previous owner.

- Check the weight of your hull. An overly heavy hull lay-up in construction is not the fastest!

As a guide I have provided some estimate figures at the mid to upper end of the weight scale for the M class. This should be achieved with everything included in your boat ready to sail, (less rig, fin & bulb). Yes the rudder is weighed with the boat for this exercise!

Marblehead 950-1050grams
(Professionally built newer designs can be in the vicinity of 840 - 900grams, though for anything but the highest level of competition, a moderate hull weight is fine)

If your total hull weight exceeds the above limits mentioned, it may be time for her to go on a diet!
This can be achieved in many ways with older boats. I have listed the most common ways in the following preferential order

- Batteries - For M racing I use 68gram 6 volt AAA packs that go the same distance as the AA ones & they are much cheaper than you would think!
Feel free to contact me on where to get these.

- Fittings - Have a look at what the fast guy's are using in your class for their own deck fit-out. You may be surprised at just how heavy some of the older deck gear can get!

- Paintwork - If your boat has seen a few laps around the block & shows signs of a few facelifts, it may be time for a full strip back & birthday.
For example a single layer topcoat on an M can weigh as little as 25grams if done professionally, or as heavy as 100grams if done by the somone less experienced.

*Note: Before taking on such a task, seek out some of the more experienced members of your club for advice as this is not always
a job best started without the knowledge gained by the many before you!

Finally, make sure that your hull's surface is clean, free from blemishes & generally as smooth as possible.
To polish or not to polish ? Ask 10 people & you will get 10 different answers on that one!

2. Fin, Bulb & Rudder

Check that all 3 of these are as specified & correct to the weights provided on your design's plan. They should be 100% blemish free & wet sanded to a super smooth finish. (1500 grade Wet & Dry paper is best to finish with).
Should you wish to upgrade to a more modern/low drag fin & rudder profile many good option's are available from leading suppliers nationally.
For instance with your M, if you sail in predominantly lighter airs, you may look at a slight reduction in bulb weight used with a deeper fin to achieve the same righting moment, yet with a lighter all up weight.

Jeff Byerley (Mirage), Lincoln Mcdowell & Chris Ryan are all supplying stiff long shaped fins. see Suppliers of M parts
Modern Rudders available to the IOM class have been used many current designs for championship wins showing the benefits of new modern shapes. My own M uses an off the shelf Craig Smith designed IOM rudder with good results.
(These are available from Radio Yacht Supplies Aust) see Suppliers of M parts

*Note: Seek advice from those skippers regularly at the front end of your class as to whether the kind of investments mentioned above are suitable to your design & would show the benefits for the work undertaken.

 

3. Rigging

Make sure that your rigging does the job that it was intended to!
Can you obtain a nice tight forestay whilst the trailing edge of your masts bend does not exceed the luff curve cut into your mainsail?
If not, may I suggest you contact some of the frontrunners in the class to discuss what they are doing to achieve the required tensions that best suit the M. Ask many questions of both the leading skippers & their suppliers of equipment as contrary to a recent article written, these skippers in our sport are happy offer their time & knowledge on a regular basis.

Ensure that your rig is not too heavy or over rigged as weight aloft & added windage are slower than the weed that drags from your fins!!

As a guide I have added some maximum weights that should not be exceeded if possible.
M A Rig (Swing)360grams Std 330g

Make sure that all stay wires are swaged evenly allowing generous adjustment with the turnbuckles if these are used.
Use dyneema/Spectra cordage as this does not absorb moisture, stretches minimally & has the least friction through sheeting eyes.

I highly recommend that you discuss with your sailmaker what type of rig construction best suits your boat before you invest in new Sails & rigging

 

4. Sails

I have left Sails to last on purpose!
A common perception out there is that your sails are the engine for your boat.
Whilst partly true, adding a nice new suit of sails to a boat that is not fully prepared or optimised to its potential, will only make minimal change to its performance.
On average, most sails should be replaced at approximately 2 years depending on the work the particular sail has done.
i.e. A 36 micron lightweight film jib will need replacing much sooner than a C2 jib that rarely see's the light of day!

In Australia we currently have numerous sailmakers in Radio Yachting making top quality sails, reflecting the growth that our sport has achieved in the last 10 or so years. Many skippers are also making themselves some great home made sails. If you have the time, give it a try!
My advice to skippers seeking to purchase sails, would be to do your homework before you place your order. Check out who is winning/consistently performing at the front end of your class both nationally & at state level.
Your decision should not only be based on the initial purchase price, as the backup service & knowledge passed on by the good sailmakers can more than make up for the added expense.

In the next edition I aim to discuss building of carbon rigs

Cheers
BG
*The above was taken from an upcoming Radio Waves article