Another Marblehead is born

Well, I finally finished my Monarch Marblehead, and she’s a beauty.

(I hope these photos come thru, since I’m cross posting from RCGroups)

I maiden-ed it for the Arizona State Championship Marblehead Regatta. I ended up in 2nd place!

If you want to see the build, go over to Monarch Marblehead Build Sorry it’s on another site, but I’m comfortable there.

Very , very , very nice, so much that it will give me the desire to make one wood model myself
Thank you

I am still stunned at how well it sailed, for a wooden boat. I was passing many a composite hull on many tacks. Especially after people telling me that the wooden hull can’t be competitive.

I still want to re-do the booms to make the out hauls more adjustable. I followed the plans and they are just 3 positions. I just don’t want to use the ‘two strings’ method. I have them on my other boats, and I can’t stand them. Adjust one string, then you have to fiddle with the other, then back to the first, rinse and repeat forever.

The only sad part is, I was told that this was probably the first Marblehead build in my area in the last 20 years :sad:

HI Guzz,
btw, do you renember the hull weight ?

Taking it to the bathroom scale, as is, but without the battery and no fin/bulb, it’s around 1 lb (.45 kg). I never did weigh it empty and stripped clean. I was trying to get it ready for the regattas.

With the fin/bulb, battery its around 7.5 lbs (3.4 kg). Add another .5 lb (.23kg) for the sails (aluminum mast, wooden spars)? So an all up weight of around 8 lbs (3.6 kg).

Thank you Guzz ,
therefore playing with the numbers I assume the following weight distribution :
3600g for the full boat against the 4250/4300g of a classical Class M with a bulb of 3000/3200g
Assumed single weights :

  • Fin …140 g ?

  • Battery … 65 g

  • Rig …230 g

  • Winch … 65 g

  • Servo …20 g

  • Receiver…15 g

  • Supports …100 g ?

  • Hull + Deck …260 g including painting and lamination ?

  • Total …895 g

  • as consequence 3600 g - 895g = 2705 g for the bulb alone offering a ratio of 2705 / 3600 = 75% that is very good !

Is this a correct assumpion or there are some mis interpretations ?

My first conclusion is that the boat is very light compared with the composite type models and is encouragging me to try the pear tree fineer laminated between two layers of epoxy glas for the class like the AC100.

Thanks for your comments


Hi Guzz -

first let me extend congratulations and envy for such a wonderful build. Obviously I enjoy the beauty of clear finsihed wood, and the boat you have built is a great example of both craftsmanship and beauty. The fact it was a second place finisher first day out is a bonus.

Having seen your photos, I think that they may inspire other woodworkers to consider the boat, and along with it, a possible renewed interest in the class. I currently have 3 projects I need to finsih and will give a build an honest consideration. Like Claudio, I think a veneer on stringers, with a layer of glass for strength would provide a lightweight, relatively inexpensive entry into this old, but famous class.

Again - well done and thanks for sharing the photos and the build log.

Best wishes for a continued great performance season.



Don’t get to detailed with my numbers. They are really rough estimates, as my bathroom scale is over 43 years old, and is analog. Meaning I have to guess at anything between whole pounds (then convert to kg), and I’m not to sure how accurate the scale is in the first place.

I know that the hull isn’t that light, but it’s acceptable. A true CF hull would easily weigh less than my hull. But I don’t think it makes that much of a difference, and that I think composite materials are sometimes overkill for certain situations. I think shape, surface area, and sails are more important, in this class (small size classes is something else).

Now I accept that I made my fin out of CF. And that is a good spot for CF. It needs to be light weight, strong, and stiff. Other materials just wouldn’t work out.

Making my rudder out of CF… Now that was overkill in my book. But I was using the rudder to learn how to vacuum bag. I could have easily just used foam and glass and gotten an acceptable rudder of proper strength and acceptable weight.

As for a hull. It is something that needs to keep it’s shape, and be light. But CF is overkill. Kevlar/Amrid is to flexible. Glass and or wood are stiff and light enough for the job.


I didn’t think about stringers/veneer for construction. Now that’s an idea. I chose Paulonia wood because of the claims that it has a higher strength to weight ratio than balsa. I can now attest to that. Granted it weighs more than contest grade balsa (it’s closer to ‘heavy’ balsa, like from Midwest). But since it is stronger you can use smaller dimensions, so it comes out as a wash. But I loved working with it.

One thing, I kept being told to be careful when sanding the wood, because it’s easy to sand through it. But they were talking about balsa hulls. With Paulonia wood, I got tired of sanding, and I wasn’t anywhere near to “sanding through”. Awesome wood, but a royal pain to get a hold of.

Personally, after doing this build, I should have spent more time in the sails. That’s your engine. Without it, your boat’s going no where, which is why I think the Skapel out did everyone. The ‘engine’ on the Skapel is incredible for it’s tune-ablity (although it sucks in light air). I but you could take the Skapel sails, put it on the boat I just built, it would keep up easily with a Skapel in heavy air.

But the hull is what everyone looks at. Just like a car. Looking a Lamborghini it looks fast. But the engine is what makes it fast. The body helps, not just as much.

I always think of a guy I knew in college. He had an OLD Triumph TR4 that he use to drive around in. Looking at it you wouldn’t think much of it, small, cute, and quaint. But the man put a Corvette V8 engine in it!!! With a really quiet muffler. Talk about a sleeper! We literally broke the seats one time when he stomped on it from a traffic light, it pushed that hard back into the seats. But it was the engine that made it fast.

So, if we could come up with a better engine for the M class, that wasn’t that expensive, or to complex… That would would be awesome!

The scalpel does have a very good rig and nice rotating spars. I have weighted one and it came in about 9 lbs with the 6lb keel. It has been a few years, so I am going from memory. My Viper was 750g hull, rudder, radio stuff. With an IOM bulb ~2500g + fin and then about 1/2 lb for the rig it came it right at 8 lbs. One of the lightest boats that I ever measured. Hull was kevlar and about 10 to 12 oz with rails and keel trunk installed.

Balsa/glass can be light but from building star 45’s (6 of them in wood) I dont think I could get as light as a good vac bagged carbon hull. Then again in the stars, the last 4 nationals have been won by boats a minimum of 1 lb over minimum weight.

Guzz - just a reference photo of my current RG65 build using stringers and veneer. The photo shows a raised foredeck, but not sure I like the looks after adding veneer panels. Since the RG class is 1/2 Marblehead, I am giving thought to blowing up a set of lines to 50 inches and see how it sails.

Anyway - this was my starting point before adding veneer

Several years ago my first Marblehead model, Studio1, wasbuilt with two cross layers of maogany fineer.
The finished hull was very heavy , by memory around 700g , I have to check again tomorrow.
The finished surface was just polyurethane dual component paint inside and outside.
I launch the boat once ready, was e very nice looking but to heavy to be a good competitor.
Couple a weeks later I obseved that few strips were deformed. Obviously the relative humidity of some days before was the origin of the problem.
I never touched again , is just sitting in one corner of my studio/lab.
Lesson learn : the paint alone is not a good barrier to humidity.
I learn also later that the problem would had not occurred if the wood was trap in between two layers of FBG.
Here some pics of that time :

Today with the view of Guzz beauty , gave me the envy, like Dick, to start up again first with a new AC100 and eventually later with the Fuxia M.


There’s a very good series of articles about building a plank on frame M on I’m guessing that Earl is the author.

2 lbs even. Fin, 10 oz. (counts toward ballast). Rig, 1 lb. 6 oz. Lead, 14 1/2 lbs. The modern version carries 1 lb. more lead than the 1949 original.
was the best weight for a vane free sailing version.
I should have read the articles before trying to build my half-sized RG65 version based on drawings mentioned in :dunce:

You guys are really obsessed with weight, aren’t ya? :stuck_out_tongue:

Tell you what, after next weekends regatta (Lost Dutchman Gold Cup), I will strip her down and start weighing everything and report back.

I want to make a new rudder anyway. When I was laying out the rudder I transposed the last two digits of a dimension, which increased the rudder size. I didn’t notice it, till someone pointed out that rudder looked big, and I went back to my notes and compared things. Yep, to big.

But I have to admit, the larger rudder has been working. Yesterday was a really windy day, 15-25 mph (24-40kph) and I never lost rudder authority, even when it bowed under to the mast once (I only have an A rig, btw. So it was really interesting, I had to call it quits when lines started breaking)

Hi Guzz,
personally I’m not too much obssesed by the weight until certain limits , the point is that when I start drawing a new plan I need to know the weight of each element in order to define the hull displacement .

The rudder: according to my knoledge, the efficiency of a rudder is proportional to the profile and the form.
The lift is fonction of speed and angle of attack.
Fast boats need smaller rudders compared to slow boats.
Large rudder increase wet surface.
Generally rudders use thick profiles to prevent stall when moved angularly over 15°


You know, that comment has made me giggle every time I read it, because it’s repeated in so many places. Do you know how fat a foil has to be to not stall at 15 degrees? Airfoil GEO 460 stalls at 13.5°, and personally I would never use it, anywhere on a boat.

Also, when you run the simulations at the Re we run at, and the surface area we use, the amount of lift generated is really, really, really small. Also, it’s really, really hard to get them to stall, or separate the boundary layer at the speeds we run.

Personally, I would look at foils with the the least amount of drag (i.e. really thin foils). If you want to have fun, go over to the Airfoil Investigation Database and start searching and comparing various airfoils. If you want symmetrical foils set the camber fields to 0.0 to 0.1 on the search page (there’s a slight bug in the search engine, just ignore any foil that has a camber of 0.1). Then sort the columns as desired.

all very nice, but my understanding is that in class M or similar the profile thickness for the fin between 6 and 8% and for the rudder between 10 and 12%

Graham Bantock has gone to 6% t/c rudders for the M class (actually for all classes from it looks like). I’m currently using S9033 (7.5%) foil for my rudder. Except for making it a bit big, it’s doing well.

Since I’m not an expert in the matter I follows what others modelers suggest for fin and rudder profiles. This is also written in some manuals I was reading many years ago.
When I read on various papers about stall published by Wikipedia I see often that stall will occur for most of the profiles around 15°-16°.
Following my readings a Naca 0006 will exibit a stall around 5° according to the polar graphs .
I found also this interesting paper :


I agree with Caudio that a thicker rudder section help with the stall. On the first stars that I built I did a really thin rudder (two 1/32 skins taped together around a 1/8 shaft), a 1/8 thick balsa rudder and a CPM/skiddo rudder. While they all worked well in the light air, when the wind got up into the 15+ range the thin rudder would quickly get overpowered and would stall. I now use a 9% NACA foil and it has much better performance in those condition. The rudder does not have to be a barn door since it doesnt stall. I personally think 6% is too thin for most people. I am sure the really good skippers can get away with it and are willing to trade a bit of stall performance for better light air speed. I am just not that good.

Guzz congrats … you did a great job on the boat… I did mine last year and was having alot of fun…
with guys like us… we might get the class going again… I dont want to hijack this thread so i will just post one pic of my marblehead

the wood though does look realy nice… I had to paint mine… I am not that good of a planker… so with paint… you dont see the mistakes…:slight_smile:
Btw … who did your sails? I have to make a set for myself when i get down to racing