Semiscale Footy Catboat

Footy Class General Discussion (Footy)
21

Flavio,

Nice boat, fast work and good applied science:D

BUT

What I want to know is - what colour is the dog that must sit in the well area of the cabin?
I am also working on the concept of a holographic projected helmsman - so that he (or she) does not violate the box-top rule, but is (virtually) there like Graham’s gentleman sailor on Pintail.

Being (slightly) more serious - when sailing downwind the Gaff rig is all that you say - but a cat rig is more off-the-boat-centre than many other rigs (since the pivot point is at the LE of the sail).
This would (it seems to me) require a little constant rudder to counter the turning pressure of the sail - so if the wind was flukey - and the pilot too slow there might be a tendency to luff up in calm moments, or zig-zag at the best.
Not a problem (I zig-zag anyway) but the cat rig seems the least balanced of all the common types. Can I move the mast back and have a whopping bowsprit and 3 jibs, please?:smiley:

andrew

22

Andrew,

I can understand that you are seriously concerned with the well known problem of “helmsman head box rule compliance”.

Anyway, I can reassure you that according supreme court of New York state, a wooden head can be considered as a “spar” and strictly speaking is allowed to be above top of the box.

Zig zagging is fun.
Straight lines are boring, and not so good even from tactical point of view ( both combat and regatta ).

I strongly advise to zig zag both downwind as well upwind ( it seems that this way boats are able to go almost against the prevailing wind direction )

Seriously speaking, our technical dept. is currently undergoing the final evaluation of a modified stern detail to improve coursekeeping and at same time fto be " hystorical correct" for this kind of boats

more next time …

flavio

23

Building is under progress :

During lthese days I have added a keel case and a watertight mast box.

Bottom plating has been glued yesterday evening, and during next days I hope to be able to finish the hull.

One or two interesting things :

topsides panels have straight line cuts… funny isn’t it ?

easier to plot
easier to cut
easier to add chine and deck stringers

last but not least, years ago I have discovered - by chance - that this is a nice way to obtain beautifully faired fair 3-dimensional curves

+++

As I have already mentioned to Andrew, I have been thinking about a modified stern detail to improve course keeping and steering control.

Adding an outer keel on the transom, will help to have :

  • an almost vertical rotation line for the rudder
  • rudder area moved about 10 mm aft, increasing blade area efficiency
  • a small shift to the stern of center of lateral plan

this detail ( shown below on “pequod” a non footy model ) is in compliance to box rule ( outer keel will fit inside stern slot ) and has been succesfully tested by Bill Hagerup on his Cobra.

And it is also hystorically correct due to the fact that has been widely used on old american sharpies.

have a fair wind :slight_smile:

Flavio

24

Gorgeous, Flavio! I love the little details on the pequod. Presumably the other pictures are construction photos of your little Brando?

-Rick

25

Hi Rick,

yes you are right, 3 pictures on my previous post are showing Brando’s hull, only one of them is about Pequod.

News :

hull shell has been finished, during next week end I am looking to add deck and other “semiscale” details : gunwales, rubstrakes, skeg and so on.

Hull budget, seems to be promising :

  • FCU ( footy control unit ) is 195 gr, using worst case scenario ( heavy batteries, heavy receiver )
  • Hull is now around 40 gr, when finished it should be 55-60 gr
  • Final displacement, most probably, will be within the planned range ( 450 - 500 gr )

small details have been modified here and there :

  • shorter deckhouse
  • larger rudder
  • a cockpit well will be added both to improve appereance, as well to be used as space for antenna coiled wire
  • due to a designer’s small mistake, hull bottom panel is slighty broader than planned 100 mm ( in order to use a single panel of balsa )

FCU has been preliminary tested on board the hull to check that it will be possible to stow everything on board without problems.

Keel slot on hull bottom is now longer than needed, in order to allow small longitudinal adjstments of of keel position looking to optimize balance after sailing test.

By the way … I have not published hull panel drawing to be used for model building because I feel that it would be unfair to do that before testing this new design .

Anyway, I confirm that I will do that as soon as possible.

… stay tuned

Flavio

26

Brando is growing, and I hope to enjoy first sail during next weekend.

Building is smoothly following my very simple plans and ,as psicological booster, I am very happy to know that all boring and disgusting problems related to rc and electrical stuff have been 90% already solved using the FCU concept.

Today I would like to write few words about the aestetical aspect of this model.

Simple beauty “workboat style” is just a simple matter of careful design ( nice sheer, flared sections, twisted topsides ), half dozen of sticks here and there, and an additional sunday afternoon of pleasant work.

No special skills, no cosmic tools ( sandpaper and razorknife only ) are required.

In my mind the overall effect of these details is very impressive - see below -
The change from a naked plain shell, to something resembling a true sharpie is evident, and I like to compare it to the difference between an arial capital such as [FONT=“Arial”][SIZE=“7”]A[/SIZE] to same letter using garamond font [SIZE=“7”][SIZE=“7”]A[/SIZE][/SIZE]

Last but not least a nice deck to hull joint improve both strenght and watertighness.

Additional weight ? : between 4 and 5 gr

Flavio

Folgore ITA 5
Brando ITA 14

[/FONT]

27

Stern details modified , as planned, to improve course keeping and maneuverability.
Now connection between servo and rudder should be easier due to the fact that both rotation axis are parallel.
Arrangement has been designed to use both whipstaff method, as well the usual push-pull rod.
Push pull is easier and simpler, but whipstaff has several technical advantages.

Forefoot has been carefully shaped into a nice curve to connect stem to bottom.
Most probably this is not so important from performances point of view, but without doubt, once again this is a nice addiction to a pretty look.

A deckhouse ( or coachroof ? ) has been build together with a cockpit coaming, its sides are vertical, straight lined and at 90° angle each other to simplify building.
The roof will be removable to install/remove the FCU block.

Dimensions :
Brando has been designed and built to the limit of box rule
Max beam is 151 mm
Lenght overall is 304 mm
( 1 mm of safety margin for varnish :slight_smile: )

Weight is - so far - 64.8 gr( a well known “racing” footy built using titanium,carbon fiber, kevlar is 79 gr - empty - )
Taking in account varnish, and missing details weight, final shell mass shoud be comparable.
A good starting point to achieve “decent” sailing performances.

Things to do
varnishing
keel and rudder
spars sail and rigging
final check
sea trials

Weather forecast for next weekend are not nice, but without doubt I am currently proceeding almost in accordance to my basic previsions.
Sea trials are to be expected soon.

It would be nice to release a Mk I version of plans in order to have , I hope, at least few of these model taking part to Mystic Show Footy Race
There are no doubts about Brando compliance to the 100% wood rule :slight_smile:

Flavio

28

Yesterday evening , I have re-read all the posts of this thread ( now almost three weeks old ) .

Quoting Rick from his wish list : " I’m obviously not looking to win regattas, but rather have fun , cute little boat to play with on lake, and on the off chance that I ever make it to a footy event, be able to “compete” …

Even if I feel confident that this catboat footy will be a “decent sailer” I have been thinking about its race potential, and I have found a specific weather condition where Brando could be unbeatable.
Hull bottom is so wide and flat that Brando should be able to stay upright without ballast keel ( yes ! ) even if in this case it would be impossible to recover from a 90° capsize.

Making simple calculations it seems tha a light rc version of this footy should be able to have positive stability at 90° heel using about only 50 gr of lead ( 2 oz - more or less ) , kissing the water with a displacement between 250 and 300 gr only.
Sailing in this ultralight displacement trim , it would be possible to withstand wind up to 5 or 6 kts ( not a gale, frankly speaking ) with a sail area to displacement ratio 150% higher than usual , and - in turn - an impressive speed both upwind as well downwind.

An interesting option ( still to be confirmed on the water ! ) for very very light weather race zones ( Italy or Florida … )

Definetely not suited for the Bikenhead 30 kts scale storms…

See enclosed computer screen shots : transom stern is high on waterline, and forefoot also is above static waterlevel.

One thing more to be tested during sea trials :slight_smile:

Flavio

29

Due to very bad weather forecast for next sunday, designer, builder and skipper have agreed to postpone Brando delivery and sea trials.
Most probably they would be happy to have only static flotation test to be carried out during weekend, in my bathroom facilities.
Anyway even if building activities are a bit more relaxed, other small details have been added here an there.

I hope it would not be too much out of topic to spend few words about raw balsa

In the past I have experienced a very uncomfortable feeling discovering that, notwistanding my careful attention, few of my model hull were unbelivably twisted .
Now, due to improved technology as well a deep experimental research, I have been able to have a better understanding of this mystery

1 - balsa specific gravity is very very very variable
I have found on different planks 1000 mm x 100 mm x 1.5 mm weights from 16-18 gr up to 40-42 gr
In other words specific density change from about 100 kg/m3 up to over 250 kg/m3

2 - wood stiffness is almost exactly related to specific density

3 - wood properties for balsa wood are different within the same plank too ( !!! )

Example

I have cut first topside panel of Brando from a good, smooth and dry plank , from a good manifacturer ( Graupner ) : Its average density was about 200 kg/m3

  • first topside : 4.1 gr ( good )
  • second cut : 7.3 gr ( ! ) due to so large discrepancy I have cut a third topside
    [FONT=“Book Antiqua”]- third cut : 5.6 gr intermediate value
    Using advanced methods ( two books, and two calibrated banana yoghurt pots ) I have done a test to check different bending of these topsides and result are very impressive - see below -

Deflection were absolutely different.

Conclusions,

1 - building a model hull using very thin balsa panel, can lead to unpleasant ugly hull shapes due to unsymmetric ( port and starboard ) stiffness of various parts.

2 - problems can be avoided using a cheap digital kitchen scales, as well making preliminary simple stiffness test ( beer cans can be used instead of yoghurt for thicker balsa :slight_smile: )

Next time few words about rudder and keel ( I hope )

Flavio[/FONT]

30

I am taking advantage of a lack of real deadline to “waste” time adding more decorative details, frankly speaking, absolutely useless from technical point of view :

[i]- A detailed companionway

  • A tapered laminated tiller
  • Few additional bright coats of varnish[/i]

( by the way, varnish weight is about 5 gr each coat, decreasing from first to following layers, most probably due to initial balsa adsorbtion and progressive saturation. )

Rudder

I have built a first rudder, may be I will do another one - slighty different -after first trials.

Span is almost to the maximum of rule box ( 200 below top of the box )
Chord is about 40 mm
Thickness is 4 mm, as a compromise between low drag, and high lift

On the leading edge there is “dent” to achieve a partial balance moving rudder area closer to pintle pivot line ( and in turn to decrease torque on the servo )

Overall side area is about 15% larger than on my Folgore, to take care of the wild steering abits of catboats

The nice shaped tiller will be linked by a whipstaff to an hitec HS - 55

Blade material is poplar plywood : light, soft and inexpensive

Pintles and gudgeons are home made using brass wire

Next steps :

Rudder linkage, and keel fin blade

Flavio

ps problems to download latest pictures today , I will try again later

31

I suppose “waste” is in the eye of the beholder, especially since “pretty” was above “fast” in the list of desires ;).

I’m amazed at how quickly this little boat has gone from idea to reality, and it’s gorgeous to boot! I just hope I can do it justice when my turn to build comes around :).

Is the companionway detail the little sliding cover on the cabin?

-Rick

32

Hi rick,

yes a companionway is a sliding cover on the deckhouse roof

In this case it is a not-sliding fake version, but it nice visual effect it is in any case very impressive

Once again, this another example of a small detail that can be discarded - or not - in order to “tune” your model midway between a naked racing Cobra, or a small museum exibition footy.

Only time is needed, no special tools, not extraordinary skills.

I will do my best to provide drawings pictures and advices to do this

Flavio

ps : this evening after dinner I will attend the lauching party into my home washbasin :slight_smile:

33

Hi Flavio,

I’m really enjoying your build thread on the Catboat, and check the group frequently for your updates. It really has taken on a real personality with the addition of the rudder, cabin and companionway. However, I’m curious as to how you plan to route the mainsail sheet to assure there is no interference or snags with the edges and corners of the coaming and cabin?

Regards,
Bill Nielsen
Oakland Park, FL USA
Footy #835

34

Hi Bill,

good question !

hull design is a simple matter in comparison to “machinery” engineerining of servos and related junk.

From the start of this project I have done my best to evaluate boom swing versus servo arm rotation ,using an home made excel spreadsheet.

After an unbelivable number of unsuccesful efforts I have found an arrangement that - at least on paper - seems to work, and at same time can be stowed within a 100 mm x 100 mm space ( 4" by 4" ) .
Last but not least, pull on the line should be maximum when going upwind.

This is the planned route of the sheet :

[i]point 0, is a cleat - or something similar - to adjust the standing end of the line ( for fine tuning setting, or for slackening of rigging to remove the sail )

point 1 is the aft portside corner of deckhouse

point 2 is the moving end of servo arm

point 3 is a brass eyelet or similar

point 4 is an fish hook to the boom[/i]

may be a bit complicated, but I hope to be able to carry out “factory tests” soon in order to have a preliminary confirm that everything is ok before sea trials

I will give notice about results…

Flavio

35

Carl Cramer,

the well known editor of wooden boat magazine, seems to be very interested to our little models, and is looking to have a nice footy event during Mystic Show next June ( see relevant thread ).

I have been in touch with him, and today Carl have posted on his blog my Brando catboat AND footy class as “the boat of the week”

A kindly and promising appreciation of wooden footy activity …

Thank you Carl !

Flavio

36

Your Footy Control Unit has me a little worried— The power loss using a hole through the servo arm, through which the sheet must run, will involve considerable friction. And, as well, you show an additional two places where the sheet runs through loops where the friction will be equally high. I saw an article in the AMYA magazine a year or so back dealing with this problem, and they concluded that the frictional losses of three such sheet guides would be so great that the wind pressure would not overcome the friction. Even a small servo might not be able to do it.

37

:zbeer:That is an honor at many levels. I have been a slave to your posts. Very few people have your skills…you think it up…you put meaning to what you do and how it came to be…and you have an eye for building in details to your plans…not to mention your fantastic building skills. I too would like to be able to build such function art:D:cool:
Have you thought of any kind of power option?
Keep up the great work:D:hammer:

jim:)

38

Hi Flavio,

Using the four point sheeting system as shown in your sketch has worked well for many others with larger boats in the past, though it does impart a fair amount of extra line friction that will have to be overcome by the sail in light winds, and by the sail servo in heavier winds. The typical hi-torque micro-servo may not have enough reserve to deal with this, which would require switching to a heavier standard sized hi-torque servo. My main concern though, is with the sheet going through a fairlead in the cabin roof (which is also the main hatch). I have been considering a Sharpie (though double-ended) with a cabin (and sheeting arrangement) similar to “Brando” for well over a year now, but the main reason my project has been stalled is over the concern that the forces placed on the cabin/hatch by the sheet will loosen it, causing it to become unseated and take on water. I suppose it could be screwed in place, but I don’t like the idea of needing to remove screws to access the battery/radio compartment (besides, small screws seem to have a way of getting lost when they are removed during access periods).

Congratulations on being featured in Carl’s blog, the character of Brando is in good keeping with wooden boat magazine.

Regards,
Bill Nielsen
Oakland Park, FL USA
Footy #835

39

Like many others, I have been following this thread with great interest. Flavio deserves the gratitude of all of us for reminding us that one of the advantages of the Footy as a class is that it can be designed, developed and built with small expense of time and money. Few of us work as fast and produce such good looking results. And with properly calculated hydrodynamics as well!

I particularly like the recent drawing of the sheeting arrangements. It’s good to know that at least some naval architects are still capable of hign quality free hand sketching.

Russell

40

Yes, I know that this solution for mainsheet arrangement is not the most efficient way to control sail trimming - let’s consider it as “experimental” -

This is an attempt to fulfill my own design breif for a removable and compact “control unit”
Anyway I feel confident that this method will be satisfactory enough at least for “cruising sailing”.
Most probably somebody else will try to use a more conventional approach to reduce frictional losses, and - may be - a more competitive minded sailing

There are several points that could be discussed about servos, fairleads, and so on, but now it’s too late because this evening ( or tomorrow ) I will do a preliminary “workshop test”

In case of a main failure it will be my own fault ( this is the reason I have not yet released plans of brando ) but in any case I will be very happy to have the opportunity to share lessons learned with other footy friends

More ( good ? ) news tomorrow

Flavio

ps : to Russel - many thanks for your kindly words about my sketches, I agree with you that unfortunately free hand drawing seems to be a vanishing art.
I have improved my skills working , years ago, as illustrator for a sailing magazine ( see examples below )