Footy & Box Tolerances

I did a quick search and did not find any discussion on this subject. If there is one, this thread can be moved to there or deleted.

Why tolerances? An engineer designs products (“The Footy”) with tolerences that can be built by the machinery in the factory (our garages ad kitchens). If the factory cannot build to the tolerances specified, then more precise equipment is needed or the investment is not made and the project is dropped. If the project goes forward, gauges (“The Box”) are specified and used to check parts to see if parts are accepted or rejected (“Footy Measurement at Regatta”).

How does this relate to the Footy & the box. I constructed a 3/8" plexiglass box and used great care in constructing it, but it is not precisely (say even within 0.001") as specified in the Footy Rules. Even the 6" width is not exactly 153 mm) Now comes a Regatta and a V-12 bow sprit would not fit in the slot even when it was tried from outside the box to eliminate alignment issues. The diameter was just to big. Now, my calculations are that 6.3 mm = 0.248", so I used a 1/4" drill bit (0.250’) as a guage to check the slot when making it and there were a few 0.001 slop, so the sprit should have fit. Was it too much varnish or expanded from humidity or what? Should the boat be rejected? I think not, but it would not fit in the box. What to say or do as this was our 1st hosted regatta?

Now think about the hundreds of Footy factories around the globe, places like yours and my shed. What tolerences can be expected from us in our building process and how do these tolerence stack up in a final build. And, what are the tolerences of a box to check any Footy from any factory? And what freedom does a measurer have when checking a Footy?

I have 2 stiff steel 1 foot rulers and they are not the same length which got me checking 6 others. You are right, there are differences.

I guess enough said for now as I wait to see if this is already a settled matter or the discussion continues.

Hi Frank;

as a professional marine surveyor I can reassure you that even on real boats there are allowances on main dimensions meausurements.

Just to make an example , there is an european standard ( iso 8666 ) for pleasure boats under 24 m where an allowance on linear dimensions of 1% has been considered.

Even on one-design yachts rules , there are measurement allowances for small builder’s mistakes, not perfect measuring tapes, and even size change due to temperature and humidity.

My opinion :
as far as possible a deviation to “perfect” rule requirements can be accepted provided that this is not an obvious performance booster.

I feel that an increase of bowsprit diameter of 1/100 of inch will not improve model speed… isn’it ?

( as alternative option we will fund the building of a perfect platinum footy box to be used a world reference :wink: )


Hi Flavio

When you host a regata and can’t fit a boat in a box and let sail, is it fair to legal skippers to allow it? If it was due to your box being slightly under size, how would you feel?

I still feel the rules need to address the spec tolerances so Joe blow can build a boat at home w/ simple tools. With bow & stern projections, missalignment alone can be a problem fitting thru slots. For example, extend all box dimensions by 1/8" and the boat must fit. So slots are 3/8" wide and 1 foot = 12 and 1/8". If a boat then doesn’t fit, sorry Charlie :frowning:

I thought the point of Footies was to have some fun not to get bogged down in endless discusions of the rules. Most boats are home built and slight deveation in tolerences are inevitable Surely all that is required is a bit of common sense by the oficial in charge and an aceptance that the point of this class was to give buliders a degree of freadom from the rigidity of other classes. Bob

I have heard of a seriously dodgy box out there once Frank but that is something an organiser had control of and shouldn’t have let happen. From the builders point of view I would suggest the tolerences be taken care of on the boat, just in case. This is the reason a Kittiwake is 11 7/8" long with a 3/16" bowsprit, there is just no point building VERY close and being disappointed in my opinion and can you imagine the trouble I would have if my designs didn’t fit!

I know zero tolerence is impossible to build to but I think the box should be as close as possible otherwise we really will come up against different boxes at different events.

Plus as Bob and Flavio say have some wiggle room when it comes to the likely performance advantage. I do see the predicament though with a bowsprit which doesn’t fit because it then becomes very difficult to check anything else. :scared:


Hi Frank,
While I haven’t seen your box, or had the opportunity to measure it, judging from the pictures I have seen of your boat, I’d say that the level of craftsmanship shown is probably higher than most, and that your box probably isn’t off it’s dimensions by that much. I would also say that even a bowsprit as large as 5/16" or 3/8" isn’t likely to have much advantage over one that is exactly .248" in diameter (unless it is being used as a ramming device!). After all, since the rules do approve a boat placed diagonally in the box, which allows a significantly longer hull, how can we quibble about a few thousandths of an inch in spar diameter? These things are all built by different people in different places using different measuring equipment, so there are bound to be slight dimensional differences built in to each one. However, any OBVIOUS attempt to use such differences to gain unfair advantage over others, should be frowned upon by the race director. It kind of brings a new appreciation for things like modern day jet liners (and the International Space Station) where individual components are brought together from all over the world and they actually FIT together!

Bill Nielsen
Oakland Park, FL USA

I agree with ya Graham. I’m gonna make sure mine hulls are a wee bit smaller.

As one of you said, the V-12 would not fit into the box at all because of the bow sprit. And yes, I was not able to measure it. The builder also seemed to have the sprits out of alignment. So, I like the build them a little smaller and they must fit. The home builder needs to have a box that is close to the rules to guage his progress.

Having just faced this issue for the first time, I thank all for the comments and will just have to roll with the punches when we measure.

By the way, I am sending Butch at the Sand Point Club in Titusville a copy of yesterdays Footy Regatta showing a picture of the winning boat that has room to spare in the box.

The point about box tolerance is an item of interest and has the potential to spoil someones perfectly good day. Some of the above replies deal with the problem quite directly. Make the boat a tad smaller.

In the bow sprit instance, it seems to me that an Xacto knife, or other tool up to and including a hammer, could have solved the problem. Especially so if one might have traveled a long distance to sail in a meet. Better to sail the slightly marred little beauty than not to sail at all.

Would you favour a tolerance on the boat or the Box? I’d go for the box, with a 1% or 2% allowance on dimensions.

The thing is that because the thing ( and the boats) are relatively small, we just need to be honest about building it all.

Hi Tomohawk

I like your comments and thinking.

The original idea is that it “had” to fit in the box which it should and along comes a V-12 that didn’t and not all boxes are equal. I couldn’t say you can’t sail which puts pressure on the hosting club as I knew he wasn’t trying to pull a fast one. Hopefully this discussion will get the builders to use more caution and it should fit in the box.

I bring my own box to the Regattas as an insurance policy. I know auto and electronics companies have specs and parts that are not in range are rejected.

Let’s let this ramble a little more and get some good group think going from those that dealt with specs thru life & then have Angus
say five words that settles it.

… and keep the discussion positive and friendly.

PS. Two more residents in Tanglewood signed up to build Footys today and we expect a lot more. Not bad since I showed up on Nov 3rd w/one Footy, we are sailing 5 now on Mondays & will have 10 by xmas. We have 1200 homes to draw skippers from, so expect a lot of Footy news from here. We are now thinking about early Friday evening fun sails using wine & cheeze snacks with wives to get them sailing. Last year it was baloons tied across the pond with pins taped to bows. Join us for some fun sailing.

I’m just not sure of what kind of % (plus side only) tolerance to use for making the box? If you go with 1% then the measurement box would be 155 x 308mm and if it was 2% then you get 156 x 311mm

You see the point? You could also use simple mm but the Footy is so small 2mm would be like 60cm on a 10m long boat! It seems like % would work better.

Aside from that, you’ve only got to worry about workmanship. One builder might be a professional modelmaker or cabinetmaker, so his box would have perfectly square corners and such. Others might be lucky if they get all 5 sides to stay together! Not to mention what the box is built of, like cheap flooring plywood or plexi or fine cabinet ply.

A thought about the slot…
Is there a requirment on how to cut the slot? It can be cut with straight sides or angled sides. In the picture below, the slots have the same width but it can be seen how an angled spar would fit through one slot and not the other. It depends on the material used to build the box. the thin-wallled material is preferred or the angled slot cut


After having the problem w/sprit alignment, I also had the thought of angled slots, but it would not have helped the V-12 in question as the combination of my box tolerences and boat tolerences had it off centered.

The 5 box pieces of 3/8" plexiglass were cut by a plastics supplier in Michigan using an 80 tooth carbide blade yielding smooth cuts. Five threaded screws form each joint and yes, the box is ridgid. I used a band saw for the slots and a magnifying hood to follow the lines closely.

I will be bringing it to the FFF II regatta in Orlando this Saturday and looking forward to learn from their I have been racing a Footy for less than 1 month.

By the way, the 5 pcs cut to size cost only $15 which I thought was fair.When ordered, I did not have a spec, so I said just cut as accurate as possible and it is not as good as I would like

Is this the same plexi measuring box that is pictured in the Special Footy issue (#152) of the AMYA magazine?

Bill Nielsen
Oakland Park, FL USA

No, but seeing the box in the AMYA magazine gave me the idea as a dark box made it difficult to see keel, ballast and rudder position. I use a 6" x 12" rectabgular piece of white melamine with two 4" x 6" pieces of same on one corner. This is handy when designing ASymetrical Sterns as everything is open and easy to work on.

When I get on a PC, I can do a photo.

Here are photos of the my latest hull in development in the plexi box and the open fixture I use for some of the work. My fixture in Michigan is the white melamine and here in Florida, I am using some scrap wood from the Tanglewood Workshop.


In all this esoteric chat about box and hull tolerances I have just noticed your photo of your hull in its box.

With the hull seemingly going diagonally from top to bottom will you not be compromising fin length for waterline length ?

Also, don’t forget Rule B.1 which requires the sail rigs to be able to move through their full range of motion with the boat in the box.

What about the rudder too ? The photo shows the deck level at the stern being below the slot which is already 200 mm from the top of the box. This only leaves 305 mm - 200 mm - freeboard at the transom for a rudder depth.



Hi First Footy

I removed the sail and spun the rig of my first boat using the same design principle and it coasted for about 20 seconds clearing the box by 1/2" on all 4sides. I took a video with my phone, but it is not campatible to post here. Darn!

The basic design of the hull is a Brett McCormack B-2 and is my first boat and actually sat higher in the box than Brett’s due to the ASymetrical Stern.

This first boat “Half @$$” finished the July Jaunt and Jostle in position 10 before completed and had a deck of blue masking tape and regular batteries. It won the Vero Beach FFF II a couple of weeks ago and finished 2nd at the Tanglewood MYC #264 club this Monday. It has only been racing against other boats for a total of 3 weeks and heads to the Orlando FFF II this coming Saturday. My first Footy, a Razor has never been raced and probably won’t be. so this Footy racing is quite new to me.

The new boat will sit in the box closer to Brett’s original design. So it’s not perfect, but so far I am kind of enjoying it.