n-Arrow3b build


This is a log of my attempt at Claudio’s n-Arrow design.
Dick and TArmstro are busy building an extremely narrow version with a chine down the side (V5 if I’m not mistaken)
Claudio kindly supplied this version based on the earlier Version3.
It has been modified for a higher PC for our wind conditions.

I mentioned that this build would be an attempt for me at doing a female mould, which I could then offer for any other local builders to use should they wish to attempt a first build.
Upon hearing this, he kindly adjusted the design to give a much more forgiving weight allowance and still be “in spec” for all us new builders.

So here are the files supplied by Claudio for V3b

Appendages and sail plans

Be very careful if you use the above graphic.
The sail plans are the correct dimensions, but the hull/appendage drawing is double the scale, so all dimensions need to be divided by 2.

The following PDFs are the line drawings which are 1:1.
You will need to adjust the printing scale to allow for the thickness of your chosen planking.

The following files have a common line added to the line drawings so you have a common flat point for when you print/cut your stations.

So in continuing with my idiots guide to building mini boats to encourage others to give scratch building a bash…

I planned to use 3mm balsa to plank the hull.
Therefore i need to adjust the scale when I print out the line drawings to make them smaller to accomodate the planking thickness. After much gnashing of teeth I did this and it worked (and should work for any drawings)

The given beam at the deck is 96mm.
I needed that to be 6mm shorter (3mm balsa for each side) which gives me 90mm

Take the desired beam (90mm) and divide it by the original Beam (96mm) and multiply by 100.
That gave me 93.75 which is the size I printed them out at and got the correct size when measured.

I then cut them out and glued them onto 3mm ply using my kid’s PritStick glue.
I literally used a blade and steel ruler to cut the frames out.
I cut the linear lines as accurately as possible and did rough cuts around the curved sections.
Then I just had to sand the final shape of the curved section. I used a piece of wood as a sanding block and 60grit sandpaper. I cleaned the edges quickly with 100 grit.

This is what they looked like.

I then placed them on a building board at 65mm spacing, using the centre line of the print outs to align them on the board

Its very hot and Summer…hence the swimming towel :stuck_out_tongue:

I then started planking. I shall refrain from any input as I did a horrible job with many holes.
Fortunately It’s going to be a plug so it doesn’t matter and I can use lots of body filler without worrying about weight etc.

Here are some progress shots.

And the finished hull before putting resin/epoxy inside to re-enforce the balsa planking for sanding.

And for those who are pondering a scratch build but are worried about the tools needed - here’s what i used so far (I see I omitted my balsa stripper for the planks but you can do that with a ruler/blade anyway)

I have started sanding and will begin attempting to build straight and consistant rudders and keelfins until I get a chance to get fibreglass :slight_smile:

Looks like you have a good start on your build. On the “nARROW” version, both Thomas and I found the bow to be really difficult to strip the entire length of the hull and still have a such a very narrow bow.

On mine, I wound up cutting and shaping a piece of foam, to which I glued my strips and then faired them in to the rest of the hull.

Keep going - and you should have a good plug from which to make your female mold.


I Andrew
Not bad at all, this is the first N-Arrow 3 under advance construction.

For sure : ‘narrower the Beam - narrower the Bow’

BTW please look at the drawing attached, any comments about the jib being masked partially by the deck sheer line when at 35° ?

Merry Christmas to all.


Hello gents :slight_smile:

When I got the hull planked I giggled to myself when I tried to imagine fitting the electronics in your V5 skinny ones.
It must be sooooo tight.

WRT the 35 degree issue - I’m no physicist but my logic would say this…

If the wind is coming at such an oblique angle then yes I assume will mess with the flow.
But then all boats will have a similar handicap unless designed to address this issue specifically.
I can imagine the “cut away” sections of the v5 would help aid this issue.
But then you could always sail a slightly different angle to avoid it?

Those are uneducated comments btw :slight_smile:

I had a sudden thought,

If the wind hits the hull it will be diverted up and cause turbulence of the wind layer( not sure of the correct term) above it, which would cause a swirl into the jib? I spend hours watching the flow in my fish tank and wherever there’s a diversion in laminar flow you get that vortex that curls around the obstruction. It’s quite a chaotic flow but it definitely curls back in after the obstruction.

During planning phase, I had corresponded with Claudio about turning the winch on it’s side and allowing the arm to travel vertically. Still limited by height of deck from bottom of keel, I could substitute a drum for an arm winch, I suppose. I just the speeds available with arm winches compared to drum winches (i.e. drum speed = money) More decisions will soon be needed, once I get the exterior of the hull cleaned up from the sandpaper sterate contamination. Photo attached is the normal winch I have used on all of my RG65’s (Hitec HS-645-MG) You are correct, however ---- very tight spaces - but once the templates are removed there is a bit more room fore and aft. The sides however aren’t going to change any.

Merry Christmas and Happy New Year to All !!!

I’ve been filling and sanding before glassing the plug as practice using body filler.
I suddenly thought I should measure the width at the station on the line drawing with the 96mm dimension.
It’s currently at 97mm and I still need to add the glass so I think I’ll sand some more to get it slightly closer to spec to allow for the glass. I have quite a bit of the balsa left so it shouldn’t be an issue.

I’m off camping so I’ll take the opportunity to wish you all a"Happy New Year!!"
Chat in 2016 :slight_smile:

Happy NEW YEAR !

I’d suggest that if you would like to install a lever arm system, even though space is rather tight , it is very feasible.
I have installed lever arm systems in my SliM and SliM2 Footys and can manage to acheive an effective arm length of about 50mm (from center of servo to sheet take-off loop). The key is to offset the servo to the point where it is very nearly touching the hull on one side to achieve sufficient clearence for the arm swing on the other side.
I have also used lever arm systems in my RG65s where, although my narrowest beam is a rather wide 110mm by todays standards, there is plenty of room to spare without the need to offset the servo much beyond the centerline.
If you’re interested, I’m happy to post some pictures, however, …
I’ve been locked out of this forum for about a year and have discovered a few friends have also been locked out but none of us are aware that we’ve contravined any regulations!
The only reason I’m accessing the forum right now is that I’m on holiday and, on the off chance, having logged in on a different computer I dicover that I can gain access!
Regards to all

Phil, please collect and send me the IP addresses of all involved, plus their screen name and current email address. I will try to see if I can access and off-set any blocks. It "might require changes to name but will do what I can as an administrator - but know that I don’t have “owner’s right”.

Blocking in the past was done by IP address so if I can find them, it is the easiest way for me to do resets.

Dick. Send all info to: Formula48[at]comcast[dot]net

Hi Phil
I appreciate your message, but the servos affair related to this design was already treated at the begin of the design of RG65 n/Arrow presentation as recalled in attachment link with both type of servo, Winch and Arm
see: http://www.rcsailing.net/forum1/showthread.php?7901-quot-nARROW-quot-starting-construction/page6

And a happy new year to you too :slight_smile:
I just got back from camping in sweltering heat so I need to catch up on the discussion :slight_smile:

Hi Claudio, and Bonne et heureuse annee 2016.

this is a good point and a lot of the new IOM design have a raised deck not only to help the boat come out of a nose dive quicker but also to bring those air flows naturally on the jib. as they follow the deck and end up on the foot of the jib. Not sure this is allowed in RG tought.

So a raised deck it shall have! There is the side profile in the one set of drawings.
Does anyone have input on the radius/angle for the raised bits?

Sanding is almost done and I just need to fill one or two spots and then do the final finishing for the mould.
My brother is going to build the mould with me. He is a commercial model maker by trade so it will be nice to help him and watch/ learn. This will also allow me to blame him for any issues :stuck_out_tongue:

I’m going to attempt the keelfin/rudder with either an NACA 0006 shape. Should be an amusing undertaking that will quite possibly be replaced by the skin method used. It’s more for me to say I attempted a foil than anything else.

Starting to be nice and smooth.
I worked out that a 0006 profile will be 3mm at the top of the fin so I think I’ll try for a 009 which gives me 4.5 thickness which seems more do-able.

Any comments will be appreciated

Hi, apparently the bow is still relatively large enough.
3 mm stain-steel rod should be OK.
Picture rezised

For my own nARROW build, I was fooling with the keel and bulb and found that I could purchase a commercial unit for far less than the time/effort to build a keel, and bulb mold, and then pour for the bulb. After looking, and considering, I proceeded to purchase a keel fin and bulb originally designed for the Dragon Force 65 (plastic) boat that is such a hit. As I recall, the entire unit (bulb and fin) came to less than $40.00 (US) and was very close to the dimensions and suggested weight originally provided by Claudio. He was looking for a bulb weight of 675 gr. and my purchased bulb came in at 557.9 gr. This is a bit less weight than his suggestions, but the keel blade is aluminum - not carbon/foam, and while I haven’t weighed it, I think it may compensate for the bulb weight difference. Also the length of the replacement keel is also very close to Claudio’s suggestions, so that is what I will be using. Photo is of my nARROW during construction, but prior to exterior hull epoxy.

Just a possible alternative for a reasonable cost.

Cheers, Dick

Thank you Dick,

Unfortunately our exchange rate has decided to kill any idea of buying anything based abroad. We went from about 10:1 to 16:1 in the last six months:(
Shipping etc. will make it even more exhorbitant as I would have to use a courier to ensure it actually arrives at my doorstep as opposed to getting “lost” in our postal system.
I will however do a search for a local reseller of the DragonForce and see if anything comes up.


Here are bulb plans using the BulbCalculater and Claudio’s dimensions.
It seems to be the closest match to his weights and dimensions, and I got the lowest wetted surface with that foil shape.
I am attaching both the txt file for people to punch in themselves or the pdf it plotted out to use the lead films.

I am thoroughly enjoying learning all this stuff and becoming very aware of how many brilliant people there are out there. That “little” app is sheer genius. Much respect to the programmer.