razor build - water line / fin angle

Footy Class General Discussion (Footy)
1

OK, so i have the keel fin all sanded & such, and a slot in the hull for it. It then orccured to me… At what angle should the fin be at? In regards to the water line / deck line / mast…

I assume the fin leading edge & mast should be parallel.
I assume the water line & deck line (top of the deck) are not parallel (but very close to it!)

I’m assuming the top of the transom is below the bow point by about 1/2" - 3/4". (If I were to invert the hull, and place a 1/2" block under the transom, the fin would then be 90° vertical…)

Oh, and the hull has a slight twist in it. I’m assuming the 1/32 balsa induced this twist when gluing. And that the deck, once fitted will remove said twist…

2

Good luck fixing the twist. It teaches you to slow down while assembling, to check it occasionally and get it right in the beginning instead of trying to fix it. You might just try the ‘chiropractic way’ (twisting it back into alignment) and one more cross-brace to hold it that way.

The orientation of the keel is up to you. Obviously it should be plumb, and square to the waterline (viewed from aft,) and in-line with the mast (viewed from aft) but the leading edge angle depends on the way the keel was made. It also affects the CLR (along with the rudder) and rig placement, so think ahead.

See if you can find some photos or other posts here somewhere, or you’ll have to just try it and see; that’s the fun of it! :smiley: It’s a real dud, you can build another hull (sans twist) and attach the the keel differently.

3

Razor’s waterline was designed to be at the lowest point of the stem and the lowest points of the outer stern corners.

Be sure to position your fin so that the center of gravity for the ballast bulb ends up where it needs to be to float the hull on the three corners of her waterline.

There’s tons of Razor pics around, so you can see that people have lots of ideas about fin and rudder shapes, etc, so you can get creative. They all seem to work reasonably well.

Hope you are having fun and learning as you go, too. It all gets easier with practice…so build lots of Footys!

Bill H

4

Lowest point on the stem… Not sure I follow you on that…

lowest point of where the two lower ‘plates’ join in the middle / center? That woud put it at about the LE of the fin… (so, it’s bow it w-a-ay up out of teh water?)

The photos of Bill’s original (plans site) and a few photos have the deck at almost 0° incline, or about 20° incline (bow above stern)

I figured I would just position the reciever & batteries where needed to float on this line…

5

Sorry Dr, I used design jargon. The stem is the vertical line at the bow. The waterline goes from the point at the bottom of the bow to the point at the outer bottom of stern. The point at the middle bottom of the stern is submerged.

I’m the Bill who designed Razor :wink:

Hope that helps…Bill H

6

Cheers! thanks Bill!!

Yes, I know what you mean now! Yeah design jargon… hehe…

I’ve built numerous planes, and too many rockets to keep count! I’ve dealt with my wife’s doll house when she gave up, and I do design work. While not new to building, I am new to boats!

Actually, another quesitn for you Bill… How did you make the formers / bulkheads? just wondering if there is a quick trick, or if it’s just trial and error with cardbard…

7

I don’t put bulkheads in my boats, Dr…Footys are stiff enough without them, so they just add uneeded weight.

If you absolutely think you need them, Sven made a plan for some a few years ago that I think is still on the USA Footy Yahoo forum.

I’ve published my build technique several times, so you can probably find more info around, but the gist of it is to cut the panels out and tape them all together. Use lots of tape and be sure to get the seams tight. Then put a couple of spreaders in to get the shape right at the deck level. Adjust to get rid of any twist, then glue the panel seams from the inside.

I’ve used 1/32" balsa, 1/16" balsa, and 1/64" ply. Balsa needs to be pre-bent by saturating with an ammonia-based cleaning product (409 here) and taping to a curved surface overnight. The ply is flexible enough without pre-bending.

For Razor, with it’s strong curves, I recommend 1/64" ply…it will be easier to work with.

Bill H

8

The patterns that Sven made are here: http://groups.yahoo.com/group/FootyUSA/files/RAZOR%20PATTERNS%20BY%20SVEN%20S./

Note: You need to be a member of the FootyUSA group for access

9

Thanks guys!

Yes, I’ve joined the Footie group. Although I haven’t posted anything. (But I’m amazed at the number of photos and designs!!)

Yes, I have the templates Sven made, and will be incorporating them, at least just to build & align the hull. I’ll probably make the center one, to ensure the hull stays ‘apart’ so I can easily work on it, without it constantly trying to close up on me! And the few spreaders constantly popping out, and cracking the thin balsa! The center frame would also serve as an anchor point for the fin & mast step… At least, that’s idea!

[insert gripe about Windows’ ‘printing wizard’ & JPGS & BMPs; that the wizard would like to resize it to fit whatever size windows feels it should be resized to… Do you want that template in 15x wallet size?!]

Yeah, balsa is cheap enough, that I’m probably gonna build another hull…

Yes, I used lots of tape. It all looked good, but the insistence that it [the hull] try to close up upon itself probably lead to the slight twist… Removing said tape after gluing (CA) was a very gingerly procedure!! I feel I should give it a layer of 1/2oz glass cloth, to seal it, and give it some extra strength…

It’ll be just a ‘day sailer’ as I don’t know of / doubt there’s a fleet in Montreal… Actually, haven’t heard too much about ‘R/C sailing’ in Montreal, but will be looking once the river un-freezes!

And yes, from my plane days, I know all about Windex (or any other ‘ammonia’ based cleaner) to bend wood. Boiling water / soaking it for a few minutes also works.

It’s been slow, but fun. Definitely not as simple as one would expect!

Thanks again!

Oh, the Papaya is going along quite well… Much easier, but then again, its really just a box compared to the razor!

10

Thre are many good image viewers you can use to print out the patterns. Irfanview (www.irfanview.com) is very good and free. After printing, you can enlarge the patterns as needed with a good photocopier.

11

When it comes to building a chined hull like Razor using 1/16" or 1/32" balsa, is there a down side to cutting the 3" or 4" x 36" balsa sheet into widths and gluing them together such that the grain runs across the sheet ?

It certainly works during the actual construction phase but can anyone vouch for its longevity ?

Cheers,

firstfooty

12

I think the downside would be that the glued joint won’t bend as well as the natural area. Like they say- the joint is stronger (or less bendable) than the wood itself.

I tried this- glueing some 1/16 balsa and bending it. The joint wouldn’t bend. So I used it for the flat bottom instad.