Thread: Drop in rudder for Quick Canoe?

After much searching, I have finally found one company that sells gaboon plywood and can offer shipping home to me. It is 6 mm thick, but has only 4 plies.

The funny thing is that it is cheaper than the Finnish pine plywood (even with the shipping included).

Well, now I know at least from where to buy, in case I do not find any good Finnish plywood.

That's very strange to find 4 plies. The normal principle of plywood is the number should be odd - 3,5,7,9 etc.

I would probably want to know more about that ply before ordering. In recent years we have had a lot of very poor Gaboon plywood from China selling very cheap. Everyone was enthusiastic until they found the quality was much worse and very variable.

Some of the Chinese gaboon was OK ... but the problem was that nobody could guess what quality they were getting.

Four plies is very strange and the cheapness makes me feel concern too.

It might be OK and you could cut the panels so the grain outside the boat was horizontal and inside it would be vertical. But I would ask more questions.

Michael

Hello,

I would especially check if all veneers are equal in thickness (outside and inside veneers). If so, it may be okay. If not (very thin outside veneers), I would not use it as it will not be strong across the grain of the thicker veneers which will most likely have the grain running in the same direction on both veneers.

Don't ask me how I know this... I was supplied with perfect plywood by a recognised manufacturer for my GIS. Two years later, for another project, I am buying the same brand and to my horror it was 4-ply stuff. I thought, well, let's give it a try whether it will work anyway and I cut out some parts of 1 sheet. That's when I found out that albeit quite strong in one direction, it is completely useless in the other direction (strength wise). I had ordered 6 sheets, returned 5 of them (got my money back) and took the sixth one as a loss. In my opinion, this stuff is meant for panels between framing (where no strength is required) and the like in outdoor conditions.

If building the GIS, I would spend money on the plywood (nice gaboon 5 ply). Yes, it is expensive stuff, but saving on it may cost more in the end...

Just my thoughts...

Best regards,

Joost

Hi. I compared Finnish birch with gaboon a while ago.

Available in 3-ply thicknesses as thin as 0.4 mm, density around 575/650 kg/m³.
WISA-Birch plywood 6.5mm
WISA-Birch Premium plywood 6.5mm
Finnforest Björk WPB comes in 3 and 4mm thickness, 710 kg/m3
KOSKISEN OY, TEHDASTIE 2, FIN-16600 JÄRVELÄ, FINLAND, TEL. +358 20 553 41, FAX +358 20 553 4207, Koskisen Oy
P L Y W O O D D E V E L O P M E N T T E A M
Koski-Standard
STRONG BASE FOR SECONDARY PROCESSING
In the harsh climatic conditions of northern Europe trees have a short growing season. The growth is slow and the annual rings are narrow. The result is a wood that is strong, homogeneous and of consistently
a high quality. It is with logs coming from the sustainable PlusForests in Finland, that Koskisen Oy produces plywood, utilising decades of experience, skilled motivated human resources and modern production technologies
and facilities.
SPECIFICATION
Bonding WBP exterior or MR according to BS 6566, BFU 100, BFU 100 G or BFU 20
according to DIN 68705, EN 636-2 and 3, EN 1084 class A.
Thicknesses 4, 6,5 , 9 , 12, 15, 18, 21, 24, 27, 30, 35, 40, 45, 50 mm,
other thicknesses at request
Sizes 1200/1220 x 2400/2440 mm
1500/1525 x 3000/3050 mm
1250 x 2500 mm , other sizes at request, in birch up to 1800 x 4000 mm
Face qualities Birch S/BB, S/WG, BB/BB, BB/WG, WG+/WG
Certificates EN ISO 9001, EN ISO 14001, SMS 1003-1 (PEFC)
STANDARD PLYWOOD
Birch plywood- Cross-banded 1,5 mm birch veneers throughout.
Recommended for the most demanding applications.
Combi plywood- Two birch veneers on each side and inner veneers alternate
conifer and birch. In mirror construction only one birch veneer
on each side. General purpose board for demanding applications.
Conifer Plywood- Light weight construction plywood of cross banded conifer veneers.

Search for "Handbook of Finnish Plywood" for more information

Okoume (or Gaboon), according to the commonwealth Scientific Industrial Research Organization, has a density of between 400 and 450 kg/m3.

Comparative density of basic timbers;
Gaboon mahogany...............32 lb/c.ft
Birch....................................40 lb/c.ft
Also:
Finnforest Spruce barrträplywood weighs ca 460 kg/m3

4 mm sheet Okoume 5.4-5.5 kg, Birch 7.74 kg

Mike Hanyi who lives near Helsinki and started Raid Finland, wrote an article in WaterCraft about Finnish birch. As I recall it is considerably stiffer than gaboon, and thus if you use the same thickness as specified for gaboon you are likely to have trouble bending it at the bow to the stempiece. So you might consider using 4mm 3-ply birch where 6 mm gaboon is specified. 6mm 5 ply for the bottom? Some sheets come with the outer layers' grain crosswise on the sheet, which would affect its use as planks. In Sweden I can buy at the local Bauhaus store 4mm birch in standard size 2240x1220mm. Sometimes it is metric 1000x2000.
Peter Lord in Uppsala, Sweden.

The last of the Shelman Okoume that Clint and I built our Goats out of was 4 ply 6mm.

Don't know if it a going-out-of-business thing or whathaveyou.

I wonder if 4 mm thick birch plywood can be used for a GIS also... (For the sides).

I have used both 4 and 6 mm gaboon and 4 mm birch and I would think you could use 4mm birch on the sides, daggerboard case and decks etc of a GIS instead of 6 mm gaboon. Probably 6 mm for bulkheads and bottom. The surface is nice and the 3 plies are of equal thickness and there are no voids in the inner ply. 6 mm birch instead of 6 mm gaboon would make a rather heavy boat. Sailing where you are, I would add at least one layer of 6 oz glass cloth to the bottom and chine to minimize damage by rocks. I have hit quite a few of them in the Finnish islands, and the best places to stop for lunch often have many rocks guarding the nice landing place in a bay. My boat has 2 layers of 6oz cloth on the vunerable parts of the bottom and the outer layer is smoothed and filled with epoxy/carbon powder (WEST)/thickener mixture which is very hard. But if you damage the layer of cloth and epoxy, water may leak into the bruised plywood. Alternatively be prepared to regularly repair the dents in the plywood bottom if you only use epoxy to seal it without cloth.

Will there be a GIS in Finland? I hope so.

Peter

I hope there will be a GIS in Finland .

This week is the first week in our new house, and we still have a lot of stuff to do at the house. I think I can have most of the stuff inside made until middle of the winter, and then it is too cold to do the outside stuff. This means I would not have time to even begin building anything until February... And then I have time until the spring. From the Spring forward I will be busy again until next winter.

The biggest obstacles are the following:
1. Money (I would need to take a loan).
2. Wife (she does not want me to build anything because of the first obstacle, and she thinks she has more important things we should put money on.)
3. A warm place for building in the middle of the winter.

I have been wanting to build the GIS now for over a year, waiting patiently to have a chance... Dreaming and planning almost daily. With good luck, there will be a GIS one day. I already bought the plans as I could not do much more planning of the project until I have more details. Having the plans also helps to dream .

So to answer your question if there will be a GIS: Maybe once in the future unless somebody rich donates money to me (which is probably not happening).

i wouldn't go for the 4mm for seats ... if everyone is careful it can be OK, but would need more framing. But 6mm is safer for seats.

There is a risk of a geometric problem with 4mm ply and the chine log. a heavy chinelog on thin ply can cause concave curvature close to the timber piece when it is bent.

I don't have any way of calculating if that will be a problem or not.

Michael