Logo Bendywood®


I. Provisional fixing:

Pre-bent handrails must be removed from the mould and immediately temporarily tied to the brackets for an adequate acclimatization period to stabilize shape and length.

Pre-bent handrails are normally over-bent to compensate for the elastic return, which will be more accentuated if not fixed immediately after removing them from the mould. 
Read more:
 Spring-back after being taken from the moulds (bendywood.com)

Pre-curved handrails normally have a moisture rate of approximately 12%.

Once pre-mounted they will be acclimatized after approximately 10 days:

  • wooden moisture will be reduced to approximately 8% 
  • length will shrink by approximately 1 cm per linear metre.

FOR THIS REASON FIX IT IN SUCH A WAY AS TO ALLOW SHRINKAGE IN LENGTH!


II. Final assembly:

Start with a fix mounting point halfway its length and mount the handrail from there towards the ends in such a way that it can still shrink a bit along its length, especially in the case of long handrails. It is best to use handrail supports which you can provide with slotted holes.  

 

Please consider that a 6 m long handrail, for instance, will further shrink by up to 1 cm (on its total length) within the first year after final assembly.
The shrinkage can be greater if the ambience is heated or air-conditioned a lot without regulating the equilibrium moisture content. 


Only in the following cases the problem of shrinkage doesn’t occur:

  • In case the handrail is bolted down to a continuous metal rail of the banister (from below) at intervals of about 20 cm. Only this type of mounting prevents shrinkage in length: however, only use strong, deep penetrating screws, especially for handrails with a diameter of ø42 mm or more;
  • In case the mitre joint is under tension: this occurs when bent parts (which always open up a little) exert pressure on the mitre joint.

III. CONNECTIONS OF HANDRAIL PARTS:

       1. MITRE JOINTS

Mitre joints at the ends should be avoided: the risk that they will "open up" in the long term is high.
Check whether a solution is possible as shown here:

     

In case mitre joints cannot be avoided, there is an option:

a. Mitre joints with synthetic resin glue and a threaded rod:

  • Drill sufficiently big and profound holes into the handrail ends that need to be jointed;
  • Fill these drill holes at both ends with a synthetic resin glue and insert a threaded rod, which diameter should be a bit smaller than the one of the drill hole;
  • Press both handrail ends together with clamps and keep them in position until the glue has dried.

The use of a threaded rod as well as the use of synthetic resin glue are both necessary to prevent the joints from opening up.

     Mitre joints

 

       2. JOINTS ON STRAIGHT PARTS

a.  Open butt joints:
     Such joints are secure and in certain cases also decorative, e.g. on platform transitions and holders.

     Is is important to drill holes at the ends and insert guide pins so that the parts stay in position: this also allows
     for further length shrinkage!

Offene Stoßfuge     Offene Gehrungsverbindung    

b. Closed butt joints

     Must be strengthened with strong and long dowels, as Bendywood® shrink in length much more than normal
     wood. For example Ø 40 mm handrails with 20 cm long dowels with a Ø of 20 mm!

c. Joints by diagonal cuts

Skizze Schrägschnitt Handlauf

     The length of the diagonal cut should equal 2 times the cross section of the handrail.
     Only long gluings prevent the bonding from collapsing under tension.

IV. Painting after Assembly:

It is recommended to use:

  1. synthetic paints or oils, such as "Danish Oil" (Rustins) or, LOBA LOBASOL® 2K ImpactOil Hartöl 750 ml - Dose, transparent kaufen (hygi.de) with hardener 
  2. Hydro-oils with hardeners for wood with waxy effect, such as the “Renner wood-oil YS---M009 with 5% hardener YC M402” tonet AG Webshop - Wasserbasierendes Holz- und Möbelöl YS---M009

Technical data: WT IP 0418 (tonet.ch)

All this and similar products can be applied on side, without having to dismantle the handrails.