Rivets

This blog covers the filling and polishing of the rivet heads

Overview
More time has been spent  trying to find a quick method of filling rivet heads. While there are a number of clues to be found on the WWW it would be easier to join the Illuminati that find a definitive method.

Regardless most methods required some sort of epoxy was used so that is were the builder decided to start. This builder tried Plasti-Bond, two part epoxy [thick stuff] and West Systems initially.

Construction
A series rivet heads were filled using a mixture of West Systems Epoxy and slow cure hardener. These were mixed in small batches of about 8 cc with a pinch of blue chalk dust added for colour, this was found to be critical to allow you to see runs in artificial light. While a good number of nice rivet fills are achieved over fills were common with the inevitable runs. 

The best technique was inject the epoxy into the rivet opening with enough resin to form a mucus before moving to the next with the results varying from wonderful, to well a mess. 

A Black Duck

This worked well in the horizontal or near horizontal but for verticals the builder waited for the epoxy to thicken for the more horizontal rivets. 

Once cured the real work begins removing the waste. This was sliced / scraped off using a 18 mm box-cutter blade with the rear end best for scraping. 

Holding a 18 mm box cutter blade [it must be sharp] in two [2] hands, bend it using the base of the curve to slice the waste off then and finish rivets by polishing with a softened 800 grip wet and dry.

All these tasks require 110% from the person applying and removing the epoxy and that's just not possible for this little black duck...!

Note: softened paper by soaked in warm water and detergent until it just turns into a soft cloth like material. 

Alternative approach
Halfway through the fuselage there had to be a better method and the idea of using an acrylic sealant filler was examined. 

A syringe was filled with grey acrylic and a 1/2'' dosing needle fitted after grinding off the sloped opening. This was inserted and the acrylic injected slowly while moving the needle out, once reaching the opening swirling to create a cone like covering over the opening in the rivet - this is important to create a seal.

Note: Best profile is like a choc top on top of the rivet head

This material must be fully cured and this will take 24 hours and even better give it a week - firmer is better.

All the tops were removed using a curved blade as described previously. This may require a few passes to cut down to the top side of the rivet. 

Grind needle end square - Acrylic must
cover the full opening of rivet head plus a bit

If you have clean rivet tops this works well but in my case a number had rims formed by the tool and the blade could slice off the smaller once but the larger one's were removed with a Dremel fitted with a 120 grit click and lock sanding disc.

Note: Set the Dremel speed to about 10K and be very gentle using the outside edge applied at a slight angle to the rivet head








Comments
This may or may be a good method but it is quick and simple compared to using epoxy. One issue is temperature as Dark Green can reach temperatures nearly equal to a black and this will be critical on the top side of the wings. 

The acrylic is used on the fuselage is good for 70 - 80 C but a little investigation shows that Selleys 3 : 1 is rated at 90 C and this will be used in future.

Small scale tests show this combination it is happy to have acrylic primer and paint applied over it but this is a suck and see job. It will in the end be a good idea or a sea of tears - we shall see will we not.