Technical Article: #004
Title: Replacement Acoustic Foam in Engine Bay
Date Added: 21st August 2011
Article Author: Andy
Boat: Hustler 30 – Harriet B
Job Time: 1 day
As the new owner of Harriet B there were a number of tasks I had to complete before I could sail her away. One of the tasks the surveyor had recommended was that the old Engine Bay acoustic foam should be replaced. The reason being was the old egg box style of foam isn’t flame or heat resistant and burns very easily. The Surveyor demonstrated by breaking a piece of the old foam off and setting light to it!
As the foam was looking quite tatty anyway and was even rubbing against some of the moving engine parts (All that black in the picture is where the foam was pressed against the fan belt!) it was time to replace the foam.
I needed new foam but I wasn’t sure how much I should order. To find out I measured each area of the Engine bay where the old Egg box foam was attached. I drew a 100 x 100 box and planned where my measurements would fit into my 100 x 100 box. The logic being I’d turn the box into a big jigsaw puzzle of Engine bay panels. Amazingly all my measurements fitted perfectly into the 100 x 100 box. So now I knew I just needed to buy a single sheet of acoustic foam.
There are many, many types of acoustic foam out there some up to the job others not and prices swing wildly from £30 to well into the £150 bracket. I eventually settled on a foam sold by Vetus. It’s official name is “Flexible sound -deadening plate 1000 x 1000 x 20 mm grey” and cost around £45.
I chose this as it seemed to offer the best compromise of heat resistance, reduced depth (20mm) and it had a self adhesive backing. I wasn’t sure about the strength of the self adhesive backing so I also purchased some self tapping screws and penny washers to help hold it in place.
I had my eye on the aluminium acoustic foam (looks more flame proof) or the white acoustic foam (could make the space look bigger by reflecting more light) but these were out of stock. I needed to fit the foam asap I had no choice but to settle on the grey
As you can see from the image it’s a pretty dark grey, I expected a much lighter grey.
Cutting to Size
Prior to installation I needed to cut the foam to size, so I marked the foam as per my 100 x 100 box drawing. I also allocated a number to each section of the engine bay so I could trace my measurements and the panels once I’d cut them.
Using a very sharp Stanley knife I proceeded to cut the foam into the mapped out blocks. The foam cut very easily and I was quite surprised that there were no rough edges. This may have been because I was cutting via multiple strokes rather than applying lots of pressure and just dragging the knife as hard as I could. As my Granddad used to say “Let the saw/knife do the work not the elbow”.
First the old Egg box foam had to be removed. The first piece to be removed was quite straight forward. However, after that things started to get a bit more difficult. The Egg box foam was well and truly stuck down. So much so that when I pulled at the foam most of it was left behind.
This was where the Stanley knife came into use again. Very carefully as I lifted the old foam I cut away as close to the wood as possible. After removing the foam I scraped any old residue off with a wallpaper scraper.
This was a very sticky and very messy part of the job so make sure you have a bucket handy to keep your hands clean. Otherwise the glue sticks to your hands and your hands start sticking to the foam!
Now the old foam is off, it’s time to stick the newly cut foam panels.
First I offered the newly cut panels up to their destination, trimmed any areas that weren’t quite in alignment then peeled the backing paper off and stuck the foam down.
WARNING: The Vetus acoustic foam self adhesive backing was even stickier than the old Egg box foam I just took off!
You get one maybe two chances (if you are really lucky) to get it right. If you get the adhesive on your fingers like I did then this happens…
Your fingers start to stick to the new panels you are installing and that makes the new panels even more awkward to install as they start sticking to anything and everything.
So, offer up the panel first, slowly peel the backing paper and place the panel down gently as you go. There is some scope for movement as you apply it slowly and gently.
After applying all the new panels this is what it looks like…
There was still some trimming to do even after it was offered up as the old foam was so flexible it just compressed when pushed into place. This new foam wasn’t so malleable therefore it was really obvious when the engine bay stairs were put into place the foam was getting in the way.
I didn’t use the screws and penny washers as extra support for the panels due to the self adhesive being so strong. I’ll be keeping an eye on it though to see if any of the self adhesive glue melts with the heat from the engine bay.
But was it worth it?
Yes, it keeps the surveyor and the insurance people happy and most important of all it actually reduced the sound coming out of the engine bay. I’m very pleased with the results as it looks a lot neater than the old Egg box foam and it’s not rubbing against any moving engine parts.
HOA NOTE: The article above is related to works that the author has carried out to their own boat at their own risk. This article is intended to share the authors experience with other readers only. It is not intended to be a comprehensive step by step instruction guide. Anyone choosing to do any work as a result of reading this article do so at their own risk. If there is any doubt about whether to conduct work on your own boat call a professional to assist.