I can say I now have a lot of experience with making airtight vacuum bags. As a matter of fact, within this project this is big hull vacuum bag number 9 and I thought it would be a piece of cake. After all, it is not just a vulnerable foam hull but a foam hull with an airtight internal laminate. And the joins of the Port and Starboard halves are covered with a glass tape. So no worries about air tightness. I thought ……..
After some more changes in the bag and improvements of the hull integrity in the past two weeks it had to happen.
Last weekend, despite the fact the vacuum bag was still not perfect the infusion started at 3.00 PM in the afternoon. There were a few precautions taken to be able to solve possible problems during the infusion and this has worked out satisfactorily. Only the end counts and despite the troublesome preparations it was again a success, a big relief and another milestone in the project. After a evening and night watch during the cure of the resin I went home at 5.00 AM the next morning, tired but with a good and happy feeling.
Furthermore I made a new photo galery in www.fram.nl with the flow prediction simulation and photo’s of the resin infusion process. Please click here or in the simulation image below.
Well, I now have a green boat, but not because of the curing epoxy, but it is still pristine resin distribution mesh behind a floppy vacuum bag.
Long story short, for the first time in my project the vacuum infusion failed, or better said, I could not run the infusion because of two persistent leaks from the inside in the aft beam area. But don’t worry, it appears to be not a big deal, it only causes slight delay.
It has been a looong day that started very hopefully:
Thursday January 5
04.00 AM
There is a violent storm going on and some areas in The Netherlands are fighting against a extremely high water level, the quay on our garden is flooded and my car alarm woke me up. The storm activated the motion sensor of the alarm system in the car. O well, it will be a busy day today, so better get up early.
04.15 AM
I receive an email of Arjen Korevaar of www.Polyworx.com containing the infusion strategy and simulation. He worked all night to design a perfect but simple infusion strategy. This comes just in time for me to translate this into the dimensions of the runners. It shows a further development of the strategies I have used so far. Yesterday evening I prepared a fore and aft pleat in the resin distribution mesh for the vacuum line on top of the hull, but that was too premature. In this new strategy there are only some single venting ports, just ingenious.
05.00 AM
It is still no winter and the heater is able to heat the workshop to a level of about 20ºC. Yesterday I’ve put the resin in the canteen with the heater high at a temperature of about 23ºC. But before going to work on Fram I have to finish some business things at the office.
The planning for today is fixing the resin distribution mesh, the resin feeder lines, the venting ports, the vacuum bag and putting the whole hull under vacuum. I prefer to let the vacuum alone during the night from Thursday to Friday. The vacuum infusion is planned tomorrow Friday 10.00 AM. and I will be assisted by some helpers including Arjen.
But it went different.
2.00 PM
Still busy with the green resin distribution mesh. I still have to buy some PVC parts for the resin traps, 1″ tube and two valves for the resin feeding line. A colleague of mine was kind enough to do that for me.
5.00 PM
It looks to become late this evening, so I phone my wife that she don’t have to count on me for supper.
9.45 PM
At 10 PM , the building alarm must be enabled and I phone the security company that enabling the alarm is not possible because I’m still at work. I also phone my wife again saying it will be very late tonight and she don’t have to wait for me.
D-Day, Friday January 6
1.00 AM
Yesterday I tested cheap insulation foam to see if it was not eaten up by epoxy resin. That seems to be not a problem and I now cut the venting ports out of this insulation foam.
I feel annoyed because it looks that I don’t have enough time to get the hull under a vacuum for several hours.
2.00 AM
Finally the resin distribution mesh is done and all the spiral tubes are in place. I prepare two pieces 53′x10′ of vacuum film and put them together to form a 53′x20′m sized vacuum bag. That must be enough to cover the 39′ hull.
6.00 AM
In the area of the fore beams the vacuum bag is too short and need a 5′x3′ extension. The second try of this extension does the job. It looks that the vacuum bag in the area of the aft beam is just wide enough, so in that place no extensions are needed.
10.00 AM
Vacuum bag is still not closed, helpers arrive.
11.30 AM
Vacuum pump is on, but there are a lot of leakages and the vacuum bag around the aft beam flanges is too tight and still needs an extension. Arjen is doing the Port side and I’m making the Satrboard side of the bag extension. The vacuum bag begins to look as a mess, but who cares, only the result counts.1.00 PM
It appears that the plastic valves are not airtight in the closed position. These valves are a bad buy and have to be replaced by the brass ones I normally use. However, I don’t have them and make a temporary seal with some tacky tape and vacuum film.
2.00 PM
Now we are getting some vacuum. My collegue Robert turns out to be the perfect leakage seeker. With unmatched patience and accurateness the one after the another leakage is being solved by him. It turns out that there are some leakages from inside. I thought that would not be possible because the inside is covered by the internal laminate and this has been resin infused too, so this must be airtight. Unfortunately that is not the case, it appears there are some very small holes. The only explanation I can think of is the following:
The fore and aft battens were 18mm. thick,
The foam is 15mm. thick,
So a total thickness of 33mm.
The temporary screws were 30mm, so in theory there is a 3mm play above the screw point.
Now what if the screw was driven to deep in the wood with the screw point just in or above the foam surface. Apparently this has been airtight during the resin infusion of the internal laminate, but leaves a very small hole after removing the screw. This is the only explanation I can think of.
And there are some holes from the inside in the bow tube area. But that is a result of my own stupid fault as I’ve used some temporary screws there without noticing I punctured the internal laminate with them.
4.00 PM
The vacuum is still not more than about 15″Hg, caused by two leakages in the aft beam area and these seems to come from inside as well. The only way to fix that is to give the sealant tape of the vacuum bag an alternative route.
But by now a jetlag feeling is overwhelming me. The alteration of the vacuum bag and putting vacuum on again will take at least another three hours and together with the infusion and geltime requires another 14 hours of me to stay awake. Saturday and Sunday I have other (family) obligations so it is not wise to go on.
But now that I know the cause of the malfunction it is easier for now to give up.
Today I finished the peelply and releasefilm layers. Tomorrow I hope to do the flow fabric and vacuum bag. This will be my biggest infusion to date and this exciting event is scheduled for Friday morning.
The WordPress.com stats helper monkeys prepared a 2011 annual report for this blog.
Here’s an excerpt:
The concert hall at the Syndey Opera House holds 2,700 people. This blog was viewed about 18,000 times in 2011. If it were a concert at Sydney Opera House, it would take about 7 sold-out performances for that many people to see it.
On one of the boat building forums there was a question about the practical aspects of doing a single side infusion and where the foam hull is the airtight mold. This for sure requires a meticulous job on the foam hull, preventing any piercing by screws, or repairing these very thoroughly, and a lot of attention for the bog in the joins between the foam sheets. It is good practice to use as large as possible foam parts to minimize the amount of seams. To be sure that the joint is airtight, I treat them in four stages. The first one is widening the seam with a Dremel tool and routing a V-shape in it. Then I fill these with a thick mixture of epoxy, aerosill and microballoons, the second layer a little thinner and the final layer again a little thinner. Of course this requires extra time, but doing this well is very important for the integrity of the vacuum bag. Taking shortcuts in this phase will lead to the nightmare of not getting enough vacuum for the infusion. In that stage it is too late for making repairs and the decision has to be made to give up the infusion and to go back to the hand-lay-up job.
Of course the single side infusion on a foam hull requires a closed cell and airtight foam. The A quality Corecell foam is a fine example of such a foam. The thickness I use is 15 mm (5/8″) Thinner will be more difficult and thicker must be easier in regards to making an airtight foam mold.
Have a look at the figures below to get an idea of the (extra) hours for making the foam hull (mold) and to infuse the internal hull laminate.
You can see there is a kind of learning curve. Only the last hull (Main hull port half) is made in the new workshop. The difference in working hours between the cramped workshop in my garage at home and the very comfortable and roomy workshop I have today is not very dramatic. All work has been done on my own. Working with two people is more efficient and I guess will save at least 25%.
In the mean time I’m working hard (well, not today to get the main hull ready for the infusion of the external laminate. I hope to be able to do this in the first week of January 2012
For this winter I have planned to build the four beams in my garage at home. De beam molds are ready and one of the first parts I need are the upper folding strut recess sides. These are made of pre-made 4mm. thick solid laminate. For the eight pieces and some smaller doublers I vacuum infused a 4′x6′ solid laminate plate.
The low viscosity epoxy resin starts to gel after 300 minutes so there is enough time for a simple version of the infusion setup. Below three photos of the infusion, the first after 15 min, than 1 hour and the bottom one after 1.5 hour.
The last things has been carried out before the external laminate can start.
The temporary hole in the bow has been closed off and some high density foam inserts has been placed in the areas where thru hull fittings are planned.
With the integrated forestay chainplate the bow pole tube is an awkward part to fit in the bow. In hindsight it would have been better to do this during the joining of both hull halves but I decided to do this afterwards as I had some various options in mind regarding an extra chainplate for a cutter stay and/or making a provision for a gooseneck for a jib boom. The jib boom didn’t made it but the base for the cutterstay chainplate has been made.
There were two possibilities to get the bow pole tube in place, by sliding it into a slot or by tilting it through a large hole. Disadvantage of the slot is the possibility that the bow deformes and needs a reconstruction afterwards and the advantage of a large hole is a better acces for the laminating work inside the bow area.
So I choose the large hole, although in two steps to keep the possibility to go back to the “slot method”. And so I went from one hole to two holes and, after gathering enough courage, to one large hole. I placed the bow pole at the right angle and distance and discoverd that the size of the forestay chainplate could have been a little shorter, about 20mm., despite the fact everything has been made according to plans. The effect is that the chainplate protrudes a little too high above the deck. Not a good sight and not good for the size of the jib. So I decided to lower the whole bow pole tube assembly with 20mm.
The plans shows two threaded stainless steel studs and together with two wingnuts and a stainless steel strip this holds the protruded bow pole in place. I don’t have experience with a retractable bow pole but I can imagine that pushing the bow pole to its protruded position gives some troubles in the last inches. Two wingnuts turn more heavily than four wingnuts so I decided to mount four studs and I replaced the stainless steel strip by a circular piece of carbon (an offcut of the sterntube skeg)
Posted by Fram 
to get the main hull ready for the infusion of the external laminate. I hope to be able to do this in the first week of January 2012
