Hello David. For building my F-85SR I am using 2 pumps, both 3/4 hp. Theoreticaly they can handle 226 Liters/minute each. The exra pump helps if you have a small leak, so you still can have a reasonable pressure. One of the pumps runs via a pressure switch. It switches off when a pressure of around 0.7 bar / 21"HG is reached. My pumps are of chinese manufacture and use quite a bit of oil, to the point that I have made exhaust tubing to lead the oil outside. But it works well.

Phill is a great source of information. I can't match his building pace but it is nice to exchange information and profit from his extensive building experience and knowledge.

As to building costs: Some builders have gone to cheaper foams to keep the cost down. My advise is to not go this route, but use the best there is: Corecell M ( IMHO ... ) I spoke to several F-82 builders here in the netherlands who went this route, but in hindsight they now say they would have done otherwise.

Regards
Nico

Thanks Phil and Nico
Great to find some builders of the F85SR Online.
I have sent off for a set of plans. My list of things before I decide is getting shorter. (Short enough to buy the plans)

Cant wait to see how the hydrofoils angle of attack is set. The ways I could think of doing this would not be easy..

Thanks for the Corecell M comment, I will do some more reading on the subject as I know little about foam core.
Did other people have delamination issues? Weight issues?

I have done smaller things with honeycomb composites with carbon fibre and got thousands of pinholes that had to be sealed. Only other foam core work I have done was all specified by someone else using vacuum bag and high pressure hot water on the outside.. Far too much work to do for fun!
I know you are vac bagging, did you do a time/cost benefit of hand layup?
Initial thoughts are to do lots of the small parts first rather than the floats due to limited space. What do you think?
I have a homebuilt CNC machine, MechMate, that I need to sort Y axis alignment on (it is about a mm in a m out of square on X versus Y before I can consider cutting forms and parts (Or would you consider this accuracy adequate?

I am expecting this to be a five year build.

Cheers
David

Ian gets you to make the bulkheads first so that is a good warm-up on vac bagging.
Most of the time, the build only involves one layer of laminate so it is quite easy to do a decent hand lay-up without vac bagging, especially if you use epoxy. Use peel-ply on everything though.
Whilst your vac-bagged bulkheads will have a nice laminate finish, I think that the main benefit of bagging them is that they will be absolutely flat and true.

David,
There is an F85SR builder who lives only a few kms from me who is building without vacuum bagging and many F82s and other size F-boats have been built without vacuum. I would not be surprised if more were built without vacuum than with vacuum. There is no doubt about it, it's quicker and cheaper to not vacuum.

I'm vacuuming because I wanted to build the best boat that I could build and over the years I've acquired 3 vacuum pumps.

As far as accuracy of your CNC Mark Hastings did our CNC work. He designed and built his own machine and does excellent work. I expect he would be a good person to answer your CNC question. I'll drop him a line and see what he has to say.

Regards,
Phill

Welkom to the club



Bagging a floathalf is a bit more complicated than bagging the bulkheads, I find. It's not really a black art, but there are a few things that have to be done exactly right. I did not compare costs. Hand layup is cheaper and faster. Bagging is stronger and lighter. I chose to go for the latter ( and also because I thought it would be fun ) When bagging, the layup is a little bit less critical. If there are a few air bubbles, they will be sucked out. I still try to get a good layup though, just in case the vacuum goes bust.... For hand layup, a wet layup seems to be the best method. For bagging, I don't think that's neccessary and a dry layup is easier.

Doing the small parts first is a good idea. As for the floats, these are my lessons learned:

- use a foam toaster/oven to heat the foam. 100C seems to be ideal. A bit lower temperature works as well, but you will have to apply a heatgun in the tight radii of the deck. If you do this the foam will fit in the mold with minimal stress.
- To avoid leakage along the screws it is important that they don't penetrate more than 7mm into the foam. Side effect is that the holding power of the screws in minimal. That is why the pre-heating of the foam is so important.
- I chose to rebate the foam strips. Advantage is that you won't have to cut the foam to size and the bog can't sag through. When bogging the seams, I do that in 2 steps. The first step is with a thin bog, that I work into the seam with a small popsicle. Before that is completely hardened I add a second layer with thicker bog to fair the joint. This assures a leak free joint between the strips.
- Tacky tape and wet epoxy don't mix. I take the easy road: I use two layers, one on the bag, and one pre-applied on the foam edge that that is left sticking out of the mold. You can also protect the foam edge with tape. The tacky tape doesn't stick to foam very well, so I apply a very thin layer of bog on the edge.


I'd try to get the mistake out, if it's not too dificult. My CNC router has the same setup as the MechMate. Because I have a rack and pinion drive, my machine is only accurate within 1 mm ( the X- axis is a bit better than the Y- axis. I should have gone for 2 stepmotors on that axis too in hindsight ) This is enough though.


That's what I expect as well. 5 - 6 years.
Regards
Nico

ps: feel free to contact me on info at nyker dot nl. I've learned a lot in the last year, not in the least because Phill was so kind to share his experience.

Hi David

The Mechmates are a really good looking design and I would have gone that way if I hadn't got most of my build out of decommissioned gear at work which dictated the design by the components I had.

Being dual slave drive rack and pinion (thats right?) dialing out any skew should be a breeze. What I would suggest you do is put two thin DF of other scrap sheets down an cut thru both a big square. Then flip the boards face to face along the X axis this will double your skew error that you can measure between the two pieces and use this value to rack the gantry. Loosen the gantry to drive sides and adjust your home sensors accordingly.

Now rotate the top test piece 90 degrees and compare the X and Y dimension and adjust you tuning as needed.

But first...check that everything on the machine and drive are snug with minimal backlash etc.

Probably telling you how to suck eggs.. I 'm sure if you built the machine you can tweak it to get it right and probably to within a fraction of a mm accurate. Just don't loose sight of what it is your cutting and the processes afterwards to the part .. lots of small variances disappear in the end product but getting stuff square is importatnt because of the doubling effect when you flip parts (think forms and mirrored sides of the floats)

PM me if you need any help.
Cheers
Mark

Thanks for the input guys.
The Mech mate has a slave on the x axis with two rack and pinion stepper motors. I used the cutting of two boards and turning one over technique to determine trueness of the straight cuts (within0.2mm) and squareness (approx 0.8mm per m out but plus or minus half depending where it is switched on. I can adjust most of that out, just take another couple of days...as it will require reseting the Z squareness and resurfacing the table.

The way I am thinking if I cut all formblocks from the same side no issue with fairness and the part must move a mm, anyway should do the correction in a couple of weeks.
It is very hard to prove these home make machines are better than a mm accuracy in their length. When I started the testing they were about five percent out because the chinese gearboxes were not the ratio advertised, That took a while to prove...

Thanks for the hints about working with quality foam and the heat it can handle. It is so much easier to follow than lead.

Plans should be here in a couple of weeks so on with the "honey do list"

Cheers
David

David,
Welcome to the F85SR club. I hope you enjoy the building as much as I am.
On another topic I still can't post pics on the catsailor photo albumn so can't show anymore pics of my build. I sent a message to Rick a while back and he said he will look into the problem.

Currently I'm sanding the folding Mech that Mark Hastings has made for me using his CNC machine. He has done a wonderful job so I'm removing the machine marks to make it perfect before it gets anodized.

I'm using 180, and 600 wet and dry. The 180 is used dry. It is quite surprising when I brush off the dust that builds up with my bare hand it takes half a dozen strokes of the 180 before the oil deposited by my fingers is removed. I can feel the 180 slide back and forth before it starts to cut again.
To me this illustrates the folly of touching sanded glass when you are about to bond something to it. No wonder Farrier is so adamant that you must not touch the areas the beams are to bond to in the floats after they are prepared.

I was quite surprised how such a small amount of contact can make such a big difference.This project is not only enjoyable it is also full of interesting observations.

Regards,
Phill

Phil, did you make the daggerboard cases yourself or get them from Ian?

Also I'm thinking about a F85 build, how much would you want for the frames and what are they made out of??

ed,
Cases came from Farrier Marine. When you see them you will realise they are really very good value.
Frames are made from MDF sealed with clear lacquer on the faces and 2 coats of epoxy along the edges.
Where are you located? I'm on the NSW Central Coast .
If you are not too far away you can send me a PM with your number we can talk about frames and any general questions that you may have re building etc.

Folks,
I have been back working on the boat for a couple weeks now after finishing the work required to make a storage space for them under my front verandah.
The chain plates are made and fitted and I'll take the folding mechanism to the anodisers later in the month when they come back from their christmas break.
Currently I'm in the process of fairing the floats.
I've made 5mmx5mm notches in 250mm long heavy duty plastic trowel with 30mm between each notch. The trowel is held at an angle when applying the filler to the hull which makes the beads of filler only 2mm high. It takes 0.95 litres of resin to bead one half of one hull. Once cured it then takes 1.5 hours to sand most of it off with a 4 ft longboard with 40 grit paper. That is working hard and sweating a lot it ends up being a full body workout but it gets good results.
It takes a similar amount of resin to fill the hollows marked by the beads remaining after the long boarding.
At this stage I'm really glad that I was so careful in placing the foam as the fairness of the hull is much better than it otherwise would be resulting in less work and less added weight in the form of fairing compound.
I'm pretty happy with the way the fairing is going.

I'd post some pics but I still cant upload pics to the catsailor.com photo albumn.

Hello everyone!

Bullit has been bit.

I'm a beginner in this boat building malarky so have a couple of questions:

What are the real world advantages of vac bagging the hulls, how much weight do you really save and what strength gain is there?

What about carbon... pro and cons, I guess you save a bunch of weight in using a lighter cloth(much more than vac bagging by my estimate). Whats the down side, I've seen something about poorer collision durability, a little bit more egg shell like, would this be fair? Would you use carbon for the hulls and not vac bag?

I've got a lot of reading to do!

So you purchased the plans? good show



Hello Ed, I can't give you any figures and it depends probably on the laminating skills as well. It might save up to 25% in weight compared to a really wet layup.


As for Carbon fibre, you will not find consensus on it. Some people swear by carbon. Others say it's not worth the cost. It certainly is lighter. But the laminate is also thinner and more prone to dents. For a racer the first point is important. For a cruiser you might be concerned about the second. I know one F-32 builder who uses carbon without vacuumbagging. It is more difficult to see if you have the laminate saturated with epoxy though.

For my boat the hulls are in (E)glass. Rudder, daggerboard and beams will be in carbon. For the mast and the wingnet beams I am thinking about carbon iso aluminium.



Handlayup (glass) F-22 Menno
Vacuum bagging and infusion (glass) F-82R Martin
Vacuumbagging (carbon) F-22 Andrew
Vacuumbagging (carbon) F-22 Tor
Handlayup (glass) F-22 Jay
Handlayup (glass) F-44SC Allen
Infusion (glass) F-39 Henny

Ed,
It is very good news that you have taken the plunge.
I hope you enjoy the building as much as I am.

As to you questions re vacuum and carbon.

I will give you my persective on these points but yours may
finally vary depending on what your intended primary use.

First vacuum- the weight that you will save will depend on how
skilled you are at hand laminating.
An unskilled person will save more weight by vacuuming than a
skilled laminator. In my case I have given figures in previous
posts in this thread as to the amount of resin used to wet out the
laminate and then how much came out in the vacuum comsumeables.
From that you can work out the weight savings. With some calculations
you could probably break that down to an average per sq metre
saving and with info in the plans work out how much I would save
given my skill level.
You may save more or less but it will put you in the ballpark.

I will use my boat in coastal sailing so my primary reason for
vacuuming is strength. The bond between the foam and laminate under
vacuum is as good as can be achieved.

The other considerations when vacuuming is the added cost and the
added time. There is the cost of the vacuum consumeables vaccum film,
tacky tape, wadding and bleeder.

It may be as much as $1,000 say 1/15 the cost of the hull materials.
Then there is time.
Once you have a structure ready to laminate you can roughly treble
the time it takes. To get a good vacuum you have to prepare a surface
that the tacky tape can form a really good seal to, laminate, apply
the vacuum consumeables and film and chase any leaks. I've managed
to get a vacuum of around 25 inches of mercury on most of my sessions
which is quite a good vacuum but there is no such thing as a free lunch.

I considered using carbon instead of glass. From the plans you could
work out the weight savings.
Three things influenced my decision.
1) Cost, I did a rough calculation on he added cost of carbon and it nearly
doubled the cost of building the basic structure. If you are seriously
considering carbon get some prices and see how it comes out for you.

2) I don't like cutting and grinding carbon. I've found nothing as sharp
as fibres of cut cured carbon. Using carbon in the beams and boards
will be enough for me.

3) Resale value- I did not think if I sold the boat in years to come that
I would get the added cost of the carbon back.

This is just the way that i see it.

Regards,
Phill

Thanks for the opinions guys.

I've got a couple of months of building bulkheads and bits before I move house and can start on the main hulls proper so will give me chance to have a bit of an experiment with materials and techniques before have to get cloth and foam in large quantities.

I'm mostly going to be racing in and out of the harbour with maybe 5 or 6 coastal races a year, plus a bit of cruising when time permits.

In a few years time there may be some mileage in organising an unofficial world champs somewhere

Cheers

And then there were 8!

As you are only dealing with a single layer of glass for the lay-up, vacuum bagging doesn't seem worth the agro. You can still batch out your resin and make sure that the lay-up is the right ratio. Peel ply everything though.

Carbon saves about 10% in total weight and can make the hull more prone to impact damage. Not worth the money in my mind.

Paul,
I'm vacuuming not so much for weight saving (as a bit more effort with a squeegee can get similar weights) but more to get the best possible bond between the layup and the foam.
If I planned on only sailing in lakes and not up and down the coast I probably wouldn't bother.
I got my folding mechanism back from the anodiser a couple days back. I'm very happy with the way it has come up.
I'd post a pic only it's been over 3 months since I could upload any photo to the photo albumn on this site.

I'm still enjoying working on the F85. The fairing was much easier than I thought it would be having faired 32ft cedar strip hulls in the past. The hulls are all faired with just 6 hours of long boarding all up. Now I'm getting the beam jig CNC cut so I can get to work on the beams.

Phil, have you got a handle on what the all up weight of the boat is going to be yet?

The class rule for the 8.5 has a minimum weight of 900kg so I'm keen to try to get close.