Originally Posted by DavidF85SR
Thanks Phil and Nico
Great to find some builders of the F85SR Online.

Welkom to the club smile

Originally Posted by DavidF85SR

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?


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.

Originally Posted by DavidF85SR

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'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.

Originally Posted by DavidF85SR

I am expecting this to be a five year build.

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.

Last edited by nico peursum; 11/24/11 03:11 PM.