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prop fiberglassing
By harrie, Section Wind Posted on Sat Feb 04, 2006 at 02:53:38 AM MST
information needed

I have done a good amount of fiberglass work on different things, but I always have a little trouble working around sharp corners like there is on our hand made props. It seems like I always get air bubbles under the fabric while trying to wrap around the leading and trailing edges. Do any of you have any tricks or comments that could help me accomplish this task. I have just finished up three nine foot props that I lamminated out of clear pine and am a little worred about the glue joints holding up, so with all the work it was to make them, I want to make sure it holds together.
Thanks in advance, harrie

prop fiberglassing | 19 comments (19 topical)

Re: prop fiberglassing (3.00 / 0) (#1)
by coldspot on Fri Feb 03, 2006 at 09:50:43 PM MST

The "Glass Work" I've done, (not a lot but have re-bottomed a 17.5' Boat).
You need to use more resin first, then lay out matting or cloth, then lots more resin, then mat/cloth, ect, ect.
Worked best as a "Team effort", I guy mixing, one cutting, (cut's can be done in advance) and one guy spreading, don't be afraid to throw away "Chip-Brushes" they are cheap for a reason.
A handy little spiked wheel roller on a handle, (name just out of reach by my coming B-day, Damm, Youth sure is wasted on the young), Sharp points help with rolling the glass down. The fiber-glass roller looks a lot like a seamstress type thing, just much larger and many wheels not just one.
I learned to mix a bit slow, (Hardner to resin ratio){LESS} in summer or large projects. Small and or cold can be mixed a bit "Hotter", {MORE}.
But like most things like this, There are artists and Good enough!

PS: learned the hard way that to patch a boat, minimum of 4-6 layers glass, 8+ better!
Build up beyond whats needed and grind back after cure!

Re: prop fiberglassing (3.00 / 0) (#2)
by amiklic1 on Sat Feb 04, 2006 at 01:50:44 AM MST

I don't think it's gonna stick with the wood the proper way. As my experiences are, fiberglass sticks to nothing but to itself. If I were fiberglasing some serious set of blades, I'd rather use epoxy, as it sticks to wood much better.
It sure looks as it's "glued"! with the wood, but don't forget all stresses and vibrations applied on the blades. Maybe some kind of primer would solve that problem. And maybe you have some fiberglass that's different than mine. I hope so.

Free energy? Yes, please!

Re: prop fiberglassing (3.00 / 0) (#3)
by hvirtane on Sat Feb 04, 2006 at 02:09:15 AM MST

Guys, who are experts of wooden
boats in general agree that
fiberglass work on wood
does not stand the time.
There is always moisture inside
the wood and if the wood is
covered by fiberglass everywhere
the wood inside will start rotting
and the bond between the wood
and fiberglass is lost.
In general they say
that epoxy is better.

- Hannu

Re: prop fiberglassing (3.00 / 0) (#7)
by dinges on Sat Feb 04, 2006 at 07:37:19 AM MST

Ask 2 experts and you get 2 different answers.

The only thing two engineers agree upon is that the 3rd one is an idiot.

Polyester does bond to wood. And it can stand the test of time and hardships of nature. But lots of little details apply. One of them, as has been mentioned, is dry wood. Not dry but -really- dry.

It can bond so well that polyester was also used in gliders (before epoxy virtually took over). Has little to do with it bonding to wood, but stiffness at higher temperatures.

Personally I prefer epoxy over polyester, but for other reasons. What does Lloyds of London think of the matter; do they forbid using polyester & wood together? If it's good enough for Lloyds...

Peter.

facts, not fiction please.

[ Parent ]

Re: prop fiberglassing (3.00 / 0) (#4)
by Propwash on Sat Feb 04, 2006 at 04:46:05 AM MST

It is not possible to get glass around a sharp corner with out getting bubbles in it. All corners must have some radius to them. A lot of your success will depend on what kind of cloth you are using, some will go around corners better than others. West system is the way to go even though it is much more expensive. West system offers a slow cure epoxy and a fast depending on what climate you are in. The bubble busting rollers work really well, but if you find a West system display in a store or on line you will see they offer a yellow plastic sqeege similar as to what you would use to trowel on bondo. These work quite well. The trick is to wet out the cloth on a board or flat surface of some kind and then wrap it around your blades after it is wet out. Use the sqeege to pull out the wrinkles and bubbles. You will probably have better luck if you only do one half of the blade at a time. If you try to do the whole blade you will be pulling bubbles out of one edge and adding them to the other. Do one edge at a time and overlap your seem in the middle of the flat area of the blade. West system sands a litte better than polyester resin so sanding the overlapped area flat isn't as bad as it sounds. I don't know exactly what your blade shape is but it might be best to do the tips first, then leading and trailing edge in three separate steps. The cloth that west system sells should work fine for this project. Hope this helps. Good luck.

Kevin

Re: prop fiberglassing (3.00 / 0) (#5)
by tecker on Sat Feb 04, 2006 at 05:15:33 AM MST

Heat the wood to 180 degrees and then soak it in resin until the the resin soaks into the wood .On the edges stop well short of a sharp turn use resin and loose glass mixture and feather past the edge . I have been using spar urethane to soak the wood in before hand very thin and soak over night with weight on to keep it's shape(during drying)I ' .This is especially good on plywood .48 hrs soaking it and I can get it to almost machine surfaces. I 'm working on plywood blades soaked in urethane and bent during drying. My jig is a little primitive but I think it will work .

Re: prop fiberglassing (3.00 / 0) (#6)
by wdyasq on Sat Feb 04, 2006 at 07:14:58 AM MST

Have a look at 'The Gougeon Brothers on Boat Construction'. It is about 2 inches thick and explains how to do what you need. The Gougeon Brothers invented and own the copywrite to 'WEST System' and their methods and materials have been tested and proven to work. I have found epoxies I like to work with better than the Gougeon Brothers brand.

'If it were mine'. and it is not. I would use a light cloth, about '6 oz', wrap the leading edge and at the trailing edge run it past letting the two layers of cloth bond together to seal the trailing edge. I would put the cloth on dry and then work it in with the squegee mentioned. I would use epoxy. There are many 'tricks' that can be shown but are difficult to explain.

Hannu and Kevin have given some good information. Polyester resin will not bond to wood. It is not a good idea to mix types of 'resins' or materials. Epoxy is not UV resistant. It needs to be painted for UV protection. 'Varnish' or any other finish one can see through does not give long term UV protection.

The editor may want to move this to the Rant and Opinion section, Some folks don't like facts and the truth.

Ron.
Adventure is just bad planning." -- Roald Amundsen

Re: prop fiberglassing (3.00 / 0) (#8)
by dinges on Sat Feb 04, 2006 at 07:41:55 AM MST

Epoxy and polyester are usually covered by a gellcoat, not painting. Gellcoat being on a polyester-basis, IIRC.

Peter.

Lover of truth.

[ Parent ]

Re: prop fiberglassing (3.00 / 0) (#9)
by zapmk on Sat Feb 04, 2006 at 09:20:58 AM MST

How about the vacuum bagging process, Like they do for foam wings on model rc planes
makes for a real nice surface. with wood cores I would think you would realy be able to get the fiberglass to lay down realy nice.

Mike

Re: prop fiberglassing (3.00 / 0) (#10)
by Propwash on Sat Feb 04, 2006 at 10:16:59 AM MST

You'll find a lot of usefull information and how to stuff on thier website. Here is the link. http://www.westsystem.com/

Kevin

[ Parent ]

Re: prop fiberglassing (3.00 / 0) (#11)
by glassman on Sat Feb 04, 2006 at 10:59:53 AM MST

Harrie,
what did you use for your glue joints ? and why are you worried about them ?
what type of resin are you planning on useing ? (epoxy or polyester)
what type of cloth do you use ? (csm, wr, or cloth and what weight ?)
bubbles are a huge problem but depending on your answers to the above they can be eliminated or at least kept to a minimum.
glassman.

Re: prop fiberglassing (3.00 / 0) (#12)
by harrie on Sat Feb 04, 2006 at 02:50:27 PM MST

Hi glassman, I guess the main trouble is I was too cheap to use the right kind of glue. I used exterior Elmers glue. Its a glue that i have had good luck in the past, and thought it would be ok, but when I started to shape the prop, cutting off the excess, I found that I could easily rip the lamminated peices apart with just my hands. I dont know what happened, it was like the glue was no good at all, otherwise I would not be worried about fiberglassing. I havent purchased any resin or cloth yet,being I wanted to wait for any suggestions that now have been posted. I guess at this time, Im leaning toward using a epoxy rather than polyester, and I think to keep the weight down, I would want to go with a lighter weight.

Thanks to all of you for your comments, Harrie

[ Parent ]

Re: prop fiberglassing (3.00 / 0) (#14)
by Don Cackleberrycreations on Sun Feb 05, 2006 at 08:52:11 AM MST

I have built nearly a dozen small light weight fishing c1 kayaks and have always used low cost materials. Such as luan paneling,styrofoam (first painted with latex befor covering with glass) canvas, and bondo brand resin. Ive never had any trouble getting the resin to bond to the wood be it the plywood ribs or the paneling. They have all lasted many years even when I forget to turn them over and they fill with standing water over the winter.
keeping the bubbles out isnt much of a trick as many have said. First paint on a light coat of resin while its still wet place your light mat on and squeegy it down.
Keep in mind people the strength comes from the glass not the resin . 3-4oz mat should be more than enought to seal and strengthen wooden blades and a quart or so of resin would do the job unless your pretty waistful. The reason you must sand between coats with polyresin is it contains wax to seal the surface for curing its also advisable to sand and paint after glassing with poly as UV will degrade it unless you use a UV stablized gel coat. Personally I whould think the very slight roughness of a 3oz mat nicely saturated would leave a good finish on a set of blades the texture working alittle like the dimples of a golf ball reducing drag at least on the back of the blade.
For laminating wood that is likely to be out in the elemnets Polyurathane glues are best IMO ,they are uneffected by moisture and provide a permenant bond . They can be a bit unforgiving as well once you get some on your skin its there until it wears off.
Just my opinion your mileage may vary.
poor unedekated redneck with attitude
[ Parent ]

Re: prop fiberglassing (3.00 / 0) (#13)
by gator on Sun Feb 05, 2006 at 08:27:18 AM MST

What kind of glue do you need to use for laminating wooden blades?

[ Parent ]

Re: prop fiberglassing (3.00 / 0) (#15)
by Propwash on Sun Feb 05, 2006 at 11:10:55 AM MST

I think West System is top banana in this dept also. I have built a few iceboats and the yack is that West system works best for laminating. A few guys are using Titebond 3. I am currently building a boat using Titebond 3 (because it is much cheaper)for laminating. I have been tearing scap wood apart after a glue job that I couldn't if I used the West system. Titebond 3 has a higher grade of water resistance than 1 and 2. I'll be able to give you a better answer on strength if we ever get cold weather again so that I can try my boat. I'm up to my ass in mud here for now.

Kevin

I

[ Parent ]

Re: prop fiberglassing (3.00 / 0) (#16)
by DanG on Sun Feb 05, 2006 at 01:43:20 PM MST

Using polyester resins on fine-grained wood isn't recommended. Here in US that'd be redwood and cedar, so coarser grained wood and a slow set polyester resin should do fine. If the wood surface is glass smooth some light sanding to open the wood grain up is called for. If you are lucky enough to have old-growth cedar definately use epoxy!

Re: prop fiberglassing (3.00 / 0) (#17)
by glassman on Sun Feb 05, 2006 at 05:22:52 PM MST

Harrie,
If you have a friend that has done vacum bagging by all means grab him/her and ask for help
Epoxy is by far the way to go (in my opinion) the "trick" is to wet out both sides of whatever you use , and for a tight radius use thin cloth and more layers or use mat (csm) mat will lay around corners much better than cloth (some will argue this)be patient the resin needs to disolve the sizing on the cloth or matt which is why it seems to be more workable the longer it is on the cloth. cut cloth , rip matt. cloth has strength in two directions mat is more unidirectional. the mat will not give as nice a finish so more sanding will be involved . 1.5 oz mat and at least 2 layers would be minimum. 1 gallon of resin will do about 3 sq. yards of 1.5 oz matt.I think you would want to use cloth everywhere except the leading and trailing edges and use matt there to tie it all together with a bubble free finish. use squeee on cloth and roller on matt . use gloves with epoxy!

Re: prop fiberglassing (3.00 / 0) (#18)
by glassman on Mon Feb 06, 2006 at 07:13:42 AM MST

just a couple of corrections i need to make here , i said matt is more unidirectional, i meant its mulitdirectional ( fingers getting ahead of brain and i apologize) when i said use a roller for matt, i meant a resin roller to relieve the air bubbles (instead of the squeegee), however you can use a paint roller.buy the cheapest shortest nap roller you can get(the ones for putting glue on formica) buy it in 9 inch and cut into 3- 3in rollers on your table saw (why is a 3in roller as much as a9 inch?) now you have 3 inch rollers that cost about fifty cents each and you won't feel bad about throwing them away , it will cost you more in acetone to clean them than they are worth. someone already mentioned chip brushes just use and throw away .
thank you

Re: prop fiberglassing (3.00 / 0) (#19)
by paradigmdesign on Wed Feb 08, 2006 at 06:10:47 AM MST

I would try using a 7725 hexcel style 0/45 degree fabric. It has a "fast wet-out and good drapeability"
"Don't worry about tomorrow, plan for it."

prop fiberglassing | 19 comments (19 topical)

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