Fiberglass Core Material - What to use?

[CaptainShack]

I have a fiberglass question for those with more experience. I need to build up and shape small pocket of fiberglass to raise two twin 6kw electric pod drives up into my catamaran so the props will stay behind my hull shoes, protected. Sadly the drives are slightly to long and would end up being the lowest part of my boat without this modification. Raising the top of the drive up into the hulls about 4-5 inches. Basically the black boot seen in the attached image. That means I need to fiberglass in a flat mounting point, that sorta matches the top of the drive up into the hull.

I was thinking a foam that can be cut and shaped would be best. Then lay on the glass over it. Nice flat mounting plate in the middle to bolt up through. But what kind of foam do people use for such a project? I'm on the East Coast of the US in North Carolina. So it would need to be a material I can find here.

Any help or advice on how to accomplish this and with what material is best would be really apricated! What type of fiberglass cloth is best for the type of stresses of a hp equivalent little drive pushing the hull long bolted to it.

[CaptainShack]

For a better example of what I'm currently thinking.. here is a normal sail drive. Something like this but with a flat top over the middle for the bolts and wire to go through. This image is actually foam cored.. I just don't know what kind of foam is used that goes well with fiberglass.

[Chotu]

Corecell is the best. I’d get higher density like 12lb. 5lb density might do it, but there will be a lot of force it looks like. 5lb density could crush.

I would taper the new platform too.

Make it the shape you want, but taper the edges around it to evenly distribute that load onto the hull. Easier to glass like that also.

An odd picture, but the taper is right on this foam pad. Lol. Tapering the edge will better distribute all that torque loading




As for the glass it depends a bit on the resin. What are you using?

[CaptainShack]

I've got some TotalBoat 5:1 epoxy resin from a project last year.
But I'm open to suggestions as that project wasn't below the waterline and has been sitting aboard through the winter. I haven't checked its data sheet for storage temps yet so I don't fully trust it. I think I see what your talking about.

I've attached a picture of my hull. Thinking the actual external pocket will be as small as I can get it, something like a standard sail drive while still getting the pod drive up and inside then building out the this tapered mounting plate like the image you supplied. What would you use for the actual flat plate? Pre-made fiberglass sheeting? Starboard like a backing plate? Rather not use wood or anything that can rot.

If anyone has any other advice please drop it in here. I'm at the planning stage at the moment before I start ordering all my components.

[coopec43]

If it is subject to force why use foam?

As I understand it it is a small area so weight would not be a problem. Why not use a solid fiberglass platform?

[CaptainShack]

I'm new to fiberglass work, but I figured it be easier to get the shape I need to make the "pocket" with a foam material. Then cover that in fiberglass vs just laying sheet after sheet of glass to build up the 4-5 inches of material?

Am I off the mark here? I'm a bit surprised by the cost of the foam. How would you do it out of just fiberglass?

[davil]

[QUOTE=CaptainShack;3736094]I've got some TotalBoat 5:1 epoxy resin from a project last year.
==================================

after having to redo a project recently because the resin will not cure due to being old,
something to think about ?

checking their website

https://support.totalboat.com/hc/en-...-a-shelf-life-

Do TotalBoat epoxy products have a shelf life?

If stored properly, with lids sealed tightly, TotalBoat epoxy products can have a shelf life of 12-24 months. Each TotalBoat epoxy resin and hardener label indicates proper storage and temperature conditions in order to extend shelf life by limiting exposure to extreme cold, heat, humidity, and contamination. Note that products containing a thickening agent, such as thixotropic adhesives, may have a shorter shelf life.

------------------------------------------------

on the core issue, my understanding is the core being used only to form the structure, the strength much like an egg is given by the layers of cloth and epoxy?

[CaptainShack]

I will double check that epoxy before I decide to use it. I want to be 100% sure its still good.

davil I think your right about the strength. I just didn't want to use some kind of foam that will react poorly to fiberglass and epoxy. Corecell or as someone else mentioned pvc foam with some heavy layers of glass sounds like what I'm in for. Though I can't find that 12lb corecell foam actually for sale. Gonna have a chat with the yard about getting the right supply's.

[coopec43]

Originally Posted by CaptainShack

I'm new to fiberglass work, but I figured it be easier to get the shape I need to make the "pocket" with a foam material. Then cover that in fiberglass vs just laying sheet after sheet of glass to build up the 4-5 inches of material?

Am I off the mark here? I'm a bit surprised by the cost of the foam. How would you do it out of just fiberglass?

I'm not suggesting a solid glass platform.



Has your wife got any Tupperware (or plastic) containers? One day (when she is out-of-town) you could borrow a suitable sized one to use as a male mold. Then lay X4 layers of Chopped Strand Mat glass over the outside of the container, trim to shape then fiberglass into the hull.

[Matt Johnson]

Look for Coosa board as a good option for this use. It's a fiberglassed layered with foam and extremely high density 15-26lbs and handles compression/ through bolting well.

[CaptainShack]

Hey!! Neat to see a name I recognize! The MJSailing channel! Nice work on that very cool cat your building. I've been running my channel full time over at https://www.youtube.com/c/TheXPGamers for the last decade. Its a
odd job / lifestyle.

Can someone explain to me this foam lbs density? Is that weight based on a cubic foot or something? Nice Coosa board has a distributer near my boat. Thats fantastic.

As for glass. Whats considered the standard all around hull work fiberglass cloths weight / Type normally used? Been watching a verity of videos but I'm getting a bit lost on what to actually order for this project. MJ if you guys have a break down on hull fiberglass layup feel free to link it.

[wyb2]

I think you need to clarify your plan a little. Is the foam just a mold that you build around, and gets completely removed? Or are you building the structure with a foam core? I think it’s the former, but I think you are getting answers for both.

[Jammer]

Hello Mr. Shack


If foam is what you want then on the East Coast you could get 5# corecell from Jamestown Distributors, in Rhode Island. They have a web store and ship out.



I have used their Corecell foam. It isn't clear to me whether the compressive strength of 5# foam will be sufficient for what you are doing. I would think it would probably be fine but I'm not a naval architect or mechanical engineer so that's just a guess.


Jamestown also have Baltek Airex PXc board which is higher strength, but I haven't used it and don't know much about it firsthand.


For smaller built-up areas you can use multiple layers of glass to get the thickness you want. You can also use G10 fiberglass board which isn't really intended as a core material but it is strong and can be used that way. Again Jamestown has G10.


Wood does rot eventually but the right wood properly installed lasts a long time...

[catsketcher]

In a small structure I would avoid cored structures. I like using margarine containers as well. Look around for a slightly tapered container in the shape that suits and then wax it. Then use multiple layers of fine glass to make the shape. I would suggest about 5-8mm of thickness for the laminate.

Be wary of using a few thick laminates. Heavier laminates are more prone to pinholes and water weeping through them after installation. Use heavy laminates by all means, but ensure you include a couple of lighter laminates too.

cheers

Phil

[CaptainShack]

Coopec. I like part 1. of the plan is to wait till she's out of town. Shes the one super hyped about having twin pod drives.
Shes ready to start mixing all the epoxy.

I'm starting to think I might have over thought my original plan with the foam. The image below is the bay the fiberglassing will be done in. After getting the info from this forum and the right terminology to start researching. "Thanks btw" now I'm thinking..

Measure and Cut the hole first after figuring out right where I want the prop to end up.

Figure out the height inside and fiberglass for my flat mounting surface from the top and sides. Fiberglassing it in, Tapering and tieing it into the side walls for strength.

From outside fiberglass the side walls of this new small well and outside of my flat mounting surface to help re-enforce it. So basically fiberglassed from inside and out.

All with 5-8mm fiberglass. A recommended Epoxy resin. (Feel free to pitch your favorite easy to find brand)
Maybe G10 fiberglass board, Baltek Airex PXc board,
Cut a board, lay it flat over my new hole in the hull. Fiberglass it in then tapper around the plate to seal it up.

and maybe run two vertically like 2 stringers and run fiberglass. Probably overkill.

Originally The foam was going to be easier in my head to shape to the hull.

Thoughts?