Fiberglassing a Trolling motor platform - Pix - your input please!

[papp101]

Hello all,

I have a 2000 Bayliner 1600 (similar to the newer 160.) Last year I put a small trolling motor on the bow of my boat using some washer, bolts and a 1/4" aluminum plate. Worked great until I found a deadhead while crusing at 2.5 mph the other day, and crushed it in. Allow me to be the first to "flame" myself here, that the temporary installation to get it running for a season wasn't really the best choice from a stress standpoint. Great proof of concept, no follow through on making it sturdy.

I am, however, excited to do some glassing on my boat in an attempt to make it appear more factory. I have no problem messing with polyester resin or spraying gelcoat, so I'm here to ask for your thoughts on the installation. I really appreciate your input!

Process in my head is to glass in the plywood to the boat, reshoot the gelcoat to blend it in, drill and attach the threaded inserts for the black trolling motor "puck" as I call it.

1. I would preseal the plywood with resin (polyester) then lay a few layers of chopped strand mat on the boat, wet it out, then place the plywood core on top. This would create and extra glass lay in between the boat and the plywood.
2. Then drape chopped strand mat over the top of the plywood, down the sides and 2-3 inches out onto the boat surface. Follow that with a layer of 1708 biaxial woven and then 1 or two more chopped strand mat.
3. Block Sand, Fill with PR-14 filler, sand again.
4. Wipe with acetone, shoot gelcoat and polish out.
5. Drill holes for threaded inserts and install trolling motor mount "puck."

Questions that keep me from finishing this project:

Will that draping method described above with the sandwiched mat in between be strong enough to hold the trolling motor?

Should I also bolt the wood core to the boat before glassing it over?


Here are some pics.

Old Mount and damage.











Ground out and glassed back up.





Wood ply platform shaped with trolling motor in place.

 

[gm280]

Very first thing I have to say papp101 is, :welcome: to iboats. Always nice to have a new boater on board...

Now let me congratulate you for a nice setup. I can't see how that will not work. You could polyester the underside of your cleverly formed wood adaptation and even CSM and 1708 if you like. Then mix up some PB to install it to the prepared area. That way you can fillet and smooth out the entire assembly to make it look like it was manufactured that way. Then follow on with the CSM and 1708. And as you use the 1708, do it is increments. Start with a 3" or 4" tabbing and follow that with a 6" tabbing where you can. It should be solid as a rock after that. Then fill any imperfections sand and Gel Coat and blend. I would think that would hold any trolling motor very well. Very nice idea in my opinion. I am certain others will chime in with their ideas and you can chose the procedures you like the best. But do post pictures however you choose to do it. I'd like to see the final product.

Oh, the PB stands for Peanut Butter which is a term we use on here to describe a mixture of Polyester Resin, with MEKP, Cabosil, and 1/4" Cropped Fiberglass material. You mix it up to give a peanut butter consistency and use it like a body type filler to fillet areas. Once it kicks and cures, it is as hard as a rock. Usually I mix the Poly resin and MEKP until they are properly mixed, then I pour in about the same amount of Cabosil powder and mix that until it is just about the thickness I want and follow up with the 1/4" cut fiberglass strands. Mix it all very well and use. It will kick depending on the amount or percentage of MEKP you use and the ambient temperature.

 

[papp101]

Thanks GM280! Excellent writeup. I really like your approach of the PB filler before fiberglassing, as I've seen some do that with stringers. My father had suggested bolting the corners of the plywood through the deck to a large metal strap or oversized backer/washer on the inside with a bolt to hold it down. I don't mind doing the but if just fiberglass would do the job I'd rather go that route.

I appreciate the input and will post pics regardless.

-Phil

 

[jbcurt00]

Yep, coat the ply w poly resin AND cover it w/ CSM. This is to seal the plywood. Then PB fillets and tabbing to attach it to the boat.

 

[papp101]

Sounds great. I didn't purchase any cabosil, and now wish I would have. Any suggestions for creating a down and dirty PB mixture without it? could I add a little long hair bondo mix in with some extra hardener and some CSM strands to make a bondo-resin blend?

Or throw some CSM in little chunks into my now "workshop-based" coffee grinder?

Or is the fillet of much more structural importance that I should order and wait for the cabosil?

Much appreciated!

 

[gm280]

Sounds great. I didn't purchase any cabosil, and now wish I would have. Any suggestions for creating a down and dirty PB mixture without it? could I add a little long hair bondo mix in with some extra hardener and some CSM strands to make a bondo-resin blend?

Or throw some CSM in little chunks into my now "workshop-based" coffee grinder?

Or is the fillet of much more structural importance that I should order and wait for the cabosil?

Much appreciated!

papp101, there are a lot of different materials some use as a thickening agent. The function of Cabosil is just that, it is a thickening agent but doesn't take any of the polyester resin qualities away when used. Some have uses flour, wood/saw dust and a lot of other materials. However, I can't recommend any of them because I have never tries any of them. I just bought and waited for the correct material to do the job right. Maybe others can make recommendations for something you may already have on hand. My personal opinion, with the effort you've already shown, I'd buy the proper Cabosil and wait. You've gone this far, why take any chances. :noidea:

 

[jbcurt00]

You might be able to grind small pieces of CSM even finer w a coffee grinder, dont know, never done it.

Avoid any filler type material that absorbs water, like sawdust and flour.

GMs right, order it. Ordered tonight, and it'll be here by the weekend, possibly sooner.

Cabosil and micro balloons are great to use for filler, and to make it even stronger, you can chop some CSM into 1/4in strands. Adding 1/4in CSM to PB makes it hairy PB. And its much stronger.

 

[Woodonglass]

If you attempt to put csm in a coffee grinder or blender all you'll get it a big "Fluff Ball"!!! Don't waste your time. Since you're using Poly resin you really can't use wood flour or talc or anything else really other than cabosil. Poly resin IS hygroscopic, meaning it can/and will absorb water to some extent and you shouldn't use a filler that encourages this such as wood dust or talc. Cabosil and 1/4" chopped fibers are very cheap so bite the bullet and buy some.

 

[papp101]

Sounds good. No problems spending the money, just hate waiting. :/ True though. I'll either order it next day from the big jungle website or try to leave work early to get to express composites in Minneapolis.

 

[papp101]

Well I didn't do the best job coating my wood core in CSM, I don't really have any air bubbles on the bottom or one side, so I'm going to cut off everything that didn't attach and work on ensuring the sides are good and covered. they've been sealed with resin, but only CSM on one side.

Below are pictures of the bottom of the wood core. Once I cover the sides, I'll attach it to the boat with another layer of CSM in between, let that harden, add the fillets, then start glassing over the top and down the sides to tab it in. Cabosil will be here tomorrow!

 

[gm280]

Okay, looks good. You have to understand that compound curves like you have with this part is very hard to get fiberglass of most any type to lay down perfectly. Just grind off any glass that didn't lay down and lay some more over those area. If will all work out in the end. And as you work with glassing more, you get better with it as well. Keep posting. :thumb:

 

[Woodonglass]

From what I can tell you probably tried to brush the resin on. Next time, just DAB it on with a cheap Chip Brush. Cut 1/2" the length of the bristles off. Also put down a coat of wet resin first and lay the CSM on top of it then pour a Little resin on top and either roll it on with a short nap 4" roller or dap at it with the brush. Dabbing works best on the edges and rolling on the flats. Always work from the middle out to the edges. Tear the edges so the strands are really "Hairy" and they'll go over the edges better. Remember you only want to use the minimum amount of resin required to make the CSM go clear. It takes less than you will think. A resin rich laminate, wastes resin and actually creates a weaker laminate.

 

[papp101]

GM280 - I agree - definitely watched a bunch of videos (mostly the Boatworks Today ones) and realized I should have pulled and frayed those edges a bit for those less than 1/4" radius corners.

Woodonglass - I did do a bit of brushing, mostly dabbing, but for sure my technique wasn't spot on! I wet the base, wet out the CSM on a table with plastic to fully saturate, then laid it on. No matter how much I dabbed those edges it wouldn't lay over, so I think you're correct on the frayed and hairy edges. Good points on less resin rather than more!

So this evening, I cleaned up the un-connected edges of the fiberglass on the wood core, laid down 1 layer of standard woven roven on the boat side as a final strengthener, then followed that with a layer of CSM. It worked pretty well, however I did a good job of keeping the resin thin which meant when I wet out the bottom of the wood core then set it down, there was no "smush" like I was hoping for. There are definitely voids under there, but once it hardened I gave it a stress test and could lift the whole nose of the boat trailer (about 190 lbs) without hearing any cracking.

In hindsight having read WOG's Stringers writup in his sig, I should have waited for the cabosil tomorrow and covered the in-between of the boat and wood core with peanut butter mixture before placing it on the boat. However, as it's all a learning process, I'm pretty happy with its strength even prior to tabbing in the top.

Now, what you've all been waiting or scrolling for, the pics.










A little test fit as well.





Comments always welcome. I really appreciate your help and input!

 

[papp101]

I added 2 layers of "Peanut Butter" (1/2 cup of 1/4" shredded CSM, 4 oz poly resin, equal amount of System Three Silica Thickener. Mix, add hardener, add silica.Put in ziplock bag, cut the corner in a pastry bag like fashion and fill the edges. Smooth with a radius stick shaped to the size desired.)









Came back and shape-sanded using some pvc pipe (1") wrapped in some 40 grit sandpaper to smooth out the fillets.a little grinding and block sanding as well. Then tabbed in the sides with some 1708 as best I could, let it set up and ground off the flakeys. Followed that with a layer of 1708 on top of the block, wrapping down the sides. I keep getting a few bubbles, but I grind them out before the next layer.












Now I'll let that set up, grind off the flakeys, wipe with acetone and glass over the whole thing with one sheet of CSM torn hairy at the edges. Once set up, I'll sand that out, wipe with acetone and use the P-14 fairing compound to prep for gelcoat. I was originally going to spray the gelcoat, but now am thinking maybe just brushing 2 coats in either direction and sanding it up.

Any thoughts on that?

Thanks!

 

[papp101]

Here are the two videos I'm referencing from Boatworks Today, I know they've been posted here before.

 

[papp101]

And the finishing steps. I do have some PVA I'll spray to cure the top coat.

 

[aptech]

Papp101 .....This is your FATHER!!! I told you to buy an aluminum boat!!! ;-) .... Great job!! Love all the great help from others!! I'm still up for a few thru bolts into a wide and long back up plare or plates possible under the hull. Just me!!

 

[papp101]

You know your dad is kewl when he posts on your projects! Thanks Dad! I agree with the desire for bolts . . some may still end up there at the end.

Added a top layer of the csm after grinding out a few bubbles.







Cant wait for it to harden! will sand and add the fairing compound.see the link below for the product I'll be using.

http://www.spartite.com/p-25-p-14-ultra-filler.aspx

 

[jbcurt00]

Papp101 .....This is your FATHER!!!

James Earl Jones* narrated this when I read it :facepalm:

I'm still up for a few thru bolts

Thru bolts to hold the new plywood platform to the hull or the motors mounting bolts thru the new platform AND hull?



*Its a Star Wars reference, for the non-nerds in the bunch.

 

[papp101]

James Earl Jones* narrated this when I read it :facepalm:



Thru bolts to hold the new plywood platform to the hull or the motors mounting bolts thru the new platform AND hull?



*Its a Star Wars reference, for the non-nerds in the bunch.

Yes, basically holes drilled through the wood around the perimeter, counter sunk, all the way through the mounting surface and bolted from the back side. Similar to how the previous aluminum mount was made.