Moomba Boomerang Rebuild

Greetings - I'm new to this forum but thankfully I located it. I'm also new to boat repair so I need some help. If I'm in the wrong forum area, please let me know.
My son and I purchased a 1996 19' Moomba Boomerang. It's a ski/wakeboarding boat. It runs a 351 Windsor motor with a straight drive propeller system. We purchased the boat knowing the engine beds were dry rotted and kinda figured there may be some stinger issues as well. We guessed right. If I can figure it out, I'll post some photos and then I'll start with the questions if allowed.
The boat has two stringers with multiple ribs that do not reach the side of the boat. The engine beds appear to be made out of 4x4 stock and glassed over. There is major damage up under the deck and getting up there will be a challenge. The top cap is glassed on so I guess the first question is how do we get the top cap off? We already removed the rub rail and all associated screws, went around (carefully) with a wide chisel and now somehow I guess we have to cut the glass that attaches the top. How do we do that?

 

Greeting !!You doing the right thing and a totall strip out is a good place to start . then clean it 100% and do any modificaions and repairs and slowly re build back to better than before Fantastic !!good luck . will be at work soom and will look closely at the pictures you have posted .

 

Thank You

I appreciate the words of encouragement. The area under the deck in the bow is so tight, we are going to have to cut the top cap off to do it right. Not looking forward to that but it's like you said. Build it back to better than it was new. I will have a lot of questions as soon as we can get everything out but right now we are concentrating on access to the bow portions. We plan on using a die grinder/cutter to cut the glass holding the hull and cap together. Just hope I don't go too deep. Yikes!

 

You come to the right place and keep posting pictures always . the deck could be just rivited or screwed and not glassed so just take it gently . Nothiing much holds those things together . A good sharp wide chisle will do a good job and is a little more forgiving
Catch ya soon !!

 

I got up in there late yesterday and from about one foot back from the bow, the glassing begins. Today I'm getting set up to cut the glass holding the cap since I just don't have enough room to get to the bow section without removing the it. I probably could but the work would not be of the quality I want. What type of wood is typically used for the engine beds (351 CI) and is angled metal ever used to cover the bed once installed - in between the bed and the motor mounts?

 

Progress report ??

How is the de-decking going ?? getting all the way round without chopping the top off the hull ??

 

No Top Cap Removal

I've decided against the removal of the top cap. It is glassed on and I am fearful of cutting too deep and going thru the hull. Same way with the stingers but I have to do them.
So far I have removed the floor and all the foam. Ribs were practically non-existent, stringers were in a little better shape and the foam was saturated with water.
My next question is how to form the stringers to the shape of the hull so there are no voids between the stringers and the hull. I am thinking that there will be a huge trial and error session until cut right. I'll send some photos tomorrow. Thanks for checking on me. Mark

 

Ok you have seen what happens if you replace what was there (wood ) with yet another lot of Wood , ok i hear yells and screams coming "but its taken 20 years or more to rot" !!
What about the weight gain as it gradually re-absorbs mostiure over time .
How about making your stringers from Glass over foam ?? Or you could simply make a U shaped mould from wood and wax it and mould over with a couple of layers of glass then release and fit to the hull shape and then do your glassing over the top and down onto the hull . Wont absorb any water forever more !!

My own boat has no wood any what , was built in 1975 and is always dry as a bone under the floors and every where else , The wooden transom i did away with 4 years ago ! ,what i built was a 100% glass complete new transom and it is much lighter and stonger than the origanal because it upped the hp from a tired old omc 70 Hp to a Yamaha 115 Hp .
Flotation Foam under floors is completely the wrong place to have any kind of flotation any way as it wants to roll the boat over upside down if it gets completely swamped to the gunwhales sometime !!.

 

Just do one stringer at a time if it's not too late. Ideally, you would have a cradle built to insure against deforming the hull as you take what's left of the original structure out.
A sawz-all works well for removing the existing stringers if you're handy with one, and I guess it's probably the best tool even if you're not. When I replaced the stringers on my boat, I cut them about 3/4" above the hull - this way I could fit the new ones exactly in the same spot, and I didn't have to put new filets along stringers as the existing ones worked fine. You just have to grind them a bit to blend them into the new stringer.

Foam stringers covered with biaxial cloth and epoxy is a good option.

What's the condition of the motor?

 

Just remember secondry bonding make sure you dont grind a bit ,but a lot !!! .The minimum for bonding is 50mm so for secondry bonding onto old glass i would go at least 80mm each side !! Stringers are a structual part of the boat . Bonding surface needs to be 110% clean clear virgin glass the more fibres sticking up from the surface of the old glass the better !!.
Remember If you start using epoxy you have to stay with epoxy , dont try to use polyester or vinylester over the top of epoxy !! there will be a inital stick But its no where near as strong !!!If you use timber do all your shaping and sanding and then 100% epoxy seal the wood like every where !! Solid timber is stronger than ply wood !! Remember also glass does not like going arond sharpe corners so a good radus on the top edge and you get smooth well stuck layers of glass . Peel ply is a good way to help hold the glass down and makes a nice smooth neat job . Thus will get rid of any surplus resin thats not needed once the glass is rolled in place !

Glass in strips along the hull up the side of the stringer and over the top then stop!!, Do the same from the other side ,along the hull up the sides and over the top and stop . The top will double up layers each time you lay up !!,sound like a hassle but you are doubleing layers on the top because the top of your stringer is what will give you a little extra stiffness and strength !! you are trying to create a "I" beam in effect !!
Because you have left a part of the old glass behind in the form of a channel A wire brush in the end of a drill and clean and scuff the inside of the channel and when you push the new stringer in place you could wrap the bottom edge and up the sides with some epoxy rich glass to help with a even better stick and stay job . Might as well get as much bonding as possibele every where !!.

 

Great Information

I was also going to use the CPES (sp?) prep to seal the wood before I installed it into place. Also, I have heard two schools of thought. One is that the stringer should never touch the hull...I guess 3M makes a wafer thin product that keeps it off and the other of course is that it has to. The theory on the first one is that the stingers (where attached to the hull) will create "hard spots" and the hull could possibly crack at those points???

When I demoed (is that even a word?) the ribs went from the stringer (glassed and stapled) but was shy of the side of the hull by at least 4-6 inches. Was that done on purpose or was someone lazy?

I have some more photos and I'll attach them.

One of them shows a rib with a hammer by it. It never was attached to the side. Another photo is one taken towards the bow under the deck. It shows a weird kind of u-shape floor pattern that dips down. It had rotten wood under it but how can I fix it now. Bring the floor up to it? And then there are the engine beds. I guess replace them by laminating two 2x4's together. Also, since the stingers should be about 17' long, should I scarf two together with epoxy mixed with chopped glass?

 

The way some things are done in boats there is never a logical reason for them . Keeping Wood away from the hull bottom means once the glass delaminates off the wood the wood is doing nothing at all the glass is doing all the work so why have it in the first place . ???
I am of the theory if its there is to be used if its not bing used then why have it !!
Any kind of wood in under floors gets wet over time be it a short time of long time it will get wet . Adds weight and then rots . but remember the age of the boat so the job you doing could have to be done again sometime in the future . . If the old glass you are wanting to rebond onto is loose rip ot out and do a total reglass !! make sure you grind the surface where the new glass will be going . Check in the west system hand book for Scarfing and what ti use to make glue the glass wont thicken the resin will only reinforge it !!!

 

Grind, grind, grind

I am taking out most, if not all of the glass that has been added over the years. In my opinion, although I am far from being educated in this area, it was improperly applied. It was the thick braided type and there were pockets where it didn't bond to the surface. If I only ground the area that had pockets, it ended up looking like the surface of the moon. So I am painfully grinding out most of it...especially on each side of the old stringers and ribs by 12".

The bilge has a gray material applied over the glass and is a bear to grind down. I will most likely leave much of that area alone except where I have to glass for the stingers.

Douglass Fir has been named several times throughout the forum as the choice of wood to use for the ribs and stringers. Is that your opinion as well? Also, should the ribs attach to both the stringers and the side of the boat?

Thanks again for your help.

Mark

 

Seems like a nothing but pictures are well worth posting redardless how insignifficant it might seem at the time . unless you are a proffessional writer !

 

Almost Done Grinding

Here are the latest photos. We still have to remove the fuel tank from the rear of the boat. Must be some hidden attachments as we are having a difficult time finding screws.
I would say we are about 95% done with the grinding. (Thank God!) It seems as though I've spent most of my budget on Tyvex suits, N95 and P100 Respirators and we haven't even glassed anything yet.
There is a gray material in the bilge area and on the sides of the boat that is very difficult removing...more so than the glass itself. Anyone know what it may be? Seems like something I may want to put back in. It's tougher than nails.
Still no opinions on Douglas Fir or Southern Pine or Spruce for the ribs and stringers. Anyone want to opine?
And do the engine beds have to be made out of some extra strength material. It's a 351 CI sitting on them.
I took a photo near the cockpit area of the gray stuff on the sides. There used top be carpet on the sides and this is what was under it. Thanks