hull repair

[eurotk1]

I am converting a inboard hull to outboard power and while filling in the 16in by 25in hole cut in the bottom I screwed up.I cut a piece of 1/2 nidacore and stuck it in the hole and layed 2 layers of woven roving with mat inbetween on the inside of the boat.What i dident realize is that the core slid down while I was rolling the resin.Now i only have room for one layer of mat and roveing on the outside.Will this be strong enough?I put a additional stringer on top of the repair on the inside to strenghten.This will keep the repair from flexing.Do i have to grind out the core and start over?

[yokebutt]

Are you bolting the outboard thru nida-core?

Yokebutt.

[eurotk1]

The outboards bolted to a transom 3'' thick composit.The nidacore is just to
fill the hole in the bottom where the shaft use to exit.

[Ssor]

If there is no load on this repair then its primary purpose is to keep the water on the outside. You should be okay. Was the thrust of the propeller previously applied to the engine or to the transom?

[eurotk1]

the transom has been reinforced to accept outboards because the load use to be applied to the stringers via the inboard engine.The fiberglass repair is on the bottom of the hull .my concern is when the hull pounds in rough seas will the fiberglassed core be strong enough.

[cyclops]

None of us can tell you that answer. But you will be the first to tell us. To really stress the patch you would be doing + 50 mph, boat goes vertical-90 degrees - hits a oncoming wave patch first. Think you can do close to that?

[eurotk1]

the hull speed will only be 30 to 35 mph max.Cruise will be approx 25mph.

[Ssor]

Originally there was a hole in the boat where the drive train poked through. It gets dragged through the water and probably never even gets wet when running at speed. Only when you come down off a plane and have the wave overtake the boat will that patch get hit by water and then not very hard. I persume that you ground a wide bevel into the existing transom and laid the glass into that in increments. Lay a straight edge across the patch and see if you have filled the space.

[gonzo]

Have you thought of what taking the wiegh of the motors forward and adding it aft will do? Usually it is impossible to make a setup like that perform. The hull is designed for a different center of gravity. It will porpoise. Also, on outboard hulls the sides and bottom take the thrust from the motors instead of the stringers. Are you sure the structure can take it?

[cyclops]

I would love to hear from people who try these center engine to stern drive conversions where the new engine is mounted close to the stern drive. How can you possibly get it to balance without putting 1500# of lead in the front of the hull? I am missing something here?

[eurotk1]

I have done the inboard to outboard conversion many times before and When you move the weight around right there are no problems.Ive done a 27 silverton ,25 chriscraft commander ,numerous pacemakers.The transoms are poured resin thickened with sawdust 2.5-3'' thick.All the boats became center consoles and the floors are moved up so they are between the upper and lower engine bolts and then fiberglassed to the transom.This is the first time that I used core in the bottom of the hull and I am unsure of the strength.I just dont want The repair to fail.The hull had twin shaft drives and when I finished cutting out the recess in the hull I was left with 2 large holes.My concern is how strong 1/2 nidacore is with 1 layer of matt and woven roving on the outside and two layers of each on the inside.I beveled the inside and layed twice the size of the hole in glass(this is the largest I could do with thestringers in place)and on the outside I ground and layed 3 x 4 feet.

[cyclops]

Euro, how can you pull heavy inboards center mounted and put 2 lighter OB's on a heavy transom and have the boat sit near level? You must move fuel tanks, batts, anything that is not the hull, up into the bow locker? The stern lights would have to go there also? How can the boats sit level without a wider stern area to support the new weight there? Replacing a sterndrive boat with OB's is easy. A larger set of stringer to transom knees and you are home.

[eurotk1]

This one was easy the engines were in the middle but fuel was in the rear.Now outboards in the rear and 320 gal fuel capacity in the middle.

[cyclops]

BIGGG tanks can do a lot on a swap.