DE25 Questions

Power Boats only. Please include the boat type in your question.
Jeff
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DE25 Questions

Post by Jeff »

This question arrived via email today: "I have several additional questions. 1. Can the De 25 be stretched by 10% in all directions. This would give me the headroom I am looking for. 2. If so, would ballast need to be added" Jeff

jacquesmm
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Re: DE25 Questions

Post by jacquesmm »

1. Yes
2. No
3. but you will need some extra fiberglass on the bottom.
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dennisb
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Re: DE25 Questions

Post by dennisb »

Hello jacquesmm

Your comment - extra fiberglass on the bottom, do you mean an extra layer of cloth + resin on the bottom and up the sides.

Thanks

OneWayTraffic
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Re: DE25 Questions

Post by OneWayTraffic »

Typically that is the case when people wish to push the limits of a boat either size wise or with increased power. I can think of other ways you could beef it up:

1. Increase the plywood thickness, assuming that you can bend it, and there is a suitable size to move up to.

2. Add some extra stringers and framing. Good luck with drawing and locating them, especially the stringers. One could add floors (small frames) between all existing frames.

3. Add another layer of biaxal cloth to both sides of the bottom and up the sides the specified height. Sometimes extra tape as well.

I've been on this forum a while, and usually the designer goes to extra glass. Adding some small frames isn't too hard, I suppose, but I wouldn't want to even think about the complications of adding stringers. Increasing the core would give the best bang for money and weight but once you get over 3/8th" I wouldn't pretend to know how you are supposed to bend it. That leaves an extra layer of cloth as the best option I suppose. Easy to put on if you accept the extra cost in labour, materials and time.

I don't think I've ever seen a recommendation for more glass on the sides, except for dock rash.

That's my synopsis of his posts anyway. If I had a beer for every time I've read a question like this on this forum, I'd be able to get all of us a good time. :D

Edit: These posts are worth reading. The whole build is fantastic, and the builder used 12mm (1/2") plywood. The designer had some comments about it.

viewtopic.php?f=12&t=62926&p=414385&hil ... od#p414385

jacquesmm
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Re: DE25 Questions

Post by jacquesmm »

Onewaytraffic is correct.
The DE23 and DE25 were designed as light boats able to get on plane with minimal HP. Over the years, builders have added features, used larger engines and each of those changes required a stronger bottom and frame. It can be done, that design can take more weight and more HP.
A good example is the DE25 built by Mark and fitted with a 150 hp.
I don't remember his screen name but he has thread about it. I am on a very slow internet connection and can't find it but it is a good example of a modified DE25.
There is also a Dutch built and stretched DE25 that is also a good example to follow.

If you want to go that route, I will help with exact specs but only after you buy the plans. It is possible to scale that boat up 10% but I will do the calculations once you are committed to the project.
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dennisb
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Re: DE25 Questions

Post by dennisb »

Hello Jacques,

Thanks again for the quick response.

I have already purchased the plans. The basic boat looks well suited for the cruising we want to do, mostly Connecticut river and Long Island Sound.

Doing the calculation, it looks like if I keep the weight down during construction I should be able to get the performance I am looking for with a 150 HP motor, 28 to 30 MPH top end. We would most likely do most of our cruising around 18 to 20 MPH.

During the build if I let the weight get out of control, I will need to add more HP, creating a snow ball effect, bigger motor, need to carry more fuel, etc. I am looking to keep the boat weight under # 4000 with a 150 HP motor, half full of fuel (~ 40 to 50 gal) and light gear.

Even with an additional layer of glass to the inside and outside bottom I think I will be OK. I am planning on using foam core for as much of the top side as I can.

Thanks

Dennis

Matt Gent
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Re: DE25 Questions

Post by Matt Gent »

What headroom are you looking for? And where? That can be solved without scaling the whole boat.

The Merc 150 is a full 50% higher displacement than the df140 I have, and the 140 already meets your speed goals. I think the 150 would be a good match, being able to cruise at lower rpm. It is under 100lb more than the 140, and I think you can get a larger diameter prop which will help at lower speeds.

I can’t imagine needing more than 150hp on a DE at any reasonable loading. I may replace with the Merc 150 when it is time.

fallguy1000
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Re: DE25 Questions

Post by fallguy1000 »

Silly to scale the boat 10% for headroom. Build the cabin a bit higher aft.

40 gallons and a 150hp seem a bit of a mismatch to me-fwiw

Power creep is ez. The Skoota was spec'd in nice light Yamaha F70s.

But alternator output is low, so went to 90s and added a jackplate and 25" shafts, now 122# xtra each hull. The 115hp is same block, weight is close, an ez leap. I said no. Harder to say no, but sometimes wiser. Still worried my boat will squat aft with the 244# added to the stern(s). I have this horrible feeling about selling like new low hours.
My boat build is here -------->

viewtopic.php?f=12&t=62495

TomW1
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Re: DE25 Questions

Post by TomW1 »

fallguy1000 wrote: Mon Jul 19, 2021 12:35 pm Silly to scale the boat 10% for headroom. Build the cabin a bit higher aft.

40 gallons and a 150hp seem a bit of a mismatch to me-fwiw

Power creep is ez. The Skoota was spec'd in nice light Yamaha F70s.

But alternator output is low, so went to 90s and added a jackplate and 25" shafts, now 122# xtra each hull. The 115hp is same block, weight is close, an ez leap. I said no. Harder to say no, but sometimes wiser. Still worried my boat will squat aft with the 244# added to the stern(s). I have this horrible feeling about selling like new low hours.
What 90's did you end up getting?

Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

fallguy1000
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Re: DE25 Questions

Post by fallguy1000 »

Yamaha vmax sho...

Sorry to the OP....i think the de25 is a great boat
My boat build is here -------->

viewtopic.php?f=12&t=62495

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